Isothermally long-term stable glass-ceramic component

Abstract

The present invention relates to an isothermally long-term stable glass-ceramic component as well as a process for producing such a glass-ceramic component and the use of such a component.

Description

[0001] Isothermally Long-Term Stable Glass-Ceramic Component

[0002] The present invention relates to an isothermally long-term stable glass-ceramic component as well as a method for manufacturing such a glass-ceramic component and the use of such glass-ceramic component.

[0003] Background of the Invention

[0004] Materials and components with low thermal expansion or low CTE (Coefficient of Thermal Expansion) are already known in the state of the art.

[0005] Ceramics, Ti-doped fused silica, and glass-ceramics are known as materials for components with low thermal expansion in the temperature range around room temperature. Glassceramics with low thermal expansion are particularly lithium-aluminum-silicate glassceramics (LAS glass-ceramics), which are described for example in US 4,851,372, US 5,591,682, EP 587979 A, US 7,226,881, US 7,645,714, DE 102004008824 A, DE 102018111144 A. Other materials for precision components are cordierite ceramics or cordierite glass-ceramics.

[0006] These materials are often used for precision components that must meet particularly strict requirements regarding their properties (e.g., mechanical, physical, optical properties). They are used especially in terrestrial and space-based astronomy and earth observation, flat panel display lithography, microlithography and EUV lithography, metrology, spectroscopy, and measurement technology. In these applications, it is necessary that the components, depending on the specific application, exhibit particularly low thermal expansion.

[0007] Thermal Expansion

[0008] In general, the determination of the thermal expansion of a material is carried out by a static method, in which the length of a test specimen is determined at the beginning and at the end of the specific temperature interval, and the mean expansion coefficient a or mean CTE (Coefficient of Thermal Expansion) is calculated from the length difference. CTE or a is then given as an average for this temperature interval, e.g., for the temperature interval from 0°C to 50°C as CTE(0;50) or a(0;50).

[0009] In addition to determining the mean CTE, the thermal expansion of a test specimen can also be determined in very small temperature intervals and then presented as a CTE-T curve. Preferably, such a CTE-T curve can have a zero crossing at one or more temperatures, preferably at or near the designated application temperature of a low thermal expansion component. At a zero crossing of the CTE-T curve, the relative change in length with temperature change is particularly low. For some glass-ceramics, such a zero crossing of the CTE-T curve can be shifted to the application temperature of the respective component by appropriate heat treatment. In addition to the absolute CTE value, the slope of the CTE-T curve around the application temperature should also be as low as possible to cause as little length change of the component as possible with slight temperature changes.

[0010] Thermal Hysteresis

[0011] A disadvantageous effect in known materials, especially in glass-ceramics such as LAS glass-ceramics, is the so-called "thermal hysteresis", hereinafter referred to simply as "hysteresis". Here, hysteresis means that the length change of a test specimen during heating at a constant heating rate differs from the length change of the test specimen during subsequent cooling at a constant cooling rate, even if the magnitude of the cooling rate and heating rate are the same. If the length change of the test specimen is graphically represented as a function of temperature for heating and cooling, a classic hysteresis loop results. The extent of the hysteresis loop also depends on the rate of temperature change. The faster the temperature change occurs, the more pronounced the hysteresis effect. The hysteresis effect underlines that the thermal expansion of an LAS glass-ceramic depends on temperature and time, i.e., for example, on the rate of temperature change, which has also been described occasionally in the technical literature, e.g., O. Lindig and W. Pannhorst, "Thermal expansion and length stability of ZERODUR® in dependence on temperature and time", APPLIED OPTICS, Vol. 24, No. 20, Oct. 1985; R. Haug et al., "Length variation in ZERODUR® M in the temperature range from -60°C to +100°C", APPLIED OPTICS, Vol. 28, No.19, Oct. 1989; R. Jedamzik et al., "Modeling of the thermal expansion behavior of ZERODUR® at arbitrary temperature profiles", Proc. SPIE Vol. 7739, 2010; D.B. Hall, "Dimensional stability tests over time and temperature for several low-expansion glass ceramics", APPLIED OPTICS, Vol. 35, No. 10, April 1996.

[0012] 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 from it shows a disruptive isothermal length change, i.e., a length change of the material occurs even after a temperature change at the time when the temperature is already held constant (so-called "isothermal holding"), until a steady state is reached. Thermal hysteresis-induced length changes are generally relaxed within a day. When the material is subsequently reheated and cooled, the same effect occurs again. This problem has been overcome for some LAS glass-ceramics, as hysteresis-free glassceramics with low thermal expansion are described in US 2022 / 0298079 A1, US 2022 / 0298062 A1 and WO2022 / 194846 A1. In the context of these applications, it was recognized that the components MgO and ZnO promote the occurrence of thermal hysteresis, and it is therefore essential to limit the content of MgO and ZnO to provide an LAS glass-ceramic that is hysteresis-free in the temperature range of 10°C to 35°C and beyond.

[0013] Isothermal Long-Term Stability

[0014] While thermal hysteresis is an effect that occurs relatively soon after a preceding heating, a very slight isothermal long-term length change can also occur independently of any heating of the material, i.e. when the material is held at constant temperature (isothermal holding) for very long periods of time such as several months or even several years. The extent of such long-term length change is described as isothermal long-term stability or long-term shrinking or contraction or long-term expansion. For ZERODUR®, for example, a relative length decrease depending on the age of the material between -0.69 x l0‘6 / a and -0.03 x l0'6 / a is known, with ZERODUR® initially i.e. in the first months and years after production showing a relatively high relative length decrease of -0.69 x l0'6 / a (see also Fig. 2) and the relative length decrease only reaching a low value of -0.03 x l0'6 / a at an age of 10 years. This isothermal long-term length change can be described using mathematical functions, see e.g. "Length stability at room temperature of samples of the glass ceramic ZERODUR®", F. Bayer, H. Darnedde, G. Exner, Metrologia 21, 49-57 (1985). For most applications, even precision applications, such a slight isothermal long-term length change is not relevant.

[0015] For some applications, however, it is desirable that the materials and / or precision components not only have low thermal expansion (CTE) and are free of hysteresis, but also exhibit isothermal long-term stability, within at most months after the production of the glassceramic. Until now, it was assumed that the isothermal long-term stability of an LAS glassceramic could not be influenced.

[0016] Thus, it is an object of the present invention to provide a low thermal expansion glassceramic and / or glass-ceramic component that does not exhibit isothermal long-term volume change or length change, as well as a method for manufacturing such a glass-ceramic component.

[0017] This object is solved by the embodiments described in the claims. A glass-ceramic component is provided which has the following properties:

[0018] - mean thermal expansion coefficient in the range of 0 to 50°C CTE(0;50) of at most 0 ± 0.1 x 10’6 / K,

[0019] - thermal hysteresis of < 0.1 ppm at least in the temperature range of 15°C to 35°C,

[0020] - relative isothermal long-term length change of < 0.06 ppm / a, preferably < 0.05 ppm / a, more preferably < 0.04 ppm / a or < 0.03 ppm / a, measured at an age of the glass-ceramic of at least 200 days and at most 6 years.

[0021] Glass-ceramics are understood here to be inorganic, non-porous materials with a crystalline phase and a glassy phase, where typically the matrix, i.e. , the continuous phase, is a glass phase in which the crystallites of the crystal phase are embedded. The relevant properties of a glass-ceramic are explained by this special structure.

[0022] Lithium-aluminum-silicate (LAS) glass-ceramics contain a negatively expanding crystal phase, the so-called high quartz solid solution, also called B-eucryptite, and a positively expanding glass phase. With a suitable composition of glass and crystal phase, the positive expansion of the glass phase and the negative expansion of the crystal phase can cancel each other out and form a glass-ceramic with overall extremely low thermal expansion.

[0023] The high quartz solid solution is a metastable phase that changes its composition and / or structure depending on the crystallization conditions or transforms into another crystal phase. In addition to SiO2 and AI2O3, U2O is a main component of the high quartz solid solution. If present, ZnO and / or MgO are also incorporated into the high quartz solid solution phase and, together with U2O, influence the expansion behavior of the crystal phase. It is suspected that thermal hysteresis is caused by short-term relaxation processes of MgO, ZnO and / or U2O, with these relaxation processes normally being completed within a day. In the glass-ceramics described in US 2022 / 0298079 A1 and US 2022 / 0298062 A1, ZnO and MgO are completely or largely replaced by phosphate P2O5, alkali metal oxides R2O (with R = Na, K, Rb, Cs) and / or alkaline earth metal oxides RO (with R = Ba, Ca, Sr).

[0024] Without wishing to be bound by theory, the long-term length change of LAS glass-ceramics is explained by more complex relaxation or rearrangement processes within the glass phase and / or between glass and crystal phases, which are different from the short-term relaxation processes responsible for hysteresis. It is assumed that various different relaxation processes occur in the glass-ceramic on a molecular level over several years that may lead to a very slight long-term length change even if the glass-ceramic is kept under isothermal conditions. In an investigation of the hysteresis-free glass-ceramics with zero expansion from US 2022 / 0298079 A1 and US 2022 / 0298062 A1 , the inventors surprisingly found that these glass-ceramics do not exhibit an isothermal long-term shrinkage like the very similar glassceramic ZERODUR®, instead an isothermal long-term length increase was observed. Just like the isothermal long-term shrinkage of ZERODUR®, however, an increase in volume is not desirable for certain high-precision components.

