Thermal shock resistant precision component and method of production thereof

Abstract

The present invention relates to a zero expansion, highly homogeneous and thermal shock resistant precision component, a method for the production thereof and the use of such a precision component.

Description

[0001] Applicant: SCHOTT AG February 17, 2026 Our File: P06243 WO

[0002] Appl. No: - 1 -

[0003] Thermal shock resistant precision component and method of production thereof

[0004] The present invention relates to a zero-expansion thermal shock resistant precision component, a method for the production thereof and the use of such a precision component.

[0005] Background of the Invention

[0006] When processing ZERODUR, heating a ZERODUR component to temperatures 130°C and above can be problematic if the ZERODUR component is not cooled with the same cooling rate as when originally produced. Since original cooling rates for precision glass-ceramics are usually rather low such as in the range of 1 to 6 K / h, more rapid cooling of such precision glassceramic will result in a slight change in the GTE of the precision glass-ceramic. However, precision glass-ceramic components are frequently exposed to such heating and rapid cooling procedures, e.g. when reflective coatings are applied to the component or possibly even when the component is polished or otherwise surface treated. Such heating and rapid cooling can also take place locally on a component, e.g. during exposure to laser beams in EUV lithography, resulting in local variations of the GTE throughout the component.

[0007] It is believed that this behavior is due to relaxation processes within the glass-ceramic and the temperature range of from 130°C to 320°C is also known as the “upper relaxation rate”. Above 320°C no further change of the GTE is observed.

[0008] O. Lindig and W. Pannhorst describe in “Thermal expansion and length stability of ZERODUR in dependence on temperature and time”, APPLIED OPTICS, Vol. 24, No 20, Oct. 1985, 3330 -3334, that the length of a glass-ceramic specimen measured at a temperature of 20°C can change after such heating and rapid cooling procedure (see Fig. 2). This length change is described as (AI / I)2O and is said to vary as a function of the MgO content in the glass-ceramic. This document describes neither the CTE(0;50) of the investigated glass-ceramics nor does this document disclose whether the CTE(0;50) of a glass-ceramic component changes when submitted to a heating and rapid cooling procedure. The authors describe in the summary of this document that a modified glass-ceramic with almost identical properties to those of ZERODUR but without the relaxation effect in the temperature interval from 130°C to 320°C was developed and was being tested.

[0009] This modified glass-ceramic has later been sold under the trade name ZERODUR M and is e.g. further described by Lindig and Pannhorst in US4,851,372. However, although the lengthFebruary 17, 2026

[0010] - 2 -change after a heating and rapid cooling procedure has been solved by this glass-ceramic, this glass-ceramic is still prone to other disadvantages such as thermal hysteresis.

[0011] Hysteresis-free glass-ceramics have e.g. been described in US2022 / 0298079 A1, US2022 / 0298062 A1 und WO2022 / 194846 A1. However, these documents do not describe glass-ceramic with extremely highly homogeneous thermal expansion properties and / or thermal shock resistant glass-ceramics.

[0012] Object of the Invention

[0013] It is an object of the invention to provide precision components that show excellent thermal expansion behaviour and are hysteresis-free and thermal shock resistant, and a process for the production. It is a further object to provide a precision component having a highly homogeneous CTE even after heating to a temperature above 130°C and rapid cooling and a process for manufacturing such a precision component.

[0014] Summary of the Invention

[0015] This object is achieved by the embodiments described in the claims.

[0016] In particular, according to a first aspect, the invention relates to a thermal shock resistant precision component, having

[0017] ACTE(0;50) = CTE(0;50) (after rapid cooling) - CTE(0;50) (before heating to TE).

[0018] a CTE(0;50) of at most 0 ± 20 ppb / K or at most 10 ppb / K or at most 5 ppb / K, and a ACTE(0;50) of at most 0 ± 10 ppb / K or at most 0 ± 5 ppb / K, after heating the component to a temperature TE of 150° or 300°C or 400°C and rapid cooling with a cooling rate of at least 100 K / h , whereas

[0019] ACTE(0;50) = CTE(0;50) (after rapid cooling) - CTE(0;50) (before heating to TE), optionally, a spatial CTE(0;50) homogeneity of at most 2 ppb / K or of at most 1.5 ppb / K,

[0020] optionally a spatial CTE(0;50) homogeneity of less than 5 ppb / K or less than 3 ppb / K or at most 2 ppb / K or of less than 2 ppb / K after heating to a temperature TE of 150° or 300°C or 400°C and rapid cooling with a cooling rate of at least 100K / h.

[0021] According to a second aspect, the invention relates to a method of manufacturing precision components comprising the steps of

[0022] melting a batch of raw materials to form a green glass melt in a melting vessel (6) wherein the melting vessel (6) is heated using two or more heating circuits, each comprising a transFebruary 17, 2026

[0023] - 3 - former (3) and at least two electrodes (5), wherein at least one heating circuit comprises an inverter (1) providing an alternating current (AC) to its heating circuit,

[0024] withdrawing the green glass melt from the melting vessel (6),

[0025] forming the green glass melt into a green glass block,

[0026] optionally, machining the green glass block into the shape of a precision component, ceramizing the green glass to a glass-ceramic,

[0027] optionally, polishing at least one surface of the precision component,

[0028] optionally, coating the polished surface of the precision component with a reflective coating.

[0029] According to a third aspect, the invention relates to a method of ceramizing a green glass component into a glass-ceramic, comprising the steps:

[0030] providing a set of green glass blocks,

[0031] determining the characteristic temperature for ceramizing a first green glass block of said set of green glass blocks to a glass-ceramic, whereas said characteristic temperature is determined by measuring the temperature on the glass block and the oven temperature and determining the difference of these temperatures,

[0032] applying the so determined characteristic temperature to (a) control the oven temperature and / or (b) the holding time during the ceramization of further blocks of the set of green glass blocks.

[0033] According to a forth aspect, the invention relates to a use in metrology, spectroscopy, measurement technology, lithography, astronomy or earth observation from space, for example as mirror or mirror carrier for segmented or monolithic astronomical telescopes or else as weight-reduced or ultra-light mirror substrates for, for example, space-based telescopes or as high-precision structure components for measurement of distance, for example in space, or optics for Earth observation, as precision components, such as standards for precision measurement technology, precision rules, reference plates in interferometers, as mechanical precision parts, for example for ring laser gyroscopes, spiral springs for the clock industry, as for example mirrors and prisms in LCD lithography, and for example as mask holders, wafer stages, reference plates, reference frames and grid plates in microlithography and in EUV microlithography, and as mirrors and / or photomask substrates, photomask carriers or reticle mask blanks in EUV microlithography.

[0034] According to a fifth aspect, the invention relates to a thermal shock resistant precision component, having

[0035] a CTE(19;25) of at most 0 ± 20 ppb / K, and

[0036] a ACTE(19;25) of at most 0 ± 10 ppb / K or at most 0 ± 5 ppb / K, after heating the component to a temperature TEof 150° or 300°C or 400°C and rapid cooling with a coolingFebruary 17, 2026

[0037] -4 - rate of at least 100K / h, whereas

[0038] ACTE(19;25) = CTE(19;25) (after rapid cooling) - CTE(19;25) (before heating to TE), optionally, a spatial CTE(19;25) homogeneity of at most 2 ppb / K or at most 1.5 ppb / K, optionally a spatial CTE(19;25) homogeneity of less than 5 ppb / K or of at most 2 ppb / K or less than 2 ppb / K after heating to a temperature TEof 150° or 300°C or 400°C and rapid cooling with a cooling rate of at least 100K / h.

