Glass-ceramics with specific thermal expansion behavior

Abstract

To provide a glass ceramic having improved thermal expansion characteristics, and the use thereof in a precision component.SOLUTION: There is provided a LAS glass ceramic which has an average coefficient of thermal expansion CTE in the range from 0 to 50°C of not more than 0±0.1×10-6 / K and thermal hysteresis at least within the temperature range from 10°C to 35°C of<0.1 ppm, and comprises the following components (in mol % based on oxide): SiO2 of 60 to 70; Li2O of 7 to 9.4; MgO + ZnO of 0 to 0.6; and at least one component selected from the group consisting of P2O5, R2O, and RO; and 5 to 6 mol % of at least one nucleating agent selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, WO3 and HfO2.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to glass ceramics which exhibit specific thermal expansion behavior while at the same time exhibiting good meltability, environmentally friendly fining, formability and ceramizability, as well as the use of the glass ceramics according to the invention in precision components.

[0002] Background of the Invention Low thermal expansion or low CTE (Coefficient of Thermal Expansion) materials and precision components are already known from the prior art.

[0003] Known precision component materials with low thermal expansion in the temperature range around room temperature include ceramics, Ti-doped quartz glass, and glass ceramics. Low thermal expansion glass ceramics are, in particular, lithium aluminum silicate glass ceramics (LAS glass ceramics), which are described, for example, in U.S. Pat. No. 4,851,372, U.S. Pat. No. 5,591,682, EP 587979, U.S. Pat. No. 7,226,881, U.S. Pat. No. 7,645,714, DE 102004008824, and DE 102018111144. Further precision component materials are cordierite ceramics or cordierite glass ceramics.

[0004] Such materials are often used in precision components that must meet particularly stringent requirements regarding their properties (e.g., mechanical, physical, and optical properties). Such materials are used, among other things, in ground- and space-based astronomy and Earth observation, LCD lithography, microlithography and EUV lithography, metrology, spectroscopy, and measurement engineering. In this case, components with particularly low thermal expansion are required, depending on the specific application.

[0005] Generally, the thermal expansion of a material is measured by a static method, in which the length of a test specimen is measured at the beginning and end of a specific temperature range, and the average coefficient of thermal expansion α or CTE (Coefficient of Thermal Expansion) is calculated from the difference in these lengths. In this case, the CTE is expressed as the average value over this temperature range, for example, CTE(0;50) or α(0;50) for the temperature range of 0°C to 50°C.

[0006] To meet the ever-increasing demand, materials have been developed with CTEs better suited to the application field of the components formed from them. For example, the average CTE can be optimized not only for a standard temperature range (CTE(0;50)) but also for a temperature range near the actual application temperature, e.g., 19°C to 25°C, i.e., CTE(19;25) for a specific lithography application. In addition to determining the average CTE, the thermal expansion of a test specimen can also be determined over a very small temperature range and expressed as a CTE-T curve. Preferably, such a CTE-T curve has zero crossings at one or more temperatures, preferably at or near the intended application temperature. The zero crossings of the CTE-T curve exhibit particularly small relative changes in length with temperature change. For some glass ceramics, the zero crossings of such CTE-T curves can be shifted toward the application temperature of the component by appropriate temperature treatment. Furthermore, to minimize the change in length of the component even with small temperature changes, it is desirable to minimize the slope of the CTE-T curve near the application temperature, in addition to the absolute value of the CTE. For these particular zero-expansion glass-ceramics, the optimization of the CTE or thermal expansion is typically achieved by varying the ceramization conditions while maintaining the same composition.

[0007] A detrimental effect in known precision components and materials, particularly glass ceramics such as LAS glass ceramics, is "thermal hysteresis," hereafter abbreviated as "hysteresis." Hysteresis refers to the difference between the change in length of a specimen when heated at a constant heating rate and when subsequently cooled at a constant cooling rate, even if the cooling and heating rates are identical. A classic hysteresis curve is obtained by plotting the change in length as a function of heating or cooling temperature. The shape of the hysteresis curve also depends on the rate of temperature change. The faster the temperature change, the more pronounced the hysteresis effect. Due to the hysteresis effect, the thermal expansion of LAS glass ceramics is temperature- and time-dependent, i.e., dependent on the rate of temperature change, as has already been shown, for example, by O. Lindig and W. Pannhorst, "Thermal expansion and length stability of ZERODUR® glass ceramics." (R) in dependence on temperature and time”, APPLIED OPTICS, Vol. 24, No. 20, Okt. 1985; R. Haug et al., “Length variation in ZERODUR (R) M in the temperature range from -60°C to +100°C”, APPLIED OPTICS, Vol. 28, No.19, Okt. 1989; R. Jedamzik ​​et al., “Modeling of the thermal expansion behavior of ZERODUR (R)at arbitrary temperature profiles”, Proc. SPIE Vol. 7739, 2010; DB Hall, “Dimensional stability tests over time and temperature for several low-expansion glass ceramics”, APPLIED OPTICS, Vol. 35, No. 10, April 1996.

[0008] Glass-ceramics that exhibit thermal hysteresis change their length slowly or quickly compared to changes in temperature, so that the material or precision components manufactured from it exhibit a disturbing isothermal length change, i.e., even when the temperature is kept constant after a temperature change (so-called "isothermal hold"), the material still changes length until a steady state is reached. If the material is then heated and cooled again, the same effect occurs again.

[0009] In previously known LAS glass-ceramics, it has not been possible to eliminate the thermal hysteresis effect without affecting other properties, even when the ceramization conditions are changed for the same composition.

[0010] The properties of materials used in precision components, especially glass ceramics, are often related to the temperature ranges of 0°C to 50°C, especially 10°C to 35°C, or 19°C to 25°C, where 22°C is usually referred to as room temperature. Because precision components are often used in this temperature range, materials that exhibit thermal hysteresis effects or isothermal length changes are disadvantageous, as they can cause optical disturbances in optical components such as lithography mirrors or astronomical or space mirrors. Other glass-ceramic precision components used in metrology (e.g., precision measuring instruments, interferometer reference plates) can cause measurement errors.

[0011] Some known materials, such as ceramics, Ti-doped fused silica, and certain glass-ceramics, have an average coefficient of thermal expansion (CTE) of 0±0.1×10 -6 / K (corresponding to 0±0.1 ppm / K). Materials with such low average CTEs in the aforementioned temperature range are referred to as zero-expansion materials for the purposes of the present invention. However, glass ceramics with such optimized average CTEs, particularly LAS glass ceramics, generally exhibit thermal hysteresis in the temperature range of 10°C to 35°C. That is, when used at temperatures around room temperature (i.e., 22°C), these materials exhibit detrimental hysteresis effects that impair the accuracy of precision components manufactured from such materials. Therefore, glass ceramic materials that do not exhibit significant hysteresis at room temperature have been developed (see U.S. Pat. No. 4,851,372). However, this effect has not disappeared, but has simply been shifted to lower temperatures, so that these glass ceramics still exhibit significant, potentially detrimental hysteresis at temperatures below 10°C. Therefore, to characterize the thermal hysteresis of a material in a given temperature range, the present invention considers the thermal behavior of the material at different temperature points within this range. Although some glass-ceramics do not exhibit significant hysteresis at 22°C and 5°C, these glass-ceramics have an average CTE(0;50) >0±0.1 ppm / K and are not zero-expansion glass-ceramics as defined above.

[0012] Further demands on glass-ceramic materials are that the glass components have good meltability, and that the base glass melt can be easily melt-controlled and homogenized in industrial production plants, so that after successful ceramization of the glass, the glass-ceramic can meet the high demands imposed on it with respect to CTE uniformity, internal quality, in particular low levels of inclusions (especially bubbles), low streak levels, and polishability.

[0013] The internal quality of glass-ceramics, especially the presence of bubbles and streaks, is influenced by the effectiveness of fining the glass melt. Fining is understood as the removal of bubbles from the glass melt. To minimize the inclusion of foreign gases and bubbles, the molten batch must be thoroughly mixed and degassed. For this purpose, so-called chemical fining agents are usually added to the melt, which decompose and release gases or become volatile at high temperatures. A particularly effective fining agent for LAS glass-ceramics is arsenic oxide (As2O3), a redox fining agent that releases O2 as a fining gas. This fining agent is particularly effective because, as disclosed in German Patent Application Publication No. 102010002188, the release of fining gases has two maxima at temperatures within the melting and fining temperature range of the glass components (approximately 1250°C and approximately 1600°C). However, As2O3 is highly toxic and has been identified as a carcinogen.

[0014] In the field of zero-expansion LAS glass-ceramics, a switch to other chemical fining agents in place of As2O3 is underway (e.g., U.S. Pat. No. 8,043,985, DE 102010002188 A1). However, a common problem with the use of fining agents is that, on the one hand, the added fining agent releases fining gases by decomposition or due to its volatility, but on the other hand, it at least partially remains as a component in the glass and / or crystalline phase and thus also determines the properties of the subsequent glass-ceramic. Fining of glass melts at very high temperatures in the range of 1700°C to 2400°C with the addition of different fining agents is also known, for example from DE 19939771 A1.

[0015] It was therefore an object of the present invention to provide an environmentally friendly fined glass-ceramic that exhibits improved expansion behavior.A further object of the present invention was to provide an environmentally friendly fined glass-ceramic that can be produced industrially and has zero expansion and low thermal hysteresis, particularly in the temperature range from 10°C to 35°C, and precision components manufactured from this material.

[0016] The above-mentioned problems are solved by the subject matter described in the claims. The invention has various aspects: According to one aspect of the present invention, there is provided an LAS glass ceramic having an average coefficient of thermal expansion (CTE) of at most 0±0.1×10 in the range of 0 to 50°C. -6 / K, and having a thermal hysteresis of <0.1 ppm over the temperature range of at least 10°C to 35°C, and containing (in mole % on an oxide basis) the following components: [Table 1] At least one component selected from the group consisting of P2O5, R2O, and RO, wherein R2O may be Na2O and / or K2O and / or Cs2O and / or Rb2O, and RO may be CaO and / or BaO and / or SrO. A nucleating agent having a content of 1.5 to 6 mol %, wherein the nucleating agent is TiO 2、 ZrO 2、 a nucleating agent, which is at least one component selected from the group consisting of Ta2O5, Nb2O5, SnO2, MoO3, WO3, and HfO2; and containing up to 0.05 mol % As2O3.

[0017] According to a further aspect, the invention relates to the use of the glass ceramic according to the invention as a substrate for precision components.

[0018] According to a further aspect, the invention relates to the use of the LAS glass ceramic according to the invention in precision components, in particular in precision components for use in metrology, spectroscopy, measurement engineering, lithography, astronomy or Earth observation from outer space, for example as mirrors or mirror supports for segmented or monolithic astronomical telescopes, or as lightweight or ultralight mirror substrates, for example for space-based telescopes, or as high-precision structural components, for example for distance measurement in outer space or optical components for Earth observation, as precision parts such as standards for precision metrology, precision measuring instruments, reference plates for interferometers, for example as mechanical precision parts, for example ring laser gyroscopes, spiral springs for the watch industry, as mirrors and prisms, for example in LCD lithography, as mask holders, wafer tables, reference plates, reference frames and grid plates, for example in microlithography and EUV (Extreme UV) microlithography where reflective optics are used, and also as mirrors and / or photomask substrates or reticle mask blanks in EUV microlithography.