[0025] While all attempts to prevent isothermal long-term shrinkage in ZERODUR® have failed, the inventors have surprisingly succeeded in modifying the ceramization process for the glassceramics known from US 2022 / 0298079 A1 and US 2022 / 0298062 A1 in such a way that the resulting glass-ceramics not only have low thermal expansion and are free of hysteresis, but also show no or only very slight isothermal long-term length change.

[0026] A method is thus also provided by which the inventive glass-ceramic component can be manufactured, and which comprises the following steps:

[0027] (1) Heating a green glass of a glass-ceramic to a ceramization temperature TK,

[0028] (2) Holding the green glass at the ceramization temperature TK while ceramizing the green glass and obtaining the glass-ceramic,

[0029] (3) Cooling the glass-ceramic at a cooling rate ATi to a holding temperature TH,

[0030] (4) Holding the glass-ceramic at a holding temperature TH, where 50°C < TH 150 °C, preferably 60°C < TH £ 100 °C, for a holding time tH,

[0031] (5) Cooling the glass-ceramic to room temperature at a cooling rate AT2.

[0032] Furthermore, the use of the inventive glass-ceramic component as a precision component is provided.

[0033] Further preferred embodiments and variants of the invention are described in the following.

[0034] Short Description of the Figures

[0035] Figure 1 schematically shows a temperature-time curve according to the inventive method for ceramizing a glass-ceramic or glass-ceramic component.

[0036] Figure 2 shows measurement results of a sample according to Example 1 in comparison with ZERODUR® and a glass-ceramic from US 2022 / 0298079 (Comp. Example 1a). While ZERODUR® shows a long-term length shrinkage and the glass-ceramic component shows a long-term expansion according to US 2022 / 0298079, the glass-ceramic component according to the invention proved to be isothermally long-term stable after already a few months after production.

[0037] Detailed Description of the Invention

[0038] Isothermal Long-Term Stability

[0039] An isothermally long-term stable component is understood to be a component which exhibits only a very small change in length or volume when held (or kept or stored) at essentially constant temperature, i.e., under isothermal conditions. Such an isothermal volume change is measured with test specimens as a long-term length change of said test specimen. Therefore, an isothermal volume change is generally measured and referred to as an isothermal long-term length change, i.e., both terms are used synonymously whereas a volume change would be a length change in more than one dimension.

[0040] Isothermal in this context means that the glass-ceramic components are kept or held at a constant temperature, i.e. the ambient temperature preferably only deviates or fluctuates by a maximum of ±3 K or a maximum of ±2 K or a maximum of ±1 K.

[0041] The inventive glass-ceramic components are isothermally long-term stable, i.e., they exhibit a relative isothermal long-term length change of < 0.06 ppm / a, preferably < 0.05 ppm / a, more preferably < 0.04 ppm / a or < 0.03 ppm / a, measured at an age of the glass-ceramic component of at least 200 days and at most 6 years.

[0042] Preferably, the glass-ceramic components exhibit a relative isothermal long-term length change of < 0.06 ppm / a, preferably < 0.05 ppm / a, more preferably < 0.04 ppm / a or < 0.03 ppm / a, measured at an age of the glass-ceramic of at least 100 days and at most 6 years.

[0043] The relative isothermal long-term length change can also be measured in a shorter period of time, for example after 3 or 6 months, and extrapolated to 12 months. Preferably, however, the relative isothermal length change is measured over a period of at least 12 months 1 1 year in order to obtain a more reliable value with regard to the measurement inaccuracies.

[0044] Of course, the glass-ceramic components also exhibit a relative isothermal long-term length change of < 0.06 ppm / a, preferably < 0.05 ppm / a, more preferably < 0.04 ppm / a or < 0.03 ppm / a at an age of more than 6 years or more than 7 years or more than 10 years.

[0045] The isothermal long-term stability depends on the "age" of the glass-ceramic. The "age of a glass-ceramic" is understood to be the time that has elapsed after production, in particular, after completion of the ceramization process including cooling of the glass-ceramic to room temperature. A glass-ceramic upon reaching room temperature after the temperature treatment as part of the ceramization process thus has an age of 0. The same applies to a glass-ceramic component made from such a glass-ceramic.

[0046] According to some embodiments, the relevant age can also start from a post-treatment under heating, such as post-ceramization and / or coating of a glass-ceramic component, i.e. according to such a variant, the age of the glass-ceramic would be 0 after cooling to room temperature after such heating.

[0047] While glass-ceramic components in the state of the art only reach an equilibrium state long after completion of the ceramization process, i.e., only at an age of the glass-ceramic of, for example, 10 years, and no length change can be measured anymore, the inventive glassceramic component is already long-term stable after a few months. Thus, isothermally longterm stable precision components can be manufactured within the framework of usual production processes and times.

[0048] Coefficient of thermal expansion (CTE)

[0049] The glass-ceramic components show zero expansion, i.e., they exhibit a mean thermal expansion coefficient CTE in the range of 0 to 50°C of at most 0 ± 0.1 x 10‘6 / K. Some advantageous variants even have a mean CTE in the range of 0 to 50°C of at most 0 ± 0.05 x 10'6 / K or at most 0 ± 0.02 x 10'6 / K or at most 0 ± 0.01 x 10'6 / K or at most 0 ± 0.005 x 10’6 / K. For certain applications, it can be advantageous if the mean CTE dis determined and specified in a larger or smaller or different temperature range, e.g., in the range of -30°C to +70°C or in the range of -40°C to +80°C. Also in this temperature ranges the CTE is at most 0 ± 0.1 x 1O'6 / K or at most 0 ± 0.05 x 10'6 / K or at most 0 ± 0.02 x 10'6 / K or at most 0 ± 0.01 x 10'6 / K or at most 0 ± 0.005 x 10’6 / K.

[0050] To determine the CTE-T curve of a glass-ceramic or glass-ceramic component, the differential CTE(T) is first determined. The differential CTE(T) is determined as a function of temperature. The CTE is then defined according to the following formula (1):

[0051] CTE (T) = (1 / Io) x (SI / ST) (1)

[0052] To create an l / l0-T curve or a strain curve or plot of the length change l / l0of a test specimen against temperature, the temperature-dependent length change of the length of a test specimen from the initial length l0at the initial temperature t0to the length ltat temperature t can be measured. Preferably, small temperature intervals of, for example, 5°C or 3°C or 1°C are chosen to determine a measurement point. Such measurements can be carried out, for example, by dilatometric methods, interferometric methods, for example the Fabry-Perot method, i.e. , the evaluation of the shift of the resonance peak of a laser beam coupled into the material, or other suitable methods. E.g. a dilatometric method with a temperature interval of 1°C on rod-shaped samples of the test specimens with 100 mm length and a diameter of 6 mm can be chosen to determine the CTE. The method for determining the CTE should have an accuracy of preferably at least ± 0.05 ppm / K. However, the CTE can of course also be determined with methods having an accuracy of at least ± 0.01 ppm / K, preferably at least ± 0.005 ppm / K or according to some embodiments even of at least ± 0.003 ppm / K or at least ± 0.001 ppm / K.

[0053] From the l / l0-T curve, the mean CTE for a specific temperature interval, for example for the temperature range from 0°C to 50°C, is calculated.

[0054] A CTE-T curve is obtained by differentiating the l / lo-T curve. From the CTE-T curve, the zero crossing and the slope of the CTE-T curve within a temperature interval can be determined. Using the CTE-T curve, the extent and position of an advantageous CTE "plateau" formed in some variants, i.e., with optimized zero expansion over a wide temperature range, is determined.

[0055] CTE Plateau

[0056] It is advantageous if the differential CTE exhibits a plateau near 0 ppm / K, i.e., the differential CTE in a temperature interval TP with a width of at least 40 K, preferably at least 50 K, is less than 0 ± 0.025 ppm / K. The temperature interval of the CTE plateau is denoted as TP. Advantageously, the differential CTE in a temperature interval TPwith a width of at least 30 K or at least 40 K can be less than 0 ± 0.015 ppm / K.

[0057] A CTE "plateau" is thus understood to be an area extending over a section of the CTE-T curve, in which the differential CTE does not exceed a value of 0 ± 0.025 ppm / K, preferably 0 ± 0.015 ppm / K, more preferably 0 ± 0.010 ppm / K, even more preferably 0 ± 0.005 ppm / K, i.e., a CTE close to 0 ppb / K.

[0058] Advantageously, the differential CTE in a temperature interval TPwith a width of at least 30 K or at least 40 K 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 20 K or at least 30 K or at least 40 or at least 50 K. It can be advantageous if the temperature interval TP is in a range of -10 to +100°C, preferably 0 to 80°C.

