Glass ceramics with specific thermal expansion properties

Abstract

The invention relates to a glass ceramic with improved thermal expansion performance and application of the glass ceramic in precision parts.

Description

Technical Field

[0001] This invention relates to a glass-ceramic with specific thermal expansion behavior and good fusibility, formability and ceramizability, and the use of the glass-ceramic according to the invention in precision components. Background Technology

[0002] Materials and precision components with low thermal expansion or low CTE (coefficient of thermal expansion) are common knowledge in the prior art.

[0003] Ceramics, titanium-doped fused silica, and glass ceramics are known materials for precision components with low thermal expansion in a temperature range around room temperature. Glass ceramics with low thermal expansion, especially lithium aluminosilicate glass ceramics (LAS glass ceramics), are described in, for example, US 4,851,372, US 5,591,682, EP 587979A, US 7,226,881, US 7,645,714, DE 102004008824 A, and DE 102018111144 A. Other materials for precision components include cordierite ceramics or cordierite glass ceramics.

[0004] These materials are typically used in precision components where performance (e.g., mechanical, physical, and optical properties) must meet extremely stringent requirements. They are particularly used in earth-based and space-based astronomy and Earth observation, LCD lithography, microlithography and EUV lithography, metrology, spectroscopy, and measurement technologies. In such cases, depending on the specific application, these components must exhibit extremely low thermal expansion.

[0005] Generally, the thermal expansion of materials is determined using a static method. The length of the test sample 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 based on the length difference. The CTE is then derived as the average value for this temperature range; for example, for a temperature range of 0–50°C, it is CTE(0;50) or α(0;50).

[0006] To meet the increasing demand, the CTE values of the developed materials are more suitable for the application of the parts made of the materials. For example, the average CTE can be optimized not only for the standard temperature interval CTE(0;50), but also for the temperature interval near the actual application temperature, for example, the interval of 19-25°C, i.e. for CTE(19;25) of some lithography applications. In addition to determining the average CTE, the thermal expansion of the test sample can also be determined in a very small temperature interval, thus as a CTE-T curve. Preferably, such a CTE-T curve can have zero crossing points at one or more temperatures, preferably at the planned application temperature or near that temperature. At the zero crossing points of the CTE-T curve, the relative length change with temperature is particularly small. For some glass-ceramics, such a zero crossing point of the CTE-T curve can be moved to the application temperature of the part by appropriate temperature treatment. In addition to the absolute CTE value, the slope of the CTE-T curve near the application temperature should also be as small as possible in order to minimize the length change of the part when the temperature changes slightly. For these special composition-constant zero-expansion glass-ceramics, the optimization of the CTE or thermal expansion described above is usually achieved by changing the ceramming conditions.

[0007] In known precision parts and materials, in particular glass-ceramics (for example LAS glass-ceramics), an adverse effect is the "thermal hysteresis", hereinafter simply "hysteresis". Hysteresis here means that the length change of a test sample during heating at a constant heating rate is different from its length change during subsequent cooling at a constant cooling rate, even if the cooling rate and the heating rate are the same size. If the length change is represented graphically as a function of the heating and cooling temperature, a typical hysteresis loop results. The extent of the hysteresis loop also depends on the rate of temperature change. The faster the temperature change, the more pronounced the hysteresis effect.

[0008] The hysteresis effect shows that the thermal expansion of LAS glass-ceramics depends on temperature and time, for example on the rate of temperature change, which is also described occasionally in the technical literature, for example O. Lindig and W. Pannhorst, "Thermal expansion and length stability of in dependence on temperature and time", APPLIED OPTICS, Vol. 24, No. 20, October 1985; R. Haug et al., "Length variation in Min the temperature range from -60°C to +100°C", APPLIED OPTICS, Vol. 28, No. 19, October 1989; R. Jedamzik et al., "Modeling of the thermal expansion behavior of arbitrary temperature profiles", Proc. SPIE Vol. 7739, 2010; D. B. Hall, "Dimensional stability tests over time and temperature for severe low-expansion glass-ceramics", APPLIED OPTICS, Vol. 35, No. 10, April 1996.

[0009] Since the length change of a glass-ceramic exhibiting thermal hysteresis lags behind or precedes the temperature change, the material or a precision component made therefrom exhibits a disruptive isothermal length change, that is to say, after a temperature change, the length of the material still changes while the temperature has remained constant (so-called "isothermal holding") until a steady state is reached. When the material is subsequently reheated and cooled again, the same effects occur again.

[0010] For the properties of materials used in precision components, in particular glass-ceramics, the temperature range of 0 to 50°C, in particular 10 to 35°C or 19 to 25°C, is usually relevant, while 22°C is often referred to as room temperature. Since many applications of precision components are carried out in the temperature range above 0°C up to room temperature, materials with thermal hysteresis effects and isothermal length changes are disadvantageous, since optical disturbances can occur, for example, in lithography mirrors and optical elements of astronomical or space-based mirrors. In other precision components made of glass-ceramics used in measurement technology, for example precision scales, reference plates in interferometers, this effect can lead to measurement inaccuracies.

[0011] Some known materials, for example ceramics, titanium-doped fused silica and certain glass-ceramics, are characterized by an average coefficient of thermal expansion CTE(0; 50) of 0 ± 0.1 x 10 -6 / K (corresponding to 0 ± 0.1 ppm / K) or less. Materials having such low average CTE values in the above-mentioned temperature range are referred to as zero expansion materials in the present application. However, glass-ceramics, especially LAS glass-ceramics, whose average CTE is optimized in this way, often exhibit thermal hysteresis in the temperature range of 10 °C to 35 °C. This means that, especially for applications around room temperature (i.e. 22 °C), these materials exhibit a disruptive hysteresis effect, which impairs the accuracy of precision parts made from such materials. Therefore, a glass-ceramic material was developed which does not exhibit a significant hysteresis at room temperature (cf. US 4,851,372), however this effect was not eliminated but only shifted to lower temperatures, so that this glass-ceramic exhibits a significant hysteresis at temperatures of 10 °C and below, which is still disruptive. Therefore, in order to characterize the thermal hysteresis of a material in a certain temperature range, it is necessary to consider the thermal behavior of the material at different temperature points within this range in the framework of the present application. There are even glass-ceramics which do not exhibit a significant hysteresis at 22 °C and 5 °C. However, the average CTE (0; 50) of these glass-ceramics is greater than 0 ± 0.1 ppm / K, which means that they are not zero expansion glass-ceramics in the sense of the above definition.

[0012] Zero expansion, hysteresis-free glass-ceramics are described in US 2022 / 0298079 A1, US 2022 / 0298062 A1 and WO 2022 / 194846 A1. In the context of these applications, it was recognized that the components MgO and ZnO promote the occurrence of thermal hysteresis, so that the content of MgO and ZnO had to be limited in order to provide LAS glass-ceramics which are hysteresis-free at least in the temperature range of 10 °C to 35 °C.

[0013] For example, for applications in EUV lithography, it is desirable to further improve the expansion properties, especially to achieve a particularly flat CTE-T curve in a particularly wide temperature range of 0 to 100 °C.

[0014] Glass-ceramics with a particularly flat CTE-T curve or CTE plateau are described in DE 10 2028 11 144 A1. According to this document, in order to achieve a CTE plateau, both ZnO and MgO need to have a specific ratio and a specific content (at least 1.8 mol% in total). However, these glass-ceramics are not hysteresis-free.

[0015] EUVL parts should also have good polishability and post-processing capability using ion beam figuring (IBF). For this purpose, the BaO content in the glass-ceramic should be as low as possible.

[0016] Another requirement for glass-ceramic materials is that the glass composition has good meltability, and that the melt can be simply managed in large production equipment and homogenized in the base glass melt so as to meet the high requirements of the glass-ceramics in terms of CTE uniformity, internal quality (especially low impurity (particularly bubble) quantity, low striation level), and polishability, etc. after glass-ceramization. SUMMARY

[0017] Therefore, it is an object of the present application to provide a glass-ceramic which not only has zero expansion and no hysteresis characteristics, but also has a flat CTE-T curve and good polishability, i.e., substantially no BaO. Another object is to provide a glass-ceramic which can be mass-produced, and a precision part made of such material, wherein the glass-ceramic has zero expansion and reduced thermal hysteresis, particularly in the temperature range of 10°C to 35°C.

[0018] The above objects are solved by the embodiments described in the patent claims. The present application has the following aspects.

[0019] According to one aspect of the present application, there is provided a LAS glass-ceramic having an average coefficient of thermal expansion CTE of at most 0 ± 0.02 x 10 -6 / K in the temperature range of 0 to 50°C, a thermal hysteresis of < 0.1 ppm at least in the temperature range of 10°C to 35°C, and comprising the following components (in terms of oxides, mol%):

[0020] SiO2 60 to 70;

[0021] Li2O 7 to 9.4;

[0022] R2O 0.7 to 2.0 (wherein R = Na, K, Cs or Rb);

[0023] MgO + ZnO 0 to 0.4;

[0024] at least one component selected from the group consisting of P2O5 and RO, wherein RO can be CaO and / or BaO and / or SrO; and

[0025] a nucleating agent in an amount of 1.5 to 6 mol%, wherein the nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3 and WO3.

[0026] According to a second aspect of the present application, there is provided a LAS glass-ceramic having an average coefficient of thermal expansion CTE of at most 0 ± 0.02 x 10 -6 / K, having a thermal hysteresis of <0.1 ppm over at least a temperature range of 10°C to 35°C, and comprising the following components (in mol% as oxides):

[0027]

[0028]

[0029] at least one component selected from the group consisting of P2O5 and RO, where RO can be CaO and / or SrO; and

[0030] a nucleating agent in an amount of 1.5 to 6 mol%, where the nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, and WO3.

[0031] According to a third aspect of the present application, there is provided a LAS glass-ceramic having an average coefficient of thermal expansion CTE of at most 0 ± 0.02 x 10 -6 / K, having a thermal hysteresis of <0.1 ppm over at least a temperature range of 10°C to 35°C, and comprising the following components (in mol% as oxides):

[0032] at least one component selected from the group consisting of P2O5 and RO, where RO can be CaO and / or BaO and / or SrO; and

[0033] a nucleating agent in an amount of 1.5 to 6 mol%, where the nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, and WO3.

[0034] According to a fourth aspect of the present application, there is provided a LAS glass-ceramic having an average coefficient of thermal expansion CTE of at most 0 ± 0.02 x 10 -6 / K, having a thermal hysteresis of <0.1 ppm over at least a temperature range of 10°C to 35°C, and comprising the following components (in mol% as oxides):

[0035] at least one component selected from the group consisting of P2O5 and RO, where RO can be CaO and / or SrO; and

[0036] - a nucleating agent in an amount of 1.5 to 6 mol%, wherein the nucleating agent is at least one component selected from the group consisting of Ti02, Zr02, Ta205, Nb205, Sn02, Mo03, W03.

[0037] According to another aspect, the present application relates to the use of such LAS glass-ceramics as a substrate for precision parts.

[0038] According to yet another aspect, the present application relates to the use of LAS glass-ceramics in precision parts, in particular in metrology, spectroscopy, measurement technology, lithography, astronomy or space-to-earth observation, for example, as a mirror or mirror substrate for segmented or monolithic astronomical telescopes, or as a weight-reducing mirror substrate or ultra-light mirror substrate for space-based telescopes; or as a high-precision structural component for distance measurement, for example, in the field of space or for earth observation, as a precision part for precision measurement technology, precision scales, reference plates within interferometers, as a mechanical precision part, for example, ring laser gyroscopes, coil springs for the watch industry, mirrors and prisms in LCD lithography; as a mask holder, wafer stage, reference plate, reference frame and grid plate in microlithography and EUV (extreme ultraviolet) microlithography with reflective optical elements, and as a mirror and / or photomask substrate or mask blank in EUV microlithography.