[0019] According to another aspect, the invention relates to a precision component comprising the LAS glass ceramic according to the invention. [Brief explanation of the drawings]

[0020] [Figure 1] 1 shows the CTE-T curves of low linear thermal expansion materials known from the prior art, e.g. for precision components. [Figure 2] Figure 1 shows the hysteresis behavior of three glass-ceramic samples, determined using the same method as used in the present invention. This figure is adapted from R. Jedamzik ​​et al., "Modeling of the thermal expansion behavior of ZERODUR® at arbitrary temperature profiles," Proc. SPIE Vol. 7739, 2010. [Figure 3]1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) for known glass-ceramic materials that can be used to manufacture precision components and have a thermal hysteresis of >0.1 ppm over a temperature range of at least 10°C to 35°C. [Figure 4] 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) for known glass-ceramic materials that can be used to manufacture precision components and have a thermal hysteresis of >0.1 ppm over a temperature range of at least 10°C to 35°C. [Figure 5] 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) for known glass-ceramic materials that can be used to manufacture precision components and have a thermal hysteresis of >0.1 ppm over a temperature range of at least 10°C to 35°C. [Figure 6] 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) for known glass-ceramic materials that can be used to manufacture precision components and have a thermal hysteresis of >0.1 ppm over a temperature range of at least 10°C to 35°C. [Figure 7] 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) for known glass-ceramic materials that can be used to manufacture precision components and have a thermal hysteresis of >0.1 ppm over a temperature range of at least 10°C to 35°C. [Figure 8] 1 shows hysteresis curves (dashed line = cooling curve, dotted line = heating curve) for known glass-ceramic materials that can be used to manufacture precision components and have a thermal hysteresis of >0.1 ppm over a temperature range of at least 10°C to 35°C. [Figure 9] Figure 1 shows the hysteresis curve (dashed line = cooling curve, dotted line = heating curve) of a prior art glass-ceramic that can be used to manufacture precision components and has a thermal hysteresis of <0.1 ppm at least in the temperature range from 10°C to 35°C, but the steep transition of the curve makes it clear that this glass-ceramic is not a zero expansion glass-ceramic. [Figure 10]1 shows the hysteresis curve (dashed line = cooling curve, dotted line = heating curve) of a glass ceramic according to the invention (composition according to Example 2 in Table 1) that can be used to manufacture precision components according to the invention and has a thermal hysteresis of <0.1 ppm in the temperature range of at least 10 ° C to 35 ° C. [Figure 11] 1 shows the hysteresis curve (dashed line = cooling curve, dotted line = heating curve) of a glass ceramic according to the invention (composition according to Example 6 in Table 1) that can be used to manufacture precision components according to the invention and has a thermal hysteresis of <0.1 ppm in the temperature range of at least 10 ° C to 35 ° C. [Figure 12] 1 shows the hysteresis curve (dashed line = cooling curve, dotted line = heating curve) of a glass ceramic according to the invention (composition according to Example 7 in Table 1) that can be used to manufacture precision components according to the invention and has a thermal hysteresis of <0.1 ppm in the temperature range of at least 10 ° C to 35 ° C. [Figure 13] FIG. 1 shows a normalized Δl / l0-T curve (also referred to as a dl / l0 curve) of a glass ceramic according to the invention (composition according to Example 7 in Table 1), and an auxiliary line for determining the parameter F as an index of the flatness of the expansion curve in the temperature range from 0°C to 50°C. [Figure 14] FIG. 1 shows another normalized Δl / l0-T curve for a glass-ceramic according to the invention based on another ceramization (composition according to Example 7 of Table 1), and an auxiliary line for determining the alternative parameter f(20;70) as an indicator of the flatness of the expansion curve in the temperature range from 20° C. to 70° C. [Figure 15] Normalized Δl / l0-T curve (also called dl / l0 curve) of a glass ceramic according to the invention (composition according to Example 6 of Table 1) and auxiliary lines for determining the alternative parameter f(-10;30) as an indicator of the flatness of the expansion curve in the temperature range from -10°C to 30°C. [Figure 16] FIG. 1 shows the normalized Δl / l0-T curve of a known material that can be used to manufacture a known precision part, and an auxiliary line for determining the parameter F as an index of the flatness of the expansion curve in the temperature range of -10°C to 70°C. [Figure 17]FIG. 1 shows the normalized Δl / l0-T curve of a known material that can be used to manufacture a known precision part, and an auxiliary line for determining the parameter F as an index of the flatness of the expansion curve in the temperature range of -10°C to 80°C. [Figure 18] FIG. 1 shows the normalized Δl / l0-T curve of a known material that can be used to manufacture a known precision part, and an auxiliary line for determining the parameter F as an index of the flatness of the expansion curve in the temperature range of -20°C to 80°C. [Figure 19] FIG. 1 shows the normalized Δl / l0-T curve of a known material that can be used to manufacture a known precision part, and an auxiliary line for determining the parameter F as an index of the flatness of the expansion curve in the temperature range of -10°C to 70°C. [Figure 20] Normalized Δl / l0-T curves for known materials over the temperature range of -20°C to +70°C. [Figure 21] FIG. 1 shows that the CTE-T curve of a glass-ceramic according to the invention (composition according to Example 6 of Table 1) that can be used to manufacture advantageous precision components advantageously exhibits a CTE "plateau". [Figure 22] FIG. 22 is a diagram showing a part of FIG. 21. [Figure 23] FIG. 1 shows that the CTE-T curve of a glass-ceramic according to the invention (composition according to Example 7 of Table 1) that can be used to manufacture advantageous precision components advantageously exhibits a CTE "plateau." [Figure 24] FIG. 24 is a diagram showing a part of FIG. 23. [Figure 25] FIG. 1 shows that the CTE-T curve of a glass-ceramic according to the invention (composition according to Example 9 of Table 1) that can be used to manufacture advantageous precision components advantageously exhibits a CTE "plateau." [Figure 26] FIG. 2 shows the slope of the CTE-T curve for a glass ceramic having a composition according to Example 6 of Table 1. [Figure 27] FIG. 2 shows the slope of the CTE-T curve for a glass ceramic having a composition according to Example 7 of Table 1. [Figure 28]FIG. 1 shows different expansion curves adjusted by different ceramization parameters for a glass ceramic according to the invention having a composition according to Example 6 of Table 1. [Figure 29] FIG. 1 shows different expansion curves adjusted by different ceramization parameters for a glass ceramic according to the invention having a composition according to Example 7 of Table 1.

[0021] The subject of the present invention is a LAS glass ceramic having an average coefficient of thermal expansion CTE in the range 0 to 50°C of at most 0±0.1 × 10 -6 / K, and having a thermal hysteresis of <0.1 ppm over the temperature range of at least 10°C to 35°C, and containing (in mole % on an oxide basis) the following components: [Table 2] At least one component selected from the group consisting of P2O5, R2O, and RO, wherein R2O may be Na2O and / or K2O and / or Cs2O and / or Rb2O, and RO may be CaO and / or BaO and / or SrO. A nucleating agent having a content of 1.5 to 6 mol %, wherein the nucleating agent is TiO 2、 ZrO 2、 a nucleating agent, which is at least one component selected from the group consisting of Ta2O5, Nb2O5, SnO2, MoO3, WO3, and HfO2; and containing up to 0.05 mol % As2O3.

[0022] The present invention provides for the first time an LAS glass ceramic (hereinafter also referred to as glass ceramic) that combines several important properties: the average coefficient of thermal expansion (CTE) in the range of 0 to 50°C is at most 0±0.1 × 10 -6 / K, i.e., the LAS glass ceramic has zero thermal expansion. Furthermore, the LAS glass ceramic has a thermal hysteresis of <0.1 ppm at least in the temperature range from 10°C to 35°C. Materials with such low hysteresis effects of <0.1 ppm in the aforementioned temperature range are hereinafter referred to as "hysteresis-free." As already mentioned above, the description of hysteresis depends on the rate of temperature change used in the measurement, and therefore, in the present invention, the description of hysteresis relates to a heating / cooling rate of 36 K / h, i.e., 0.6 K / min. In an advantageous embodiment, the LAS glass ceramic can be hysteresis-free at least in the temperature range from 5°C to 35°C, or at least in the temperature range from 5°C to 40°C, advantageously at least in the temperature range from >0°C to 45°C, and preferably at least in the temperature range from -5°C to 50°C.

[0023] Furthermore, the zero-expansion, hysteresis-free glass ceramics according to the present invention, which have an As2O3 content of at most 0.05 mol%, contain only small amounts of environmentally undesirable fining agents. Advantageously, the As2O3 content in the glass ceramic is ≦0.04 mol%, preferably ≦0.03 mol%, preferably ≦0.025 mol%, preferably ≦0.02 mol%, and preferably ≦0.015 mol%. It is advantageous for the glass ceramic to contain as little As2O3 as possible. Particularly preferred variants of the glass ceramic are substantially As2O3-free, where "substantially As2O3-free or As-free" means that the component As2O3 is not intentionally added to the composition as a component but is present at most only as an impurity. For As2O3-free glass ceramics, the impurity limit for As2O3 is ≦0.01 mol%, preferably 0.005 mol%. According to a particular embodiment, the glass ceramic is As2O3-free.

[0024] The parameters of CTE and thermal hysteresis are discussed in more detail below.

[0025] According to the present invention, glass ceramics are understood to be non-porous inorganic materials having a crystalline phase and a glass phase, with the matrix, or continuous phase, usually being the glass phase. To produce a glass ceramic, the components of the glass ceramic are first mixed, melted, and refined to form a so-called green glass. After cooling, the green glass is reheated to crystallize in a controlled manner (so-called "controlled volume crystallization"). The green glass and the glass ceramic produced therefrom have the same chemical composition (analytical values); only the internal structure of the material changes due to ceramization. Therefore, when the composition of a "glass ceramic" is mentioned below, the same statement also applies to the precursor of the glass ceramic, i.e., the green glass.

[0026] In the present invention, it has been discovered that because both MgO and ZnO contribute to the development of thermal hysteresis in the temperature range of interest, limiting the MgO and ZnO contents as claimed is essential to providing a zero-expansion LAS glass-ceramic that is hysteresis-free at least in the temperature range of 10°C to 35°C. In contrast, it has previously been assumed that these glass components, either in combination or individually, are necessary to achieve zero expansion and to make the CTE-T curve of the material "flat," i.e., to reduce the slope of the CTE-T curve over the temperature range, particularly in zero-expansion LAS glass-ceramics. Thus, there exists a trade-off between an LAS glass-ceramic being either zero-expansion or hysteresis-free.

[0027] According to the present invention, this trade-off is eliminated not only by substantially omitting the use of MgO and ZnO, but also by selecting the SiO2 and Li2O contents within the ranges specified by the present invention. It has been surprisingly found that within the ranges given by the SiO2 (60-71 mol%) and Li2O (7-9.4 mol%) contents, zero-expansion and hysteresis-free glass-ceramics are obtained, even when the glass-ceramics are environmentally friendly refined, i.e., contain a maximum of 0.05 mol% As2O3, and preferably are substantially free of As2O3.

[0028] LAS glass-ceramics comprise a negatively expanding crystalline phase, which may comprise or consist of a high-quartz solid solution, also advantageously referred to in the present invention as β-eucryptite, and a positively expanding glassy phase. In addition to SiO and AlO, LiO is also a major component of the solid solution. Also, if present, ZnO and / or MgO are incorporated into the solid solution phase and, together with LiO, affect the expansion behavior of the crystalline phase. This means that the aforementioned provisions of the present invention (reducing, preferably eliminating, MgO and ZnO and using a maximum of 0.05 mol% AsO) significantly affect the type and properties of the solid solution formed during ceramization, as well as the composition of the remaining glassy phase. In contrast to known zero-expansion glass-ceramics, in which MgO and ZnO are used inter alia to adjust the desired expansion behavior of the glass-ceramic, the present invention uses for this purpose at least one component selected from the group consisting of P2O5, R2O, and RO, where R2O may be Na2O and / or K2O and / or Rb2O and / or Cs2O, and RO may be CaO and / or BaO and / or SrO. In addition to MgO and ZnO, the aforementioned alkaline earth metal oxides and alkali metal oxides, if present, remain, provided that they remain in the glass phase and are not incorporated into the high-quartz solid solution.

[0029] In the present invention, it has been found that it can be advantageous to provide a zero-expansion and hysteresis-free glass-ceramic if the composition satisfies the condition: mole fraction of SiO + (5 × mole fraction of LiO) ≥ 10 or preferably ≥ 10.5, preferably mole fraction of SiO + (5 × mole fraction of LiO) ≥ 10 or ≥ 10.5. Alternatively or additionally, advantageous upper limits for this "mole fraction of SiO + (5 × mole fraction of LiO)" condition are ≤ 115.5, ≤ 114.5, or ≤ 113.5.

[0030] In an advantageous development, the glass ceramic can comprise the following components in molar percentages, alone or in any combination: Al2O310~22 P2O50~6 MgO 0~0.35 ZnO 0~0.5 R2O 0~6 RO 0~6 TiO2+ZrO21.5~6

[0031] More preferably, the glass-ceramic may contain the following components, in mole %, alone or in any combination, within the above-mentioned limits for R2O, RO and the sum of TiO2 + ZrO2: Na2O 0-3 K2O 0~3 Cs2O 0~2 Rb2O 0~2 CaO 0-5 BaO 0~4 SrO 0-3 TiO20~5 ZrO20~3

[0032] In an advantageous embodiment, the LAS glass ceramic comprises (in mole % on an oxide basis): Al2O310~22 P2O50~6 MgO 0~0.35 ZnO 0~0.5 R2O 0~6 RO 0~6 Nucleating agent 1.5~6 wherein the nucleating agent is preferably TiO2 and / or ZrO2.

[0033] In an advantageous embodiment, the LAS glass ceramic comprises (in mole % on an oxide basis): Al2O310~22 P2O50~6 MgO 0~0.3 ZnO 0~0.4 R2O 0~6 RO 0~6 Nucleating agent 1.5~6 wherein the nucleating agent is preferably TiO2 and / or ZrO2.

[0034] In a further advantageous embodiment, the LAS glass ceramic comprises (in mole % on an oxide basis): SiO260.50~69 Li2O 8~9.4 Al2O311~21 P2O50.5~6 MgO 0~0.2 ZnO 0~0.3 R2O 0~4 RO 0.2~4.5 As2O3≦0.04 Nucleating agent 2.5~5 wherein the nucleating agent is preferably TiO2 and / or ZrO2.