[0039] These and other aspects and objects, features and advantages of the present invention will become apparent upon a consideration of the following detailed description and the invention when read in conjunction with the drawing Figures.

[0040] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention and are intended to provide an overview or framework for understanding the nature and character of the invention as claimed.

[0041] Brief description of the drawings

[0042] Figure 1 schematically shows a melting furnace with three heating circuits.

[0043] Figure 2 shows the length change of ZERODUR after rapid heating (state of the art example).

[0044] Figure 3 shows the thermal shock resistance of Example 1 vs. Comparative Example 1.

[0045] Figure 4 schematically shows a precision component 40 and test samples 44 to be cut out of a blank 42.

[0046] Detailed description of the invention

[0047] Surprisingly the precision components according to the invention do not show an upper relaxation range, i.e. the CTE of the precision component does not change after a heating and cooling cycle, neither globally nor locally and such a precision component is therefore thermal shock resistant.

[0048] Compositions of green glass and glass-ceramic

[0049] The precision component may comprise an LAS glass-ceramic or green glass of an LAS glass- SiO235 - 72

[0050] Li2O 2 -6

[0051] MgO 0 - 0.5, preferably 0 - 0.1February 17, 2026

[0052] - 5 - ZnO 0 - 1 , preferably 0 - 0.5 or 0 - 0.1

[0053] at least one component selected from the group consisting of P2O5, R2O, where R2O may be Na2O and / or K2O and / or CS2O and / or Rb2O, and RO, where RO may be CaO and / or BaO and / or SrO,

[0054] and at least one nucleating agent in a content of 1.0 to 6 wt.-%, where nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2Os, Nb2Os, SnO2, MoOs, WO3.

[0055] The precision component may comprise an LAS glass-ceramic or green glass of an LAS glassceramic comprising the following composition (in wt.-% based on oxide):

[0056] SiO235 - 72

[0057] AI2O315 - 33

[0058] P2O50 - 12

[0059] Li2O 2 - 6

[0060] Na2O 0 - 2

[0061] K2O 0 - 3

[0062] MgO 0 - 0.5, preferably 0 - 0.1

[0063] CaO 0 - 4

[0064] BaO 0 - 5

[0065] SrO 0 - 3

[0066] ZnO 0 - 1 , preferably 0 - 0.5 or 0 - 0.1

[0067] TiO20 - 6

[0068] ZrO20 - 5

[0069] and at least one nucleating agent in a content of 1.0 to 6 wt.-%, where nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2Os, Nb2Os, SnC>2, MoOs, WO3.

[0070] In one embodiment, the glass which can be ceramized to form glass-ceramic or the glassceramic comprises the following composition (in wt.-% on an oxide basis):

[0071] SiO245 - 72

[0072] AI2O3 15 - 33

[0073] P2O5 0 - 12

[0074] Li2O 2 - 6

[0075] Na2O 0 - 2February 17, 2026

[0076] - 6 -

[0077] K2O 0 - 3

[0078] MgO 0 - 0.5, preferably 0 - 0.1

[0079] CaO 0 - 4

[0080] BaO 0 - 5

[0081] SrO 0 - 3

[0082] ZnO 0 - 1 , preferably 0 - 0.5 or 0 - 0.1

[0083] TiO20 - 6

[0084] ZrO20 - 5

[0085] and at least one nucleating agent in a content of 1.0 to 6 wt.-%, where nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2Os, Nb20s, SnC>2, MoOa, WO3.

[0086] In a further embodiment, the glass which can be ceramized to form glass-ceramic or the glassceramic comprises the following composition (in wt.-% on an oxide basis):

[0087] SiO250 - 70

[0088] AI2O3 17 - 32

[0089] P2O5 3 - 12

[0090] Li2O 2 - 5

[0091] Na2O 0 - 2

[0092] K2O 0 - 2

[0093] MgO 0 - 0.1

[0094] CaO 0 - 4

[0095] BaO 0 - 5

[0096] SrO 0 - 2

[0097] ZnO 0 - 0.1

[0098] TiO20 - 5

[0099] ZrO20 - 5

[0100] and at least one nucleating agent in a content of 1.0 to 6 wt.-%, where nucleating agent is at least one component selected from the group consisting of TiO2, ZrO2, Ta2Os, Nb2Os, SnC>2, MoOs, WO3.

[0101] The glass-ceramic preferably has a proportion of SiC>2 of 35 to 72 wt.-%. The proportion of SiC>2 is furthermore preferably at most 62 wt.-%, further preferably at most 60 wt.-%. The proportion of SiC>2 is further preferably at least 45 wt.-%, preferably at least 50 wt.-% and further preferably at least 54 wt.-%.February 17, 2026

[0102] - 7 - The proportion of AI2O3 is preferably 15 to 33 wt.-%. The glass-ceramic more preferably contains at least 17 wt.-%, preferably at least 20 wt.-%, yet more preferably at least wt.-% AI2O3. The proportion of AI2O3 is more preferably at least 32 wt.-%, more preferably at most 28 wt.-%. The phosphate content P2O5 of the glass-ceramic is 0 to 12 wt.-%. The glass-ceramic more preferably contains at least 3 wt.-%, more preferably at least 4 wt.-%, yet more preferably at least 5 wt.-%, P2O5. The proportion of P2O5 is preferably restricted to at most 10 wt.-%, more preferably at most 8 wt.-%.

[0103] The glass-ceramic contains at least one nucleating agent in a content of 1.0 to 6 wt.-%, where nucleating agent is at least one component selected from the group consisting of TiCh.ZrCh, Ta2Os, Nb20s, SnO2, MoOs, WO3.

[0104] The glass-ceramic preferably also contains TiC>2 in a proportion of 0 to 6 wt.-%, with a preference of at least 1 wt.-%, preferably at least 1.5 wt.-%, TiC>2. The proportion of TiC>2 is, however, preferably restricted to at most 4 wt.-%, more preferably at most 3 wt.-%.

[0105] The glass-ceramic can also contain ZrC>2 in a proportion of at most 5 wt.-%, preferably at most 4 wt.-%. ZrC>2 is preferably present in a proportion of at least 0.5 wt.-%, more preferably at least 1 wt.-%.

[0106] The glass-ceramic can furthermore contain alkali metal oxides, such as U2O, Na2O and K2O. U2O is preferably present in a proportion of at least 2 wt.-%, preferably at least 3 wt.-%. The proportion of Li2O is preferably restricted to at most 6 wt.-%, more preferably at most 5 wt.-%, more preferably at most 4 wt.-%. Na2O and K2O are optionally present in the glass-ceramic. Na2O is preferably present in a proportion of at most 2 wt.-%, preferably at most 1 wt.-%. The proportion of K2O is preferably at most 3 wt.-%, preferably at most 2 wt.-%, most preferably at most 1 wt.-%. Na2O and K2O can in any event and independently of one another be present in a proportion of at least 0.01 wt.-% in the glass-ceramic, preferably at least 0.02 wt.-%, more preferably at least 0.05 wt.-%.