[0039] According to still another aspect, the present application relates to a precision part comprising a LAS glass-ceramic. BRIEF DESCRIPTION OF DRAWINGS

[0040] The drawings are as follows:

[0041] Figure 1 A CTE-T curve of a LAS glass-ceramic according to Example 4 is shown.

[0042] Figure 2 and Figure 3 A CTE-T curve of a LAS glass-ceramic according to Example 2 is shown.

[0043] Figure 4 A CTE-T curve of a LAS glass-ceramic according to Example 6 is shown.

[0044] Figure 5 A hysteresis curve of a LAS glass-ceramic according to Example 4 is shown.

[0045] Figure 6 A CTE-T curve of a LAS glass-ceramic according to Example 2 is shown.

[0046] Figures 7 to 9Normalized l / l0-T curves (also called dl / l0 curves) of the glass-ceramics according to the present application (compositions according to examples 4, 5 and 3) are shown.

[0047] Figures 10 to 13 Normalized l / l0-T curves (also called dl / l0 curves) of the glass-ceramics according to the present application (compositions according to examples 4, 5 and 3) are shown. Figure 1 , 2 Slopes of the CTE-T curves in examples 4 and 9 are shown.

[0048] Figure 14 Hysteresis curves of the LAS glass-ceramics according to example 23 are shown. DETAILED DESCRIPTION

[0049] The present application provides for the first time a LAS glass-ceramic (also referred to as glass-ceramic hereinafter) which combines all the following relevant properties:

[0050] - an average coefficient of thermal expansion CTE in the range of 0 to 50 °C of at most 0 ± 0.02 x 10 -6 / K, i.e. it is zero expansion.

[0051] - Furthermore, it has a thermal hysteresis of less than 0.1 ppm, preferably less than 0.08 ppm, more preferably less than 0.05 ppm, at least in the temperature range of 10 °C to 35 °C. Materials having such a low (less than 0.1 ppm) hysteresis effect in the above-mentioned temperature range are referred to as "hysteresis-free" hereinafter. As mentioned above, the degree of hysteresis depends on the temperature change rate used for the determination, so the specification in the present application with regard to hysteresis refers to a heating rate / 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 of 5 °C to 35 °C or at least 5 °C to 40 °C, advantageously at least in the temperature range of > 0 °C to 45 °C, and according to the specific embodiment even at least in the temperature range of -5 °C to 50 °C.

[0052] - The glass-ceramic also exhibits a flat CTE-T curve or CTE plateau in the relevant temperature range and contains no or only a small amount of BaO.

[0053] - Furthermore, the viscosity of the glass melt is at most 10 3 dPas at a temperature of at most 1480 °C, preferably at most 1460 °C, i.e. at a temperature T3.

[0054] - The variant of the present application contains no BaO and is thus suitable for IBF treatment.

[0055] In particular, the properties CTE, thermal hysteresis and flat CTE-T curve or CTE plateau are described in detail hereinafter.

[0056] Glass-ceramics are understood to be inorganic, non-porous materials having a crystalline phase and a glass phase, wherein the matrix, i.e. the continuous phase, is usually the glass phase. In order to produce a glass-ceramic, the components of the glass-ceramic are first mixed, melted and fined, and a so-called raw glass is then cast. After cooling, the raw glass is subjected to controlled crystallization by reheating (so-called “controlled bulk crystallization”). The chemical composition (analysis) of the raw glass and the glass-ceramic produced therefrom is identical; the ceramization only changes the internal structure of the material. Therefore, the following discussion of the composition of the glass-ceramic also applies to the precursor of the glass-ceramic, i.e. the raw glass.

[0057] Hitherto, it has been assumed that both glass components MgO and ZnO are necessary, either in combination or individually, especially for zero-expansion LAS glass-ceramics, in order to impart a flat CTE-T curve to the material, i.e. a low CTE-T curve slope or a CTE plateau in the relevant temperature range. On the other hand, it has been found that for LAS glass-ceramics without hysteresis, the components MgO and ZnO can at most only have a small share in the glass-ceramic. Therefore, LAS glass-ceramics either have a flat CTE-T curve or are without hysteresis, which is a target conflict.

[0058] LAS glass-ceramics contain a crystalline phase with negative expansion and a glass phase with positive expansion, which, within the scope of the present application, advantageously comprises or consists of a high-quartz solid solution (also referred to as beta-eucryptite). In addition to SiO2 and Al2O3, the high-quartz solid solution also has Li2O as a main component. If ZnO and / or MgO are present, they also melt into the high-quartz solid solution phase and, together with Li2O, influence the expansion properties of the crystalline phase. This means that by the above-mentioned provisions of the present application (reduction, preferably exclusion of MgO and ZnO), a significant influence on the type and properties of the high-quartz solid solution formed during ceramization is exerted. In the context of US 2022 / 0298079 A1, US 2022 / 0298062 A1 and WO 2022 / 194846 A1, in order to adjust the desired expansion properties of the glass-ceramic, instead of MgO and ZnO, at least one component selected from the group consisting of P2O5, R2O (wherein R2O can be Na2O and / or K2O and / or Rb2O and / or Cs2O) and RO (wherein RO can be CaO and / or BaO and / or SrO) is used. Unlike MgO and ZnO, the above-mentioned alkaline earth metal oxides and alkali metal oxides, if present, remain in the glass phase and do not bond into the high-quartz solid solution.

[0059] In a further advantageous development, the glass-ceramic can comprise the following components in mol% individually or in any combination:

[0060]

[0061] In another advantageous development, the glass-ceramics can comprise, alone or in any combination, in mol%:

[0062]

[0063]

[0064] Furthermore preferably, within the above ranges for the sum of R2O, RO and Ti02+Zr02, the following components can be contained, alone or in any combination, in mol%:

[0065]

[0066] In an advantageous embodiment, the LAS glass-ceramics comprise the following components (in oxides, in mol%):

[0067]

[0068] wherein the nucleating agent is preferably Ti02and / or Zr02.

[0069] In an advantageous embodiment, the LAS glass-ceramics comprise the following components (in oxides, in mol%):

[0070]

[0071] wherein the nucleating agent is preferably Ti02and / or Zr02.

[0072] In an advantageous embodiment, the LAS glass-ceramics comprise the following components (in oxides, in mol%):

[0073]

[0074] wherein the nucleating agent is preferably Ti02and / or Zr02.

[0075] The share of silicon dioxide (Si02) in the glass-ceramic is at least 60 mol-%, preferably at least 60.5 mol-%, further preferably at least 61 mol-%, more further preferably at least 61.5 mol-%, again further preferably at least 62.0 mol-%. The share of Si02is at most 70 mol-% or less than 70 mol-%, preferably at most 69 mol-%, more preferably at most 68.5 mol-%. The higher the share of Si02, the more difficult the batch is to melt and the higher the viscosity of the melt, which can lead to problems with homogenization of the melt in large production plants. Therefore, the content should not exceed 70 mol-%. If the viscosity of the melt is higher, the processing temperature Va of the melt will increase. Very high temperatures are required for refining and homogenizing the melt, but since the aggressiveness of the melt increases with increasing temperature, this will lead to the inner lining of the melting plant being attacked. Furthermore, even higher temperatures can not be sufficient to produce a homogenous melt, resulting in the raw glass possibly showing streaks and inclusions, in particular bubbles and particles from the inner lining of the melting unit, so that, after ceramming, the resulting glass-ceramic does not meet the requirements for uniformity of properties, for example, uniformity of the coefficient of thermal expansion. For this reason, a Si02content below the upper limit mentioned above can be preferable.

[0076] The share of AI2O3 is advantageously at least 10 mol-%, preferably at least 11 mol-%, more preferably at least 12 mol-%, again preferably at least 13 mol-%, again more preferably at least 14 mol-%, again more preferably at least 14.5 mol-%, further preferably at least 15 mol-%. If the content is too low, no or too little low expansion solid solution is formed. The share of AI2O3 is advantageously at most 22 mol-%, preferably at most 21 mol-%, more preferably at most 20 mol-%, again preferably at most 19.0 mol-%, further preferably at most 18.5 mol-%. Too high a content of AI2O3 leads to an increase in viscosity and to uncontrolled devitrification of the material.

[0077] According to a variant of the LAS glass-ceramic with a content of AI2O3 of less than 17.0 mol-%, it is advantageous to meet one or more of the following conditions for the CTE plateau:

[0078] - the content of AI2O3 is at least 15.0 mol-%, at least 15.8 mol-%, at least 16.0 mol-% or at least 16.1 mol-% or more than 16.1 mol-%;

[0079] - the content of Si02 is at least 63.5 mol-%, at least 63.75 mol-% or at least 64.0 mol-% and / or at most 65.6 mol-% or 65.0 mol-%,

[0080] - the following is satisfied: 30.7 < (molar content of SiO2- (2.0 x molar content of Al2O3)) or 30.9 < (molar content of SiO2- (2.0 x molar content of Al2O3)) or 31.0 < (molar content of SiO2- (2.0 x molar content of Al2O3)),

[0081] - the following is satisfied: (molar content of SiO2- (2.0 x molar content of Al2O3)) < 34.0.

[0082] According to another variant of LAS glass-ceramics with an Al2O3 content of > 17.0 mol%, it is advantageous to satisfy one or more of the following conditions for the CTE plateau:

[0083] - the Al2O3 content is at most 19.5 mol% or 19.0 mol%,

[0084] - the SiO2 content is at least 62.0 mol% or > 62.0 mol%, and / or at most 66.0 mol%,

[0085] - the following is satisfied: 142.5 < (molar content of SiO2+ (4.6 x molar content of Al2O3)) or 143.0 < (molar content of SiO2+ (4.6 x molar content of Al2O3)) or 143.0 < (molar content of SiO2+ (4.6 x molar content of Al2O3)),

[0086] - at least one of the following conditions is satisfied:

[0087] o (molar content of SiO2+ (4.6 x molar content of Al2O3)) < 149.0, or

[0088] o (molar content of SiO2+ (2.0 x molar content of Al2O3)) < 101.0 or < 100.5.

[0089] According to one variant, the following conditions are satisfied:

[0090] - the Al2O3 is > 17.0 mol% or < 19.0, and

[0091] - the molar content of SiO2 is between 62.0 mol% and 66.0 mol%, and

[0092] - the following is satisfied: 142.5 < (molar content of SiO2+ (4.6 x molar content of Al2O3)) < 149.0.

[0093] Within the scope of the present application, it was found that for the non- hysteresis glass-ceramics essentially free of ZnO and MgO, the SiO2-Al2O3 ratio mentioned in DE 10 2028 11 144 A1 is ideal, but this ratio alone is not sufficient. Surprisingly, it was found that for the non-hysteresis glass-ceramics which should exhibit a CTE plateau, the alkali metal oxides Na2O, in particular K2O, play an important role. While according to DE 10 2028 11 144 A1 the sum of sodium oxide (Na2O) and / or potassium oxide (K2O) is between 0.1 mol% and 0.7 mol%, according to other embodiments it can even be zero, for the non-hysteresis glass-ceramics it must be maintained that the total content of R2O (R = Na, K and / or Cs) is greater than 0.7 mol% to obtain a CTE plateau.