[0035] The glass ceramic contains at least 60 mol% silicon dioxide (SiO2), more preferably at least 60.5 mol%, also preferably at least 61 mol%, also preferably at least 61.5 mol%, and even more preferably at least 62.0 mol%. The SiO2 content is at most 71 mol% or less, more preferably at most 70 mol% or less, even more preferably at most 69 mol%, and even more preferably at most 68.5 mol%. A high SiO2 content can make the batch difficult to melt and increase the viscosity of the melt, which can cause problems with melt homogenization in industrial production plants. Therefore, it is recommended not to exceed a content of 71 mol%, preferably 70 mol%. A high melt viscosity increases the melt processing temperature (Va). Very high temperatures are required for melt clarification and homogenization, which results in attacking the internal surfaces of the melting unit due to the aggressiveness of the melt, which increases with temperature. Furthermore, even higher temperatures may not be sufficient to produce a homogeneous melt, resulting in a green glass containing streaks and inclusions (especially bubbles and particles originating from the inner surfaces of the melting unit). This means that after ceramization, the requirements for homogeneity of the properties of the produced glass-ceramic, such as the uniformity of the thermal expansion coefficient, are not met. For this reason, a SiO2 content lower than the stated upper limit may be preferable.

[0036] The Al2O3 content is advantageously at least 10 mol%, preferably at least 11 mol%, preferably at least 12 mol%, more preferably at least 13 mol%, also preferably at least 14 mol%, also preferably at least 14.5 mol%, and even more preferably at least 15 mol%. If the content is too low, the low-expansion solid solution is not formed or is formed in too small an amount. The Al2O3 proportion is advantageously at most 22 mol%, preferably at most 21 mol%, preferably at most 20 mol%, even more preferably at most 19.0 mol%, and even more preferably at most 18.5 mol%. If the Al2O3 content is too high, the viscosity increases and promotes disordered devitrification of the material.

[0037] The glass ceramic according to the present invention can contain 0 to 6 mol% P2O5. The phosphate P2O5 content of the glass ceramic can be advantageously at least 0.1 mol%, preferably at least 0.3 mol%, preferably at least 0.5 mol%, also preferably at least 0.6 mol%, more preferably at least 0.7 mol%, and even more preferably at least 0.8 mol%. P2O5 is essentially incorporated into the crystalline phase of the glass ceramic and positively influences the expansion behavior of the crystalline phase and, therefore, the expansion behavior of the glass ceramic. Furthermore, the melting of the components and the fining behavior of the melt are improved. However, if the P2O5 content is too high, the CTE-T curve in the temperature range from 0°C to 50°C will no longer exhibit the advantageously flat progression. Therefore, it is advantageous to include a maximum of 6 mol%, preferably a maximum of 5 mol%, more preferably at most 4 mol%, and even more preferably less than 4 mol% P2O5 in the glass ceramic. According to some embodiments, the glass ceramic may be free of P2O5.

[0038] In the present invention, the components SiO2, Al2O3 and / or P2O5, i.e., specific sums and ratios of components that form a high-quartz solid solution, can contribute to the formation of a glass-ceramic according to the present invention.

[0039] The total proportion in mole percent of the LAS glass ceramic basic components SiO2 and Al2O3 is advantageously at least 75 mole percent, preferably at least 78 mole percent, preferably at least 79 mole percent, more preferably at least 80 mole percent, and / or preferably at most 90 mole percent, preferably at most 87 mole percent, preferably at most 86 mole percent, more preferably at most 85 mole percent. If this total is too high, the viscosity curve of the melt will be shifted to higher temperatures, which is disadvantageous as already explained in connection with the SiO2 component. If this total is too low, too little solid solution will be formed.

[0040] The total proportion in mol % of the LAS glass ceramic basic components SiO2, Al2O3 and P2O5 is preferably at least 77 mol %, advantageously at least 81 mol %, advantageously at least 83 mol %, more preferably at least 84 mol % and / or preferably at most 91 mol %, advantageously at most 89 mol %, more preferably at most 87 mol %, and according to one variant at most 86 mol %.

[0041] The ratio in molar % of P2O5 to SiO2 is preferably at least 0.005, advantageously at least 0.01, preferably at least 0.012, and / or preferably at most 0.1, more preferably at most 0.08 and according to one variant at most 0.07.

[0042] As an additional component, the glass ceramic contains lithium oxide (LiO) in a proportion of at least 7 mol%, advantageously at least 7.5 mol%, preferably at least 8 mol%, and particularly preferably at least 8.25 mol%. The proportion of LiO is limited to at most 9.4 mol%, more preferably at most 9.35 mol%, and even more preferably at most 9.3 mol% or less. LiO is a component of the solid solution phase and contributes significantly to the thermal expansion of the glass ceramic. Exceeding the aforementioned upper limit of 9.4 mol% is undesirable, because otherwise a glass ceramic with a negative coefficient of thermal expansion (CTE) of (0:50) would be produced. If the LiO content is less than 7 mol%, the amount of solid solution formed is too small, and the CTE of the glass ceramic remains positive.

[0043] The glass ceramic may contain at least one alkaline earth metal oxide selected from the group consisting of CaO, BaO, and SrO, collectively referred to as "RO." Components of the group RO remain substantially in the amorphous glass phase of the glass ceramic and may be important for maintaining the zero expansion of the ceramized material. If the sum of CaO + BaO + SrO is too high, the CTE (0:50) targeted by the present invention is not achieved. Therefore, the RO proportion is advantageously at most 6 mol%, or at most 5.5 mol%, preferably at most 5 mol%, advantageously at most 4.5 mol%, preferably at most 4 mol%, preferably at most 3.8 mol%, even more preferably at most 3.5 mol%, and preferably at most 3.2 mol%. If the glass ceramic contains RO, an advantageous lower limit may be at least 0.1 mol%, advantageously at least 0.2 mol%, preferably at least 0.3 mol%, and preferably at least 0.4 mol%. According to some embodiments, the glass-ceramic may be RO-free.

[0044] The proportion of CaO may be preferably at most 5 mol%, advantageously at most 4 mol%, advantageously at most 3.5 mol%, advantageously at most 3 mol%, further preferably at most 2.8 mol%, and more preferably at most 2.6 mol%. The glass ceramic may advantageously contain at least 0.1 mol%, advantageously at least 0.2 mol%, preferably at least 0.4 mol%, and preferably at least 0.5 mol% of CaO. The glass ceramic may advantageously contain the component BaO, which is a good glass former, in a proportion of at least 0.1 mol%, preferably at least 0.2 mol% and / or at most 4 mol%, advantageously at most 3 mol%, advantageously at most 2.5 mol%, preferably at most 2 mol%, preferably at most 1.5 mol%, and preferably at most 1.4 mol%. The glass ceramic may contain at most 3 mol %, advantageously at most 2 mol %, preferably at most 1.5 mol %, preferably at most 1.3 mol %, preferably at most 1.1 mol %, more preferably at most 1 mol %, also preferably at most 0.9 mol %, and / or preferably at least 0.1 mol % of SrO. According to some embodiments, the glass ceramic does not contain CaO and / or BaO and / or SrO.

[0045] The glass ceramic optionally contains sodium oxide (NaO) and / or potassium oxide (KO) and / or cesium oxide (CsO) and / or rubidium oxide (RbO), i.e., NaO-free and / or KO-free and / or CsO-free and / or RbO-free variants are possible. The proportion of NaO may advantageously be at most 3 mol%, preferably at most 2 mol%, preferably at most 1.7 mol%, preferably at most 1.5 mol%, preferably at most 1.3 mol%, preferably at most 1.1 mol%. The proportion of KO may advantageously be at most 3 mol%, preferably at most 2.5 mol%, preferably at most 2 mol%, preferably at most 1.8 mol%, preferably at most 1.7 mol%. The proportion of CsO may advantageously be at most 2 mol%, preferably at most 1.5 mol%, preferably at most 1 mol%, preferably at most 0.6 mol%. The proportion of RbO may advantageously be at most 2 mol%, preferably at most 1.5 mol%, preferably at most 1 mol%, preferably at most 0.6 mol%. According to some embodiments, the glass-ceramic does not comprise NaO and / or KO and / or CsO and / or RbO.

[0046] NaO, KO, CsO, and RbO may each be present in the glass-ceramic, independently of one another, in a proportion of at least 0.1 mol %, preferably at least 0.2 mol %, and more preferably at least 0.5 mol %. The NaO, KO, CsO, and RbO components remain essentially in the amorphous glass phase of the glass-ceramic and can be important for maintaining the zero expansion properties of the ceramized material.

[0047] Thus, the sum of the R2O contents of Na2O, K2O, Cs2O, and Rb2O may be advantageously at least 0.1 mol%, preferably at least 0.2 mol%, advantageously at least 0.3 mol%, and preferably at least 0.4 mol%. A low R2O content, advantageously at least 0.2 mol%, can contribute to extending the temperature range over which the expansion curve of the glass ceramic exhibits a flat profile. The sum of the R2O contents of Na2O, K2O, Cs2O, and Rb2O may advantageously be at most 6 mol%, preferably at most 5 mol%, preferably at most 4 mol%, preferably at most 3 mol%, and preferably at most 2.5 mol%. If the sum of Na2O + K2O + Cs2O + Rb2O is too low or too high, the CTE(0:50) targeted by the present invention may not be achieved. According to some embodiments, the glass ceramic may be free of R2O.

[0048] The glass ceramic may contain up to 0.35 mol % magnesium oxide (MgO). Further advantageous upper limits may be up to 0.3 mol %, up to 0.25 mol %, up to 0.2 mol %, up to 0.15 mol %, up to 0.1 mol %, or up to 0.05 mol %. Particularly preferably, the glass ceramic according to the invention is free of MgO. As mentioned above, the MgO component contained in the glass ceramic causes thermal hysteresis in the temperature range from 0°C to 50°C. The less MgO contained in the glass ceramic, the smaller the hysteresis in the aforementioned temperature range.

[0049] The glass ceramic may contain up to 0.5 mol % zinc oxide (ZnO). Further advantageous upper limits may be up to 0.45 mol %, up to 0.4 mol %, up to 0.35 mol %, up to 0.3 mol %, up to 0.25 mol %, up to 0.2 mol %, up to 0.15 mol %, up to 0.1 mol %, or up to 0.05 mol %. Particularly preferably, the glass ceramic according to the invention is free of ZnO. As already mentioned above, the inventors have found that the component ZnO contained in the glass ceramic causes thermal hysteresis in the temperature range from 0°C to 50°C. The less ZnO contained in the glass ceramic, the smaller the hysteresis in the aforementioned temperature range.

[0050] For the hysteresis-free properties of the glass-ceramics according to the invention, it is important that the condition that MgO+ZnO is less than 0.6 mol% is met. Further advantageous upper limits for the sum of MgO+ZnO can be at most 0.55 mol%, at most 0.5 mol%, less than 0.5 mol%, at most 0.45 mol%, at most 0.4 mol%, at most 0.35 mol%, at most 0.3 mol%, at most 0.25 mol%, at most 0.2 mol%, at most 0.15 mol%, at most 0.1 mol%, or at most 0.05 mol%.

[0051] The glass ceramic further comprises at least one nucleating agent selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, WO3, and HfO2. The nucleating agent may be a combination of two or more of the aforementioned components. The total proportion of the nucleating agents is preferably at least 1.5 mol%, preferably at least 2 mol% or more than 2 mol%, more preferably at least 2.5 mol%, and according to certain variants, at least 3 mol%. The upper limit may be at most 6 mol%, preferably at most 5 mol%, preferably at most 4.5 mol%, or at most 4 mol%. In particularly advantageous variants, the above-mentioned upper and lower limits apply to the sum of TiO2 and ZrO2.

[0052] The glass ceramic preferably contains titanium oxide (TiO) in a proportion of at least 0.1 mol%, advantageously at least 0.5 mol%, preferably at least 1.0 mol%, preferably at least 1.5 mol%, preferably at least 1.8 mol% and / or preferably at most 5 mol%, advantageously at most 4 mol%, more preferably at most 3 mol%, even more preferably at most 2.5 mol%, preferably 2.3 mol%. TiO-free variants of the glass ceramic according to the invention are possible.

[0053] The glass ceramic can advantageously further comprise zirconium oxide (ZrO) in a proportion of at most 3 mol%, preferably at most 2.5 mol%, more preferably at most 2 mol%, preferably at most 1.5 mol%, or at most 1.2 mol%. Preferably, ZrO is present in a proportion of at least 0.1 mol%, more preferably at least 0.5 mol%, at least 0.8 mol%, or at least 1.0 mol%. ZrO-free variants of the glass ceramic according to the invention are possible.

[0054] According to some advantageous variants of the invention, 0 to 5 mol % of Ta2O5 and / or Nb2O5 and / or SnO2 and / or MoO3 and / or WO3 and / or HfO2 may be present in the glass ceramic, individually or in total, and these may serve, for example, as alternative or additional nucleating agents or for adjusting optical properties, such as the refractive index. To adjust the optical properties, in some advantageous variants, for example, Gd2O3, YO3, HfO2, Bi2O3 and / or GeO2 may be present.