[0107] The glass-ceramic can also contain alkaline earth metal oxides, such as MgO, CaO, BaO and / or SrO, and also further bivalent metals such as ZnO. The proportion of CaO is preferably at most 4 wt.-%, more preferably at most 3 wt.-%, yet more preferably at most 2 wt.-%. The glassceramic preferably contains at least 0.1 wt.-%, more preferably at least 0.5 wt.-%, CaO. The glass-ceramic can contain BaO in a proportion of less than 5 wt.-%, preferably at most 4 wt.-%, and / or preferably at least 0.1 wt.-%. In individual embodiments, the glass-ceramics are BaO-free. The glass-ceramics can contain SrO in a proportion of at most 3 wt.-% and / or preferably at least 0.1 wt.-%. In individual embodiments, the glass-ceramics are SrO-free.February 17, 2026

[0108] - 8 -

[0109] The addition of larger amounts of MgO is not preferred according to the present invention because MgO impairs the thermal shock resistance of the glass-ceramic. It should be restricted in the glass-ceramic and the green glass thereof to a proportion of at most 0.5 wt.-%, preferably at most 0.1 wt.-%, and / or at most 0.05 wt.-%. Embodiments are essentially free from MgO.

[0110] The addition of larger amounts of ZnO is also not preferred according to the present invention since it also impairs the thermal shock resistance of the glass-ceramic. ZnO should be restricted to a proportion of at most 1 wt.-%, more preferably at most 0.5 wt.-% or at most 0.1 wt.-%. Some embodiments are essentially free from ZnO.

[0111] For the modulation of the optical properties, e.g. refractive index, for example, Gd2Oa, Y2O3, HfO2, Bi2Oa and / or GeO2 can be contained in some advantageous variants.

[0112] The above glass compositions can optionally contain additions of colouring oxides, such as e.g. Nd20s, Fe2O3, CoO, NiO, V2O5, MnO2, CuO, CeO2, CT2O3, rare earth oxides in contents of in each case individually or in total 0-3 wt.-%. Preferred variants are free from colouring oxides. In some embodiments, the glass-ceramic according to the invention comprises from 1.5 wt.-% to 6 wt.-% of at least one component, selected from the group comprising TiO2, ZrO2, Ta2Os, Nb20s, SnO2, MoOs and WO3.

[0113] According to one advantageous embodiment of the present invention, the composition is free from components which are not mentioned above.

[0114] According to one embodiment of the present invention, a transparent glass-ceramic is generated. As a result of the transparency, many properties of such a glass-ceramic, in particular naturally their inner quality are better influenced. The glass-ceramics according to the invention are transparent, i.e. they have a pure transmission of at least 70% in the wavelength range from 350 to 650 nm. B2O3 and / or higher fluoride contents can reduce transparency. Advantageous variants therefore do not contain one or both of the stated components.

[0115] The glass-ceramics generated in the context of the invention are furthermore pore-free and crack-free. In the context of the invention, “pore-free” means a porosity of less than 1%, preferably less than 0.5%, more preferably less than 0.1%. A crack is a gap, i.e. a discontinuity, in an otherwise continuous structure.February 17, 2026

[0116] - 9 -

[0117] Definitions

[0118] Thermal shock resistance or thermo-shock resistance is the ability of a solid to withstand sudden changes in temperature either during heating or cooling. According to this invention, thermal shock resistance particularly means that a precision component - either across the complete component or only locally - is heated to a temperature in the range of from 130°C to 600°C and afterwards cooled rapidly, in particular with a cooling rate of at least 100 K / h or at least 500 K / h or even at least 800 K / h.

[0119] According to the present invention, the precision component has excellent thermal shock resistance, meaning that the precision component has a ACTE(0;50) of at most 0 ± 10 ppb / K, preferably at most 0 ± 5 ppb / K, after heating the component to a temperature TE of 150° or 300°C or 400°C and rapid cooling with a cooling rate of at least 100K / h, whereas ACTE(0;50) = CTE(0;50) (after heating to TE and rapid cooling) - CTE(0;50) (before heating to TE).

[0120] Thermal Expansion Properties

[0121] The Coefficient of Thermal Expansion (CTE) describes how the size of an object changes with a change in temperature. In the context of this application, “CTE” means the linear coefficient of thermal expansion also denoted as a. “CTE” and “a” are used interchangeably in this application.

[0122] The CTE can firstly be specified as the “mean CTE” or “average CTE” of a material or component in a given temperature interval. The mean CTE can e.g. be determined by a static method in which the length of a test specimen is determined at the start and at the end of a temperature interval, and the difference in length is used to calculate the mean CTE in this temperature interval. A typical temperature interval for the determination of the mean CTE is temperature interval from 0°C to 50°C and when this temperature interval is used the CTE is denoted as CTE(0;50) or a(0;50).

[0123] The mean CTE may be determined not only for the temperature interval CTE(0;50) but also, for example, for a temperature interval around the application temperature of a component, such as for example the interval from 19°C to 25°C, resulting in a mean CTE(19;25).

[0124] The components provided according to the invention show “(near) zero expansion”, meaning that they have a mean coefficient of thermal expansion CTE in the range from 0 to 50°C of at most 0 ± 0.02 x 10'6 / K or at most 0 ± 0.01 x 10'6 / K or at most 0 ± 0.007 x 10'6 / K or at most 0 ±February 17, 2026

[0125] - 10 -

[0126] 0.005 x 106 / K or at most 0 ± 0.002 x 106 / K, whereas e.g. “0 ± 0.002 x 10’6 / K” can also be written as “0 ± 0.002 ppm / K” or “0 ± 2 ppb / K” or “0 ± 2 ppb / °C”.

[0127] For particular applications, it may be advantageous to specify the mean CTE within a different temperature range, in particular, for a temperature interval around the actual application temperature of a material or component, for example, in the temperature interval from -30°C to +70°C or from -40°C to +80°C or from 19°C to 25°C. Also in these ranges, the mean CTE may have a value of 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 or at most 0 ± 0.002 x 10-6 / K. If the mean CET was determined e.g. in the temperature interval from 19°C to 25°C, it is then denoted as CTE(19;25).

[0128] The CTE can also be determined as a function of the temperature, i.e. as the differential CTE(T). The differential CTE(T) is defined according to the following formula (1):

[0129] CTE (T) = (1 / Io) x (3 I / ST) (1)

[0130] The graph of the function CTE(T) - T is also called CTE-T curve in this application and shows the temperature dependency of the differential CTE(T). A CTE-T curve can be obtained by differentiation of the AI / lo-T curve or expansion curve or plot of the change in length Al / lo of a test specimen against the temperature.

[0131] For the creation of a AI / lo-T curve, the temperature-dependent change in length of a test specimen from the starting length l0at the initial temperature to to the length ltat the temperature t is measured. Here, preferably, small temperature intervals of 5 K or 3 K or 1 K or even less than 1 K, for example, are chosen for determining a measurement point. Such measurements may be carried out, for example, by dilatometry methods, interferometry methods, as for example the Fabry-Perot method, i.e., the evaluation of the shift in the resonance peak of a laser beam injected into the material, or other suitable methods.