[0094] The glass-ceramics according to the present application can contain 0 to 6 mol% P2O5. The phosphate content P2O5 of the glass-ceramics can advantageously be at least 0.1 mol%, preferably at least 0.3 mol%, more preferably at least 0.5 mol%, again preferably at least 0.6 mol%, again more preferably at least 0.7 mol%, further preferably at least 0.8 mol%. P2O5 essentially incorporates into the crystalline phase of the glass-ceramics and has a positive influence on the expansion properties of the crystalline phase and of the glass-ceramics. Furthermore, the melting of the components and the fining properties of the melt are improved. However, if the P2O5 content is too high, the CTE-T curve does not exhibit the advantageous flat course in the temperature range from 0°C to 50°C. Therefore, the P2O5 content in the glass-ceramics is advantageously at most 6 mol%, preferably at most 5 mol%, more preferably at most 4 mol%, again preferably less than 4 mol%. According to individual embodiments, the glass-ceramics can be free of P2O5.

[0095] Within the scope of the present application, a certain total amount and ratio of the components SiO2, Al2O3 and / or P2O5 (i.e. components forming high-quartz solid solutions) can be advantageous for the formation of the glass-ceramics according to the present application.

[0096] The total share (in mol%) of the essential components SiO2 and Al2O3 of the LAS glass-ceramics is advantageously at least 75 mol%, preferably at least 78 mol%, more preferably at least 79 mol%, again preferably at least 80 mol%, and / or preferably at most 90 mol%, more preferably at most 87 mol%, again preferably at most 86 mol%, again more preferably at most 85 mol%. If this total amount is too high, the viscosity curve of the melt shifts to higher temperatures, which is undesirable, as explained above with regard to the component SiO2. If this total amount is too low, too little high-quartz solid solution is formed.

[0097] The total share (in mol%) of the basic constituents Si02, AI2O3 and P2O5 of the LAS glass-ceramic is preferably at least 77 mol%, advantageously at least 81 mol%, more advantageously at least 83 mol%, more preferably at least 84 mol%, and / or is preferably at most 91 mol%, advantageously at most 89 mol%, more preferably at most 87 mol%, according to a variant at most 86 mol%.

[0098] The ratio of the share (in mol%) of P2O5 to the share (in mol%) of Si02 is preferably at least 0.005, advantageously at least 0.01, more preferably at least 0.012, and / or is preferably at most 0.1, more preferably at most 0.08, according to a variant at most 0.07.

[0099] As a further constituent, the share of lithium oxide (Li20) in the glass-ceramic is at least 7 mol%, advantageously at least 7.5 mol%, preferably at least 8 mol%, particularly preferably at least 8.25 mol%. The share of Li20 is limited to at most 9.4 mol%, more preferably at most 9.35 mol%, further preferably at most or below 9.3 mol%. Li20 is a constituent of the high-quartz solid-solution phase, which makes a significant contribution to the thermal expansion of the glass-ceramic. If the upper limit of 9.4 mol% is exceeded, a glass-ceramic with a negative coefficient of thermal expansion CTE(0; 50) is formed. If the content of Li20 is below 7 mol%, too little high-quartz solid solution is formed and the CTE of the glass-ceramic remains positive.

[0100] According to a variant of the glass-ceramic, the composition can satisfy the condition: molar content of Si02 + (5 x molar content of Li20) > 106 or preferably > 106.5, preferably molar content of Si02 + (5 x molar content of Li20) > 107 or > 107.5. Alternatively or additionally, for the condition "molar content of Si02 + (5 x molar content of Li20)", an advantageous upper limit of < 115.5 or < 114.5 or < 113.5 can be applied.

[0101] The glass-ceramic can contain at least one alkaline earth oxide selected from the group consisting of CaO, BaO, SrO, wherein the constituents of this group are collectively referred to as "RO". The constituents of the group RO are essentially retained in the amorphous glass phase of the glass-ceramic and can be important for maintaining the zero expansion of the ceramized material. If the total amount of CaO, BaO, SrO is too high, the target CTE (0; 50) of the present application cannot be achieved. Therefore, the share of RO is advantageously at most 6 mol% or 5.5 mol%, preferably at most 5 mol%, more advantageously at most 4.5 mol%, more preferably at most 4 mol%, again preferably at most 3.8 mol%, further preferably at most 3.5 mol%, likewise preferably at most 3.2 mol%. If RO is contained in the glass-ceramic, an advantageous lower limit can be at least 0.1 mol%, advantageously at least 0.2 mol%, preferably at least 0.3 mol%, more preferably at least 0.4 mol%. According to individual embodiments, the glass-ceramic can be free of RO.

[0102] According to one variant, the glass-ceramic contains only a small share of the constituent BaO, the share of which is at most < 0.5 mol%, preferably at most 0.3 mol%, more preferably at most 0.1 mol%. Some variants of the glass-ceramic are free of BaO, i.e. they contain no BaO other than the usual impurities. If BaO is contained, the share thereof can be at least 0.1 mol% or at least 0.2 mol%. Surprisingly, even if only a small amount of the high-quality glass precursor BaO is used or even if no BaO is used at all, the LAS glass-ceramic produced has good processability, in particular good polishability and post-IBF processability.

[0103] According to the present application, CaO is the preferred RO constituent, the content of CaO in the LAS glass-ceramic preferably being at least 0.1 mol% or at least 0.2 mol% or at least 0.4 mol% or at least 0.5 mol%. The share of CaO can preferably be at most 5 mol%, advantageously at most 4 mol%, more advantageously at most 3.5 mol%, again advantageously at most 3 mol%, further preferably at most 2.8 mol%, more preferably at most 2.6 mol%.

[0104] The share of SrO in the glass-ceramic can be at most 3 mol%, advantageously at most 2 mol%, preferably at most 1.5 mol%, more preferably at most 1.3 mol%, again preferably at most 1.1 mol%, again more preferably at most 1 mol%, likewise preferably at most 0.9 mol% and / or preferably at least 0.1 mol%. According to individual embodiments, the glass-ceramic is free of SrO other than impurities.

[0105] The glass-ceramic can contain at most 0.4 mol% of magnesium oxide (MgO). A further advantageous upper limit can be at most 0.2 mol%, 0.1 mol% or 0.05 mol%. Particularly preferably, the glass-ceramic according to the application contains no MgO. The component MgO leads to thermal hysteresis of the glass-ceramic in the temperature range from 0°C to 50°C. The lower the content of MgO in the glass-ceramic, the smaller the hysteresis in the above-mentioned temperature range.

[0106] The glass-ceramic can contain at most 0.4 mol% of zinc oxide (ZnO). A further advantageous upper limit can be at most 0.2 mol%, 0.1 mol% or 0.05 mol%. Particularly preferably, the glass-ceramic according to the application contains no ZnO. The component ZnO leads to thermal hysteresis of the glass-ceramic in the temperature range from 0°C to 50°C. The lower the content of ZnO in the glass-ceramic, the smaller the hysteresis in the above-mentioned temperature range.

[0107] Overall, according to the application, the share of MgO and ZnO in the LAS glass-ceramic without hysteresis should be relatively small, the total share being at most 0.4 mol% or 0.3 mol%. In a preferred variant, at most 0.2 mol%, 0.1 mol% or 0.05 mol% of MgO and ZnO are contained, or the glass-ceramic contains no MgO and ZnO.

[0108] Surprisingly, it has been found that, contrary to the teachings of the prior art, LAS glass-ceramics with a flat CTE-T curve or CTE plateau can still be obtained which have both zero expansion and no hysteresis properties. To this end, the share of alkali metal oxides in the LAS glass-ceramic is set to be from 0.7 mol% to 2.0 mol%. A content of less than 0.7 mol% or more than 2.0 mol% leads to no CTE plateau or not a sufficiently wide CTE plateau of the LAS glass-ceramic.

[0109] The content of sodium oxide (Na2O) and / or potassium oxide (K2O) and / or cesium oxide (Cs2O) and / or rubidium oxide (Rb2O) is therefore at least 0.7 mol% and at most 2.0 mol%, 1.9 mol% or 1.8 mol%, according to a preferred variant at least 0.8 mol%, 0.9 mol% or 1.0 mol%. The components Na2O, K2O, Cs2O and Rb2O are essentially retained in the amorphous glass phase of the glass-ceramic, which is important for maintaining the zero expansion of the ceramised material.

[0110] Na2O, K2O, Cs2O, Rb2O can each independently be contained in the glass-ceramic in a share of at least 0.1 mol%, 0.2 mol%, 0.3 mol%, 0.4 mol% or 0.5 mol% and / or at most 2.0 mol%, 1.5 mol%, 1.0 mol%, 0.5 mol% or 0.4 mol%.

[0111] According to a preferred variant, the LAS glass-ceramic contains only or predominantly K2O as alkali metal oxide. It has surprisingly been found that a larger amount of K2O, i.e. a share of at least 0.7 mol%, 0.8 mol%, 0.9 mol%, 1.0 mol%, 1.1 mol%, 1.2 mol% or 1.3 mol% can be introduced into the LAS glass-ceramic without affecting the zero expansion of the LAS glass-ceramic. At the same time, the share of K2O ensures a flat CTE-T curve. Furthermore, K2O reduces the temperature T3, thus ensuring a better meltability and processability of the glass melt. According to this variant, the content of Na2O is at most 0.5 mol%, 0.2 mol% or 0.1 mol%. The LAS glass-ceramic can also be free of Na2O, i.e. the content of Na2O is at most 0.05 mol% or 0.01 mol%, apart from the usual impurities.

[0112] The share of Cs2O can be at most 2 mol%, 1.5 mol%, 1 mol%, 0.5 mol% or 0.1 mol%. The share of Rb2O can be at most 2 mol%, 1.5 mol%, 1 mol%, 0.5 mol% or 0.1 mol%.

[0113] According to individual embodiments, the glass-ceramic is free of Na2O and / or Cs2O and / or Rb2O.

[0114] The glass-ceramic also contains at least one crystal nucleating agent selected from the group consisting of Ti02, Zr02, Ta205, Nb205, Sn02, M0O3 and W03. The nucleating agent can be a combination of two or more of the above-mentioned components. Another advantageous nucleating agent can be Hf02. Thus, in an advantageous embodiment, the glass-ceramic comprises Hf02and at least one crystal nucleating agent selected from the group consisting of Ti02, Zr02, Ta205, Nb205, Sn02, M0O3 and W03. The sum of the fractions of the nucleating agents is preferably at least 1.5 mol%, more preferably at least 2 mol% or more than 2 mol%, again preferably at least 2.5 mol%, according to certain variants at least 3 mol%. The upper limit can be at most 6 mol%, preferably at most 5 mol%, more preferably at most 4.5 mol% or 4 mol%. In particularly advantageous variants, the mentioned upper and lower limits apply to the total amount of Ti02and Zr02.

[0115] The glass-ceramic can contain titanium oxide (Ti02) in a fraction of preferably at least 0.1 mol%, advantageously at least 0.5 mol%, preferably at least 1.0 mol%, more preferably at least 1.5 mol%, again preferably at least 1.8 mol%, and / or preferably at most 5 mol%, advantageously at most 4 mol%, more preferably at most 3 mol%, further preferably at most 2.5 mol%, preferably 2.3 mol%. The glass-ceramic according to the application can be a variant without Ti02.