[0055] In order to provide the hysteresis-free, zero-expansion glass-ceramics according to the invention with the desired internal quality, in particular with a low number of bubbles and few streaks, despite a reduced As2O3 content or even without As2O3, in an advantageous embodiment at least one chemical fining agent is used.

[0056] In an advantageous embodiment, the glass ceramic can have, as chemical fining agent, at least one alternative redox fining agent and / or at least one evaporative fining agent and / or at least one decomposition fining agent instead of As2O3 or in addition to a small amount of As2O3 (up to 0.05 mol %). Since As2O3 is also a redox fining agent, redox fining agents used as an alternative to or in addition to As2O3 are referred to in the present invention as "alternative redox fining agents".

[0057] In advantageous variants, the total content of chemical fining agents detectable in the glass ceramic (excluding the content of As2O3, if present in the glass ceramic) can be in the range of 0 mol% to 1 mol%. In advantageous embodiments, the total content of fining agents detectable in the glass ceramic (excluding As2O3) is greater than 0.01 mol%, preferably at least 0.05 mol%, preferably at least 0.1 mol%, preferably at least 0.15 mol%, advantageously at least 0.2 mol% and / or at most 1 mol%, preferably at most 0.7 mol%, preferably at most 0.5 mol%, preferably at most 0.4 mol%. Some advantageous variants can also contain at most 0.3 mol%, preferably at most 0.25 mol%, or at most 0.2 mol% of fining agents. The proportion of each component can be detected by analysis of the glass ceramic. This applies in particular to all fining agents except for the sulfate components described below.

[0058] Redox fining agents contain polyvalent ions that can exist in at least two oxidation states, which are in temperature-dependent equilibrium with each other and release gases, usually oxygen, at high temperatures. Therefore, certain polyvalent metal oxides can be used as redox fining agents. In an advantageous variant, the alternative redox fining agent can be at least one component selected from the group consisting of Sb2O3, SnO2, CeO2, MnO2, and Fe2O3. However, other redox compounds are also suitable in principle, provided they release fining gases in the temperature range relevant for fining and the valence of the metal ion changes to a different oxide or to the metallic form. Many such compounds are described, for example, in German Patent Application Publication No. 19939771. Preference is given to alternative redox fining agents that release fining gases, especially oxygen, at temperatures below 1700°C, such as Sb2O3, SnO2, and CeO2.

[0059] By analyzing the glass ceramic, the content of As2O3 and / or the content of at least one alternative redox fining agent can be determined, from which a person skilled in the art can draw conclusions about the type and amount of fining agent used. The alternative redox fining agent can be added to the batch, for example, as an oxide.

[0060] In advantageous variants, the total content of alternative redox fining agents can be in the range of 0 mol% to 1 mol%. In advantageous embodiments, the total content of alternative redox fining agents detectable in the glass ceramic is greater than 0.01 mol%, preferably at least 0.05 mol%, preferably at least 0.1 mol%, advantageously at least 0.15 mol%, advantageously at least 0.2 mol% and / or at most 1 mol%, preferably at most 0.7 mol%, preferably at most 0.5 mol%, preferably at most 0.4 mol%. Some advantageous variants can also contain at most 0.3 mol%, preferably at most 0.25 mol%, or at most 0.2 mol% of alternative redox fining agents.

[0061] The glass ceramic can contain 0 mol % to 1 mol % of antimony oxide (Sb2O3) as an alternative redox fining agent. In an advantageous embodiment, the glass ceramic contains more than 0.01 mol %, preferably at least 0.05 mol %, advantageously at least 0.1 mol %, preferably at least 0.15 mol %, preferably at least 0.2 mol %, and / or preferably at most 1 mol %, advantageously at most 0.7 mol %, even more preferably at most 0.5 mol %, even more preferably at most 0.4 mol %, preferably at most 0.3 mol % of Sb2O3. Due to the environmental impact of Sb2O3, it may be advantageous to use as little Sb2O3 as possible for fining. A preferred embodiment of the glass-ceramic is substantially SbO-free or Sb-free, where "substantially SbO-free" means that SbO is not intentionally added to the composition as a raw material component, but is present at most as an impurity, with the impurity limit being at most 0.01 mol %, preferably at most 0.005 mol %, for SbO-free glass-ceramics. According to a particular embodiment, the glass-ceramic is SbO-free.

[0062] The glass ceramic can contain 0 mol% to 1 mol% tin oxide (SnO2) as an alternative redox fining agent. In advantageous embodiments, the glass ceramic contains more than 0.01 mol%, preferably at least 0.05 mol%, advantageously at least 0.1 mol%, advantageously at least 0.15 mol%, preferably at least 0.2 mol%, preferably at least 0.3 mol%, and / or preferably at most 1 mol%, advantageously at most 0.7 mol%, and more preferably at most 0.6 mol% of SnO2. In some variations, an upper limit of at most 0.5 mol%, more preferably at most 0.4 mol%, and preferably at most 0.3 mol% can be advantageous. Too high a SnO2 content can make the ceramization process of green glass difficult to control, since SnO2 acts not only as a fining agent but also as a crystal nucleating agent. SnO2-free or Sn-free variants of the glass-ceramics according to the invention are possible and advantageous, i.e., no Sn-containing raw materials are added to the batch for fining the base green glass, with the limit for raw material or process-introduced SnO2 impurities being at most 0.01 mol %, preferably at most 0.005 mol %.

[0063] The glass ceramic may contain 0 mol % to 1 mol % of CeO2 and / or MnO2 and / or Fe2O3 as alternative redox fining agents, each of which may be present independently of one another in a proportion of preferably more than 0.01 mol %, preferably at least 0.05 mol %, advantageously at least 0.1 mol %, advantageously at least 0.15 mol %, preferably at least 0.2 mol % and / or preferably at most 1 mol %, advantageously at most 0.7 mol %, further preferably at most 0.5 mol %, further preferably at most 0.4 mol %, preferably at most 0.3 mol %. A preferred variant of the glass-ceramic is free of CeO2 and / or MnO2 and / or Fe2O3, i.e. no Ce-containing and / or Mn-containing and / or Fe-containing raw materials are added to the batch for fining the base green glass, with the limit for raw material or process-introduced CeO2 and / or MnO2 and / or Fe2O3 impurities being at most 0.01 mol %, preferably at most 0.005 mol %.

[0064] The evaporative fining agent is a component that volatilizes at high temperatures due to its vapor pressure, and the gas generated in the melt exerts a fining effect.

[0065] In an advantageous variant, the evaporative fining agent can have a halogen component.

[0066] In an advantageous variant, the evaporative fining agent can contain at least one fining halogen, in particular one selected from the group consisting of chlorine (Cl), bromine (Br) and iodine (I). A preferred fining halogen is chlorine. Fluorine is not a fining halogen, since it volatilizes at too low a temperature. However, the glass ceramic can still contain fluorine. However, since fluorine can reduce the transparency of the glass ceramic, this component, if present, is preferably limited to a maximum of 0.5 mol %, preferably a maximum of 0.3 mol %, preferably a maximum of 0.1 mol %. Preferably, the glass ceramic is fluorine-free.

[0067] The fining halogen can be added in various forms. In one embodiment, the halogen is added to the batch as a salt with an alkali metal cation or alkaline earth metal cation, or as an aluminum halide. In one embodiment, the halogen is used as a salt, and the cation in the salt corresponds to the cation present as an oxide in the glass ceramic. The fining halogen can be used in the form of a halide compound, particularly a halide compound. Suitable halide compounds are, in particular, salts of chloride, bromide, and / or iodide anions with alkali metal cations, alkaline earth metal cations, or aluminum cations. Preferred examples are chlorides, such as LiCl, NaCl, KCl, CaCl2, BaCl2, SrCl2, AlCl3, and combinations thereof. Corresponding bromides and iodides are also possible, such as LiBr, LiI, NaBr, NaI, KBr, KI, CaI2, CaBr2, and combinations thereof. Other examples are BaBr2, BaI2, SrBr2, SrI2, and combinations thereof.

[0068] In advantageous variants, the total content of fining halogens (i.e., Cl and / or Br and / or I) can be in the range of 0 mol% to 1 mol%. In advantageous embodiments, the total content of fining halogens detectable in the glass ceramic is greater than 0.03 mol%, preferably at least 0.04 mol%, preferably at least 0.06 mol%, preferably at least 0.08 mol%, preferably at least 0.1 mol%, preferably at least 0.15 mol%, advantageously at least 0.2 mol% and / or at most 1 mol%, preferably at most 0.7 mol%, preferably at most 0.5 mol%, preferably at most 0.4 mol%. Some advantageous variants can also contain fining halogens in an amount of up to 0.3 mol%, preferably at most 0.25 mol%, or at most 0.2 mol%. The stated contents are the amounts of halogen detectable in the glass ceramic. Those skilled in the art are familiar with using these data to calculate the amount of halogen or halide compounds required for fining.

[0069] The glass ceramic can contain 0 mol% to 1 mol% chlorine (determined atomically and designated Cl). In advantageous embodiments, the glass ceramic contains more than 0.03 mol%, advantageously at least 0.04 mol%, advantageously at least 0.05 mol%, advantageously at least 0.1 mol%, advantageously at least 0.15 mol%, preferably at least 0.2 mol%, and / or preferably at most 1 mol%, advantageously at most 0.7 mol%, more preferably at most 0.5 mol%, even more preferably at most 0.4 mol%, and preferably at most 0.3 mol% of Cl. Some advantageous glass ceramics can be Cl-free, i.e., no Cl-containing raw materials are added to the batch for fining the base green glass. Cl is present at most as an impurity, with the Cl impurity limit being a maximum of 0.03 mol%.

[0070] The same ranges and limits as above apply to Br as a fining halogen. The same ranges and limits as above apply to I as a fining halogen. A preferred variant of the glass-ceramic does not contain Br and / or I.

[0071] Alternatively or in addition to the evaporative fining agents and / or alternative redox fining agents, the chemical fining agent may include at least one decomposition fining agent, which decomposes at high temperatures to release fining gases, and the gas pressure of the decomposition products is particularly high at 10 5 The decomposition fining agent is an inorganic compound with a sufficiently high pH of more than Pa. Preferably, the decomposition fining agent may be a salt containing an oxoanion, particularly a sulfate component. Preferably, the decomposition fining agent contains a sulfate component. When the component added as sulfate decomposes, SO2 gas and O2 gas are released at high temperatures, which contribute to the fining of the melt.

[0072] The sulfate component can be added in various forms. In one embodiment, the sulfate component is added to the batch as a salt with an alkali metal cation or an alkaline earth metal cation. In one embodiment, the sulfate is added as a salt, and the cations in the salt correspond to the cations present as oxides in the glass ceramic. For example, the following components can be advantageously used as sulfate sources: Li2SO4, Na2SO4, K2SO4, CaSO4, BaSO4, and SrSO4.

[0073] In the present invention, sulfate is measured as SO3 in material analysis. However, since the solubility of LAS glass ceramics in sulfate is very low, the sulfate component (i.e., SO3) is no longer detectable in the molten product after melting by normal X-ray fluorescence analysis. Therefore, in the case of the examples (described later) that were refined with sulfate, the molten glass melt synthesis was measured using the SO4 mole percentage. 2- The use of sulfate components as fining agents can be determined, for example, by analyzing the residual gas content (SO2) in the glass-ceramic.

[0074] In preferred sulfate-fined glass-ceramics, more than 0.01 mol %, preferably at least 0.05 mol %, advantageously at least 0.1 mol %, advantageously at least 0.15 mol %, preferably at least 0.2 mol % and / or preferably at most 1 mol %, advantageously at most 0.7 mol %, more preferably at most 0.5 mol %, even more preferably at most 0.4 mol %, preferably at most 0.3 mol % of SO3 is added during synthesis via at least one corresponding sulfate compound. 2- Advantageously, a fining glass-ceramic (free of SO3) is possible. The proportion of fining sulfates added during the synthesis of the glass-ceramic can therefore be in the range of 0 mol % to 1 mol % SO3.

[0075] According to one variant of the invention, the glass ceramic or the base glass may be refined using a suitable metal sulfide as a decomposition fining agent, as described, for example, in US Patent Application Publication No. 2011 / 0098171. In one embodiment, the sulfide cations correspond to the cations present as oxides in the glass ceramic. Examples of suitable metal sulfides are alkali metal sulfides, alkaline earth metal sulfides, and / or aluminum sulfide, which release SO3 into the melt under oxidizing conditions. In order for metal sulfides to fully function as fining agents, it is advantageous to use them in combination with an oxidizing agent, preferably a nitrate and / or sulfate.