[0132] The chosen method of determining the CTE should have an accuracy of at least ± 5 ppb / K or at least ± 3 ppb / K or at least ± 1 ppb / K or at least 0.5 ppb / K or at least 0.3 ppb / K or at least 0.1 ppb / K.

[0133] The AI / lo-T curve also can be used to calculate the mean CTE for a particular temperature interval.February 17, 2026

[0134] - 11 - The AI / lo-T curve can furthermore be used to determine the total change of length “TCL” within a temperature interval. The “total change of length” or “TCL” value is the distance between the highest dl / l0value and the lowest dl / l0value within a given temperature range, e.g. the temperature range of from 0°C (starting temperature) to 50°C:

[0135] TCL (0;50°C) = | dl / l0max. | + | dl / l0min.| (2)

[0136] where “dl” denotes the change in length at the respective temperature and “l0“ denotes the length of the test specimen at 0°C, as the starting and / or lowest temperature for TCL(0;50°C). The calculation is based in each case on the magnitudes of the dl / lo values.

[0137] Within the context of the invention, the TCL value can be reported for the temperature range of 0°C and 50°C and / or in the range of from 10 to 30°C and / or in the range of from 20 to 24°C and / or in the range of from 20 to 60°C. It is ascertained from the normalized AI / lo-T curve, with “normalized” meaning that the change in length at 0°C is set to 0 ppm for TCL(0;50), or set at 10°C for TCL(10;30), or set at 20°C for TCL(20;24) and TCL(20;60).

[0138] The TCL(0;50) preferably is in the range of at most 100 ppb or at most 50 ppb or at most 40 ppb or at most 20 ppb. The TCL(10;30) preferably is in the range of at most 50 ppb or at most 40 ppb or at most 20 ppb or at most 10 ppb or at most 5 ppb. The TCL(20;24) preferably is in the range of at most 20 ppb or at most 10 ppb or at most 5 ppb or at most 2 ppb or at most 1 ppb or less than 1 ppb. The TCL(20;60) preferably is in the range of at most 100 ppb or at most 50 ppb or at most 40 ppb or at most 20 ppb or at most 10 ppb or at most 5 ppb.

[0139] Further details of the thermal expansion of a material or component can be derived from the CTE-T curve such as the zero crossing of the CTE-T curve and the slope of the CTE-T curve.

[0140] A CTE-T curve preferably has at least one or two or three or more zero crossing, i.e. temperatures at which of the CTE-T curve crosses the T-axis and the CTE is 0 ppb / K. Around the temperature of such a zero-crossing, the glass-ceramic or component shows the least expansion with a temperature change. Zero crossings of the CTE-T curve are therefore preferred around the application temperature of the glass-ceramic or component such as e.g. zero crossings in the temperature range of from 20°C to 24°C, i.e. ambient temperature.

[0141] The CTE-T curve is also used to determine the shaping and position of a so-called CTE plateau.February 17, 2026

[0142] - 12 - CTE-T curve of a glass-ceramic or component having a “CTE plateau” means that the glassceramic or component shows an optimized zero expansion over a certain temperature range. The location of a CTE plateau is defined by its start temperature Tp(start) and its end temperature Tp(end) on the temperature axis of the CTE-T graph and by the width of the plateau whereas Tp(end) - TP(start) = width of CTE plateau [K], e.g. a CTE plateau may start at 10°C and end at 50°C having a width of 40 K or 40°C. “Optimized zero expansion” means that the differential CTE across the width of the CTE plateau (i.e. from TP(start) to TP(end)) only varies in an very small amount close to 0 ppb / K and / or that the slope of the CTE-T curve across the width of the CTE plateau is 0 ppb / K2or close to 0 ppb / K2. For example, the differential CTE may vary across the width of the CTE plateau at most 0 ± 20 ppb / K or at most 0 ± 10 ppb / K or at most 0 ± 5 ppb / K or at most 0 ± 2 ppb / K. The slope of the CTE-T curve may vary across the width of the CTE plateau at most 0 ± 2.5 ppb / K2or at most 0 ± 2 ppb / K2or at most 0 ± 1.5 ppb / K2or at most 0 ± 1 ppb / K2or at most 0 ± 0.8 ppb / K2or at most 0 ± 0.5 ppb / K2.

[0143] A CTE plateau advantageously includes the application temperature (range) of the glassceramic or the component, e.g. a CTE plateau typically be located within the range of from 0 to 100°C. The CTE plateau preferably has a width of at least 20 K or at least 30 K or at least 40 K or at least 50 K or at least 60 K. Preferably the width of the CTE plateau overlaps or covers the application temperature range of the glass-ceramic or component.

[0144] Examples of CTE-plateaus within the temperature range of from 0°C to 100°C may have a width of at least 20 K and a CTE variation of at most 0 ± 10 ppb / K or at most 0 ± 5 ppb / K; or a width of at least 30 K and a CTE variation of at most 0 ± 10 ppb / K or at most 0 ± 5 ppb / K; or a width of at least 40 K and a CTE variation of at most 0 ± 20 ppb / K or at most 0 ± 10 ppb / K or at most 0 ± 5 ppb / K; or any other combination.

[0145] Spatial homogeneity of thermal expansion properties

[0146] The present invention relates to precision components with spatial homogeneous thermal expansion properties, i.e. even if the thermal expansion properties are measured at different locations of the precision component, these thermal expansion properties only vary to a very small amount. With “spatial homogeneous thermal expansion properties” or “total spatial variation of thermal expansion properties” the so-called “peak-to-valley value”, i.e. the difference between the respective highest and lowest value of a given thermal expansion property measured at different locations of a precision component is meant.

[0147] The spatial homogeneity of all of the above discussed thermal expansion properties can be determined for a precision component, for example, the spatial homogeneity of the mean CTE, aFebruary 17, 2026

[0148] - 13 - CTE-plateau, the zero crossing of a CTE-T curve or the slope of the CTE-T curve at the zero crossing of the CTE-T curve can be determined and specified.

[0149] To determine the spatial homogeneity of a thermal expansion property, said thermal expansion property is measured at at least two different locations of a precision component. Preferably, such measurement is performed at at least 6 or at least 10 or even at more than 15 different locations of a precision component.

[0150] For such measurements, preferably a non-destructive CTE measurement method is used. Alternatively, two or more samples from different locations of the precision components can be used to determine the spatial homogeneity of the thermal expansion properties.

[0151] Since it is usually desirable to cut samples from a precision component itself, such samples 14 can be taken from the blank 12 from which the precision component 10 is produced within the scope of raw glass machining as shown in Figure 4. These samples 14 can then be laid out near the unceramized precision component in the ceramization furnace and ceramized together with the precision component. These samples represent a sufficient representation of the spatial fluctuations of the thermal expansion properties and can thus be used to determine the spatial distribution of the thermal expansion properties of a precision component.

[0152] Frist of all, the “spatial homogeneity of the linear mean CTE” or CTE homogeneity can be determined.