[0059] The position of the CTE plateau of a glass-ceramic or component thereof is preferably adapted to the application temperature TAof the precision component. Preferred application temperatures TAare in the range of -60°C to +100°C, more preferably from -40°C to +80°C. Particular variants concern application temperatures TAof 0°C, 5°C, 10°C, 22°C, 40°C, 60°C, 80°C and 100°C. The CTE plateau, i.e., the curve region with the small deviation of the differential CTE in the temperature interval TP, 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], In other advantageous glass-ceramics or precision components, the CTE plateau can also be in the temperature range of [-10;30], [0;50], [19:25°C]; [20;40] and / or [20;70],

[0060] Low Slope CTE-T Curve

[0061] According to an advantageous embodiment of the invention, the CTE-T curve of the glassceramic or component exhibits at least one curve section with low slope in a temperature interval which has a width of at least 30 K, preferably at least a width of 40 K, more preferably at least a width of 50 K, in particular a slope of at most 0 ± 2.5 ppb / K2, advantageously of at most 0 ± 2 ppb / K , advantageously of at most 0 ± 1.5 ppb / K , 9 9 preferably of at most 0 ± 1 ppb / K , preferably of at most 0 ± 0.8 ppb / K , according to special variants even only of at most 0 ± 0.5 ppb / K

[0062] The temperature interval with low slope is preferably adapted to the application temperature TAof the glass-ceramic component. Preferred application temperatures TAare in the range of -60°C to +100°C, more preferably from -40°C to +80°C. Particular variants of the present invention concern glass-ceramics and glass-ceramic components for application temperatures T of 0°C, 5°C, 10°C, 22°C, 40°C, 60°C, 80°C and 100°C. The temperature interval with low slope 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], In other advantageous glassceramics or glass-ceramic components, the temperature interval with low slope can also be in the temperature range of [-10;30], [0;50], [19:25°C], [20;40] and / or [20;70],

[0063] CTE Homogeneity

[0064] An advantageous embodiment of a glass-ceramic component comprising an inventive glassceramic (particularly in the form of a substrate) exhibits high CTE homogeneity. The value of CTE homogeneity (in English: "total spatial variation of CTE") is understood to be the so- called peak-to-valley value, i.e., the difference between the highest and lowest CTE value of samples taken from a glass-ceramic component. The CTE homogeneity thus does not refer to the CTE of the material of the component, but to the spatial variation of the CTE over the considered section or the entire glass-ceramic component. To determine the CTE homogeneity, a multitude of samples are taken from different locations of a glass-ceramic component and the CTE value is determined for each, which is given in ppb / K, where 1 ppb / K = 0.001 x 10-6 / K. The CTE homogeneity, i.e., the spatial variation of the CTE, is advantageously at most 5 ppb / K over the entire glass-ceramic component, preferably at most 4 ppb / K, most preferably at most 3 ppb / K. A method for determining the CTE homogeneity and measures for achieving the CTE homogeneity are described in WO 2015 / 124710 A, the disclosure content of which is fully incorporated into this application.

[0065] Thermal Hysteresis

[0066] The glass-ceramic exhibits a thermal hysteresis of < 0.1 ppm at least in the temperature range of 15°C to 35°C within and is therefore hysteresis-free. Thus, at any temperature within the temperature interval of 15°C to 35°C, after being subjected to a temperature change with a heating rate or cooling rate of 36 K / h, i.e., 0.6 K / min, the glass-ceramic shows an isothermal long-term length change of less than 0.1 ppm after a holding time of 5 hours at constant temperature.

[0067] "Thermal hysteresis of < 0.1 ppm at least in the temperature interval of 15°C to 35°C" therefore means that the glass-ceramic in this temperature interval has a length change of < 0.1 ppm after thermal treatment and subsequent holding at constant temperature, based on a heating rate or cooling rate of 36 K / h, i.e., 0.6 K / min, and a holding time of 5 hours at -10°C. The characteristic of thermal hysteresis thus describes the thermal behavior of the glass-ceramic or a component made from it over time.

[0068] In advantageous embodiments, his hysteresis-free behavior exists at least in a temperature range of 15 to 40°C or at least in the temperature range 10°C to 35°C, preferably at least in the temperature range 15 to 45°C, preferably at least in the temperature range 15°C to 50°C. Particularly preferred is an even wider temperature range of hysteresis-free behavior, so that the material or component is also suitable for applications at temperatures up to at least 100°C and advantageously even beyond. Particularly preferred is an even wider temperature range of hysteresis-free behavior.

[0069] Preferred application temperatures are in the range of -60 to 100°C, more preferably from -40°C to +80°C. Particular variants of the present invention concern glass-ceramics and glass-ceramic components for application temperatures TAfor example in the range of 5°C to 20°C or TA of 22°C, 40°C, 60°C, 80°C and 100°C, which are preferably also hysteresis-free at these temperatures.

[0070] Glass-ceramic

[0071] Glass-ceramics are understood to be inorganic, non-porous materials with a crystalline phase and a glassy phase, where typically the matrix, i.e. , the continuous phase, is a glass phase. To produce the glass-ceramic, the components are first mixed, melted and refined, and a so-called green glass is cast. After cooling, the green glass is controllably crystallized by reheating (so-called "controlled volume crystallization"). The chemical composition (analysis) of the green glass and the glass-ceramic produced from it are the same; only the internal structure of the material is changed by ceramization. Therefore, when the composition of a glass-ceramic is discussed in the following, the same applies equally to the precursor object of such a glass-ceramic, i.e., the green glass.

[0072] The inventive glass-ceramic component preferably comprises an LAS glass-ceramic, which comprises the following components (in mol% on an oxide basis):

[0073] SiO2 60 - 71

[0074] Li2O 7 - 9.4

[0075] MgO+ZnO 0 - < 0.6, preferably < 0.5 and at least one component selected from the group consisting of P2O5, R2O, where R2O can be Na2O and / or K2O and / or Cs2O and / or Rb2O, and RO, where RO can be CaO and / or BaO and / or SrO, and nucleating agents with a content of 1.5 to 6 mol%, where nucleating agents are at least one component selected from the group consisting of TiO2, ZrO2, Ta2O5, Nb2O5, SnO2, MoOs, WO3, HfO2.

[0076] Preferably, the composition of the glass-ceramic fulfills the condition mole content SiO2+ (5 x mole content Li2O) > 106 or preferably > 106.5, preferably mole content SiO2+ (5 x mole content Li2O) > 107 or > 107.5. Alternatively or additionally, an advantageous upper limit of < 115.5 or < 114.5 or < 113.5 may apply for the condition "mole content SiO2+ (5 x mole content Li2O)".

[0077] The glass-ceramic may comprise the following components individually or in any combination in mol%: AI2O3 10 to 22

[0078] P2O5 0 to 6

[0079] MgO 0 to 0.35

[0080] ZnO 0 to 0.5

[0081] R2O 0 to 6

[0082] RO 0 to 6

[0083] TiO2+ZrO2 1.5 to 6

[0084] Furthermore, within the above-mentioned limits for the sums R2O, RO and TiO2+ZrO2, the following components may be contained individually or in any combination in mol%:

[0085] Na2O 0 to 3

[0086] K2O 0 to 3

[0087] CS2O 0 to 2

[0088] Rb2O 0 to 2

[0089] CaO 0 to 5

[0090] BaO 0 to 4

[0091] SrO 0 to 3

[0092] TiO2 0 to 5

[0093] ZrO2 0 to 3

[0094] In one embodiment, the glass-ceramic comprises (in mol% on an oxide basis):

[0095] AI2O3 10 to 22

[0096] P2O5 0 to 6

[0097] MgO 0 to 0.35

[0098] ZnO 0 to 0.5

[0099] R2O 0 to 6

[0100] RO 0 to 6 and nucleating agents 1.5 to 6, where nucleating agents are preferably TiO2 and / or ZrO2.

[0101] In one embodiment, the glass-ceramic comprises (in mol% on an oxide basis): AI2O3 10 to 22

[0102] P2O5 0 to 6

[0103] MgO 0 to 0.3

[0104] ZnO 0 to 0.4

[0105] R2O 0 to 6

[0106] RO 0 to 6

[0107] Nucleating agents 1.5 to 6, where nucleating agents are preferably TiO2 and / or ZrO2.

[0108] In another embodiment, the glass-ceramic comprises (in mol% on an oxide basis):

[0109] SiO2 60.50 to 69

[0110] U2O 8 to 9.4

[0111] AI2O3 11 to 21

[0112] P2O5 0.5 to 6

[0113] MgO 0 to 0.2

[0114] ZnO 0 to 0.3

[0115] R2O 0 to 4

[0116] RO 0.2 to 4.5

[0117] AS2O3 0.04

[0118] Nucleating agents 2.5 to 5, where nucleating agents are preferably TiO2 and / or ZrO2.

[0119] The glass-ceramic preferably contains a proportion of silicon dioxide (SiO2) of at least 60 mol%, more preferably at least 60.5 mol%, also preferably at least 61 mol%, more preferably at least 61.5 mol%, more preferably at least 62.0 mol%. The proportion of SiO2 is preferably at most 71 mol% or less than 71 mol%, more preferably at most 70 mol% or less than 70 mol%, more preferably at most 69 mol%, also preferably at most 68.5 mol%. With larger proportions of SiO2, the batch is more difficult to melt, and the viscosity of the melt is higher, which can lead to problems in homogenizing the melts in large-scale production facilities. Therefore, a content of 71 mol%, preferably 70 mol%, should not be exceeded. If the viscosity of a melt is high, the processing temperature Vaof the melt increases and very high temperatures are required for the refining and homogenization of the melt, which can lead to the linings of the melting units being attacked due to the increasing aggressiveness of the melt with temperature. In addition, even higher temperatures may not be sufficient to produce a homogeneous melt, resulting in the green glass having streaks and inclusions (particularly bubbles and particles originating from the lining of the melting units), so that after ceramization, the requirements for the homogeneity of the properties of the produced glassceramic, for example the homogeneity of the thermal expansion coefficient, are not met. Lower SiO2 contents than the stated maximum upper limit may be preferred for this reason.