[0116] Advantageously, the glass-ceramic can also contain zirconium oxide (Zr02) in a fraction of at most 3 mol%, preferably at most 2.5 mol%, more preferably at most 2 mol%, again preferably at most 1.5 mol% or at most 1.2 mol%. Preferably, the fraction of Zr02is at least 0.1 mol%, preferably at least 0.5 mol%, 0.8 mol% or 1.0 mol%. The glass-ceramic according to the application can be a variant without Zr02.

[0117] According to some advantageous variants of the application, 0 to 5 mol% of Ta205and / or Nb205and / or Sn02and / or M0O3and / or W03may be contained in the glass-ceramic individually or jointly and can serve, for example, as a replacement or additional nucleating agent or for adjusting optical properties, for example the refractive index. Hf02may also be used as a replacement or additional nucleating agent. In order to adjust optical properties, some advantageous variants can be contained, for example Gd203, Y203, Hf02, Bi203and / or Ge02.

[0118] The glass-ceramic can also contain one or more conventional fining agents, selected from the group consisting of components of the As2O3, Sb2O3, SnO2, SO4 2- , Cl - , Br - or mixtures thereof, in a proportion greater than 0.05 mol% or at least 0.1 mol% and / or at most 1 mol%.

[0119] In order to provide a glass-ceramic according to the application which is hysteresis-free and zero-expansion, the desired internal quality, in particular a low number of bubbles and few striae, is achieved despite the reduced content of As2O3, even without using As2O3. In an advantageous embodiment, at least one chemical fining agent is used.

[0120] In an advantageous embodiment, the glass-ceramic can contain, as a substitute for As2O3 used as a chemical fining agent, or in addition to a small amount of As2O3 (at most 0.05 mol%), at least one alternative redox fining agent and / or at least one evaporation fining agent and / or at least one decomposition fining agent. Since As2O3 is also a redox fining agent, a redox fining agent used as a substitute or in addition to As2O3 is referred to as an "alternative redox fining agent" within the scope of the application.

[0121] In an advantageous variant, the total content of detectable chemical fining agents in the glass-ceramic, if As2O3 is present in the glass-ceramic, not including the content of As2O3, can be in the range from 0 mol% to 1 mol%. In an advantageous embodiment, the total content of detectable fining agents in the glass-ceramic, not including As2O3, is greater than 0.01 mol%, preferably at least 0.05 mol%, more preferably at least 0.1 mol%, even more preferably at least 0.15 mol%, advantageously at least 0.2 mol%, and / or at most 1 mol%, preferably at most 0.7 mol%, more preferably at most 0.5 mol%, even more 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 the individual components can be detected by analysis of the glass-ceramic. This applies in particular to all the fining agents mentioned below, with the exception of the sulphate components mentioned above.

[0122] The redox fining agent contains polyvalent or polyvalent ions which can occur in at least two oxidation states which are in a temperature-dependent equilibrium with one another, and thus release a gas, typically oxygen, at high temperatures. Thus, certain polyvalent metal oxides can be used as redox fining agents. In an advantageous variant, the optional redox fining agent can be at least one component selected from the group consisting of Sb2O3, SnO2, CeO2, MnO2and Fe2O3. However, in principle, it is also applicable to other redox compounds which release their fining gas in the temperature range relevant for fining and which are converted into an oxide or metal form with a different valence state of the metal ion. A number of such compounds have been described, for example, in DE 19939771 A. Preferred are optional redox fining agents which release a fining gas, in particular oxygen, at temperatures below 1700°C, such as Sb2O3, SnO2and CeO2.

[0123] From the analysis of the glass-ceramic, it is possible to determine the content of As2O3and / or the content of at least one optional redox fining agent. Thereby, the expert can draw conclusions about the type and amount of the fining agent used. The optional redox fining agent, for example as an oxide, can be added to the batch.

[0124] In an advantageous variant, the total content of the optional redox fining agent can be in the range of 0 mol% to 1 mol%. In an advantageous embodiment, the total content of the optional redox fining agent detectable in the glass-ceramic 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%. In certain advantageous variants, it is also possible to contain up to 0.3 mol%, preferably up to 0.25 mol% or up to 0.2 mol% of the optional redox fining agent.

[0125] The glass-ceramic can comprise from 0 mol% to 1 mol% of antimony oxide (Sb2O3) as an optional redox fining agent. In advantageous embodiments, the content of Sb2O3 in the glass-ceramic is greater 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%, further preferably at most 0.4 mol%, preferably at most 0.3 mol%. Since Sb2O3 is considered to be harmful to the environment, it can be advantageous to use as little Sb2O3 as possible when fining. Preferred embodiments of the glass-ceramic are essentially free of Sb2O3 or Sb, wherein "essentially free of Sb2O3" means that Sb2O3 is not intentionally added to the composition as a raw material constituent, but is present at most as an impurity. For a glass-ceramic free of Sb2O3, the impurity limit is at most 0.01 mol%, preferably at most 0.005 mol%. Depending on the specific embodiment, the glass-ceramic is free of Sb2O3.

[0126] The glass-ceramic can comprise from 0 mol% to 1 mol% of tin oxide (SnO2) as an optional redox fining agent. In advantageous embodiments, the content of SnO2 in the glass-ceramic is greater 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%, more preferably at most 0.6 mol%. For certain variants, it can be advantageous for the upper limit to be at most 0.5 mol%, further preferably at most 0.4 mol%, preferably at most 0.3 mol%. If the content of SnO2 is too high, the ceramming process of the raw glass can be more difficult to control, since SnO2 not only acts as a fining agent at higher contents, but can also act as a crystal nucleating agent. Variants of the glass-ceramic according to the application which are free of SnO2 or free of Sn are feasible and advantageous, i.e. raw materials which are free of Sn are added to the batch for fining the base raw glass, the content of SnO2 impurities introduced by the raw materials or the process is at most 0.01 mol%, preferably at most 0.005 mol%.

[0127] The glass-ceramic can comprise 0 to 1 mol% of Ce02and / or Mn02and / or Fe203as optional redox fining agents. The individual content fraction of these components is preferably greater 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%, further preferably at most 0.4 mol%, preferably at most 0.3 mol%. A preferred variant of the glass-ceramic is free of Ce02and / or Mn02and / or Fe203, i.e. raw materials free of Ce and / or raw materials free of Mn and / or raw materials free of Fe are added to the batch for fining the base raw glass, the upper limit for the content of Ce02and / or Mn02and / or Fe203introduced by the raw materials or the process being at most 0.01 mol%, preferably at most 0.005 mol%.

[0128] Evaporative fining agents are components which, at high temperatures, volatilize due to their vapor pressure, so that the gas formed in the melt produces a fining effect.

[0129] In an advantageous variant, the evaporative fining agent can comprise a halogen component.

[0130] In an advantageous variant, the evaporative fining agent can comprise at least one halogen having a fining effect, in particular a halogen selected from the group consisting of chlorine (CI), bromine (Br) and iodine (I). The halogen having a fining effect is preferably chlorine. Fluorine is not a halogen having a fining effect, since it already volatilizes at too low a temperature. The glass-ceramic can nevertheless contain fluorine. However, since fluorine reduces the transparency of the glass-ceramic, if this component is present, its content is preferably limited to not more than 0.5 mol%, preferably not more than 0.3 mol%, preferably not more than 0.1 mol%. Preferably, the glass-ceramic is free of fluorine.

[0131] The halogen with a clarifying effect can be added in different forms. In one embodiment, the halogen is added to the batch as a salt with an alkali metal cation or an alkaline earth metal cation or as an aluminum halide. In one embodiment, the halogen is used as a salt, the cation in the salt corresponding to the cation present as an oxide in the glass-ceramic. The halogen with a clarifying effect can be used in the form of a halogen compound, in particular a halide. In particular, suitable halides are salts of a chloride anion, a bromide anion and / or an iodide anion with an alkali metal cation or an alkaline earth metal cation or an aluminum cation. Preferred examples are chlorides, for example LiCI, NaCI, KCI, CaCI2, BaCI2, SrCI2, AICI3 and combinations thereof. Also possible are the corresponding bromides and iodides, for example LiBr, Lil, NaBr, Nal, KBr, KI, Cai2, CaBr2 and combinations thereof. Further examples are BaBr2, Bai2, SrBr2, Sri2 and combinations thereof.

[0132] In an advantageous variant, the total content of the halogen with a clarifying effect (i.e. CI and / or Br and / or I) can be in the range of 0 mol% to 1 mol%. In an advantageous embodiment, the total content of the halogen with a clarifying effect 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%. Certain advantageous variants can also comprise at most 0.3 mol%, preferably at most 0.25 mol% or at most 0.2 mol% of the halogen with a clarifying effect. The above-mentioned contents refer to the amount of halogen detectable in the glass-ceramic. Experts will generally calculate the amount of halogen compound or halide required for clarification from these indicators.

[0133] The glass-ceramic can comprise 0 to 1 mol% of chlorine (measured as atoms and specified as Cl). In an advantageous embodiment, the content of Cl in the glass-ceramic is greater 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%, further preferably at most 0.4 mol%, preferably at most 0.3 mol%. Certain advantageous glass-ceramics can be free of Cl, i.e. the raw materials added to the batch for the clarification of the base raw glass will be free of Cl. The Cl is present at most as an impurity, the upper limit of the Cl impurity being at most 0.03 mol%.

[0134] The ranges and limits mentioned above apply equally to the halogen Br which has a clarifying effect. The ranges and limits mentioned above apply equally to the halogen I which has a clarifying effect. Preferred variants of the glass-ceramic are free of Br and / or I.

[0135] Alternatively or in addition to the evaporation clarifiers and / or optional redox clarifiers, the chemical clarifiers can also comprise at least one decomposition clarifier. A decomposition clarifier is an inorganic compound which decomposes at high temperatures with the release of a clarifying gas, the decomposition products having a sufficiently large gas pressure, in particular greater than 10 5 Pa. Preferably, the decomposition clarifier can be a salt containing an oxygen anion, in particular a sulfate component. Preferably, the decomposition clarifier comprises a sulfate component. By decomposition of the component added as a sulfate at high temperatures, SO2 and O2 gases are released which contribute to the clarification of the melt.

[0136] The sulfate component can be added in different forms. In one embodiment, the sulfate component is added to the batch as a salt with an alkali or alkaline earth metal cation. In one embodiment, the sulfate is used as a salt, the cation in the salt corresponding to the cation present as an oxide in the glass-ceramic. For example, the following components can advantageously be used as a source of sulfate: Li2SO4, Na2SO4, K2SO4, CaSO4, BaSO4, SrSO4.

[0137] Within the scope of the present application, the sulfate is determined as SO3 in the material analysis. However, due to the very low solubility of the sulfate in LAS glass-ceramics, the sulfate component (i.e. SO3) cannot be detected in the melt product after melting with conventional X-ray fluorescence analysis. Therefore, for the embodiments of the sulfate clarification (see below), it is explicitly stated how many mol% of SO4 2-or in how many mol% of SO3. For example, by analyzing the content of residual gas (SO2) in the glass-ceramic it can be determined whether a sulfate component has been used as fining agent.

[0138] During synthesis, 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%, further preferably at most 0.4 mol%, preferably at most 0.3 mol% of SO3 is added to the advantageous glass-ceramic that is fined with a sulfate component by at least one corresponding sulfate compound. The fining glass-ceramic is free of sulfate, i.e. free of SO3 or SO4 2- ) is feasible and advantageous. Thus, the share of effective fining sulfate added during synthesis of the glass-ceramic can range from 0 mol% to 1 mol% of SO3.