[0153] The CTE homogeneity for the temperature range from 0°C to 50°C, i.e., the spatial variation of the linear mean CTE(0;50), is also called CTE homogeneity(0;50) below. The CTE homogeneities for other temperature ranges may be identified analogously. Thus, for example, the CTE homogeneity for the temperature range from 19°C to 25°C, i.e., the spatial variation of the linear mean CTE(19;25), is also called CTE homogeneity(19;25) below.

[0154] In some embodiments, the precision component provided according to the invention has a CTE homogeneity(0;50) over the entire precision component of less than 3 ppb / K or at most 2.5 ppb / K or at most 2 ppb / K or less than 2 ppb / K or at most 1.75 ppb / K or at most 1.5 ppb / K and / or a CTE homogeneity(19;25) over the entire precision component of less than 2 ppb / K, or at most 1.9 ppb / K ppb / K or at most 1.75 ppb / K or at most 1.5 ppb / K or at most 1 ppb / K.

[0155] The CTE homogeneity depends on the size of the precision component. It is easier to achieve a highly homogeneous CTE in a smaller precision component and increasingly difficult with increasing size of the precision component.February 17, 2026

[0156] - 14-

[0157] As shown in Figure 4, a precision component 40 usually has a top and bottom surface with, in case of components having a round or ellipsoid surface, i.e. cylindric components, has a (surface) diameter D and a height h. In case of cubic or cuboid precision components, either the diagonal or the edge length of a top and bottom surface can be defined in addition to the height h of the components. Precision components or blanks therefore may have planar surfaces and simple geometric forms as shown in Figure 4. According to further embodiments, they have concave or convex surfaces or any other irregular shapes. In case a component has either more than one (surface) diameter, e.g. in case of ellipsoid components, or, in case of (rect)angular or polygona components, edges and / or diagonals with different length, the maximum diameter, edge length or diagonal, respectively, is the relevant parameter.

[0158] One embodiment relates to precision components with small dimensions i.e. components with a surface diameter or edge length of less than 500 mm, in particular in the case of (rect)angular shapes with edge lengths (width and / or depth) or with round surfaces with diameters of at least 50 mm or at least 100 mm and / or a less than 500 mm or less than 400 mm and / or a thickness of at most 50 mm or less than 20 mm or less than 10 mm and / or at least 1 mm or at least 2 mm or at least 5 mm.

[0159] One embodiment relates to precision components with very small dimensions, in particular with edge lengths (width and / or depth) or diameters and / or thicknesses of a few mm (for example less than 50 mm or at most 40 mm or 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 elements can be, for example, a spacer, for example in an interferometer, or a component for ultra-stable clocks in quantum technology.

[0160] Such small or very small precision components with a surface diameter or edge length of less than 500 mm show a CTE homogeneity of at most 1.8 ppb / K or at most 1.5 ppb / K or at most 1.0 ppb / K.

[0161] However, it is also possible to produce large precision components i.e. components with a surface diameter or edge length of at least 500 mm. One embodiment of the invention thus relates to components with a large volume. For the purposes of this application, this should be understood to mean 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 5 t, or with edge lengths (width and / or depth) in the case of (rect)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, as a furtherFebruary 17, 2026

[0162] - 15 -preference at least 250 mm, or in the case of 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, more preferably at least 250 mm.

[0163] Specific embodiments of the invention may also be very large 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 relates to rectangular components, wherein 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 more preferably at least 3 m2or at least 4 m2and / or the thickness is 50 mm to 400 mm, preferably 50 mm to 300 mm. As a rule, large-volume components which have a significantly larger base area than height are produced. However, they may also be large-volume components which have a shape approximated to a cube or a sphere.

[0164] Large or very large precision components have a CTE homogeneity of less than 3 ppb / K or at most 2.5 ppb / K or at most 2.0 ppb / K or at most 1.8 ppb / K or at most 1.5 ppb / K.

[0165] Thermal Hysteresis

[0166] In the context of the invention, the glass-ceramic, at least within the temperature range of 10°C to 35°C, has thermal hysteresis of < 0.1 ppm and is therefore hysteresis-free. Thus, at any temperature within the temperature interval of 10°C to 35°C, the glass-ceramic, once it has been subjected to a change in temperature, shows an isothermal change in length of less than 0.1 ppm at a subsequently constant temperature.

[0167] In advantageous embodiment, this freedom from hysteresis is preferably at least within a temperature range from 5 to 35°C, preferably at least within the temperature range from 5 to 45°C, preferably at least within the temperature range from > 0°C to 45°C, with preference at least within the temperature range from -5°C to 50°C. More preferably, the temperature range for the freedom from hysteresis is even broader, such that the material or component is also suitable for applications at temperatures up to at least 100°C and advantageously also even higher. More preferably, the temperature range for the freedom from hysteresis is even broader. Preferred application temperatures are in the range of -60 to 100°C, more preferably of -40°C to +80°C. Particular variants of the present invention relate to glass-ceramics and precision components for application temperatures TA, for 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 hysteresis-free even at these temperatures as well.February 17, 2026

[0168] - 16 - Thermal hysteresis was determined for the glass-ceramics and precision components according to the invention and for the comparative examples using a precision dilatometer capable of ascertaining the CTE with a reproducibility of ± 0.001 ppm / K and ± 0.003 ppm / K absolute, with a temperature interval of 1°C, on rod-shaped samples of length 100 mm and diameter 6 mm of the test specimens (i.e. sample of the precision component or sample of the glass-ceramic), in accordance with the method and apparatus construction disclosed in DE 102015113548 A, the disclosure-content of which is incorporated into this application in full. For every sample examined, the change in length Al / lo was determined as a function of temperature between 50°C to -10°C, cooling at a cooling rate of 36 K / h. After an isothermal hold time of 5 hours at -10°C, the sample was heated at a heating rate of 36 K / h to 50°C, and the change in length Al / lo was recorded as a function of temperature. The thermal hysteresis characteristics of a test specimen are considered at-5°C, 0°C, 5°C, 10°C, 22°C, 35°C, 40°C. These points are representative of the temperature range from -10°C to 50°C, since hysteresis decreases with rising temperature within the temperature interval mentioned. Thus, a sample which is hysteresis-free at 22°C or 35°C also shows no hysteresis in the range up to 50°C.

[0169] For determination of thermal hysteresis at 10°C, the individual measurement values of the change in length for the five temperatures of 8°C, 9°C, 10°C, 11°C and 12°C, i.e. two temperature points above and two temperature points below 10°C, were recorded both in the course of heating and in the course of cooling of the sample within the range of -10°C to 50°C at the rate of 36 K / h. The differences between the measurement values for heating curve and cooling curve at these five measurement points were used to form the average, which is listed in the tables as “Hyst.@10°C” in the unit [ppm].

[0170] For determination of thermal hysteresis at 35°C, correspondingly, the individual measurement values of change in length for the five temperatures 33°C, 34°C, 35°C, 36°C and 37°C, i.e. two temperature points above and two temperature points below 35°C, were recorded both in the course of heating and in the course of cooling of the sample within the range of -10°C to 50°C at the rate of 36 K / h. The differences between the measurement values for heating curve and cooling curve of these five measurement points were used to form the average, which is listed in the tables as “Hyst.@35°C” in the unit [ppm].

[0171] The corresponding procedure was followed for the other abovementioned temperature points.