[0120] The proportion of AI2O3 is advantageously at least 10 mol%, preferably at least 11 mol%, preferably at least 12 mol%, more preferably at least 13 mol%, also preferably at least 14 mol%, also preferably at least 14.5 mol%, even more preferably at least 15 mol%. If the content is too low, no or too little low-expanding high quartz solid solution is formed. The proportion of AI2O3 is advantageously at most 22 mol%, preferably at most 21 mol%, preferably at most 20 mol%, furthermore preferably at most 19.0 mol%, more preferably at most 18.5 mol%. A too high AI2O3 content leads to increased viscosity and promotes uncontrolled devitrification of the material.

[0121] The glass-ceramic may contain 0 to 6 mol% P2O5. The phosphate content P2O5 of the glassceramic can advantageously be at least 0.1 mol%, preferably at least 0.3 mol%, preferably at least 0.5 mol%, also preferably at least 0.6 mol%, more preferably at least 0.7 mol%, furthermore preferably at least 0.8 mol%. P2O5 is essentially incorporated into the crystal phase of the glass-ceramic and positively influences the expansion behavior of the crystal phase and thus of the glass-ceramic. In addition, melting of the components and refining behavior of the melt are improved. However, if too much P2O5 is contained, the course of the CTE-T curve in the temperature range 0°C to 50°C does not show an advantageous flat course. Therefore, advantageously a maximum of 6 mol%, preferably a maximum of 5 mol%, more preferably at most 4 mol%, even more preferably less than 4 mol% of P2O5 should be contained in the glass-ceramic. According to individual embodiments, the glass-ceramics can be free of P2O5.

[0122] Certain sums and ratios of the components SiO2, AI2O3 and / or P2O5, i.e., the components that form the high quartz solid solution, can be conducive to the formation of the glassceramic.

[0123] The sum content in mol% of the basic components of the LAS glass-ceramic SiO2 and AI2O3 is advantageously at least 75 mol%, preferably at least 78 mol%, preferably at least 79 mol%, more preferably at least 80 mol% and / or preferably at most 90 mol%, preferably at most 87 mol%, preferably at most 86 mol%, more preferably at most 85 mol%. If this sum is too high, the viscosity curve of the melt is shifted to higher temperatures, which is disadvantageous, as already explained above in connection with the component SiO2. If the sum is too low, too little high quartz solid solutionl is formed.

[0124] The sum content in mol% of the basic components of the LAS glass-ceramic SiC>2, AI2O3 and P2O5 is preferably at least 77 mol%, advantageously at least 81 mol%, advantageously at least 83 mol%, more preferably at least 84 mol% and / or preferably at most 91 mol%, advantageously at most 89 mol%, more preferably at most 87 mol%, according to one variant at most 86 mol%.

[0125] The ratio of the mol% proportions of P2O5 to SiO2 is preferably at least 0.005, advantageously at least 0.01, preferably at least 0.012 and / or preferably at most 0.1 , more preferably at most 0.08, according to one variant at most 0.07.

[0126] As a further component, the glass-ceramic can contain lithium oxide (U2O) in a proportion of at least 7 mol%, advantageously at least 7.5 mol%, preferably at least 8 mol%, particularly preferably at least 8.25 mol%. The proportion of U2O is limited to at most 9.4 mol%, more preferably at most 9.35 mol%, furthermore preferably at most or less than 9.3 mol%. U2O is a component of the high quartz solid solution phase and contributes significantly to the thermal expansion of the glass-ceramic. The stated upper limit of 9.4 mol% U2O should not be exceeded, as otherwise glass-ceramics with negative thermal expansion coefficient CTE (0;50) result. If the content of U2O is less than 7 mol%, too little high quartz solid solution is formed and the CTE of the glass-ceramic remains positive.

[0127] The glass-ceramic can contain at least one alkaline earth metal oxide selected from the group consisting of CaO, BaO, SrO, this group being collectively referred to as "RO". Components from the RO group remain essentially in the amorphous glass phase of the glass-ceramic and can be important for maintaining the zero expansion of the ceramized material. If the sum of CaO+BaO+SrO is too high, a low CTE (0;50) is not achieved. Therefore, the proportion of RO is advantageously at most 6 mol% or at most 5.5 mol%, preferably at most 5 mol%, advantageously at most 4.5 mol%, preferably at most 4 mol%, preferably at most 3.8 mol%, furthermore preferably at most 3.5 mol%, also preferably at most 3.2 mol%. If the glass-ceramic contains RO, an advantageous lower limit can be at least 0.1 mol%, advantageously at least 0.2 mol%, preferably at least 0.3 mol%, also preferably at least 0.4 mol%. According to individual embodiments, a glass-ceramic can be free of RO.

[0128] The proportion of CaO can preferably be at most 5 mol%, advantageously at most 4 mol%, advantageously at most 3.5 mol%, advantageously at most 3 mol%, more preferably at most 2.8 mol%, even more preferably at most 2.6 mol%. The glass-ceramic can advantageously contain at least 0.1 mol%, advantageously at least 0.2 mol%, preferably at least 0.4 mol%, preferably at least 0.5 mol% CaO. The glass-ceramic can advantageously contain the component BaO, which is a good glass former, in a proportion of at least 0.1 mol%, preferably at least 0.2 mol% and / or at most 4 mol%, advantageously at most 3 mol%, advantageously at most 2.5 mol%, preferably at most 2 mol%, preferably at most 1.5 mol%, also preferably at most 1.4 mol%. The glass-ceramic can contain SrO in a proportion of at most 3 mol%, advantageously at most 2 mol%, preferably at most 1.5 mol%, preferably at most 1.3 mol%, preferably at most 1.1 mol%, more preferably at most 1 mol%, also preferably at most 0.9 mol% and / or preferably at least 0.1 mol%. According to individual embodiments, the glass-ceramics are free of CaO and / or BaO and / or SrO.

[0129] Sodium oxide (Na2O) and / or potassium oxide (K2O) and / or cesium oxide (CS2O) and / or rubidium oxide (Rb2O) are optionally contained in the glass-ceramic, i.e. , Na2O-free and / or K2O-free and / or Cs2O-free and / or Rb2O-free variants are possible. The proportion of Na2O can advantageously be at most 3 mol%, preferably at most 2 mol%, preferably at most 1.7 mol%, preferably at most 1.5 mol%, preferably at most 1.3 mol%, preferably at most 1.1 mol%. The proportion of K2O can advantageously be at most 3 mol%, preferably at most 2.5 mol%, preferably at most 2 mol%, preferably at most 1.8 mol%, preferably at most 1.7 mol%. The proportion of CS2O can advantageously be at most 2 mol%, preferably at most 1.5 mol%, preferably at most 1 mol%, preferably at most 0.6 mol%. The proportion of Rb2O can advantageously be at most 2 mol%, preferably at most 1.5 mol%, preferably at most 1 mol%, preferably at most 0.6 mol%. According to individual embodiments, the glass-ceramics are free of Na2O and / or K2O and / or CS2O and / or Rb2O.

[0130] Na2O, K2O, CS2O, Rb2O can each be contained in the glass-ceramic in a proportion of at least 0.1 mol%, preferably at least 0.2 mol%, more preferably at least 0.5 mol%, independently of each other. The components Na2O, K2O, CS2O and Rb2O remain essentially in the amorphous glass phase of the glass-ceramic and can be important for maintaining the zero expansion of the ceramized material. Therefore, the sum R2O of the contents of Na20, K2O, CS2O and Rb2O can advantageously be at least 0.1 mol%, preferably at least 0.2 mol%, advantageously at least 0.3 mol%, preferably at least 0.4 mol%. A low R2O content of advantageously at least 0.2 mol% can contribute to enlarging the temperature range in which the expansion curve of the glassceramic shows a flat course. The sum R2O of the contents of Na2O, K2O, CS2O and Rb2O can advantageously be at most 6 mol%, preferably at most 5 mol%, preferably at most 4 mol%, preferably at most 3 mol%, preferably at most 2.5 mol%. If the sum of Na2O+K2O+Cs2O+Rb2O is too low or too high, it may be possible that a low CTE (0;50) is not achieved. According to individual embodiments, the glass-ceramics can be free of R2O.

[0131] The glass-ceramic can contain a maximum of 0.35 mol% magnesium oxide (MgO). A further advantageous upper limit can be a maximum of 0.3 mol%, a maximum of 0.25 mol%, a maximum of 0.2 mol%, a maximum of 0.15 mol%, a maximum of 0.1 mol% or a maximum of 0.05 mol%. Particularly preferably, the glass-ceramic is free of MgO. The component MgO can cause thermal hysteresis in the glass-ceramic in the temperature range of 0°C to 50°C. The less MgO contained in the glass-ceramic, the smaller the hysteresis in the mentioned temperature range.