[0139] According to a variant of the application, the glass-ceramic or the base glass can be fined using a suitable metal sulfide as a decomposition fining agent, as described in US 2011 / 0098171 A. In one embodiment, the cation in the sulfide corresponds to the cation present as an oxide in the glass-ceramic. Examples of suitable metal sulfides are alkali metal sulfides, alkaline earth metal sulfides and / or aluminum sulfide, which release SO3 in the melt under oxidizing conditions. In order for the metal sulfide to function well as a fining agent, it is preferably used in combination with an oxidizing agent, preferably a nitrate and / or a sulfate.

[0140] The advantageous glass-ceramic with reduced As2O3 content or the advantageous glass-ceramic free of As2O3 can have various chemical fining agent combinations. The following combinations can be comparatively advantageous, the content of the above-mentioned fining agents in the corresponding glass-ceramic preferably not exceeding the limit values mentioned above for each component and / or the total amount. Advantageous embodiments include:

[0141] - SnO2 and / or Sb2O3, each in combination with at most 0.05 mol% of As2O3; or

[0142] - combinations free of As2O3, for example: Sb2O3 in combination with SnO2, Sb2O3 in combination with Cl, Sb2O3 in combination with SO3; or

[0143] - combinations free of As2O3 and free of Sb2O3, for example: SnO2 in combination with Cl, SnO2 in combination with SO3, Cl in combination with SO3.

[0144] Alternatively, it is also advantageous for the glass-ceramics to be clarified with only one clarifier, for example, glass-ceramics containing only Sb2O3 or only SnO2 as clarifier.

[0145] As an alternative or in addition to the clarification of the melt using chemical clarifiers, whose principle consists in the addition of compounds which decompose and release gas at high temperature, or compounds which are volatile at high temperature, or compounds which release gas at high temperature by equilibrium reaction, it is also advantageous to use known physical clarification methods, for example, reduction of the viscosity of the glass melt by increasing the temperature, vacuum clarification, high-pressure clarification, etc.

[0146] In an advantageous variant of the application, the batch can comprise nitrates (NO3) which act as oxidizing agents during the melting and clarification process, ensuring the presence of oxidizing conditions in the melt, in order to increase the effectiveness of the clarifiers used, in particular of the optional redox clarifiers. In one embodiment, the nitrates are used as salts, while the cations in the salts correspond to the cations present in the glass-ceramics in the form of oxides. Examples in this regard are aluminum nitrate, alkali metal nitrates, alkaline earth metal nitrates, zirconium nitrate. Advantageously, however, ammonium nitrate can also be used as a source of nitrates. A nitrate compound or a mixture of several nitrate compounds can be used. If a nitrate compound or a mixture of nitrate compounds is contained in the batch to support the clarification process, the sum of NO3 - 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%. For certain advantageous variants, it is also possible to use up to 3 mol% of nitrates. Due to the volatility, the nitrates are not detectable in the glass or glass-ceramics.

[0147] The glass compositions described above can comprise an additional component of coloring oxides, for example, Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, CuO, CeO2, Cr2O3, rare earth oxides, alone or in total content of 0-3 mol%. Preferred variants do not contain coloring oxides.

[0148] B2O3 has a negative effect on the transparency of the glass-ceramics. Therefore, in advantageous variants, the content of this component is limited to < 0.2 mol%, preferably at most 0.1 mol%. Preferred variants do not contain B2O3.

[0149] Preferably, the LAS glass-ceramics do not contain fluorine. Fluorine reduces the transparency of the glass-ceramics and has a negative effect on zero expansion. If this component is present, its content is preferably limited to not more than 0.5 mol%, preferably not more than 0.3 mol%, preferably not more than 0.1 mol%. Preferably, the glass-ceramics do not contain fluorine.

[0150] According to an advantageous embodiment of the application, the composition does not contain the above-mentioned components not mentioned.

[0151] According to an advantageous embodiment of the application, the glass-ceramic or the raw glass according to the application consists preferably of at least 90 mol%, more preferably of at least 95 mol%, most preferably of at least 99 mol% of the above-mentioned components, or preferably of the components SiO2, Al2O3, Li2O, P2O5, R2O, RO and nucleating agent.

[0152] According to a further advantageous development of the glass-ceramic, it consists essentially of none or several glass components selected from the group consisting of PbO, CrO3and Cd compounds.

[0153] According to the application, the expression "free of X" or "free of component X" means that the glass-ceramic consists essentially of no such component X, i.e. such a component is at most present in the glass as an impurity, but is not added as a separate component to the composition. With regard to impurities, in particular with regard to impurities containing MgO and / or ZnO, the impurity content of each component in the variants free of MgO and / or free of ZnO does not exceed the limit value of 0.03 mol%, preferably of 0.01 mol%. With regard to other glass components, the impurity content does not exceed a limit value of 0.1 mol%, preferably of 0.05 mol%, advantageously of 0.01 mol%, advantageously of 0.005 mol%, and with regard to certain components, the impurity content of each component advantageously does not exceed 0.003 mol%. X here stands for any component, for example PbO.

[0154] The glass-ceramic according to the application has a high quartz solid solution as the main crystalline phase. The main crystalline phase is the crystalline phase having the largest volume percentage in the crystalline phase. The high quartz solid solution is a metastable phase whose composition and / or structure changes with the crystallization conditions or changes into another crystalline phase. The thermal expansion coefficient of the high quartz solid solution crystals becomes very low and even decreases with increasing temperature. In an advantageous embodiment, the crystalline phase is free of β-spodumene and of hydrothermal quartz.

[0155] The crystalline phase content of the advantageous embodiment of the LAS glass-ceramic is less than 70 vol% and / or advantageously greater than 45 vol%. The crystalline phase consists of high quartz solid solution, which is also referred to as β-eucryptite. The average crystallite size of the high quartz solid solution is advantageously < 100 nm, preferably < 80 nm, preferably < 70 nm. A smaller crystallite size makes it possible for the glass-ceramic to have better transparency and polishability. In certain advantageous variants, the average crystallite size of the high quartz solid solution can be < 60 nm, preferably < 50 nm. The crystalline phase, the crystalline phase fraction and the average crystallite size can be determined by means of known X-ray diffraction analysis methods.

[0156] According to embodiments of the present application, a transparent glass-ceramic is produced. Due to the transparency, many properties of this glass-ceramic, in particular its internal quality, can be better assessed. The glass-ceramic according to the present application is transparent, i.e. has a pure transmission of at least 70% in the wavelength range of 350 nm to 650 nm. B2O3 and / or a higher fluorine content can reduce the transparency. Therefore, advantageous variants do not contain one or both of the above-mentioned components. Furthermore, the glass-ceramic produced within the scope of the present application is pore-free and crack-free. Within the scope of the present application, "pore-free" means a porosity of less than 1%, preferably less than 0.5%, more preferably less than 0.1%. Cracks mean gaps, i.e. discontinuities, in an otherwise continuous structure.

[0157] In order to be able to produce a homogeneous glass-ceramic in large-scale production plants, it is advantageous if the processing temperature Vaof the original glass on which the glass-ceramic is based (and of the glass-ceramic) is at most 1330°C, preferably at most 1320°C. Some advantageous variants can have a processing temperature of at most 1310°C or at most 1300°C, or below 1300°C or below 1280°C or below 1270°C. The processing temperature Va is the temperature at which the melt viscosity is 10 4 dPas, and is therefore also referred to as temperature T4. Correspondingly, the temperature at which the melt viscosity is 10 3 dPas is referred to as temperature T3. Preferably, the temperature T3 is at most 1480°C or at most 1460°C or at most 1450°C or at most 1440°C or at most 1435°C. In particular, homogeneity means the homogeneity of the CTE of the glass-ceramic over a large volume and a small number, preferably without inclusions such as bubbles and particles. This is a quality feature of the glass-ceramic and a prerequisite for the use in precision parts, in particular large precision parts.

[0158] The processing temperature is determined by the composition of the glass-ceramic. Since the glass network-forming component SiO2 is considered to be the decisive component for increasing the viscosity and the processing temperature, the maximum content of SiO2 should be chosen according to the above-mentioned criteria.

[0159] The coefficient of thermal expansion CTE

[0160] The glass-ceramic according to the present application is zero-expanding, i.e. its average coefficient of thermal expansion CTE in the range of 0 to 50°C is at most 0 ± 0.02 x 10 -6 / K. Certain advantageous variants even have an average CTE in the range of 0 to 50°C of at most 0 ± 0.01 x 10 -6 / K. In certain applications, it can be advantageous if the average CTE is at most 0 ± 0.02 x 10 -6 / K, i.e. zero expansion occurs, over a larger temperature range, for example in the range of -30°C to +70°C, preferably in the range of -40°C to +80°C.

[0161] In order to determine the CTE-T curves of the glass-ceramics and precision parts according to the present application and of comparative examples, the differential CTE(T) has to be determined first. The differential CTE(T) is determined as a function of temperature. Then the CTE is defined according to the following equation (1):

[0162]

[0163] In order to plot the l / l0-T curve or strain curve or graph of the length change l / l0 of a sample (glass-ceramic or precision part) as a function of temperature, the length l of the sample can be measured from the initial length l0 at the initial temperature t0 to the temperature t t The length change as a function of temperature. Preferably, a smaller temperature interval, for example 5°C or 3°C or 1°C is chosen for determining the measurement points. Such a measurement can be performed, for example, by dilatometry, interferometry (e.g. Fabry-Perot, i.e. evaluating the shift of a resonance peak of a laser beam coupled into the material) or other suitable methods. Within the scope of the present application, the CTE is determined on a rod-shaped sample of a sample having a length of 100 mm and a diameter of 6 mm by dilatometry with a temperature interval of 1°C. The accuracy of the chosen CTE determination method is preferably at least ± 0.05 ppm / K, preferably at least ± 0.03 ppm / K. However, it is of course also possible to determine the CTE with an accuracy of at least ± 0.01 ppm / K, preferably at least ± 0.005 ppm / K or according to some embodiments even at least ± 0.003 ppm / K or at least ± 0.001 ppm / K.

[0164] From the l / l0-T curve, the average CTE of a certain temperature interval (e.g. a temperature range from 0°C to 50°C) can be calculated.

[0165] The CTE-T curve is obtained by differentiating the l / l0-T curve. From the CTE-T curve, the zero-crossing and the slope of the CTE-T curve within a certain temperature interval can be determined. From the CTE-T curve, the range and the position of the advantageous CTE plateau formed in some variants can be determined (see below, e.g. Figure 1 and 2 ).

[0166] According to the present application, the advantageous embodiment of a precision component comprising a glass-ceramic, in particular in the form of a substrate, has a high CTE homogeneity. The value of the CTE homogeneity (English: "total spatial variation of CTE") is to be understood as the so-called peak-to-valley value, i.e. the difference between the highest CTE value and the lowest CTE value sampled from the precision component. The CTE homogeneity thus does not refer to the CTE of the component material itself, but rather to the spatial variation of the CTE over the cross-section or the entire precision component considered. In order to determine the CTE homogeneity, a large number of samples is to be taken from different locations of the precision component and the CTE value (in ppb / K) of each sample is to be determined, wherein 1 ppb / K = 0.001 * 10 -6 / K. The CTE homogeneity of the entire precision component, i.e. the spatial variation of the CTE, is advantageously at most 5 ppb / K, preferably at most 4 ppb / K, most preferably at most 3 ppb / K. The method for determining the CTE homogeneity and the measures for achieving the CTE homogeneity are described in WO 2015 / 124710 A, the disclosure of which is fully incorporated into the present application.