[0172] Further physical properties

[0173] Advantageous glass-ceramics and precision components additionally have good internal quality. They preferably have at most 5 inclusions per 100 cm3, more preferably at most 3 inclusions per 100 cm3, most preferably at most 1 inclusion per 100 cm3. Inclusions are understood in ac-February 17, 2026

[0174] - 17 -cordance with the invention to refer both to bubbles and to crystallites having a diameter of more than 0.3 mm.

[0175] According to one variant of the invention, precision components are provided which have a diameter or an edge length of at most 800 mm and a thickness of at most 100 mm and have at most 5, preferably at most 3, more preferably at most 1 inclusion(s), in each case per 100 cm3, having a diameter of a size of more than 0.03 mm.

[0176] As well as the number of inclusions, the maximum diameter of the inclusions detected also serves as a measure of the level of the internal quality. The maximum diameter of individual inclusions within the total volume of a precision component having a diameter of less than 500 mm or edge lengths of less than 500 mm is preferably at most 0.6 mm, in the critical volume for the application, for example close to the surface, preferably at most 0.4 mm. The maximum diameter of individual inclusions in glass-ceramic components having a diameter of 500 mm to less than 2 m or edge lengths of 500 mm to less than 2 m is preferably at most 3 mm, in the volume critical for the application, for example close to the surface, preferably at most 1 mm. This may be advantageous in order to achieve the surface quality needed for the application.

[0177] Method of production

[0178] Process for producing a precision component - Melting

[0179] A further aspect of the invention relates to a process for producing a precision component comprising the steps of

[0180] melting a batch of raw materials to form a green glass melt in a melting vessel (6), heating the batch and / or the green glass melt in the melting vessel using two or more heating circuits, each comprising a transformer (3) and at least two electrodes (5), wherein at least one heating circuit comprises an inverter (1) providing an alternating current (AC) to its heating circuit,

[0181] withdrawing the green glass melt from the melting vessel (6),

[0182] forming the green glass melt into a green glass block,

[0183] ceramizing the green glass block to form a glass-ceramic component.

[0184] A specific aspect of the invention relates to a process for producing a precision component comprising the steps of

[0185] melting a batch of raw materials to form a green glass melt in a melting vessel (6), heating the batch and / or the green glass melt in the melting vessel using two or more heating circuits, each comprising a transformer (3) and at least two electrodes (5),February 17, 2026

[0186] - 18 - wherein at least one heating circuit comprises an inverter (1) providing an alternating current (AC) to its heating circuit and adjusting the amplitude and / or phase angle of this current independently of the amplitudes and / or phase angles of the currents of the other heating circuits and applying a phase angle shift to its current relative to at least one other heating circuit; and

[0187] withdrawing the green glass melt from the melting vessel (6),

[0188] forming the green glass melt into a green glass block,

[0189] ceramizing the green glass block to form a glass-ceramic component.

[0190] A state-of-the-art melting vessel utilizable for producing LAS glass-ceramics is e.g. described in “Low Thermal Expansion Glass-ceramics”, Hans Bach (editor), Springer-Verlag, 1995, pages 131 -133. Heating of such conventional melting vessels generally is affected via burner flames in the superstructure of the melting vessel. Recently, attempts have been made to replace fossil fuels by hydrogen in melting processes for LAS glass-ceramics, see US 2013 / 0081248A. However, since green hydrogen is not yet sufficiently available for glass melting processes, the inventors also indulged in the development of melting vessels and processes that use substantial amounts electrical power in the glass melting of LAS glass-ceramics. State-of-the-art processes using electrical power in the glass melting process are not flexible enough for the production of LAS glass-ceramics, however, the inventors have found that when using two or more heating circuits, each comprising a transformer and at least two electrodes, wherein at least one heating circuit comprises an inverter, it is possible to flexibly provide heat to a melting vessel and to stably produce LAS glass-ceramics. Moreover, the inventors have found that by using such a process, the temperature distribution within the melting vessel can be controlled very precisely and surprisingly, a very homogeneous green glass can be produced that can be ceramized to yield a glass-ceramic component with an extremely high homogeneous spatial CTE.

[0191] This disclosure relates to methods which allow for the electric heating of a glass melt with multiple heating circuits at least one or some or all of which can be influenced independently of the others in amplitude and / or phase of the current supplied to the electrodes. This allows for the creation of different heating zones in the glass melt by targeted current and power distribution in the glass melt and an optimal current distribution in the glass melt based on desired patterns can be achieved. This flexibility is not fixed by construction measures but can be controlled and adjusted as necessary during the melting process. Thus, an optimal melting of a glass batch in the melting vessel is achieved and the homogeneity of the green glass melt is improved.

[0192] A "melting vessel" is a vessel used for holding a glass melt. A melting vessel may have a superstructure above the glass melt surface. The melting vessel comprises at least two heating circuits.February 17, 2026

[0193] - 19 -

[0194] A ’’heating circuit” as used herein is meant to comprise a power source and at least two electrodes immersible into the glass melt (and of course the electric lines required for connecting them).

[0195] “Each heating circuit comprising at least two electrodes” means that each heating circuit is electrically connected to at least two electrodes. These electrodes can be electrically connected exclusively to one heating circuit, they can also be electrically connected to one or more other heating circuits, i.e. electrodes can be shared between two or more heating circuits. Hence, the total number of (physical) electrodes in a melting vessel may be less than the sum of the (logical) electrodes in the defined heating circuits in the melting vessel. However, the number of heating circuits in a melting vessel is not particularly limited. Depending on the size of the melting vessel, the melting vessel may comprise at least 2 or at least 3 or at least 6 or at least 8 heating circuits or at least 10 and / or up to 10 or up to 20 circuits.

[0196] One or more or all of the electrodes may be rod-shaped and / or plate-shaped and / or domeshaped and / or tube-shaped and / or block-shaped. One or more or all of the electrodes may be arranged horizontally extending from a wall of the melting vessel or vertically extending from a bottom of the melting vessel or from a surface of the glass melt. In further embodiments, one or more or all of the electrodes may be located partially or completely in or on a wall of the melting vessel and / or in or on the bottom of the melting vessel and / or in the super-structure of the melting vessel (6) and / or constitute a wall section and / or a bottom section and / or a superstructure section of the melting vessel. In further embodiments of the method, the electrode material of one or more or all of the electrodes is selected from Pt, Rh, Ir, Pd, alloys of these noble metals, Ta, Mo, MoSi2, MoZrC>2, W, SnC>2, C, and combinations thereof.

[0197] The electrodes may be operated at a current frequency of at least 20 Hz and at most 25,000 Hz, optionally of at least 50 Hz and at most 25,000 Hz, optionally of at least 50 Hz and at most 15,000 Hz, optionally of at least 50 Hz and at most 10,000 Hz, optionally of at least 100 Hz and at most 10,000 Hz, optionally of at least 1,000 Hz and at most 5,000 Hz, optionally of at least 1 ,000 Hz and at most 3,000 Hz. The electrodes may be operated at a current frequency of less than 25,000 Hz, less than 15,000 Hz, less than 12,500 Hz, less than 10,000 Hz, less than 7,500 Hz, less than 5,000 Hz, less than 4,500 Hz, less than 4,000 Hz, less than 3,500 Hz, or less than 3,000 Hz. The electrode may be operated at a current frequency of at least 20 Hz, at least 50 Hz, at least 100 Hz, at least 1,000 Hz, at least 1,500 Hz, at least 2,000 Hz, or at least 2,500 Hz.February 17, 2026

[0198] - 20 - In further embodiments, additional heating is provided by a fuel burner, or no fuel burner is used for additional heating. This burner may then be fueled by a "green gas", i.e. hydrogen produced from renewable energies.