[0132] The glass-ceramic can contain a maximum of 0.5 mol% zinc oxide (ZnO). A further advantageous upper limit can be a maximum of 0.45 mol%, a maximum of 0.4 mol%, a maximum of 0.35 mol%, a maximum of 0.3 mol%, a maximum of 0.25 mol%, a maximum of 0.2 mol%, a maximum of 0.15 mol%, a maximum of 0.1 mol% or a maximum of 0.05 mol%. Particularly preferably, the glass-ceramic is free of ZnO. The component ZnO can cause thermal hysteresis in the glass-ceramic in the temperature range of 0°C to 50°C. The less ZnO contained in the glass-ceramic, the smaller the hysteresis in the mentioned temperature range.

[0133] Regarding the hysteresis-free nature of the glass-ceramic, the condition MgO+ZnO less than 0.6 mol% should be fulfilled. A further advantageous upper limit for the sum MgO+ZnO can be a maximum of 0.55 mol%, a maximum of 0.5 mol%, less than 0.5 mol%, a maximum of 0.45 mol%, a maximum of 0.4 mol%, a maximum of 0.35 mol%, a maximum of 0.3 mol%, a maximum of 0.25 mol%, a maximum of 0.2 mol%, a maximum of 0.15 mol%, a maximum of 0.1 mol% or a maximum of 0.05 mol%. It was found that variants of the glass-ceramic with a proportion of at most 0.5 mol% or less MgO+ZnO are also particularly long-term stable.

[0134] The glass-ceramic further contains at least one crystal nucleating agent selected from the group consisting of TiC>2, ZrO2 Ta2Os, Nb20s, SnO2, MoOs, WO3, HfO2. The nucleating agent can also be a combination of two or more of the mentioned components. The sum of the proportions of the nucleating agents is preferably at least 1.5 mol%, preferably at least 2 mol% or more than 2 mol%, more preferably at least 2.5 mol%, according to certain variants at least 3 mol%. An upper limit can be a maximum of 6 mol%, preferably a maximum of 5 mol%, preferably a maximum of 4.5 mol% or a maximum of 4 mol%. In particularly advantageous variants, the mentioned upper and lower limits apply to the sum of TiO2 and

[0135] ZrO2.

[0136] The glass-ceramic can contain titanium oxide (TiO2), preferably with a proportion of at least 0.1 mol%, advantageously at least 0.5 mol%, preferably at least 1.0 mol%, preferably at least 1.5 mol%, preferably at least 1.8 mol% and / or preferably at most 5 mol%, advantageously at most 4 mol%, more preferably at most 3 mol%, further preferably at most 2.5 mol%, preferably 2.3 mol%. TiO2-free variants of the glass-ceramic are possible.

[0137] The glass-ceramic can further contain zirconium oxide (ZrO2) in a proportion of at most 3 mol%, preferably at most 2.5 mol%, more preferably at most 2 mol%, preferably at most 1.5 mol% or at most 1.2 mol%. Preferably, ZrO2 can be contained in a proportion of at least 0.1 mol%, more preferably at least 0.5 mol%, at least 0.8 mol% or at least 1.0 mol%. ZrO2-free variants of the glass-ceramic are possible.

[0138] According to some variants, 0 to 5 mol% of Ta2Os and / or Nb20s and / or SnO2 and / or MoOs and / or WO3 and / or HfO2 can be contained individually or in sum in the glass-ceramic and serve, for example, as alternative or additional nucleating agents or for modulating the optical properties, e.g., the refractive index. To modulate the optical properties, some advantageous variants may contain, for example, Gd2O3, Y2O3, HfO2, Bi2O3 and / or GeO2.

[0139] The glass-ceramic may contain fluorine. However, fluorine can reduce the transparency of the glass-ceramic, so that this component, if present, is preferably limited to a maximum of 0.5 mol%, preferably a maximum of 0.3 mol%, preferably a maximum of 0.1 mol%.

[0140] Preferably, the glass-ceramic is free of fluorine. F increases the expansion, therefore not preferred.

[0141] The glass-ceramic may further contain one or more conventional refining agents, selected from the group consisting of AS2O3, Sb2O3, SnO2, SO4 , OF, Br', F or a mixture thereof, in a proportion of more than 0.05 mol% or at least 0.1 mol% and / or at most 1 mol%. A variant of the glass-ceramic contains only a low AS2O3 content of maximum 0.05 mol% AS2O3. Instead of AS2O3 or in addition to the small proportion of AS2O3 (maximum 0.05 mol%), at least one alternative redox refining agent and / or at least one evaporation refining agent and / or at least one decomposition refining agent may be contained in the glassceramic. Since AS2O3 is also a redox refining agent, redox refining agents used alternatively or in addition to AS2O3 are referred to as "alternative redox refining agents" within the scope of the invention.

[0142] In an advantageous variant, the total content of chemical refining agents detectable in the glass-ceramic (excluding the content of AS2O3 - if AS2O3 is present in the glass-ceramic) can be in the range of 0 mol% to 1 mol%. In an advantageous embodiment, the total content of refining agents detectable in the glass-ceramic (excluding AS2O3) is more than 0.01 mol%, preferably at least 0.05 mol%, preferably at least 0.1 mol%, preferably at least 0.15 mol%, advantageously at least 0.2 mol% and / or at most 1 mol%, preferably at most 0.7 mol%, preferably at most 0.5 mol%, preferably at most 0.4 mol%. Some advantageous variants may also contain at most 0.3 mol%, preferably at most 0.25 mol% or at most 0.2 mol% of refining agent. The proportions of the respective components are detectable in an analysis of the glass-ceramic. This applies in particular to all refining agents mentioned below, with the exception of the described sulfate component.

[0143] Redox refining agents contain multivalent or polyvalent ions that can occur in at least two oxidation states, which are in a temperature-dependent equilibrium with each other, whereby at high temperatures a gas, usually oxygen, is released. Certain multivalent metal oxides can therefore be used as redox refining agents. In an advantageous variant, the alternative redox refining agent can be at least one component selected from the group consisting of Sb2O3, SnO2, CeO2, MnO2, Fe2O3. In principle, however, other redox compounds are also suitable if they release their refining gas in the temperature range relevant for refining and either transition into an oxide with a different valence state of the metal ion or into a metallic form. Numerous such compounds are described, for example, in DE 19939771 A. Preferred is an alternative redox refining agent that releases refining gas, especially oxygen, at a temperature of less than 1700°C, such as Sb2O3, SnO2, CeO2.

[0144] Through an analysis of the glass-ceramic, the content of AS2O3 and / or the content of at least one alternative redox refining agent can be determined, from which experts can draw conclusions about the type and amount of refining agent used. The alternative redox refining agents can be added to the batch, for example, as oxides.

[0145] In an advantageous variant, the total content of alternative redox refining agents can be in the range of 0 mol% to 1 mol%. In an advantageous embodiment, the total content of alternative redox refining agents detectable in the glass-ceramic is more than 0.01 mol%, preferably at least 0.05 mol%, preferably at least 0.1 mol%, preferably at least 0.15 mol%, advantageously at least 0.2 mol% and / or at most 1 mol%, preferably at most 0.7 mol%, preferably at most 0.5 mol%, preferably at most 0.4 mol%. Some advantageous variants may also contain at most 0.3 mol%, preferably at most 0.25 mol% or at most 0.2 mol% of alternative redox refining agent.

[0146] The glass-ceramic can contain 0 mol% to 1 mol% antimony oxide (Sb20s) as an alternative redox refining agent. In an advantageous embodiment, the glass-ceramic contains Sb2O3 in a proportion of 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%. Since Sb2O3 is considered environmentally hazardous, it may be advantageous to use as little Sb2O3 as possible for refining. A preferred embodiment of the glass-ceramic is essentially Sb2O3-free or Sb-free, where "essentially Sb2O3-free" means that Sb2O3 is not intentionally added to the composition as a raw material component, but is at most contained as an impurity, with a contamination limit for Sb2O3-free glass-ceramics being at most 0.01 mol%, preferably at most 0.005 mol%. According to specific embodiments, the glass-ceramic is Sb2O3-free.

[0147] The glass-ceramic can contain 0 mol% to 1 mol% tin oxide (SnO2) as an alternative redox refining agent. In an advantageous embodiment, the glass-ceramic contains SnO2 in a proportion of more than 0.01 mol%, preferably at least 0.05 mol%, advantageously at least 0.1 mol%, advantageously at least 0.15 mol%, preferably at least 0.2 mol%, preferably at least 0.3 mol% and / or preferably at most 1 mol%, advantageously at most 0.7 mol%, more preferably at most 0.6 mol%. For some variants, an upper limit of at most 0.5 mol%, further preferably at most 0.4 mol%, preferably at most 0.3 mol% may be advantageous. If the content of SnO2 is too high, it may be possible that the ceramization process of the green glass is more difficult to control, as SnO2 at higher contents acts not only as a refining agent but also as a crystal nucleating agent. SnO2-free or Sn-free variants of the glass-ceramic are possible and advantageous, i.e., no Sn-containing raw material was added to the batch for refining the underlying green glass, with a limit for SnO2 contamination introduced by raw materials or the process being at most 0.01 mol%, preferably at most 0.005 mol%.