[0076] Advantageous glass ceramics with reduced As2O3 content or advantageous glass ceramics free of As2O3 can have a combination of chemical fining agents. In this case, the following combinations may be advantageous, with each glass ceramic preferably comprising the above-mentioned fining agents within the above-mentioned limits for the individual components and / or their sum. Advantageous embodiments are: - SnO2 and / or Sb2O3, each containing up to 0.05 mol% As2O3, or - As2O3-free combinations, such as Sb2O3 and SnO2, Sb2O3 and Cl, Sb2O3 and SO3, or - Combinations that do not contain As2O3 and do not contain Sb2O3, for example, a combination of SnO2 and Cl, a combination of SnO2 and SO3, a combination of Cl and SO3 Includes.

[0077] Alternatively, glass-ceramics that have been refined with only one fining agent, such as glass-ceramics containing only Sb2O3 or only SnO2 as a fining agent, may also be advantageous.

[0078] The principle of the melt fining treatment using the above-mentioned chemical fining agents is to add a compound that decomposes to release a gas, or a compound that is volatile at high temperatures, or a compound that releases a gas through an equilibrium reaction at high temperatures. However, instead of or in addition to such fining treatments, known physical fining processes, such as reducing the viscosity of the glass melt by increasing the temperature, vacuum fining, high-pressure fining, etc., can also be used advantageously.

[0079] In an advantageous variant of the invention, the batch may contain nitrates (NO3), which act as oxidizing agents in the melting and fining processes and ensure that oxidizing conditions exist in the melt to enhance the action of the fining agents used, in particular alternative redox fining agents. In one embodiment, the nitrates are used as salts, the cations in the salts corresponding to the cations present as oxides in the glass-ceramic. Examples of this may be: aluminum nitrate, alkali metal nitrates, alkaline earth metal nitrates, zirconium nitrate. However, ammonium nitrate may also advantageously serve as a nitrate source. A nitrate compound or a mixture of several nitrate compounds may also be used. When a nitrate compound or a mixture of nitrate compounds is included in the batch to support the fining process, NO3 -The sum of is preferably at least 0.4 mol%, preferably at least 0.5 mol%, preferably at least 0.8 mol%, preferably at least 1 mol% and / or advantageously at most 5 mol%, preferably at most 4 mol%. In some advantageous variants, it is also possible to use at most 3 mol% of nitrates. Due to their volatility, the nitrates are no longer detectable in the glass or glass ceramic.

[0080] The above-mentioned glass compositions can optionally contain additives of coloring oxides, such as, for example, Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, CuO, CeO2, Cr2O3, rare earth oxides, each individually or in total in a content of 0 to 3 mol %. A preferred variant is one that does not contain any coloring oxides.

[0081] B2O3 can have a negative effect on the transparency of the glass-ceramic. Therefore, in an advantageous variant, the content of this component is limited to <0.2 mol %, preferably at most 0.1 mol %. A preferred variant is one that is free of B2O3.

[0082] According to an advantageous embodiment of the invention, the composition does not contain any ingredients not mentioned above.

[0083] According to an advantageous embodiment of the invention, the glass ceramic or green glass according to the invention preferably consists of at least 90 mol %, more preferably at least 95 mol %, most preferably at least 99 mol % of the above-mentioned components, or preferably of the components SiO2, Al2O3, Li2O, PO5, R2O, RO and nucleating agents.

[0084] According to an advantageous development of the glass ceramic, the glass ceramic is substantially free of one or more glass components selected from the group consisting of MgO, ZnO, PbO, B2O3, CrO3, F, Cd compounds.

[0085] According to the present invention, the expressions "free of X" or "free of component X" mean that the glass-ceramic is substantially free of this component X, i.e., such component is present at most only as an impurity in the glass and is not added to the composition as a single component. Regarding impurities, particularly MgO and / or ZnO, in the MgO-free and / or ZnO-free variants, the limits of 0.03 mol % and preferably 0.01 mol % for each single component should not be exceeded. For other glass components, higher impurity contents may be possible, up to 0.1 mol %, preferably up to 0.05 mol %, advantageously up to 0.01 mol %, advantageously up to 0.005 mol %, and for some components, advantageously up to 0.003 mol %, for each single component. Here, X represents any component, such as PbO. These limits do not apply to fining agents, for which the limits for intrinsic impurities are previously set forth.

[0086] The glass ceramic according to the present invention has a high-quartz solid solution as the predominant crystalline phase. The predominant crystalline phase is the crystalline phase with the highest volume percentage. The high-quartz solid solution is a metastable phase that can change compositionally and / or structurally or transform into other crystalline phases depending on the crystallization conditions. The high-quartz solid solution has very low thermal expansion, or even decreases with increasing temperature. In an advantageous embodiment, the crystalline phase does not include β-spodumene and keatite.

[0087] Advantageous embodiments of the LAS glass ceramic have a crystalline phase fraction of less than 70% by volume and / or advantageously more than 45% by volume. The crystalline phase consists of a high-quartz solid solution, also called β-eucryptite solid solution. The average crystallite size of the high-quartz solid solution is advantageously <100 nm, preferably <80 nm, preferably <70 nm. Due to the small crystallite size, the glass ceramic is transparent and can be polished better. In an advantageous variant, the average crystallite size of the high-quartz solid solution can be ≦60 nm, preferably ≦50 nm. The crystalline phases, their fraction, and the average crystallite size are determined by X-ray diffraction analysis, as known per se.

[0088] According to one embodiment of the present invention, transparent glass ceramics are produced. Transparency allows for better evaluation of many of the properties of such glass ceramics, particularly, of course, their internal quality. The glass ceramics according to the present invention are transparent, i.e., have a net transmittance of at least 70% in the wavelength range from 350 to 650 nm. High B2O3 and / or fluorine contents can reduce transparency. Therefore, advantageous variants do not contain one or both of the aforementioned components. Furthermore, the glass ceramics produced according to the present invention are porosity-free and crack-free. In the present invention, "porosity-free" refers to a porosity of less than 1%, preferably less than 0.5%, and more preferably less than 0.1%. Cracks are gaps, i.e., discontinuities, in a continuous structure.

[0089] To be able to produce homogeneous glass ceramics in industrial production plants, it is advantageous if the processing temperature Va of the green glass on which the glass ceramic is based (and thus of the glass ceramic) is advantageously at most 1330° C., preferably at most 1320° C. Some advantageous variants can have processing temperatures of at most 1310° C., or at most 1300° C., or even below 1300° C. The processing temperature Va is determined so that the viscosity of the melt is 10 4 Homogeneity is the temperature at which the viscosity reaches 1000 dPa·s. Homogeneity refers in particular to the uniformity of the CTE of the glass-ceramic over a large volume, as well as the low number and preferably absence of inclusions such as bubbles or particles. This is a quality characteristic of glass-ceramics and a prerequisite for their use in precision components, especially very large ones.

[0090] The processing temperature is determined by the composition of the glass-ceramic. In particular, the glass network former SiO2 is considered to be the component that determines the increase in viscosity and therefore the processing temperature, so the maximum SiO2 content should be selected in accordance with the above-mentioned regulations.

[0091] CTE The glass ceramic according to the invention is zero-expansion (see Table 1), i.e. the average coefficient of thermal expansion CTE in the range of 0 to 50°C is at most 0±0.1×10 -6 / K. In some advantageous variations, the average CTE in the range of 0 to 50°C is at most 0±0.05×10 -6 In certain applications, the average CTE over a wider temperature range, for example, from -30°C to +70°C, preferably from -40°C to +80°C, is at most 0±0.1×10 -6 / K, i.e., zero expansion.

[0092] To determine the CTE-T curves of the glass ceramics and precision components according to the present invention and comparative examples, the differential CTE (T) is first determined. The differential CTE (T) is determined as a function of temperature. The CTE is defined by the following equation (1):

number

[0093] To create a Δl / l0-T curve, or expansion curve, or a plot of the change in length Δl / l0 of a test piece (glass ceramic or precision part) versus temperature, the initial length l0 at initial temperature t0 is changed to the length l at temperature t. tThe temperature-dependent change in the length of the specimen can be measured up to 100°C. In this case, a small temperature interval, such as 5°C, 3°C, or 1°C, is preferably selected to determine the measurement points. Such measurements can be performed, for example, by dilatometry, interferometry, e.g., the Fabry-Perot method, i.e., evaluating the shift of the resonance peak of a laser beam coupled to the material, or other suitable methods. In the present invention, the dilatometry method was selected to measure the CTE of a rod-shaped specimen 100 mm long and 6 mm in diameter over a temperature interval of 1°C. The selected CTE measurement method preferably has an accuracy of at least ±0.05 ppm / K, preferably at least ±0.03 ppm / K. However, it should be understood that it is also possible to measure the CTE using a method with an accuracy of at least ±0.01 ppm / K, preferably at least ±0.005 ppm / K, or even at least ±0.003 ppm / K according to some embodiments, or at least ±0.001 ppm / K.

[0094] From the Δl / l0-T curve, the average CTE in a predetermined temperature range, for example, a temperature range of 0°C to 50°C, can be calculated.

[0095] By deriving the Δl / l0-T curve, the CTE-T curve can be obtained. From the CTE-T curve, the zero crossings and the slope of the CTE-T curve within the temperature interval can be determined. The CTE-T curve can also determine the occurrence and location of the advantageous CTE plateaus that form in some variations (see below and Figures 21, 23, and 25).

[0096] Advantageous embodiments of precision components comprising the glass ceramic according to the invention (especially in the form of a substrate) exhibit a high CTE uniformity. Here, the value of the CTE uniformity (English: total spatial variation of CTE) is understood to be the so-called peak-to-valley value, i.e. the difference between the highest and lowest CTE values ​​of samples taken from the precision component. The CTE uniformity therefore refers not to the CTE of the component material, but to the spatial variation of the CTE across the part or precision component. To determine the CTE uniformity, a number of samples are taken from the precision component at different positions, and the CTE value is determined for each. This value is given in ppb / K, where 1 ppb / K=0.001×10 -6 / K. The CTE uniformity, i.e., the spatial variation of the CTE, is advantageously at most 5 ppb / K, preferably at most 4 ppb / K, and most preferably at most 3 ppb / K across the precision component. Methods for determining CTE uniformity and strategies for achieving CTE uniformity are described in WO 2015 / 124710, the disclosure of which is incorporated herein by reference in its entirety.

[0097] Thermal Hysteresis In the present invention, the glass-ceramic is hysteresis-free because it exhibits a thermal hysteresis of <0.1 ppm at least in the temperature range of 10°C to 35°C (see Figures 10 to 12). Thus, at any temperature within the temperature range of 10°C to 35°C, the glass-ceramic, after undergoing a temperature change, exhibits an isothermal length change at a subsequent constant temperature of less than 0.1 ppm.

[0098] In an advantageous embodiment, this hysteresis-free property exists over a temperature range of at least 5 to 35°C, preferably at least 5 to 45°C, preferably at least >0°C to 45°C, preferably at least -5°C to 50°C. Particularly preferred is a wider temperature range for the hysteresis-free property, so that the material or component is also suitable for use at temperatures up to, advantageously above, at least 100°C. Particularly preferred is a wider temperature range for the hysteresis-free property. Preferred use temperatures are in the range of -60 to 100°C, more preferably -40°C to +80°C. A particular variant of the invention is suitable for use at a temperature T, for example in the range of 5°C to 20°C. A , or operating temperatures T of 22°C, 40°C, 60°C, 80°C, and 100°C A The present invention relates to glass ceramics and precision components at these temperatures, which are preferably hysteresis-free even at these temperatures.

[0099] For the glass ceramics and precision components according to the present invention, as well as comparative examples, thermal hysteresis was measured on rod-shaped samples (i.e., precision component samples or glass ceramic samples) with a length of 100 mm and a diameter of 6 mm at a temperature interval of 1°C using a precision dilatometer capable of measuring CTE with a reproducibility of ±0.001 ppm / K or ±0.003 ppm / K (absolute) according to the method and apparatus structure disclosed in German Patent Application Publication No. 102015113548, the disclosure of which is incorporated herein by reference in its entirety. Each tested sample was cooled from 50°C to -10°C at a cooling rate of 36 K / h, and the length change Δl / l0 was measured as a function of temperature. After a 5-hour isothermal hold at -10°C, the sample was heated to 50°C at a heating rate of 36 K / h, and the length change Δl / l0 was recorded as a function of temperature. The thermal hysteresis behavior of the specimens is studied at -5°C, 0°C, 5°C, 10°C, 22°C, 35°C, and 40°C. These points are representative of the temperature range from -10°C to 50°C, since the hysteresis in the aforementioned temperature intervals decreases with increasing temperature. Thus, samples that are hysteresis-free at 22°C and 35°C do not exhibit hysteresis even in the range up to 50°C.

[0100] To determine the thermal hysteresis at 10°C, the sample was heated and cooled at a rate of 36 K / h in the range of -10°C to 50°C, and individual measurements of the length change were recorded for five temperatures: 8°C, 9°C, 10°C, 11°C, and 12°C, i.e., two temperature points above 10°C and two below 10°C. The average value was calculated from the differences between the measurements of the heating curve and the cooling curve at these five measurement points, and this was shown in the table in ppm as "Hyst.@10°C."