[0199] As a power source for the heating circuit the heating circuit may comprise a transformer or an inverter as a power source.

[0200] A “transformer” is a power electronic component that regulates the power by transferring electrical energy from one electrical circuit to another circuit thereby allowing for a change of the power and / or voltage supplied within e.g. the grid frequency to a heating circuit and may e.g. be a thyristor power controller or a regulating transformer or any other suitable power electronic components.

[0201] A ’’thyristor controller” or “thyristor power controller” controls the power and / or voltage supplied within the grid frequency to a heating circuit.

[0202] A “matching transformer” is used to match current and voltage of a heating circuit to the conductivity of the glass melt and is typically positioned close to the electrodes of a heating circuit. In addition, a matching transformer provides galvanic isolation of the heating circuits. A matching transformer can be provided in each heating circuit in addition to a power electronic component such as an inverter, regulating transformer or thyristor power controller.

[0203] “Power grid frequency” or utility frequency or power line frequency or mains frequency is the nominal frequency of the oscillations of alternating current (AC) in a wide area synchronous grid transmitted from a power station to the end-user. Typically, the power grid frequency is 50 Hz or 60 Hz.

[0204] According to one embodiment, at least one heating circuit comprises an inverter. An “inverter” or “frequency changer” is a power electronic component which converts one alternating current of one frequency and / or phase to an alternating current of another frequency and / or phase, in particular an alternating current the frequency and / or phase of which is different from the frequency and / or phase of the grid. For example, an inverter may comprise of (a) a rectifier transforming alternating current (AC) into DC, followed by (b) an intermediate circuit e.g. comprising a capacitor and (c) an inverted rectifier transforming DC into an alternating current. Using such an inverter enables to convert a given AC (e.g. the power grid frequency) into an alternating current with any desired frequency and / or phase.February 17, 2026

[0205] - 21 - Not all heating circuits have to comprise an inverter which are comparatively expensive components. In particular, if the operating current frequency is not changed from the grid frequency, it is advantageous from an economical point of view to realize the power supply of at least one heating circuit by using e.g. a thyristor power controller and / or a regulating transformer. Such heating circuits without inverters can particularly be used in parts of the melting vessel where specifically tailored heat distribution profiles in the glass melt are not essential and / or the available frequencies from the primary transformers are sufficient and a phase angle shift for these heating circuits is not required. Heating circuits in parts of the melting vessel in which specific heat distribution profiles are essential are preferably equipped with inverters and thus the phase angle adjustment possibility of this invention in order to optimize the flow pattern and / or dwell time of the glass melt as described above.

[0206] The feature of "controlling the amplitude and / or phase of a current independently of the amplitudes and / or phase angles of the currents of other heating circuits" means that the one or more inverters can provide currents of different amplitudes and / or phase angles, i.e. the amplitude and / or phase angle of the current provided by one inverter is not affecting the amplitudes and / or phase angles of currents provided by other inverters in other heating circuits. It does not exclude that two or more inverters operate at different amplitudes and / or phase angles in a predetermined relationship, e.g. controlled by a common controller.

[0207] “Phase angle of the supplied current” encompasses also phase angle of the supplied voltage or power. Due to the relationship P = II * I, instead of the phase angle of the current I as well the phase of the power P or the phase of the voltage II can be controlled. The phases of II and I in a certain heating circuit at the electrodes are preferably in phase.

[0208] The “phase” or “phase angle” or “phase shift” or “phase angle shift” of an electrical circuit is a measure of the relative timing between two sinusoidal waveforms. It represents the delay or lead of one waveform to another. A phase angle is measured in degrees or radians and can be positive or negative, indicating whether one waveform leads or lags the other. The phase angle <p can also be expressed as a time delay At or “phase shift” according to the following formular

[0209] phase angle cp = (time delay At I period T) X 360° = (time delay At x frequency) x 360°.

[0210] In the context of electrical circuits, the expression “phase” or “phase angle” often used to describe the relationship between voltage and current in one AC (alternating current) circuit. If not otherwise specified, according to the present invention, “phase” or “phase angle” or “phase shift” or “phase angle shift” is defined as the phase difference of one specific physical quantity in one heating circuit (measured preferably near the electrodes of the heating circuit) relative toFebruary 17, 2026

[0211] - 22 -the same physical quantity in one or more other heating circuits, e.g. the phase angle of the current in one heating circuit is compared to the phase angle of the current in the other heating circuits and the difference is defined as the phase shift or phase angle or delay.

[0212] A “common controller” as used herein takes on several tasks and / or functions. First of all, the common controller collects some or all measurement data that are generated in some or preferably all heating circuits and optionally other parts of the melting vessel. Secondly, the common controller utilizes the collected measurement data to compare the actual values to the stored or set target values and sends out control signals to the control units such as e.g. thyristor power controllers, inverters and / or delay generators.

[0213] The common controller furthermore comprises or is connected to a clock generator or global clock generating a global clock signal. The global clock acts as a frequency control unit which provides an external time base for all inverters. It is used to provide a global clock signal to the delay generators providing an individual shift of the phase angle of the current provided by each inverter. In the case of one or more heating circuits using power grid frequency and phase, the global clock is synchronized to the power grid frequency and phase. “A heating circuit using power grid frequency and phase” means that such heating circuit does not comprise a rectification device such as e.g. an inverter.

[0214] All tasks and / or functions of the common controller can be concentrated in a single central common controller device; it is also possible that certain tasks and / or functions of the common controller are handled decentrally by further controllers or specialized devices such as e.g. a delay generator. One or more controlling tasks and / or functions of the common controller can also be executed by qualified workers.

[0215] According to a further embodiment, the present invention can also be used for phase angle correction of the current in one heating circuit relative to the phase of the voltage within the same heating circuit. As the phase angle of the voltage may shift relative to the phase angle of the current along the path from the inverter to the electrodes, a correction of this phase shift of the voltage relative from the phase of the current is particularly advantageous in two aspects. A detector which is installed at the electrodes can detect and measure the phase angle shift of the voltage relative to the current. Since the present method and apparatus allow for the free adjustment of the phase angle of the current, this detected shift can be corrected. To assure the maximum power at the electrodes, the phases of current and voltage of a heating circuit should be in phase. Thus, the detection of the phase angle between the phases of current and voltage allows for a correct assessment of the actual heating power distribution in the glass melt and optimized power in the melt. Such a correction is useful in a first aspect for the correct estab-February 17, 2026

[0216] - 23 -lishment of the intended heating profile and hotspot creation for influencing the flow pattern of the glass melt. In a second aspect, this can also be an important factor for minimizing the occurrence of parasitic currents and the power loss associated with them in a melting vessel which is operated with parallel heating circuits having a phase angle difference of 0° like the standard heating circuits used in prior art. This way, electrical efficiency may be improved when operating at higher frequencies and, consequently, either energy can be saved, or the operation frequency may be increased for lowering the electro corrosion further.