[0167] thermal hysteresis

[0168] Within the scope of the present application, the glass-ceramic exhibits a thermal hysteresis of < 0.1 ppm at least in the temperature range from 10 °C to 35 °C and has thus been considered to be hysteresis-free (see Figure 5 and Figure 6 ). Thus, at any temperature within the temperature interval from 10 °C to 35 °C, the glass-ceramic exhibits a change in the positive or negative isothermal length after a temperature change of less than 0.1 ppm, i.e. < |0.1 ppm| or < ± 0.1 ppm. Preferably, the LAS glass-ceramic exhibits a thermal hysteresis of < |0.08 ppm| or < |0.05 ppm| at least in the temperature range from 10 °C to 35 °C.

[0169] In an advantageous embodiment, this hysteresis-free behavior is present at least in the temperature range from 5 °C to 35 °C, preferably at least in the temperature range from 5 °C to 45 °C, preferably at least in the temperature range from > 0 °C to 45 °C, preferably at least in the temperature range from -5 °C to 50 °C. Particularly preferably, the temperature range of the hysteresis-free behavior is even larger, so that the material or component is also suitable for applications up to a temperature of at least 100 °C or even higher. Particularly preferably, the temperature range of the hysteresis-free behavior is even larger. Preferred application temperatures are in the range from -60 °C to 100 °C, more preferably in the range from -40 °C to + 80 °C. A special variant of the present application relates to glass-ceramics and precision components whose application temperature TA is, for example, in the range from 5 °C to 20 °C or TA is 22 °C, 40 °C, 60 °C, 80 °C and 100 °C, preferably which also do not exhibit a hysteresis at these temperatures.

[0170] According to the method and equipment setup disclosed in DE 102015113548 A (the disclosure of which is incorporated herein in its entirety), the thermal hysteresis of the glass-ceramics and precision parts according to the present application and comparative examples was determined using a precision dilatometer with a reproducibility of ±0.001 ppm / K and ±0.003 ppm / K absolute values, a temperature interval of 1 °C, and a rod-shaped sample (i.e., a precision part sample or a glass-ceramic sample) with a length of 100 mm and a diameter of 6 mm. For each sample under examination, the change in length l / l0as a function of temperature was determined during cooling from 50 °C to -10 °C at a cooling rate of 36 K / h. After isothermal holding at -10 °C for 5 hours, the sample was heated to 50 °C at a heating rate of 36 K / h, and the change in length l / l0as a function of temperature was recorded. The thermal hysteresis performance of the sample was considered at -5 °C, 0 °C, 5 °C, 10 °C, 22 °C, 35 °C, and 40 °C. These temperature points represent the temperature range from -10 °C to 50 °C, because the hysteresis decreases as the temperature increases within the above-mentioned temperature interval. Therefore, a sample that exhibits no hysteresis at 22 °C or 35 °C will also exhibit no hysteresis at temperatures up to 50 °C.

[0171] To determine the thermal hysteresis at 10 °C, the sample was heated and cooled at a rate of 36 K / h in the range from -10 °C to 50 °C, and the change in length was recorded at five temperature points (i.e., two temperature points above and below 10 °C) of 8 °C, 9 °C, 10 °C, 11 °C, and 12 °C, respectively. The average value was calculated from the difference between the heating curve and the cooling curve measurement values at these five measurement points, and the “hysteresis @ 10 °C” was listed in the table in [ppm].

[0172] To determine the thermal hysteresis at 35 °C, the sample was heated and cooled at a rate of 36 K / h in the range from -10 °C to 50 °C, and the change in length was recorded at five temperature points (i.e., two temperature points above and below 35 °C) of 33 °C, 34 °C, 35 °C, 36 °C, and 37 °C, respectively. The average value was calculated from the difference between the heating curve and the cooling curve measurement values at these five measurement points, and the “hysteresis @ 35 °C” was listed in the table in [ppm].

[0173] The same procedure was followed for the other temperature points mentioned above.

[0174] Figure 3 、 Figure 4 and Figure 14The thermal hysteresis curves of the glass-ceramics according to the present application are shown. The cooling curve (dotted line) and the heating curve (dashed line) overlap at least in the temperature range from 10 °C to 35 °C, i.e. the glass-ceramics are hysteresis-free. However, these materials are not only hysteresis-free in the range from 10 °C to 35 °C, but also at least in the range from 5 °C to 35 °C or 5 °C to 45 °C, preferably at least in the range from > 0 °C to 45 °C.

[0175] Further expansion characteristics

[0176] The advantageous embodiments of the present application also have further advantageous expansion characteristics:

[0177] For describing the expansion behavior of a test specimen (glass-ceramic or precision part), the TCL value is usually given, wherein TCL stands for "Total Change of Length". In the context of the present application, the TCL value is given in the temperature range from 0 °C to 50 °C or in the temperature range from 0 °C to 80 °C or in the temperature range from 0 °C to 100 °C. It is determined from the normalized dl / l0-T curve (also referred to as Δl l / l0-T curve) of the respective test specimen, wherein "normalized" means that the length change at 0 °C is 0 ppm. In the context of the present application, the dl / l0-T curve for determining the TCL is plotted using the same method as described above with regard to the determination of the CTE.

[0178] The TCL value is the distance between the highest dl / l0 value and the lowest dl / l0 value in this temperature range (here: from 0 °C to 50 °C):

[0179] TCL(0; 50 °C) = |dl / l0max| + |dl / l0min|... (2)

[0180] wherein "dl" denotes the length change at the respective temperature and "l0" denotes the length of the test specimen at 0 °C. The calculation is based on the absolute values of the dl / l0 values.

[0181] Figures 7 to 9 The expansion curves of known materials are shown, from which the dl / l0max and the dl / l0min for calculating the TCL value can be read (see also below). Each expansion curve is curved in the temperature range from 0 °C to 50 °C.

[0182] However, in the context of the present application, a flat course of the expansion curve in the temperature range from 0 °C to 50 °C is an advantageous feature of the glass-ceramics and precision parts (see Figure 12 and Figure 13). For certain advantageous variants, a flat expansion curve profile can also be required in different temperature ranges, depending on the field of application of the component, in particular in the temperature ranges (0; 80), (0; 100), (20; 40), (20; 70) and / or (-10; 30).

[0183] Preferably, TCL is at most 1.00 ppm or at most 0.50 ppm or at most 0.01 ppm over the selected temperature range, for example, over a temperature range of 0°C to 50°C.

[0184] To illustrate the extent to which the thermal expansion curve deviates from a simple linear profile, a parameter F is introduced in advantageous embodiments of the application as a measure of the flatness of the expansion curve in order to classify the CTE curve:

[0185] F = TCL(0; 50°C) / |expansion(0; 50°C)| (3)

[0186] The parameter F is calculated as the quotient of the TCL(0; 50) value [unit: ppm] (see above) and the expansion difference [unit: ppm] between the temperature points of 0°C and 50°C. Since the expansion curve from which TCL is determined is by definition normalized, i.e. the length change at 0°C is 0 ppm, the "expansion difference between the temperature points of 0°C and 50°C" corresponds to the "expansion at 50°C" given in the table. The absolute value of the expansion at 50°C is used when calculating the parameter F.

[0187] It is advantageous if the parameter F of the respective material or component is < 1.10 or < 1.05 or < 1.03. The closer the parameter F is to 1, the flatter the expansion curve.

[0188] Thus, the advantageous glass-ceramics and precision components of the application exhibit a very flat expansion curve, for example, over a temperature range of 0°C to 50°C, i.e. they not only exhibit zero expansion over the temperature range considered, but also exhibit a small change in length expansion and thus in the differential CTE over this range. It can be seen from Figure 9 It can be seen from Table 1 that the advantageous embodiments of the application also exhibit a flat expansion curve over an even larger temperature range (here exemplified by 0°C to 65°C). The expansion behavior can also be considered in other selected temperature ranges, in particular in the temperature ranges (0; 80), (0; 100), (-10; 30), (20; 40), (20; 70), etc., which will be further illustrated below.

[0189] Glass-ceramics with a flatly shaped dilatation curve have great advantages, because such precise components can not only be optimized for the subsequent application temperature, but also exhibit equally low thermal expansion under higher and / or lower temperature stresses, for example, during the manufacturing process. Precise components for microlithography, EUV microlithography (also referred to simply as "EUV lithography" or "EUVL") and metrology are usually used under the conditions of a standard clean room, in particular at room temperature of 22°C. The CTE can be adapted to this application temperature. However, these components need to be subjected to various process steps, for example, metal layer coating, cleaning, structuring and / or exposure processes, in which temperatures can occur which are higher or in some cases lower than the temperatures employed in the subsequent clean room for the application. Therefore, advantageous glass-ceramics and precise components made thereof, which exhibit a parameter F of less than 1.10 and thus exhibit optimized zero expansion not only at the application temperature, but also at higher and / or lower temperatures during the manufacturing process, are of great advantage. If precise components or glass-ceramics are used in EUV lithography, i.e. if the precise components are, for example, EUVL mirrors or EUVL mask substrates or corresponding substrates therefor, properties such as no hysteresis and a parameter F < 1.10 are particularly advantageous, because in EUV lithography the mirrors or masks are heated very non-uniformly due to the irradiation with high-energy radiation, in particular at certain points or in the beam direction. For such working conditions, it is advantageous if the precise components or glass-ceramics have a lower CTE-T curve slope (see below) in the temperature range around the application temperature.

[0190] The advantageous glass-ceramics and precise components can be better optimized for a subsequent application temperature of 20°C or 22°C, characterized in that the relative length change (dl / lo) is ≤ |0.10| ppm, preferably ≤ |0.09| ppm, particularly preferably ≤ |0.08| ppm, especially preferably ≤ |0.07| ppm in the temperature range from 20°C to 30°C and / or the relative length change (dl / lo) is ≤ |0.17| ppm, preferably ≤ |0.15| ppm, particularly preferably ≤ |0.13| ppm, especially preferably ≤ |0.11| ppm in the temperature range from 20°C to 35°C. Alternatively or additionally, such optimized glass-ceramics and precise components are characterized in that the relative length change (dl / lo) is ≤ |0.30| ppm, preferably ≤ |0.25| ppm, particularly preferably ≤ |0.20| ppm, especially preferably ≤ |0.15| ppm in the temperature range from 20°C to 40°C. The relative length change characteristics in relation to the different temperature intervals can preferably be obtained from the dl / lo curve of Figures 7 to 9 When the relative length change (dl / lo) is mentioned, the index naturally refers to the absolute value of the respective value.

[0191] A zero-expansion, hysteresis-free material with such advantageous expansion properties is particularly suitable for use as a substrate for an EUVL mirror or as an EUVL mirror, which, during operation, is heated to different extents in bright and dark regions, for example, as a result of the influence of individual exposure masks. Due to the above-mentioned lower relative length change, an EUVL mirror formed from the advantageous glass-ceramic exhibits a lower local gradient (local gradient or local slope) in the topography of the mirror surface than an EUVL mirror produced from a known material. The same applies to an EUVL mask blank or an EUVL mask or an EUVL photomask.

[0192] In particular for glass-ceramics whose expansion curve is very flat, close to 0 ppm or fluctuates around 0 ppm in the temperature range considered - which is generally an advantageous expansion property - it is advantageous to introduce another method for measuring the flatness of the expansion curve as an alternative or in addition to the parameter F, in which the expansion curve is not in the temperature range (0; 50) but in another temperature interval (T.i.), preferably in the temperature ranges (0; 80), (0; 100), (20; 40), (20; 70) and / or (-10; 30). This allows a better classification of the expansion properties depending on the subsequent field of application.