[0101] Accordingly, to determine the thermal hysteresis at 35°C, the sample was heated and cooled at a rate of 36 K / h in the range of -10°C to 50°C, and the individual measurements of the length change were recorded for five temperatures: 33°C, 34°C, 35°C, 36°C, and 37°C, i.e., two temperature points above and below 35°C. The average value was calculated from the differences between the measurements of the heating curve and the cooling curve at these five measurement points, and this was shown in the table as "Hyst.@35°C" in ppm.

[0102] The same procedure was followed for the other temperature points mentioned above.

[0103] The figures show the thermal hysteresis curves of the glass-ceramics according to the invention (FIGS. 10 to 12) and of the known glass-ceramics (FIGS. 2 to 9). For ease of comparison, a spacing of 6 ppm was always chosen on the Y-axis for the illustrations.

[0104] 2-8 show thermal hysteresis curves of known materials used in precision components. The cooling curves (dashed lines) and heating curves (dotted lines) are clearly spaced apart, i.e., extend apart, especially at low temperatures. At 10°C, this separation is greater than 0.1 ppm, and in some comparative examples, up to about 1 ppm. That is, the materials and precision components made therefrom exhibit significant thermal hysteresis at least in the temperature range of 10°C to 35°C.

[0105] The tested LAS glass ceramics shown in Figures 2-5 (Comparative Examples 7, 9, and 10 in Table 2) all contain MgO and ZnO and exhibit thermal hysteresis over a wide temperature range between 10°C and 35°C. Figures 6 and 7 show the hysteresis curves of LAS glass ceramics containing ZnO but not MgO (Comparative Examples 8 and 14 in Table 2). Both materials exhibit a strong increase in thermal hysteresis below 15°C. Figure 8 shows the hysteresis curve of LAS glass ceramic containing MgO but not ZnO (Comparative Example 15 in Table 2). This material also exhibits a strong increase in thermal hysteresis below 15°C. As can be seen in Figure 9, this known material (Comparative Example 1 in Table 2) does not exhibit thermal hysteresis, but the steep curve indicates that it is not a zero-expansion material. The average CTE here is -0.24 ppm / K.

[0106] The LAS glass ceramics and precision components according to the present invention have very low MgO and / or ZnO contents, or preferably are free of MgO and ZnO. As can be seen from Figures 10-12, the heating and cooling curves overlap at least in the temperature range of 10°C to 35°C, i.e., the glass ceramics are hysteresis-free. However, these materials are not only hysteresis-free in the range of 10°C to 35°C, but also in the range of at least 5°C to 35°C or 5°C to 45°C, preferably at least in the range of >0°C to 45°C. Furthermore, Examples 6 and 7 in Figures 11 and 12 are hysteresis-free in the temperature range of at least -5°C to 50°C.

[0107] Further expansion properties Advantageous embodiments of the present invention have further advantageous expansion features: To express the expansion behavior of a test specimen (glass ceramic or precision component), a TCL value is often given, where TCL stands for "total change in length." In the present invention, TCL values ​​are given in the temperature range of 0°C and 50°C. This TCL value is determined from the normalized Δl / l0-T curve (also referred to as dl / l0-T curve in the figures) of each test specimen, where "normalized" means that the length change at 0°C is set to 0 ppm. The Δl / l0-T curve for determining the TCL is prepared according to the same method as described above for determining the CTE in the present invention.

[0108] The TCL value is the difference between the highest and lowest dl / l0 values ​​in the temperature range:

number

[0109] Figures 16-19 show expansion curves for known materials, from which the maximum and minimum dl / l0 values ​​can be read to calculate the TCL values ​​(see below). Each of these expansion curves shows a curved transition over the temperature range 0°C to 50°C.

[0110] In contrast, the glass ceramic and precision component according to the invention are advantageously characterized by a flat expansion curve in the temperature range from 0° C. to 50° C. (see FIGS. 13 to 15). In some advantageous variants, depending on the application of the component, a flat expansion curve may also be desirable in other temperature ranges, in particular in the ranges (20:40), (20:70) and / or (-10:30).

[0111] As an indicator of the extent to which the course of the thermal expansion curve deviates from a simple linear course, in an advantageous embodiment of the invention, a parameter F is introduced as an indicator of the flatness of the expansion curve, which allows the classification of CTE graphs:

number

[0112] The parameter F is calculated by taking the quotient of the TCL(0;50) value (unit: ppm) (see above) and the difference in expansion between the temperature points 0 °C and 50 °C (unit: ppm). The expansion curve is normalized so that the length change at 0 °C is 0 ppm, as defined for the determination of the TCL, so the "difference in expansion between the temperature points 0 °C and 50 °C" corresponds to the "expansion at 50 °C" as shown in the table. The expansion at 50 °C is used to calculate the parameter F.

[0113] Here, it is advantageous if, for each material or component, the parameter F is <1.2, preferably <1.1, and preferably at most 1.05. The closer the parameter F is to 1, the flatter the expansion curve will be.

[0114] 13 to 15 show that advantageous embodiments of LAS glass ceramics have a flat expansion curve progression (e.g., F=1) in the temperature range 0° C. to 50° C., and preferably also in the wider temperature range of −10° C. to 70° C. In contrast, FIGS. 16 to 20 show that known materials exhibit a much steeper and more curved expansion curve progression in this temperature range.

[0115] FIG. 13 shows an exemplary expansion curve for the advantageous glass-ceramic based on the advantageous ceramization of Example 7 (maximum temperature 830°C, duration 3 days). For illustration purposes, a 2.4 ppm interval was selected on the Y-axis. The highest expansion value (dl / l0 max.) is at +50°C (dl / l0 is +0.57 ppm, i.e., |0.57 ppm|), and the lowest expansion value (dl / l0 min.) is 0 ppm. The expansion difference between the 0°C and 50°C temperatures, which corresponds to the amount of "expansion at 50°C," is 0.57 ppm. From this, the parameter F for this material is calculated as follows: F (Example 7 in Table 1) = 0.57 ppm / 0.57 ppm = 1.

[0116] 14 shows the same advantageous flattening of the expansion curve in the temperature range from −10° C. to 80° C. for another ceramization (maximum temperature 825° C., duration 3 days) of the glass-ceramic of Example 7 of Table 1. Such advantageous expansion behavior is also shown in FIG. 15 for Example 6.

[0117] Thus, advantageous glass ceramics and precision components of the present invention not only exhibit a very flat progression of their expansion curves in the temperature range from 0°C to 50°C, i.e., they not only exhibit zero expansion in this temperature range, but also exhibit a small variation in the change in linear expansion, and thus in the differential CTE, in this range. As can be seen in Figures 14 and 15, advantageous embodiments of the present invention also exhibit a flat progression of their expansion curves over an even wider temperature range (here, illustratively, from -10°C to +70°C or +80°C). See, by comparison, the much steeper progression of the expansion curves of known materials over the same temperature range in Figure 20. The expansion behavior can also be examined in other selected temperature ranges, in particular (-10;30), (20;40), and (20,70), which are further described below.

[0118] In comparison with preferred embodiments of the glass ceramic and precision components, Figures 16 to 19 show the expansion behavior of known materials and precision components manufactured therefrom, from which the parameter F can be calculated. The expansion behavior of the materials or precision components shown in Figures 16 to 20 was measured using the same dilatometer under conditions comparable to those of the preferred embodiments of the glass ceramic shown in Figures 13 to 15. Overall, it can be seen that the known materials exhibit curved expansion curves.

[0119] Figure 16 shows the expansion curve of commercially available titanium-doped silica glass in the same dl / l0 region as Figures 13-15. Adding the expansion value at +50°C (dl / l0 max. is +0.73 ppm, or |0.73 ppm|) and the expansion value at 14°C (dl / l0 min. is -0.19 ppm, or |0.19 ppm|) yields a TCL(0:50) value of approximately 0.92 ppm. The difference in expansion between 0°C and 50°C, corresponding to the "expansion at 50°C" amount, is 0.73 ppm. From this, the parameter F of this material is calculated as follows: F(Ti-doped SiO2) = 0.92 ppm / 0.73 ppm = 1.26.

[0120] Correspondingly, the parameter F (see FIG. 17) for the known LAS glass ceramic or its corresponding precision component is calculated as follows: F(known LAS glass ceramic)=1.19 ppm / 0.11 ppm=10.82.

[0121] Correspondingly, the parameter F (see FIG. 18) for the known cordierite-glass ceramic or its corresponding precision component is calculated as follows: F(known cordierite-glass ceramic)=2.25 ppm / 0.25 ppm=9.

[0122] Correspondingly, the parameter F (see FIG. 19) of the known sintered cordierite ceramic or its corresponding precision component is calculated as follows: F(known sintered cordierite ceramic)=4.2 ppm / 2.71 ppm=1.55.

[0123] Glass ceramics with a flat expansion curve are highly advantageous because they allow precision components to be optimized for subsequent use temperatures and also exhibit low thermal expansion even at higher and / or lower temperature loads, such as during production. Precision components for microlithography, EUV microlithography (also abbreviated as "EUV lithography" or "EUVL"), and metrology are typically used under standard cleanroom conditions, particularly at room temperature of 22°C. The CTE may be adapted to this use temperature. However, such components are subjected to various processing steps, such as coating with metal layers, cleaning, structuring, and / or exposure processes, during which temperatures higher or, in some cases, lower than those encountered during subsequent cleanroom use may be present. Therefore, advantageous glass ceramics and precision components manufactured therefrom, having a parameter F of less than 1.2 and thus optimally zero expansion not only at use temperatures but also, in some cases, at higher and / or lower temperatures during production, are highly advantageous. Properties such as hysteresis-freeness and a parameter F<1.2 are particularly advantageous when precision components or glass-ceramics are used in EUV lithography, i.e., when the precision components are, for example, EUVL mirrors or EUVL mask blanks or corresponding substrates for these, since, in particular in EUV lithography, the mirrors or masks are heated very non-uniformly in the pointwise or beam direction by the high-energy radiation. Under these conditions of use, it is advantageous for the precision components or glass-ceramics to have a small slope of the CTE-T curve in the temperature range close to the use temperature (see below).

[0124] Advantageous glass ceramics and precision components that are even better optimized for the latter use temperatures of 20 or 22°C are characterized by a relative change in length (dl / l0) in the temperature range from 20°C to 30°C of ≦|0.10| ppm, preferably ≦|0.09| ppm, particularly preferably ≦|0.08| ppm, and especially preferably ≦|0.07| ppm, and / or a relative change in length (dl / l0) in the temperature range from 20°C to 35°C of ≦|0.17| ppm, preferably ≦|0.15| ppm, particularly preferably ≦|0.13| ppm, and especially preferably ≦|0.11| ppm. Alternatively or additionally, such optimized glass ceramics and precision components can be characterized by a relative change in length (dl / l0) in the temperature range from 20°C to 40°C of ≦|0.30| ppm, preferably ≦|0.25| ppm, particularly preferably ≦|0.20| ppm, and especially preferably ≦|0.15| ppm. The characteristics of the relative length change for the different temperature ranges can preferably be read from the dl / l0 curves in Figures 13 to 19. When referring to the relative change in length (dl / l0), these data naturally refer to the amount of the respective value.

[0125] Zero-expansion, hysteresis-free materials exhibiting such advantageous expansion behavior are particularly suitable for use as substrates for EUVL mirrors, or as EUVL mirrors that are heated to different degrees in light and shadow areas during operation, for example, due to a respective exposure mask. Due to the small relative changes in length described above, EUVL mirrors formed from advantageous glass-ceramics exhibit smaller local gradients (local tilts) in the topography of the mirror surface than EUVL mirrors made from known materials. The same is true for EUVL mask blanks, EUVL masks, or EUVL photomasks.

[0126] In particular for glass-ceramics that exhibit a very flat progression of the expansion curve, which fluctuates around or around 0 ppm in the temperature range in question and results in an overall favorable expansion behavior, it is advantageous, alternatively or additionally, to introduce a further indicator of the flatness of the expansion curve into the parameter F, whereby the expansion curve is considered not only in the temperature range (0;50) but also in other temperature intervals (Ti), preferably in the temperature ranges (20;40), (20;70) and / or (-10;30), which allows for a better classification of the expansion behavior in relation to the subsequent field of application.

[0127] Alternative parameter f T.i. has units (ppm / K),

number

[0128] TCL (T.i.) The value is the difference between the maximum and minimum dl / l0 values ​​in each temperature range (Ti), and the expansion curve is (T.i.) For the determination of , it is also normalized so that the length change at 0 °C is 0 ppm according to the definition.

number

[0129] Alternative parameter f T.i. is expressed as TCL according to equation (4). (T.i.)It is calculated by taking the quotient of the value [unit: ppm] (see above) and the width of the temperature interval (Ti) given in [K] taking into account the expansion difference. The width of the relevant temperature interval from 20°C to 40°C is 20 K. On the other hand, if the transition of the expansion curve in the interval Ti = (20; 70) or (-10; 30) is taken into account, the divisors in equation (4) are 50 K and 40 K, respectively.