[0148] The glass-ceramic can contain 0 mol% to 1 mol% CeO2 and / or MnO2 and / or Fe2O3 as alternative redox refining agents. These components can each be contained independently of each other preferably in a proportion of 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%. Preferred variants of the glass-ceramic are free of CeO2 and / or MnO2 and / or Fe2O3, i.e., no Ce-containing raw material and / or Mn-containing raw material and / or Fe-containing raw material was added to the batch for refining the underlying green glass, with a limit for contamination of CeC>2 and / or MnO2 and / or Fe2O3 introduced by raw materials or the process being at most 0.01 mol%, preferably at most 0.005 mol%.

[0149] Evaporation refining agents are components that are volatile at high temperatures due to their vapor pressure, so that the gas formed in the melt develops a refining effect.

[0150] In an advantageous variant, the evaporation fining agent can have a halogen component.

[0151] In an advantageous variant, the evaporation fining agent can include at least one halogen with fining effect, particularly selected from the group consisting of chlorine (Cl), bromine (Br) and iodine (I). The preferred halogen with fining effect is chlorine.

[0152] The halogen with fining effect can be added in different forms. In one embodiment, it is added to the batch as a salt with an alkali metal cation or alkaline earth metal cation or as aluminum halogen. In one embodiment, the halogen is used as a salt and the cation in the salt corresponds to a cation present as an oxide in the glass-ceramic. The halogen with fining effect can be used in the form of a halogen compound, particularly a halide compound. Suitable halide compounds are particularly salts of chlorine anions, bromine anions and / or iodine anions with alkali metal cations or alkaline earth metal cations or aluminum cations. Preferred examples are chlorides such as LiCI, NaCI, KCI, CaCl2, BaCl2, SrCl2, AICI3 and combinations thereof. Corresponding bromides and iodides such as LiBr, Lil, NaBr, Nal, KBr, KI, Cal2, CaBr2 and combinations thereof are also possible. Other examples are BaBr2, Bal2, SrBr2, Srl2 and combinations thereof. In an advantageous variant, the total content of halogen with fining effect (i.e., Cl 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 halogen with fining effect that is detectable in the glass-ceramic is more than 0.03 mol%, preferably at least 0.04 mol%, preferably at least 0.06 mol%, preferably at least 0.08 mol%, preferably at least 0.1 mol%, preferably at least 0.15 mol%, advantageously at least 0.2 mol% and / or at most 1 mol%, preferably at most 0.7 mol%, preferably at most 0.5 mol%, preferably at most 0.4 mol%. Some advantageous variants may also contain at most 0.3 mol%, preferably at most 0.25 mol% or at most 0.2 mol% of halogen with fining effect. The mentioned contents refer to the amounts of halogen detectable in the glass-ceramic. It is common for experts to calculate the amount of halogen or halide compound needed for fining based on these specifications.

[0153] The glass-ceramic can contain 0 mol% to 1 mol% chlorine (atomically determined and specified as Cl). In an advantageous embodiment, the glass-ceramic contains Cl with a proportion of more than 0.03 mol%, advantageously at least 0.04 mol%, advantageously at least 0.05 mol%, advantageously at least 0.1 mol%, advantageously at least 0.15 mol%, preferably at least 0.2 mol% and / or preferably at most 1 mol%, advantageously at most 0.7 mol%, more preferably at most 0.5 mol%, even more preferably at most 0.4 mol%, preferably at most 0.3 mol%. Some advantageous glass-ceramics can be Cl-free, i.e., no Cl-containing raw material was added to the batch for fining the underlying green glass. Cl is present, if at all, as an impurity, with the limit for a Cl impurity being a maximum of 0.03 mol%.

[0154] The same mentioned ranges and limits apply to Br as a halogen with fining effect. The same mentioned ranges and limits apply to I as a halogen with fining effect. Preferred variants of the glass-ceramic are free of Br and / or I.

[0155] Alternatively, or in addition to an evaporation fining agent and / or an alternative redox fining agent, the chemical fining agent can contain at least one decomposition fining agent. A decomposition fining agent is an inorganic compound that decomposes at high temperatures with the release of fining gas and the decomposition product has a sufficiently high gas c pressure, particularly greater than 10 Pa. Preferably, the decomposition fining agent can be a salt that contains an oxo anion, particularly a sulfate component. Preferably, the decomposition fining agent comprises a sulfate component. Through decomposition of the component added as sulfate, SO2 and O2 gas are released at high temperatures, which contribute to the fining of the melt.

[0156] A sulfate component can be added in different forms. In one embodiment, it is added to the batch as a salt with an alkali metal or alkaline earth metal cation. In one embodiment, the sulfate is used as a salt and the cation in the salt corresponds to a cation present as an oxide in the glass-ceramic. For example, the following components can be advantageously used as sulfate sources: U2SO4, Na2SO4, K2SO4, CaSCM, BaSCM, SrSC .

[0157] In the context of the invention, sulfate is determined as SO3 in material analysis. However, since LAS glass-ceramics have only a very low solubility for sulfate, the sulfate component (i.e. , SO3) in the melt product is no longer detectable by conventional X-ray fluorescence analysis after melting. Therefore, for sulfate-fined embodiments (see below), the amount of p mol% SO4 or mol% SO3 used in relation to the synthesis of the glass melt is specified. The use of a sulfate component as a fining agent can be determined, for example, by analyzing the residual gas content (SO2) in the glass-ceramic.

[0158] An advantageous glass-ceramic that is fined with a sulfate component was added more than 0.01 mol%, preferably at least 0.05 mol%, advantageously at least 0.1 mol%, advantageously at least 0.15 mol%, preferably at least 0.2 mol% and / or preferably at most 1 mol%, advantageously at most 0.7 mol%, more preferably at most 0.5 mol%, even more preferably at most 0.4 mol%, preferably at most 0.3 mol% SO3 through at least one p corresponding sulfate compound during synthesis. Sulfate-free (i.e., SO3-free or SO4 -free) fined glass-ceramics are possible and advantageous. The proportion of fining-effective sulfate added in the synthesis of a glass-ceramic can thus be in the range of 0 mol% to 1 mol% SO3.

[0159] According to one variant of the invention, the glass-ceramic or the underlying glass can be fined using a suitable metal sulfide as a decomposition fining agent, as described, for example, in US 2011 / 0098171 A. In one embodiment, the cation in the sulfide corresponds to a cation present as an oxide in the glass-ceramic. Examples of suitable metal sulfides are alkali metal sulfide, alkaline earth metal sulfide and / or aluminum sulfide, which release SO3 in the melt under oxidizing conditions. For a metal sulfide to fulfill the role of a fining agent well, it is advantageously used in combination with an oxidizing agent, preferably a nitrate, and / or sulfate.

[0160] Glass-ceramics with reduced AS2O3 content or As2O3-free glass-ceramics can have a combination of chemical fining agents. The following combinations can be advantageous, with the respective glass-ceramic preferably containing the mentioned fining agents within the above-mentioned limits for the individual components and / or the sums. Advantageous embodiments include: SnO2 and / or Sb2O3 each with max. 0.05 mol% AS2O3; or

[0161] - As2O3-free combinations such as: Sb2O3 with SnO2; Sb2O3 with Cl, Sb2O3 with SO3; or

[0162] - As2O3-free and Sb2O3-free combinations such as: SnO2 with Cl, SnO2 with SO3, Cl with SO3.

[0163] Alternatively, glass-ceramics fined with only one fining agent can also be advantageous, e.g., glass-ceramics that contain only Sb2O3 or only SnO2 as a fining agent.

[0164] As an alternative or in addition to the above-described fining of the melt with chemical fining agents, whose principle consists in the addition of compounds that decompose and release gases or that are volatile at higher temperatures or that release gases in an equilibrium reaction at higher temperatures, known physical fining processes can also be advantageously used, such as lowering the viscosity of the glass melt by increasing temperature, vacuum fining, high-pressure fining, etc.

[0165] The batch can also contain nitrates (NO3) that act as oxidizing agents in the melting and fining process and ensure that oxidizing conditions are present in the melt to increase the effectiveness of the fining agents used, especially the alternative redox fining agents. Nitrate can be used as a salt and the cation in the salt corresponds to a cation present as an oxide in the glass-ceramic. Examples of this can be aluminum nitrate, alkali metal nitrate, alkaline earth metal nitrate, zirconium nitrate. However, ammonium nitrate can also serve advantageously as a nitrate source. 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 fining 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%. In some advantageous variants, a maximum of 3 mol% nitrate can also be used. Due to its volatility, no nitrate can be detected in the glass or in the glass-ceramic.

[0166] The glass-ceramic may optionally contain additions of coloring oxides, such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, CuO, CeO2, C Os, rare earth oxides in contents of 0 - 3 mol% each individually or in total. Preferred variants are free of coloring oxides. B2O3 can have a negative effect on the transparency of the glass-ceramic. Therefore, in an advantageous variant, the content of this component is limited to < 0.2 mol%, preferably at most 0.1 mol%. Preferred variants are free of B2O3.

[0167] According to one embodiment, the glass-ceramic is substantially free of one or more glass components selected from the group consisting of MgO, ZnO, PbO, B2O3, CrOs, Cd compounds.

[0168] According to one embodiment, the glass-ceramic is free of components not mentioned above.

[0169] According to one embodiment, the glass-ceramic preferably consists of at least 90 mol%, more preferably at least 95 mol%, most preferably at least 99 mol% of the components mentioned above or preferably of the components SiO2, AI2O3, U2O, P2O5, R2O, RO and nucleating agents.