[0193] Instead of the parameter f T.i. with the unit (ppm / K), which is defined as:

[0194] f T.i . = TCL (T.i.) / temperature interval (T.i.) width (4)

[0195] where T.i. describes the respective temperature interval considered.

[0196] TCL (T.i.) is the distance between the maximum and minimum dl / l0 values in the respective temperature range (T.i.) considered, wherein the expansion curve is also normalized according to the definition of TCL (T.i.) , so that the length change at 0°C is 0 ppm. For example:

[0197] TCL (20； 40℃) = |dl / l0 max| + |dl / l0 min| (5)

[0198] where "dl" denotes the length change at the respective temperature and "l0" denotes the length of the test specimen at 0°C. The calculation is based on the absolute values of the dl / l0 values.

[0199] By obtaining TCL (T.i.)The quotient of the value [in ppm] (see above) and the width [in K] of the temperature interval (T.i.) replaces the parameter f according to formula (4) T.i. where the difference in expansion is taken into account. The width of the temperature interval considered between 20°C and 40°C is 20 K. On the other hand, if the trend of the expansion curve is considered within the interval T.i. = (20; 70) or (-10; 30), the divisor of formula (4) is 50 K or 40 K, respectively.

[0200] In an advantageous embodiment, the glass-ceramic has a replacement parameter f (20；40) <0.024 ppm / K and / or the replacement parameter f (20；70) <0.039 ppm / K and / or the replacement parameter f (-10；30) <0.015 ppm / K.

[0201] Glass-ceramics whose expansion curve has a very gentle trend are very advantageous, because now not only can the precision parts be optimized according to the subsequent application temperature, but also, for example, according to the expected higher and / or lower temperature stresses. The replacement parameter f T.i. are suitable for determining suitable materials according to the required criteria for certain component applications, and for providing corresponding precision parts. Special precision parts and their applications will be presented below and are included here.

[0202] According to advantageous embodiments of the glass-ceramics or of the parts made therefrom, if the replacement parameter f (20；40) <0.024 ppm / K, preferably <0.020 ppm / K, preferably <0.015 ppm / K, are advantageous. Non-retarded, zero-expansion parts having such expansion properties in the temperature range (20; 40) are particularly suitable as precision parts for microlithography and EUV microlithography at room temperature. Figure 9 Examples of such advantageous glass-ceramics are shown.

[0203] According to advantageous embodiments of the glass-ceramics or of the parts made therefrom, if the replacement parameter f (20；70) <0.039 ppm / K, preferably <0.035 ppm / K, preferably <0.030 ppm / K, preferably <0.025 ppm / K, preferably <0.020 ppm / K, are advantageous. Non-retarded, zero-expansion parts having such expansion properties in the temperature range (20; 70) are also particularly suitable as precision parts for microlithography and EUV microlithography. It is particularly advantageous if the parts also exhibit equally low thermal expansion under higher temperature stresses that can occur locally or over the entire area, for example, during the production of the precision parts and also during operation. Further details regarding the temperature stresses occurring in EUVL precision parts have already been described above in connection with the parameter F, and are referred to here for the avoidance of repetition.Figure 7 Examples of such advantageous glass-ceramics are shown.

[0204] According to advantageous embodiments of the glass-ceramics or of the parts made thereof, if the substitution parameter f (-10；30) <0.015 ppm / K, preferably <0.013 ppm / K, preferably <0.011 ppm / K, is advantageous. Non-hysteresis, zero-expansion parts having such expansion properties in the temperature range (-10; 30) are particularly suitable as precision parts, especially as mirror substrates in applications where temperatures can be below room temperature, for example as mirror substrates for astronomy or space-to-ground observation. Corresponding parts will be presented below.

[0205] Particularly advantageous embodiments of the glass-ceramics or of the parts made thereof have an expansion curve with a parameter F and at least one substitution parameter f (T.i.) is applicable to this expansion curve.

[0206] Particularly advantageous embodiments of the glass-ceramics or of the parts made thereof have an expansion curve with a parameter F and at least one substitution parameter f (T.i.) is applicable to this expansion curve.

[0207] CTE plateau

[0208] Figures 1 to 4 Advantageous embodiments of LAS glass-ceramics and precision parts are shown to exhibit a CTE plateau. Glass-ceramics having a plateau, i.e. an optimized zero-expansion over a wider temperature range, have the same advantages as mentioned in the above description related to the flat course of the expansion curve and the parameter F.

[0209] If the differential CTE exhibits a plateau close to 0 ppm / K, i.e. the differential CTE is less than 0 ± 0.015 ppm / K in a temperature interval T P with a width of at least 40 K or at least 50 K or at least 60 K or at least 70 K, is advantageous. The temperature interval of the CTE plateau is denoted by T P . Advantageously, the differential CTE can be less than 0 ± 0.010 ppm / K or less than 0 ± 0.005 ppm / K in a temperature interval T P with a width of at least 40 K or at least 50 K.

[0210] The CTE plateau is thus understood as a region extending over a section of the CTE-T curve, wherein the differential CTE does not exceed a value of 0 ± 0.015 ppm / K or 0 ± 0.010 ppm / K or 0 ± 0.005 ppm / K, i.e. the CTE is close to 0 ppb / K.

[0211] Advantageously, the differential CTE can be less than 0 ± 0.010 ppm / K or less than 0 ± 0.005 ppm / K in a temperature interval T PIn particular, the differential CTE can 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) can be formed over a temperature interval of at least 50 K.

[0212] It can be advantageous for the temperature interval T P ranges from -10°C to +100°C or 0 to 80°C or 15°C to 80°C.

[0213] Preferably, the position of the CTE plateau of the glass-ceramic is adapted to the application temperature T A such that T P = T A ± x, x being 20, 25, 30 or 40. Preferred application temperatures T A range from -60°C to +100°C, more preferably from -40°C to +80°C. Particular variants of the application relate to precision parts and glass-ceramics for the following application temperatures T A 0°C, 5°C, 10°C, 22°C, 40°C, 60°C, 80°C and 100°C. The CTE plateau, i.e. the region of the curve where the differential CTE is less, can also be in the temperature range [-10; 100], [0; 80], [0; 30°C], [10; 40°C], [20; 50°C], [30; 60°C], [40; 70°C] and / or [50; 80°C]. P

[0214] Example 4 in Table 1, Figure 1 shows that the CTE of this glass-ceramic is 0 ± 0.010 ppm / K over a temperature range of 15°C to 90°C, i.e. presents a 10-ppb plateau with a width of 75 K. The CTE of this glass-ceramic is even 0 ± 0.005 ppm / K over a temperature range of 17°C to 85°C, i.e. presents a 5-ppb plateau with a width close to 70 K.

[0215] For Example 2 in Table 1, Figure 2 shows that the CTE of the glass-ceramic is 0 ± 0.010 ppm / K over a temperature range of 12°C to 90°C, i.e. presents a 10-ppb plateau with a width of 78 K.

[0216] For Example 2, Figure 3 shows that the glass-ceramic has an optimized CTE plateau in the range -10°C to 23°C, with a CTE of 0 ± 0.005 ppm / K, i.e. presents a 5-ppb plateau.

[0217] For Example 6 in Table 1, Figure 4 ​The glass-ceramic shows a CTE of 0 ± 0.005 ppm / K in the range relevant for EUV lithography between 15 °C and 30 °C, i.e. a 5-ppb plateau is exhibited. This glass-ceramic complies with the requirements for the average CTE (19; 25) of EUVL substrates and blanks in the SEMI P37-1109 standard. The zero-crossing of the CTE-T curve is at 22 °C.

[0218] Another measure for a beneficial thermal expansion is the slope of the CTE-T curve, which can be obtained by differentiating the CTE-T curve. According to advantageous embodiments of the present application, the CTE-T curve of the glass-ceramic or precision part thus has at least one curve segment with a low slope, in particular a slope of at most 0 ± 1.5 ppb / K 2 , advantageously at most 0 ± 1.0 ppb / K 2 , advantageously at most 0 ± 0.8 ppb / K 2 , preferably at most 0.7 ppb / K 2 , preferably at most 0.6 ppb / K 2 , according to a special variant even at most only 0.5 ppb / K 2 .

[0219] Preferably, the low-slope temperature interval is adapted to the application temperature T A of the precision part, such that T P = T A ± x, x being 10, 15, 20, 25, 30 or 40. Preferred application temperatures T A range from -60 °C to +100 °C, more preferably from -40 °C to +80 °C. Special variants of the present application relate to glass-ceramics and precision parts with an application temperature T A of 0 °C, 5 °C, 10 °C, 22 °C, 40 °C, 60 °C, 80 °C and 100 °C. The low-slope temperature interval can also be in the temperature range 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].

[0220] Figures 10 to 12 The slope of the CTE-T curve of the advantageous glass-ceramics according to examples 4, 2 and 5 is shown in the temperature range from -10 °C or 5 °C to 45 °C. The CTE slope is below 0 ± 1.0 ppb / K 2 over the entire temperature range.

[0221] Figure 13 The slope of the CTE-T curve of a glass-ceramic with the same composition as example 9 is shown in the temperature range from -5 °C to 45 °C, which is cerammed to have an average CTE [0; 50 °C] of -0.009 ppm / K.

[0222] Glass-ceramics and precision parts having such expansion properties are particularly suitable for EUV lithography applications (e.g. as mirrors or mirror substrates or masks or mask blanks) since in this field the requirements for materials for optical components and precision parts are increasing, involving very low thermal expansion, zero-crossing of the CTE-T curve in the vicinity of the application temperature and, in particular, low slope of the CTE-T curve. Within the scope of the present application, advantageous embodiments of the glass-ceramics or precision parts exhibit a very flat CTE curve, wherein the curve shows both a zero-crossing and a very low CTE slope and possibly a very flat plateau as well.

[0223] The low slope feature can be present, whether or not an advantageous CTE plateau is formed.

[0224] Further properties

[0225] The advantageous glass-ceramics and precision parts made thereof also exhibit a good internal quality. Preferably, per 100 cm 3 have at most 5 inclusions, more preferably per 100 cm 3 have at most 3 inclusions, most preferably per 100 cm 3 have at most 1 inclusion. According to the present application, inclusions are to be understood as bubbles and microcrystals having a diameter of more than 0.3 mm.

[0226] According to a variant of the present application, the precision parts provided have a diameter or edge length of at most 800 mm, a thickness of at most 100 mm and per 100 cm 3 have at most 5, preferably at most 3, more preferably at most 1 inclusions having a diameter of more than 0.03 mm.

[0227] In addition to the number of inclusions, the maximum diameter of the detected inclusions can also be used as a measure of the internal quality. For glass-ceramics having a diameter of less than 500 mm, the maximum diameter of the individual inclusions in the total volume is preferably at most 0.6 mm, while in the volume which is of importance for the application, for example in the vicinity of the surface, the maximum diameter of the individual inclusions is preferably at most 0.4 mm. For precision parts having a diameter of 500 mm to less than 2 m, the maximum diameter of the individual inclusions in the interior is preferably at most 3 mm, while in the volume which is of importance for the application, for example in the vicinity of the surface, the maximum diameter of the individual inclusions is preferably at most 1 mm.

[0228] The present application also relates to the use of the glass-ceramics according to the present application for precision parts. For example, the glass-ceramics can form a substrate for a precision part or represent the precision part itself.