[0130] In an advantageous embodiment, the glass ceramic has a substitution parameter f (20;40) <0.024 ppm / K, and / or alternative parameter f (20;70) <0.039 ppm / K, and / or alternative parameter f (-10;30) <0.015 ppm / K.

[0131] Glass-ceramics with very flat expansion curves are very advantageous because they allow precision components to be optimized not only for the subsequent use temperature but also for loading at higher and / or lower temperatures, for example, and can be used to calculate the alternative parameter f T.i. is suitable for determining the appropriate material according to the specifications required for a particular part application and for providing a corresponding precision part. Specific precision parts and their applications are further described and included below.

[0132] According to an advantageous embodiment of the glass ceramic or a component manufactured therefrom, the alternative parameter f (20;40) It may be advantageous for the expansion coefficient to be <0.024 ppm / K, preferably <0.020 ppm / K, more preferably <0.015 ppm / K. Hysteresis-free, zero-expansion components exhibiting expansion behavior in such a temperature range (20:40) can be particularly well used as precision components for room temperature microlithography and EUV microlithography. Examples of such advantageous glass-ceramics are shown in Figures 14 and 15.

[0133] According to an advantageous embodiment of the glass ceramic or a component manufactured therefrom, the alternative parameter f (20;70)It may be advantageous if the thermal expansion coefficient is <0.039 ppm / K, preferably <0.035 ppm / K, preferably <0.030 ppm / K, preferably <0.025 ppm / K, preferably <0.020 ppm / K. Hysteresis-free, zero-expansion components exhibiting expansion behavior in such a temperature range (20:70) can also be particularly well suited for use as precision components for microlithography and EUV microlithography. It is particularly advantageous for the components to also exhibit low thermal expansion even under higher temperature loads, which may occur, for example, locally or extensively, during the manufacture of precision components as well as during operation. Further details of the temperature loads occurring in EUVL precision components have already been described above with respect to parameter F and will be mentioned here to avoid repetition. An example of such an advantageous glass-ceramic is shown in FIG. 14.

[0134] According to an advantageous embodiment of the glass ceramic or a component manufactured therefrom, the alternative parameter f (-10;30) It can be advantageous if the expansion coefficient is <0.015 ppm / K, preferably <0.013 ppm / K, preferably <0.011 ppm / K. Hysteresis-free, zero-expansion components exhibiting expansion behavior in such a temperature range (-10;30) can be particularly well used as precision components, in particular as mirror substrates for applications where temperatures below room temperature may occur, such as in astronomy or Earth observation from space. Corresponding components are described below. An example of such an advantageous glass-ceramic is shown in FIG. 15.

[0135] A particularly advantageous embodiment of the glass ceramic or a component manufactured therefrom is characterized by the substitution parameter f (T.i.) At least two of the above have suitable expansion curves.

[0136] A particularly advantageous embodiment of the glass ceramic or a component manufactured therefrom is characterized in that the parameter F and at least one alternative parameter f (T.i.) has an expansion curve where

[0137] 21 to 25 show that advantageous embodiments of LAS glass ceramics and precision components have a "plateau" of CTE. Glass ceramics that exhibit a plateau, i.e., optimized zero expansion over a wide temperature range, offer the same advantages already mentioned above in relation to the flat progression of the expansion curve and the parameter F.

[0138] When the differential CTE has a plateau around 0 ppm / K, that is, a temperature interval T P Advantageously, the differential CTE at T is less than 0±0.025 ppm / K. P Advantageously, the temperature interval T has a width of at least 40 K. P The differential CTE at may be less than 0±0.015 ppm / K.

[0139] A CTE plateau is therefore understood to be the range spanning the portion of the CTE-T curve where the differential CTE does not exceed a value of 0±0.025 ppm / K, preferably 0±0.015 ppm / K, more preferably 0±0.010 ppm / K, even more preferably 0±0.005 ppm / K, i.e. a CTE around 0 ppb / K.

[0140] Advantageously, the temperature interval T has a width of at least 40 K. P The differential CTE at may be less than 0±0.015 ppm / K, i.e., 0±15 ppb / K. In a preferred embodiment, a CTE plateau of 0±0.01 ppm / K, i.e., 0±10 ppb / K, may be formed over a temperature interval of at least 50 K.

[0141] Temperature interval T P It may be advantageous if the temperature is in the range of -10 to +100°C, preferably 0 to 80°C.

[0142] The position of the CTE plateau of the glass ceramic is determined by the operating temperature T A The preferred operating temperature is T AThe temperature T ranges from -60°C to +100°C, more preferably from -40°C to +80°C. Particular variations of the invention are suitable for use at temperatures T of 0°C, 5°C, 10°C, 22°C, 40°C, 60°C, 80°C, and 100°C. A The CTE plateau, i.e., the temperature range T P Curve ranges with small deviations in the differential CTE may also exist in the temperature ranges of [-10;100];[0;80], [0;30°C], [10;40°C], [20;50°C], [30;60°C], [40;70°C] and / or [50;80°C].

[0143] Figure 21 shows that the glass-ceramic from Example 6 in Table 1 has a CTE of 0±0.010 ppm / K, i.e., a 10 ppb plateau, over the entire temperature range shown, from -10°C to 90°C. A closer look at a portion of this curve (see Figure 22) reveals that the glass-ceramic has a CTE of 0±0.005 ppm / K over the temperature range from -5°C to 32°C. These glass-ceramics meet the average CTE(19;25) requirements set forth in standard SEMI P37-1109 for EUVL substrates and blanks.

[0144] Figure 23 shows that for Example 7 of Table 1, ceramized for 3 days at temperatures up to 825°C, the glass-ceramic has a CTE of 0±0.010 ppm / K from 12°C, i.e., a 10 ppb plateau with a width of >40 K. As shown in Figure 24, this example even exhibits a CTE of 0±0.005 ppm / K in the range of 16°C to 40°C, thus also meeting the average CTE(19;25) requirements listed for EUVL substrates and blanks in standard SEMI P37-1109.

[0145] FIG. 25 shows that for Example 9 of Table 1, ceramized at temperatures up to 830°C for 3 days, the glass-ceramic has a CTE of 0±0.010 ppm / K, i.e., a 10 ppb plateau, over the indicated range of -5°C to 45°C.

[0146] According to an advantageous embodiment of the invention, the CTE-T curve of the glass ceramic or precision component has a small slope, in particular a slope of at most 0±2.5 ppb / K, in a temperature range having a width of at least 30 K, preferably at least 40 K, more preferably at least 50 K. 2 , advantageously at most 0±2 ppb / K 2 , advantageously at most 0±1.5 ppb / K 2 , preferably at most 0±1 ppb / K 2 , preferably at most 0±0.8 ppb / K 2 , and according to certain variants even at most only 0±0.5 ppb / K 2 The curved line has at least one curved portion where

[0147] The temperature range with a small slope is the operating temperature T A The preferred operating temperature is T A The temperature T ranges from -60°C to +100°C, more preferably from -40°C to +80°C. Particular variations of the invention are suitable for use at temperatures T of 0°C, 5°C, 10°C, 22°C, 40°C, 60°C, 80°C and 100°C. A The temperature intervals with shallow slopes may also be present in the temperature ranges [-10; 100]; [0; 80], [0; 30°C], [10; 40°C], [20; 50°C], [30; 60°C], [40; 70°C] and / or [50; 80°C].

[0148] FIG. 26 shows the slope of the CTE-T curve for the advantageous glass ceramic or precision component based on the composition of Example 6 in Table 1 over the temperature range of 0° C. to 45° C. The CTE slope is 0±1 ppb / K over the entire temperature range. 2 and 0±0.5 ppb / K for at least a 30 K wide interval (starting from about 12 °C). 2 is less than.

[0149] In FIG. 27, the CTE slope of the advantageous glass ceramic and precision component corresponding to Example 7 in Table 1 is 0±1.0 ppb / K over the entire temperature range of 0° C. to 45° C. with a width of at least 45 K. 2 and 0±0.5 ppb / K over an interval of at least 40 K (in the indicated range of 0 to 42°C). 2 It can be seen that it is less than

[0150] Glass ceramics and precision components exhibiting such expansion behavior are particularly well suited for EUV lithography applications (e.g., as mirrors or substrates for mirrors or masks or mask blanks), since in this field increasingly high demands are placed on materials and precision components used in optical components with extremely low thermal expansion, zero crossings of the CTE-T curve near the application temperature, and in particular low slopes of the CTE-T curve. In accordance with the present invention, advantageous embodiments of the glass ceramic or precision component have a very flat CTE curve, where the curve exhibits both a zero crossing and a very low CTE slope, and in some cases even a very flat plateau.

[0151] The low slope feature can be present with or without the formation of a favorable CTE plateau.

[0152] 28 and 29 show how the expansion curve can be adapted to different use temperatures by varying the ceramization temperature and / or ceramization time.

[0153] Figure 28 shows from Example 6 that the expansion curve of the resulting glass-ceramic can be specifically influenced by the selection of the maximum ceramization temperature during processing of the initial green glass. The dotted curve shows the expansion curve of the glass-ceramic obtained by ceramizing the base green glass at up to 810°C for 2.5 days, while the dash-dot curve shows the expansion curve of the glass-ceramic obtained by ceramizing the base green glass at up to 820°C for 2.5 days. Figure 28 also illustrates the possibility of post-ceramization for glass-ceramics according to the present invention, which means that the expansion curve of the glass-ceramic can be specifically fine-tuned by subjecting an already ceramized material to a new temperature treatment. In this case, the glass-ceramic material ceramized for 2.5 days at up to 810°C was post-ceramized again at 810°C for 1.25 days, i.e., a shorter holding time. The effect of this post-ceramization is shown by the dashed expansion curve. Comparison of the expansion curves shows that the expansion curves, and therefore the average CTE(0;50), are different before and after post-ceramization. However, XRD analysis of the samples before and after post-ceramization shows the same average crystallite size and crystalline phase fraction, respectively, within the limits of measurement accuracy.

[0154] Figure 29 shows the tunability of the expansion curve for different maximum ceramization temperatures when ceramizing the same initial green glass for Example 7. The dashed line shows ceramization up to 830°C for 3 days, and the dotted line shows ceramization up to 825°C for 3 days.

[0155] Alternatively, instead of increasing the ceramization temperature, the ceramization time can be correspondingly extended.

[0156] The advantageous glass ceramics and precision components further have a good internal quality. Preferably, the advantageous glass ceramics and precision components have a thickness of 100 cm 3The number of inclusions per particle is at most 5, more preferably at most 3, and most preferably at most 1. According to the invention, inclusions are understood to mean both bubbles and crystallites with a diameter of more than 0.3 mm.

[0157] According to a variant of the invention, the diameter or side length is at most 800 mm and the thickness is at most 100 mm, 3 The present invention provides a precision component having at most 5, preferably at most 3, and more preferably at most 1 inclusion having a diameter of more than 0.03 mm per unit area.

[0158] In addition to the number of inclusions, the maximum diameter of the detected inclusions also serves as an indicator of the internal quality. The maximum diameter of an individual inclusion in the total volume of a precision part with a diameter of less than 500 mm is preferably at most 0.6 mm, and in the volumes that are important for use, e.g., near the surface, it is preferably at most 0.4 mm. The maximum diameter of an individual inclusion in a glass-ceramic part with a diameter of 500 mm to less than 2 mm is preferably at most 3 mm, and in the volumes that are important for use, e.g., near the surface, it is preferably at most 1 mm.

[0159] The invention further relates to the use of the glass ceramic according to the invention in precision components, for example the glass ceramic can form the substrate of a precision component.

[0160] The invention further relates to the use of the LAS glass ceramics according to the invention in precision components, in particular in precision components for use in metrology, spectroscopy, measurement engineering, lithography, astronomy or Earth observation from outer space, for example as mirrors or mirror supports for segmented or monolithic astronomical telescopes, or as lightweight or ultralight mirror substrates, for example for space-based telescopes, or as high-precision structural components, for example for distance measurement in outer space or optical components for Earth observation, as precision parts such as standards for precision metrology, precision measuring instruments, reference plates for interferometers, as mechanical precision parts, for example ring laser gyroscopes, spiral springs for the watch industry, as mirrors and prisms, for example in LCD lithography, and as mask holders, wafer tables, reference plates, reference frames and grid plates, for example in microlithography and EUV (Extreme UV) microlithography, and also as mirrors or mirror substrates and / or photomask substrates or photomask blanks or reticle mask blanks in EUV microlithography.

[0161] The glass ceramic according to the invention allows precision components of different sizes to be produced.

[0162] One embodiment relates to precision parts of smaller dimensions, in particular (right)angled or rounded faces, with a diameter of at least 100 mm and / or up to 1500 mm, and / or a thickness of less than 50 mm, preferably less than 10 mm and / or at least 1 mm, more preferably at least 2 mm, such that they can be used, for example, in microlithography or EUV lithography.