[0170] According to the invention, the expression "X-free" or "free of a component X" means that the glass-ceramic essentially does not contain this component X, i.e. , that such a component is present in the glass at most as an impurity but is not added to the composition as an individual component. Regarding impurities, particularly with MgO and / or ZnO, a limit of 0.03 mol%, preferably 0.01 mol%, should not be exceeded for MgO-free and / or ZnO-free variants, referring to each individual component. For other glass components, higher impurity contents up to a maximum of 0.1 mol%, preferably a maximum of 0.05 mol%, advantageously a maximum of 0.01 mol%, advantageously a maximum of 0.005 mol%, for some components advantageously a maximum of 0.003 mol% referring to each component, may be possible. X here stands for any component, such as PbO. These mentioned limits do not apply to the fining agents, for which separate impurity limits are described above.

[0171] Manufacturing process

[0172] The glass-ceramic compositions described above already fulfill most of the requirements for glass-ceramic components, such as low thermal expansion and freedom from hysteresis. However, under usual ceramization conditions, glass-ceramic components exhibit a very small and very slow isothermal long-term length change. Surprisingly, however, it has been possible to obtain a glass-ceramic component that does not show any isothermal long-term change by modifying the ceramization process or heat treatment process. In particular, to obtain a long-term stable glass-ceramic component, an additional holding time at relatively low temperature must be carried out following the ceramization. Figure 1 schematically shows the temperature treatment program for producing the glassceramic component according to the invention, which comprises the following steps: a) Heating a green glass of a glass-ceramic to a ceramization temperature TK (1), b) Ceramizing the green glass at a ceramization temperature TK, obtaining a glassceramic component (2), c) Cooling the glass-ceramic component with a cooling rate ATi to a holding temperature TH (4), d) Holding the glass-ceramic component at a holding temperature TH, where 50°C < TH < 150 °C, preferably 60°C < TH 100 °C, for a holding time tH (5), e) Cooling the glass-ceramic component to room temperature with a cooling rate AT2 (6).

[0173] According to a further aspect, the process according further comprises between step d) and e) the additional steps of cooling the glass-ceramic to room temperature, holding the glassceramic at room temperature and reheating the glass-ceramic to the holding temperature TH, so that the process comprises the following steps: a) Heating a green glass of a glass-ceramic to a ceramization temperature TK (1), b) Ceramizing the green glass at a ceramization temperature TK, obtaining a glassceramic component (2), c) optionally, increasing the temperature after completion of ceramization to a temperature TR and holding at this temperature TR (3), d) Cooling the glass-ceramic component with a cooling rate AT4 to room temperature, e) Holding the glass-ceramic component at room temperature, f) Heating the glass-ceramic component to the holding temperature TH, g) Holding the glass-ceramic component at a holding temperature TH, where 50°C < TH < 150 °C, preferably 60°C < TH 100 °C, for a holding time tH (5), h) Cooling the glass-ceramic component to room temperature with a cooling rate ATe (6).

[0174] First, the green glass is heated to a ceram icization temperature for LAS glass-ceramics (1) and then kept at the ceram icization temperature (2). Ceramic treatment temperatures of 600 to 850°C can be considered. The exact temperature and holding time depend on the composition of the glass-ceramic and the size and shape of the component and can be determined appropriately by a specialist according to common methods. During ceramization (2), the temperature can be kept constant or, as shown in Figure 1, it can also rise slightly.

[0175] Following the actual ceramization (2), an additional holding time can be carried out at a slightly higher temperature, for example at TR750 - 880°C for stress relaxation (3), at which stresses in the glass-ceramic can be reduced.

[0176] Subsequently, the glass-ceramic is cooled (4) with a cooling rate AT 1 to the temperature of the additional holding time (5) according to the invention.

[0177] Until now, it was assumed that the temperature range 50°C < TH 150 °C, preferably 60°C < TH 100 °C, does not play a significant role in the heat treatment of glass-ceramics to positively influence the properties of a glass-ceramic.

[0178] Surprisingly, for the glass-ceramics described above, the additional step of holding the already ceramized glass-ceramic at a holding temperature TH with 50°C < TH 150 °C, preferably 60°C < TH £ 100 °C, can prevent isothermal long-term expansion, resulting in a long-term stable glass-ceramic component.

[0179] The holding time tH for step (5) is preferably at least 12 hours, preferably at least 18 hours, more preferably at least 24 hours and / or at most 7 days, preferably at most 3 days, more preferably at most 2 days.

[0180] After the holding time tn by step (5), the glass-ceramic or glass-ceramic component is cooled t room temperature with a cooling rate AT2 (6).

[0181] Preferably, cooling rates AT 1 and AT2 of at most -10 K / h, preferably at most -5 K / h, more preferably at most -4 K / h and / or at least -0.5 K / h, preferably at least -1 K / h are used. The cooling rates AT1 and AT2 in step (4) and (6) can be the same or different within these limits. Exact cooling rates depend on the size of the glass-ceramic component. To obtain a uniform and stress-free glass-ceramic component, larger components must be cooled more slowly, smaller components can be cooled homogeneously with a higher cooling rate.

[0182] Use of the glass-ceramic component and precision components

[0183] The invention further relates to the use of a glass-ceramic component according to the invention as a precision component, for example as a substrate for a precision component as well as precision components comprising the glass-ceramic component according to the invention.

[0184] The glass-ceramic component can be used as a precision component, particularly for use in metrology, spectroscopy, measurement technology, lithography, astronomy or Earth observation from space, for example as mirrors or mirror supports for segmented or monolithic astronomical telescopes or also as weight-reduced or ultra-light mirror substrates for space-based telescopes, for instance, or as high-precision structural components for distance measurement, e.g. in space or optics for Earth observation, as precision components such as standards for precision measurement technology, precision scales, reference plates in interferometers, as mechanical precision parts, e.g. for ring laser gyroscopes, spiral springs for the watch industry, as mirrors and prisms in flat panel display lithography, for example for LC or OLED displays, as well as for example as mask holders, reticle stages, wafer stages, reference plates, reference frames and grid plates in microlithography and in EUV (extreme UV) microlithography and additionally as mirrors or mirror substrates and / or photomask substrates or photomask blanks or reticle mask blanks in EUV microlithography.

[0185] With a glass-ceramic component according to the invention, precision components of different sizes can be produced:

[0186] One embodiment concerns components with smaller dimensions, particularly for rectangular shapes with edge lengths (width and / or depth) or for round surfaces with diameters of at least 50 mm, preferably at least 100 mm and / or maximum 1500 mm, preferably maximum 1000 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 components can be used, for example, in microlithography and EUV lithography.

[0187] Another embodiment concerns components with very small dimensions, particularly with edge lengths (width and / or depth) or diameters and / or thickness of a few mm (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 a few tenths of a mm (for example, at most 0.7 mm or at most 0.5 mm). These precision components can be, for example, a spacer in an interferometer or a component for ultrastable clocks in quantum technology.

[0188] However, very large components can also be produced. One embodiment of the invention thus concerns components with large volume. In the sense of this application, this should be understood as a component with 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 invention at least 51, or with edge lengths (width and / or depth) for (right) angular shapes of at least 0.5 m, more preferably at least 1 m and / or with a thickness (height) of at least 50 mm, preferably at least 100 mm, preferably at least 200 mm, further preferably at least 250 mm, or for round shapes with a diameter of at least 0.5 m, more preferably at least 1 m, more preferably at least 1.5 m and / or with a thickness (height) of at least 50 mm, preferably at least 100 mm, preferably at least 200 mm, further preferably at least 250 mm.

[0189] Special embodiments relate to be even larger components with, for example, a diameter of at least 3 m or at least 4 m or larger and / or a thickness of 50 mm to 400 mm, preferably 50 mm to 300 mm. According to one variant, the invention also concerns rectangular components, where preferably at least one surface has an area of at least 1 m2, preferably at least 1.2 m2, more preferably at least 1.4 m2, for some variants further preferably at least 3 m2 or at least 4 m2 and / or the thickness is 50 mm to 400 mm, preferably 50 mm to 300 mm.

[0190] Generally, large-volume components are produced which have a significantly larger base area than height. However, it can also be large-volume components which have a shape approximating a cube or a sphere.

[0191] Precision components can be, for example, optical components, namely a so-called normal incidence mirror, i.e. a mirror which is operated near perpendicular radiation incidence, or a so-called grazing incidence mirror, i.e. a mirror which is operated at grazing radiation incidence. Such a mirror comprises, in addition to the substrate, a coating that reflects the incident radiation. Particularly in the case of a mirror for X-ray radiation, the reflective coating is, for example, a multilayer system or multilayer with a plurality of layers with high reflectivity in the X-ray range at non-grazing incidence. Preferably, such a multilayer system of a normal incidence mirror comprises 40 to 200 layer pairs, consisting of alternating layers of, for example, one of the material pairs Mo / Si, Mo / Bi, Ru / Si and / or MoRu / Be.

[0192] Optical components can be X-ray optical components, i.e. optical components which are used in connection with X-ray radiation, especially soft X-ray radiation or EUV radiation, in particular reticle masks or photomasks operated in reflection, especially for EUV microlithography. They can be mask blanks or mask substrates. Furthermore, an optical component can be a mirror for EUV lithography or as a substrate for a mirror for EUV lithography.