[0229] All properties and ranges of the above glass-ceramics also apply to precision parts comprising or consisting of the glass-ceramics.

[0230] Furthermore, the present application also relates to the use of the glass-ceramics according to the present application in precision parts, in particular in metrology, spectroscopy, measurement technology, lithography, astronomy or space-to-earth observation, for example, as mirror or mirror substrate of a segmented or monolithic astronomical telescope, or as weight-reducing mirror substrate or ultra-light mirror substrate of a space-based telescope; or as high-precision structural part for distance measurement, for example, in the field of space or for earth observation, as precision part for precision measurement technology, precision scales, reference plate within an interferometer, as mechanical precision part, for example, ring laser gyroscope, coil spring for the watch industry, mirrors and prisms in LCD lithography; for example, as mask holder, wafer table, reference plate, reference reference system and grid plate in micro-lithography and EUV (extreme ultraviolet) micro-lithography, and additionally as mirror or mirror substrate and / or photomask substrate or mask blank in EUV micro-lithography.

[0231] Precision parts of different sizes can be produced using the glass-ceramics according to the present application:

[0232] One embodiment relates to precision parts of smaller size, in particular (straight) angular parts with edge length (width and / or depth) or circular surface parts with a diameter of at least 100 mm and / or at most 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 precision parts can be used, for example, in micro-lithography and EUV lithography.

[0233] Another embodiment relates to precision parts of very small size, in particular parts with an edge length (width and / or depth) or diameter and / or thickness of a few millimeters (for example, 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 tenths of a millimeter (for example, at most 0.7 mm or at most 0.5 mm). For example, these precision parts can be spacers in interferometers or parts for ultra-stable clocks in quantum technology.

[0234] However, large precision parts can also be produced. Thus, one embodiment of the present application relates to large-volume parts. For the present application, this is to be understood as meaning parts having a mass of 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, according to one variant of the application at least 5 t; or (straight) angular parts having an edge 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 circular parts 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. For the special embodiment of the present application, it is also possible that larger parts are produced, for example, having a diameter of at least 3 m or at least 4 m or more. According to one variant, the present application also relates to rectangular parts, wherein preferably at least one surface has an area of at least 1 m 2 , preferably at least 1.2 m 2 , more preferably at least 1.4 m 2 . Generally, large-volume parts produced have a base area which is much larger than the height. However, it is also possible that large-volume parts having approximately cubic or spherical shapes are produced.

[0235] For example, the precision part can be an optical part, i.e. a so-called normal-incidence mirror (i.e. a mirror which works at near-vertically incident radiation) or a so-called grazing-incidence mirror (i.e. a mirror which works at grazingly incident radiation). In addition to the substrate, such a mirror comprises a coating which reflects the incident radiation. In particular in the case of X-ray radiation mirrors, the reflective coating is a multilayer system or a multilayer in a multilayer system which has a high reflectivity in the X-ray range under non-grazing incidence conditions. Preferably, the multilayer system of such a normal-incidence mirror comprises 40 to 200 layer pairs, consisting of alternating layers of one of the material pairs Mo / Si, Mo / Bi, Ru / Si and / or MoRu / Be, for example.

[0236] In particular, the optical element according to the present application can be an X-ray optical element, i.e. an optical element which is used in combination with X-ray radiation (in particular soft X-ray radiation) or EUV radiation (in particular a mask or photomask which operates in reflection, in particular for EUV microlithography). Advantageously, the optical element can be a mask blank. Furthermore, the precision part can advantageously be used as a mirror for EUV lithography or as a substrate for a mirror for EUV lithography.

[0237] Furthermore, the precision part according to the present application can be a part, in particular a mirror, for astronomical applications. Such astronomical application parts can be used both on the ground and in space. Another advantageous field of application is high-precision structural parts for distance measurement, for example in space.

[0238] The precision component according to the present application can be a lightweight structure. The component according to the present application can also comprise a lightweight structure. This means that in certain areas of the component, cavities are provided in order to reduce the weight. Preferably, the weight of the component is reduced by at least 80%, more preferably by at least 90% by lightweight processing compared to the unprocessed component.

[0239] The present application also relates to a precision component comprising the LAS glass-ceramic according to the present application. Details in this regard have been described above in connection with the glass-ceramic and its use in precision components. This disclosure is fully incorporated into the description of the precision component.

[0240] It is to be understood that the features mentioned above and those to be explained below can be used not only in the respective combinations indicated, but also in other combinations or in isolation without departing from the scope of the present application.

[0241] Example

[0242] Tables 1 to 4 list the compositions of the glass-ceramic examples according to the present application, the compositions of comparative examples and their properties.

[0243] These compositions were produced by melting commercial raw materials such as oxides, carbonates and nitrates using conventional manufacturing processes. The produced raw glasses were first cerammed at the respective specified maximum temperature for the specified time.

[0244] For example, the production process of a glass-ceramic for precision components, in particular large precision components, is described in WO 2015 / 124710 A1.

[0245] If the field for the information on the components in the following tables is empty, this means that this component was not intentionally added or was not contained. The table shows the absolute value of the hysteresis.

[0246] Table 1: Compositions (in mol%), ceramming and properties

[0247]

[0248]

[0249] Table 2: Compositions (in mol%), ceramming and properties

[0250]

[0251]

[0252] Table 3: Compositions (in mol%), ceramming and properties

[0253]

[0254]

[0255] Table 4: Composition (in mol%), ceramicization and properties

[0256]

[0257]

Claims

1. A LAS glass-ceramic, characterized in that, Its average coefficient of thermal expansion (CTE) in the temperature range of 0–50℃ is at most 0 ± 0.02 × 10⁻⁶. -6 / K, and with a thermal hysteresis of <0.1ppm in a temperature range of at least 10–35°C, and including the following components in mol% of oxides: At least one component selected from the group consisting of P2O5 and RO, wherein RO can be CaO and / or BaO and / or SrO; and The nucleating agent has a content of 1.5 to 6 mol%, wherein the nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, and WO3.

2. The LAS glass-ceramic according to claim 1, characterized in that, Includes the following components, expressed as mol% of oxides: At least one component selected from the group consisting of P2O5 and RO, wherein RO can be CaO and / or SrO; and The nucleating agent has a content of 1.5–6 mol%, wherein the nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, and WO3. Alternatively, the LAS glass-ceramic comprises the following components in mol% of oxides: At least one component selected from the group consisting of P2O5 and RO, wherein RO can be CaO and / or BaO and / or SrO; and The nucleating agent has a content of 1.5–6 mol%, wherein the nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, and WO3. Alternatively, the LAS glass-ceramic comprises the following components in mol% of oxides: At least one component selected from the group consisting of P2O5 and RO, wherein RO can be CaO and / or SrO; and The nucleating agent has a content of 1.5 to 6 mol%, wherein the nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoO3, and WO3.

3. The LAS glass-ceramic according to claim 1, wherein, The LAS glass-ceramic contains 10–22 mol%, preferably 11–21 mol%, of Al₂O₃ and / or 0.1–6 mol%, preferably 0.3–5 mol%, of P₂O₅. Preferably, wherein, -If the molar content of Al2O3 is <17.0 mol%, and preferably ≥15.8 mol%, then -SiO2 content is 63.5 mol% to 65.6 mol%, and - Satisfies: 30.7 ≤ (molar content of SiO2 - (molar content of 2 × Al2O3)); or -If the molar content of Al2O3 is ≥17.0 mol% and preferably ≤19.0 mol%, then -SiO2 content is 62.0 mol% to 66.0 mol%, and - Satisfies: 142.5≤(molar content of SiO2+(4.6×molar content of Al2O3))≤149.

0.

4. The LAS glass-ceramic according to claim 1, wherein, The total content of ZnO and MgO is ≤0.2 mol%, ≤0.1 mol%, or ≤0.05 mol%, and / or the content of MgO is ≤0.4 mol%, ≤0.2 mol%, ≤0.1 mol%, or ≤0.05 mol%, and / or the content of ZnO is ≤0.4 mol%, ≤0.2 mol%, ≤0.1 mol%, or ≤0.05 mol%, and / or the LAS glass-ceramic does not contain ZnO and / or MgO, and / or Wherein, the total content of the nucleating agent is ≥1.5 mol%, preferably ≥2.5 mol%, advantageously ≥3 mol% and / or ≤6 mol%, advantageously ≤5 mol%, preferably ≤4.5 mol%, preferably ≤4 mol%, and / or The LAS glass-ceramic contains up to 0.05 mol% As₂O₃ as a clarifying agent, and / or The LAS glass-ceramic contains a substitute for As2O3 as a clarifying agent, or, in addition to a maximum of 0.05 mol% of As2O3, contains at least one optional redox clarifying agent and / or at least one evaporation clarifying agent and / or at least one decomposition clarifying agent; and / or wherein the optional redox clarifying agent is at least one component selected from the group consisting of Sb2O3, SnO2, MnO2, CeO2, and Fe2O3; and / or wherein the evaporation clarifying agent includes a halogen having a clarifying effect; and / or wherein the decomposition clarifying agent includes a sulfate component.

5. The LAS glass-ceramic according to claim 1, wherein the total length variation TCL of the LAS glass-ceramic is TCL(0; 50) < 0.2 or TCL(0; 50) < 0.

1.

6. The LAS glass-ceramic according to claim 1, wherein the differential CTE of the LAS glass-ceramic exhibits a plateau near 0 ppm / K, that is, within a temperature range TP with a width of at least 40 K or at least 50 K, its differential CTE is less than 0 ± 0.010 ppm / K or less than 0 ± 0.005 ppm / K.

7. The LAS glass-ceramic according to claim 1, wherein, The temperature range TP is within the range of -10℃ to +100℃, or 0℃ to 80℃, or 15℃ to 80℃, and / or Specifically, within a temperature range TP with a width of at least 30 K, the slope of the CTE-T curve is at most ±1 ppb / K. 2 .

8. The LAS glass-ceramic according to claim 1, wherein, The processing temperature Va is a maximum of 1330°C, preferably a maximum of 1320°C, and / or Specifically, the slope of the CTE-T curve is ≤0±2.5ppb / K within a temperature range of at least 30K. 2 Preferred density ≤0±2ppb / K 2 Preferred concentration: ≤0±1.5 ppb / K 2 ≤0±1ppb / K 2 .

9. The LAS glass-ceramic according to claim 1, wherein, The thermal hysteresis of the LAS glass-ceramic is <0.1 ppm, at least in the temperature range of 5 to 45°C, advantageously at least in the temperature range of >0 to 45°C, and preferably at least in the temperature range of -5 to 50°C.

10. A precision component comprising LAS glass-ceramic according to any one of claims 1 to 9, said precision component being used in metrology, spectroscopy, measurement technology, photolithography, astronomy, or space-based Earth observation, for example, as a mirror or mirror substrate for segmented or integrated astronomical telescopes, or as a weight-reducing mirror substrate or ultralight mirror substrate for space-based telescopes; or as a high-precision structural component for distance measurement, such as in optical systems for space applications or for Earth observation, as a precision component for reference in precision measurement technology, a precision scale, a reference plate within an interferometer, as a precision mechanical part, such as a ring laser gyroscope, a helical spring for the watchmaking industry, a mirror and prism in LCD photolithography; for example, as a mask holder, wafer stage, reference plate, reference reference system, and grid plate in microlithography and EUV microlithography, and as a mirror and / or photomask substrate or mask blank in EUV microlithography.

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