[0163] Another embodiment relates to precision components with very small dimensions, in particular side lengths (width and / or depth) or diameters and / or thicknesses of a few mm (e.g., at most 20 mm, or at most 10 mm, or at most 5 mm, or at most 2 mm, or at most 1 mm) to a few tenths of a mm (e.g., at most 0.7 mm, or at most 0.5 mm). Such precision components can be used, for example, as spacers in interferometers or as components of ultrastable clocks in quantum engineering.

[0164] However, it is also possible to manufacture very large precision parts. Thus, one embodiment of the present invention relates to large-volume parts. This means in the present application a part weighing at least 300 kg, preferably at least 400 kg, preferably at least 500 kg, preferably at least 1 t, more preferably at least 2 t, and according to a variant of the invention at least 5 t, or, if rectangular, having a side length (width and / or depth) of at least 0.5 m, more preferably at least 1 m, and a thickness (height) of at least 50 mm, preferably at least 100 mm, or, if round, having a diameter of at least 0.5 m, more preferably at least 1 m, more preferably at least 1.5 m, and / or a thickness (height) of at least 50 mm, preferably at least 100 mm. In certain embodiments of the present invention, this may also be an even larger part, for example having a diameter of at least 3 m or at least 4 m or more. According to one variant, the present invention also relates to rectangular parts, preferably having at least one surface with a thickness of at least 1 m. 2 , preferably at least 1.2 m 2 , more preferably at least 1.4 m 2 This also applies to rectangular parts with an area of ​​100 mm or less. Large volume parts are typically manufactured with a base area that is significantly greater than the height. However, large volume parts with shapes similar to cubes or spheres can also be manufactured.

[0165] The precision component can be, for example, an optical component, a so-called normal incidence mirror, i.e., a mirror operating at near-normal incidence of radiation, or a so-called grazing incidence mirror, i.e., a mirror operating at grazing incidence of radiation. Such mirrors include, in addition to a substrate, a coating that reflects the incident light. In particular, in the case of an X-ray mirror, the reflective coating is a multilayer system or multilayer, which includes multiple layers with high reflectivity in the X-ray range, for example, at incidence angles that are not too small. Preferably, the multilayer system of such a normal incidence mirror includes 40 to 200 alternating layers of one of the following material pairs: Mo / Si, Mo / Bi, Ru / Si, and / or MoRu / Be.

[0166] In particular, the optical element according to the invention may be an X-ray optical element, i.e. an optical element used in combination with X-rays, in particular soft X-rays or EUV radiation, in particular a reticle mask or photomask operating in reflection for EUV microlithography. Advantageously, it may be a mask blank. Even more advantageously, the precision component can be used as a mirror for EUV lithography or as a substrate for a mirror in EUV lithography.

[0167] Furthermore, the precision component according to the invention can be a component, in particular a mirror for astronomy, where such an astronomy component can be used both on the ground and in space. High-precision structural components for distance measurement in space, for example, are also advantageous applications.

[0168] The precision part according to the present invention may have a lightweight structure. The part according to the present invention may further include a lightweight structure. That is, a cavity is provided in a certain area of ​​the part to reduce its weight. Preferably, the weight of the part is reduced by at least 80%, more preferably at least 90%, compared to the unprocessed part through the lightweight processing.

[0169] The subject of the invention is also a precision component comprising an LAS glass ceramic according to the invention, the details of which have already been given above with regard to the glass ceramic and its use in precision components, the disclosure of which is incorporated in its entirety by reference for the description of the precision component.

[0170] It will be understood that the features of the invention mentioned above and those to be described below can be used not only in the respective combinations shown but also in other combinations without departing from the scope of the invention.

[0171] Example Tables 1 and 2 show the compositions of examples of glass ceramics according to the present invention and comparative examples, as well as their properties.

[0172] The compositions shown in Table 1 were melted using conventional manufacturing methods from commercially available raw materials such as oxides, carbonates, and nitrates, using different fining agents or combinations of fining agents. In the present invention, the As2O3 fining agent was significantly reduced or no As2O3 was used. In Example 7, which was refined with SnO2 and sulfate, 0.19 mol% SO3 was added as Na2SO4 in the synthesis, which corresponds to 0.22 mol% SO4. 2- X-ray fluorescence analysis of the green glasses or glass-ceramics revealed SO3 contents below the detection limit of <0.02 wt. %. The green glasses produced according to Table 1 were first ceramized at the indicated maximum temperatures for the indicated times. In Examples 6 and 7, samples were also produced that were ceramized with other ceramization parameters (in particular, different maximum temperatures), as already explained above in connection with the figures.

[0173] The production of glass ceramics for precision components, in particular large precision components, is described, for example, in WO 2015 / 124710.

[0174] Table 1 lists 15 examples of the present invention that exhibit zero expansion and are hysteresis-free at least over the temperature range of 10°C to 35°C. Examples 1, 8, and 13 exhibit no thermal hysteresis up to approximately 5°C, and Examples 2 and 9 exhibit no thermal hysteresis up to approximately -5°C. Examples 3, 5, 6, and 7 are hysteresis-free over the entire temperature range of -5°C to 45°C. Furthermore, the parameter F is <1.2, i.e., the progression of the expansion curves in the temperature range of 0°C to 50°C is advantageously flat in all examples. Furthermore, these examples have processing temperatures of ≤1330°C, enabling the production of highly homogeneous glass ceramics in industrial production plants. The processing temperatures listed in Tables 1 and 2 were determined in accordance with DIN ISO 7884-1 (2014 - Source: Schott Techn. Glas-Katalog).

[0175] For Example 7, after ceramization for 2.5 days at a maximum temperature of 810°C, the average CTE was determined for additional temperature intervals, yielding the following results: CTE(20; 300°C): +0.13 ppm / K, CTE(20; 500°C): +0.34 ppm / K, CTE(20; 700°C): +0.59 ppm / K.

[0176] In Examples 6 and 7, the average CTE was determined over the temperature range of 19°C to 25°C, and in Example 6, the CTE (19:25) was 0.77 ppb / K, and in Example 7, the CTE (19:25) was 0.37 ppb / K.

[0177] In Example 10, SnO2 was used for the refining treatment. Nitrate was also included as an oxidizing agent, and BaO and Na2O were used as nitrate raw materials for oxidizing the melt.

[0178] Example 15 was refined using SnO2, which also served as a nucleating agent. An additional nucleating agent was ZrO2.

[0179] Table 2 shows comparative examples. Comparative examples 1, 2, 5, and 6 contain neither MgO nor ZnO, but have an average CTE(0;50) of 0±0.1×10 -6 / K, i.e., these comparative examples are not zero-expansion. Furthermore, the processing temperatures of Comparative Examples 1 and 2 are above 1330°C. These materials have such high viscosities that they cannot be used to produce highly homogeneous parts in industrial production plants.

[0180] Comparative Examples 7 to 16 all contain MgO and / or ZnO, and most of them have zero thermal expansion. However, these comparative examples exhibit thermal hysteresis far exceeding 0.1 ppm at least in the temperature range of 10°C to 35°C. At room temperature, i.e., 22°C, all comparative examples exhibit thermal hysteresis except for Comparative Examples 14 and 16. Furthermore, although Comparative Example 9 has zero thermal expansion, it exhibits an undesirably steep transition in the expansion curve in the temperature range of 0 to 50°C, as evidenced by the high value of parameter F.

[0181] Blank entries in the composition data tables below mean that these ingredients are not intentionally added or included.

[0182] Table 3 shows the calculated surrogate parameters f for different temperature intervals for some advantageous embodiments of the present invention and comparative examples. (T.i.) , which shows that the expansion curves of the Examples in the indicated temperature ranges show a flatter progression than the Comparative Examples.

[0183] It will be clear to those skilled in the art that depending on the temperature at which the glass ceramic or precision component containing it will be used, a glass ceramic will be selected that exhibits the desired properties, in particular with regard to thermal hysteresis and / or average CTE.

[0184] [Table 3-1]

[0185]

Table 3-2

[0186]

Table 3-3

[0187]

Table 4-1

[0188]

Table 4-2

[0189]

Table 4-3

[0190]

Table 5

Claims

1. LAS glass ceramics having an average coefficient of thermal expansion (CTE) of at most 0±0.1×10 in the range of 0°C to 50°C －６ / K, a thermal hysteresis of <0.1 ppm in the temperature range of at least 10°C to 35°C, and containing (in mole % on an oxide basis) the following components: 【Table 1】 P ２ O ５ , R ２ At least one component selected from the group consisting of O, and RO, wherein R ２ O is Na ２ O and / or K ２ O and / or Cs ２ O and / or Rb ２ O, and RO may be CaO and / or BaO and / or SrO. A nucleating agent having a content of 1.5 to 6 mol %, said nucleating agent being TiO ２、 ZrO ２、 Ta ２ O ５ , Nb ２ O ５ , SnO ２ , MoO ３ , W.O. ３ , HfO ２ a nucleating agent, which is at least one component selected from the group consisting of and containing As as a fining agent ２ O ３ %.

2. The LAS glass ceramic is Al ２ O ３ and / or P ２ O ５ 2. The LAS glass ceramic according to claim 1, wherein the LAS glass ceramic has a content of 0.1 to 6 mol %.

3. 3. The LAS glass ceramic according to claim 1, wherein the total content of ZnO+MgO is ≦0.55 mol % and / or the content of MgO is ≦0.35 mol % and / or the content of ZnO is ≦0.5 mol %.

4. SiO ２ 4. The LAS glass ceramic according to claim 1, wherein the content of is ≦69 mol %.

5. 5. The LAS glass ceramic according to claim 1, wherein the total content of RO (CaO+BaO+SrO) is ≧0.1 mol % and / or ≦6 mol %.

6. R ２ O(Na ２ O+K ２ O+Cs ２ O+Rb ２ 6. The LAS glass ceramic according to claim 1, wherein the total content of SiO.sub.2 is ≧0.1 mol.% and / or ≦6 mol.%.

7. 7. The LAS glass ceramic according to claim 1, wherein the total content of nucleating agents is ≧1.5 mol % and / or ≦6 mol %.

8. SiO ２ Molar fraction of + (5 × Li ２ and / or SiO ２ Molar fraction of + (5 × Li ２ 8. The LAS glass ceramic according to claim 1, wherein the following condition holds: (molar fraction of SiO)≦115.

5.

9. 9. The LAS glass ceramic according to claim 1, wherein the processing temperature Va is at most 1330°C.

10. 10. The LAS glass ceramic according to claim 1, wherein the main crystalline phase is a high-quartz solid solution, the high-quartz solid solution having an average crystallite size of <100 nm and / or a proportion of crystalline phase of less than 70% by volume.

11. 11. The LAS glass ceramic according to claim 1, wherein the parameter F is <1.2, where F=TCL(0; 50°C) / |Expansion(0; 50°C)|.

12. Alternative parameter f （２０；４０） <0.024 ppm / K, and / or alternative parameter f （２０；７０） <0.039 ppm / K, and / or alternative parameter f （－１０；３０） 12. The LAS glass ceramic according to claim 1, wherein the LAS content is <0.015 ppm / K.

13. The relative change in length (dl / l) in the temperature range of 20°C to 30°C ０ ) is ≦|0.10| ppm, and / or the relative change in length (dl / l) in the temperature range of 20° C. to 35° C. ０ 13. The LAS glass ceramic according to claim 1, wherein .gtoreq.|0.17| ppm.

14. The relative change in length (dl / l) in the temperature range of 20°C to 40°C ０ 14. The LAS glass ceramic according to claim 1, wherein .gtoreq.|0.30| ppm.

15. 15. The LAS glass ceramic according to claim 1, wherein the CTE-T curve has a slope of ≦0±2.5 ppb / K 2 in a temperature interval at least 30 K wide.

16. 16. The LAS glass ceramic according to claim 1, wherein the LAS glass ceramic exhibits a thermal hysteresis of <0.1 ppm at least in the temperature range from 5°C to 45°C.

17. The LAS glass ceramic is As ２ O ３ 17. The LAS glass ceramic according to claim 1, wherein the LAS glass ceramic contains ≦0.04 mol % of

18. The LAS glass ceramic contains As as a fining agent. ２ O ３ Alternatively, or at most 0.05 mol % As ２ O ３ 18. The LAS glass ceramic according to claim 1 , further comprising at least one alternative redox fining agent and / or at least one evaporative fining agent and / or at least one decomposition fining agent.

19. The alternative redox fining agent is Sb ２ O ３ , SnO ２ , MnO ２ , CeO ２ , Fe ２ O ３ and / or the evaporative fining agent comprises a fining halogen and / or the decomposition fining agent comprises a sulfate component.

20. The LAS glass ceramic is B ２ O ３ 2. The LAS glass-ceramic of claim 1, wherein the LAS glass-ceramic is free of 21. Use of the LAS glass ceramic according to any one of claims 1 to 20 in precision components for use in metrology, spectroscopy, measurement engineering, lithography, astronomy or Earth observation from outer space.

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