[0193] Further precision components can be mirrors for astronomical applications. Such components for astronomical applications can be used both terrestrially and in space. High-precision structural components for distance measurements, e.g. in space, are another advantageous field of application.

[0194] The glass-ceramic component can be a lightweight structure. The component may further comprise a lightweight structure. This means that in some areas of the component, cavities are provided for weight reduction. Preferably, the weight of a component is reduced by lightweight processing by at least 80%, more preferably at least 90%, compared to the unprocessed component.

[0195] The invention further relates to a precision component comprising a glass-ceramic component according to the invention. Details of this have already 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.

[0196] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations without departing from the scope of the invention.

[0197] Examples

[0198] Green glasses for analogous US 2022 / 0298079 A1 were melted and ceramized, whereby the ceramization in the examples of the invention was supplemented by step 5, i.e. a holding time in a temperature range of at least 50°C and at most 150°C (step 5 in Figure 1).

[0199] Table 1 shows the compositions of the glass-ceramics or green glasses used in the examples and comparative examples.

[0200] Table 1: Compositions green glasses (and corresponding glass-ceramics) (in molar % based on oxide)

[0201] Table 2 shows the holding times and temperatures of the additional step 5, as well as the properties of the glass-ceramics obtained according to the examples and comparative examples. In each case, examples and comparative examples were compared, which differed only in the additional holding time for step 5 (if available). All other manufacturing conditions were kept constant for each for a green glass composition (hereinafter also mentioned corresponding examples).

[0202] Table 2: Examples and comparative examples

[0203] Table 2 shows the relative long-term length changes of isothermally held glass-ceramic specimens to different ages of the glass-ceramic. The relative isothermal change in length per year for the age of 100 days was determined from the difference in length of the relative change in length Al 100 d [ppb] and Al 465 d [ppb] as Al od , the relative isothermal change in length per year for the age of 200 days was determined from the difference in length of the relative change in length Al 200 d [ppb] and Al 565 d [ppb] as Afeood.

[0204] Examples 1 to 4 already show a relative long-term length change of less than 30 ppb / a for Al-iood-

[0205] Comparative examples 1a, 2a, 3a and 4a were ceramized without an additional holding time (step 5) and thus correspond to the glass-ceramics of the state of the art. These samples showed a relative isothermal long-term length change of more than 60 ppb / a. In Comp. Ex. 1c, a holding temperature that is too low was chosen for step 5. The values for the relative isothermal long-term length change correspond to the values of comparative example 1a without step 5 within the framework of the measurement inaccuracies.

[0206] In Comp. Example 1b, a higher holding temperature was chosen in step 5. This sample initially shows an increase in length, but after reaching a maximum, a decrease in length. However, the values for Al od and Afeood are not in the claimed range.

[0207] For the samples from example 1 and comparative example 1a, further values were measured and plotted in a graph (see Figure 2). It can be seen that the sample according to Example 1 shows no further relative isothermal long-term length change after less than 100 days within the framework of the measurement inaccuracies, while the sample according to Comparative Example 1a still shows a slight relative isothermal length change even after more than two years. Figure 2 also shows the long-term shrinkage of ZERODUR® as a further comparison from the state of the art.

[0208] It is expected that the samples of the comparative examples, in the same manner as known for ZERODUR®, will approach a constant length asymptotically after an age of 6 or more years.

[0209] Other properties of glass-ceramics according to examples and comparative examples:

[0210] The crystal phase fraction of all manufactured glass-ceramics was between 50 and 60 Vol- %, the crystallite size between 38 and 55 nm. The difference between the crystal phase content and crystallite size of an example and the corresponding comparative example was within the scope of the measurement inaccuracies. The thermal hysteresis determined in the temperature range of 15° to 50°C was < 0.1 ppm in all examples and comparative examples in Table 2.

[0211] Differences in the CTE of the example and the corresponding comparative example are within the framework of usual production fluctuations or measurement inaccuracies.

Claims

Claims1. Glas-ceramic component comprising a glass-ceramic and having the following properties:- mean thermal expansion coefficient in the range of 0 to 50°C CTE(0;50) of at most 0 ± 0.1 x 1O’6 / K,- thermal hysteresis at least in the temperature range of 15°C to 35°C of < 0.1 ppm,- relative isothermal length change of < 0.06 ppm / a, preferably < 0.05 ppm / a, more preferably < 0.04 ppm / a or < 0.03 ppm / a, measured at an age of the glass-ceramic of at least 200 days and at most 6 years.

2. Component according to claim 1, wherein the glass-ceramic has a relative isothermal length change of < 0.06 ppm / a, preferably < 0.05 ppm / a, more preferably < 0.04 ppm / a or < 0.03 ppm / a, measured at an age of the glass-ceramic of at least 100 days and at most 6 years.

3. Component according to any of the preceding claims, wherein it has a thermal hysteresis of < 0.1 ppm at least in the temperature range of 15°C to 40°C, advantageously at least in the temperature range 15°C to 45°C, preferably at least in the temperature range of 15°C to 50°C.

4. Component according to any of the preceding claims, comprising the following components (in mol% on an oxide basis):SiO260 - 71Li2O 7 - 9.4MgO+ZnO 0 - < 0.6 at least one component selected from the group consisting of P2O5, R2O, where R2O can be Na2O and / or K2O and / or CS2O and / or Rb2O, and RO, where RO can be CaO and / or BaO and / or SrO, and nucleating agents with a content of 1.5 to 6 mol%, where nucleating agents are at least one component selected from the group consisting of TiO2, ZrO2, Ta2Os, Nb20s, SnO2, MoOs, WO3, HfO2.

5. Component according to claim 4, further comprising AI2O3 with a content of 10 to 22 mol%, preferably from 11 to 21 mol% and / or P2O5 with a content of 0.1 to 6 mol%, preferably from 0.3 to 5 mol%.

6. Component according to claim 4 or 5, wherein the content of the sum ZnO + MgO is < 0.5 mol%, advantageously < 0.45 mol%, advantageously < 0.4 mol%, preferably < 0.3 mol%, preferably < 0.2 mol% and / or the content of MgO is < 0.35 mol%, preferably < 0.3 mol%, preferably < 0.25, preferably < 0.2 mol%, more preferably < 0.1 mol% and / or the content of ZnO is < 0.5 mol%, preferably < 0.45, preferably < 0.4 mol%, preferably < 0.3 mol%, preferably < 0.2 mol%, more preferably < 0.1 mol%.

7. Component according to any of claims 4 to 6, wherein the content of the sum RO (CaO + BaO + SrO) is > 0.1 mol%, preferably > 0.2 mol%, advantageously > 0.3 mol%, preferably > 0.4 mol% and / or < 6 mol%, preferably < 5 mol%, advantageously < 4.5 mol%, advantageously < 4.0 mol%, preferably < 3.8 mol%, preferably < 3.5 mol%, preferably < 3.2 mol%.

8. Component according to any of claims 4 to 7, wherein the content of the sum R2O (Na2O + K2O + Cs2O + Rb2O) is > 0.1 mol%, preferably > 0.2 mol%, advantageously > 0.3 mol%, preferably > 0.4 mol% and / or < 6 mol%, advantageously < 5 mol%, preferably < 4 mol%, preferably < 3 mol%, preferably < 2.5 mol%.

9. Process for producing a component according to any of claims 1 to 8, comprising the following steps: a. Heating a green glass of a glass-ceramic to a ceramization temperature TK, b. Ceramizing the green glass at a ceramization temperature TK, obtaining a glassceramic component, c. Cooling the glass-ceramic component with a cooling rate AT1 to a holding temperature TH, d. Holding the glass-ceramic component at a holding temperature TH, where 50°C < TH < 150 °C, preferably 60°C < TH 100 °C, for a holding time tH, e. Cooling the glass-ceramic component to room temperature with a cooling rate AT2.

10. Process according to claim 9, wherein the holding time tH, of at least 12 hours, preferably at least 18 hours, more preferably at least 24 hours and / or at most 7 days, preferably at most 3 days, more preferably at most 2 days are used.

11. Process according to claim 9 or 10, wherein cooling rates ATi and / or AT2 of at most -10 K / h, or of at most -5 K / h, or of at most -4 K / h and / or at least -0.5 K / h, or at least -1 K / h are used.

12. Use of a glass-ceramic component according to any one of claims 1 to 8, as a precision component in particular for use in metrology, spectroscopy, metrology, lithography, astronomy or earth observation from space, for example as a mirror or mirror substrate for segmented or monolithic astronomical telescopes or also as weight-lightened or ultralight mirror substrates for e.g. space-based telescopes or as high-precision structural components for distance measurement, e.g. in space or optics for earth observation, as precision components, such as standards for precision metrology, precision scales, reference plates in interferometers, as mechanical precision parts, e.g. for ring laser gyroscopes, hairsprings for the watch industry, as mirrors and prisms in flat-panel display lithography, for example for LC or OLED displays, as well as mask holders, wafer tables, reference plates, Reference frames and grid plates in microlithography and in EUV (extreme UV) microlithography and additionally as mirrors or mirror substrates and / or photomask substrates or photomask blanks or reticle mask blanks in EUV microlithography.

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