[0217] The common controller is preferably also connected to one or more heating circuits without inverters, can thus detect the phase angle of such heating circuits and can generate a clock signal relative to these heating circuits. The delay generators of the heating circuits with inverters can thus provide a shift of the phase angle of the current by applying a delay At > 0 ps to the clock signal of the common controller (8).

[0218] For example, the delay At applied by one the inverters to its heating circuit relative to a second heating circuit may differ by 0.1 ps (At2 = Ah + 0.1 ps) while the further heating circuits have the same or a different or no delay applied, i.e. At = Ah or At2, At Ah or At2, or At = 0 ps, respectively. As a result, between at least two heating circuits a certain shift in current phase angle will occur while the other heating circuits may have the same relative shift or a different one. According to one embodiment, one or more or all At > 0 ps.

[0219] The feature of "independently applying a delay At" means that the various inverters can be operated with different time delays applied to the clock signal, i.e. the inverters work with differently timewise modified clock signals by keeping the frequency constant resulting in a different phase angle of the supplied current. It does neither exclude that two or more inverters operate with different timewise modified clock signals in a predetermined relationship nor that two or more inverters operate with identically timewise modified clock signals.

[0220] In embodiments, the phase angle shift between the heating circuits with inverters is freely adjustable in a range of 0° to 360° relative to other heating circuits.

[0221] In embodiments, in one or more or all of the heating circuits a phase detector may be installed between the transformers and the electrodes which measures the actual current signal at the electrodes and the common controller detects a phase angle shift by comparing this actual current signal with the clock signal provided to the inverters including any applied delay At and adjusts the clock signal and / or the delay At in order to compensate for an undesired shift along the current flow from the inverter to the electrodes.February 17, 2026

[0222] - 24- Electrotechnically, the glass melting system of the present disclosure can be seen as a complex meshed network. Each inverter can initially feed into the glass melt with different power, current, voltage, and phase. Due to a typical resistivity of the glass melt in a range of from 0,3 Q cm to 200 Q cm at a temperature of 1,600 °C, the inverters as sources of power are not independent from each other but electrically coupled via the glass melt. A change in a parameter at one inverter may cause a change in all other inverters being part of the same network. All heating circuits are to be operated with the same frequency in the range of from 20 Hz to 25,000 Hz and to have a defined phase relative to each other. These two conditions are achieved by a clock generator in a common controller which provides an external time base for all inverters connected to that common controller.

[0223] In a first mode of operation, where At = 0 for all heating circuits, all inverters have no phase angle shift relative to each other since all oscillations and / or sinusoidal or other periodical currents start at a certain point in time t = 0, which is defined by the common controller. In a second mode of operation, where a shift in the phase angle of a certain inverter is desired, a respective delay At in the clock signal supplied to this inverter will be applied. This can be done individually and independently from each other for all inverters. The delay in the trigger signals may be implemented either by means of separate delay generators installed between the common controller (i.e. decentrally) and the respective inverters or by delay generators integrated within the common controller (i.e. centrally). With the delay set to zero, the system works like in the first mode of operation.

[0224] Using a phase detector which is installed at or in proximity of the electrode, it is possible to measure the actual signal curve of the current at the electrode and compare it to the signal of the clock generator in the common controller (including any applied delay At) for determining the phase angle shift of each electrode or heating circuit, respectively. This information can be used for varying the applied delay time At to precisely set a desired phase angle shift at an electrode or to readjust the electrode to be in phase with the others if no shift in phase angle is intended.

[0225] In embodiments of the method, the common controller may synchronize its clock signal with an external clock signal e.g. the phase of the power grid. The global clock e.g. within the common controller may synchronize to the external clock signal which is equivalent to a frequency by detecting the zero crossings of the external frequency signal and adjusting its own zero crossings of the clock signal with them. The frequencies may in this case be identical, but they do not have to be identical. In the latter case, the zero crossings of the lower frequency first signal may be matched with the nthzero crossing of the higher frequency second signal wherein n is dependent on the frequency difference. Such an external clock signal synchronization may be ad-February 17, 2026

[0226] - 25 -vantageous for adapting to the continuously slightly changing power grid frequency of neighboring components in a melting facility which is operated at the power grid frequency of 50 / 60 Hz.

[0227] The signal lines of the apparatus may be a direct or indirect connection by wire or wireless technique.

[0228] According to further embodiments, desired thermal zones are created within the glass melt in the melting vessel (6) by setting the amplitude and / or the phase of the current of each individual heating circuit. Heating circuits in parts of the melting vessel in which specific heat distribution profiles are essential are preferably equipped with inverters and thus the phase angle adjustment possibility of this invention in order to optimize the flow pattern and / or dwell time of the glass melt as described above.

[0229] The above-described process adds to the flexibility of a continuous melting process, where each phase of the glass melting process has a dedicated part of the furnace with individually optimized heating geometries. However, changes in glass types, glass composition, glass flow rates can require flexible adjustments to the distribution of the electrical heating power, which is ensured by the described method.

[0230] In a discontinuous melting process, the fixed geometry of the heating circuits strongly limits the ability to adjust the local distribution of the electrical heating power to the different melting phases. The method described is particularly suitable to adapt the heat distribution in the melting vessel to the different melting phases, in particular, the melting down phase, the fining phase and the conditioning phase. E.g. during the melting down phase, defined hot spots in the melt can be created by adjusting heat distribution. During the fining phase, a different heat distribution can flexibly be created by the described method in order to optimize the bubble release from the glass melt and an effective glass flow can be created within the melt to optimize the homogenization of the melt. Finally, during the conditioning phase a homogeneous heat distribution in the melt can be set to effectively condition the homogenized melt before the casting phase. For example, convective currents can be counter-acted by a dedicated heat power distribution.

[0231] In further embodiments, the current density used at one or more or all of the electrodes is 0.2 A / cm2- 2.0 A / cm2. This range provides good balance between power input into the melt and corrosion as well as a possible reduction of the number of electrodes. The current density may be 0.2 A / cm2- 2.0 A / cm2or 0.3 A / cm2- 1.8 A / cm2or 0.4 A / cm2- 1.65 A / cm2or 0.5 A / cm2-1.5 A / cm2. The current density may be at least 0.2 A / cm2or at least 0.3 A / cm2or at leastFebruary 17, 2026

[0232] - 26 - 0.4 A / cm2or at least 0.5 A / cm2. The current density may be at most 2.0 A / cm2or at most 1.8 A / cm2or at most 1.65 A / cm2or at most 1.5 A / cm2.

[0233] Figure 1 schematically shows a melting vessel comprising three heating circuits whereas two heating circuits comprise inverters. In Figure 1, the three conductors (Li, L2, L3) of a three-phase power line provided from the power grid are shown which are connected to three heating circuits either each comprising an inverter (1) or a thyristor power controller (11) for varying the power output from 0 % to 100 %. The inverters (1) are connected via a power factor correction (2) for keeping the phase difference between current and voltage minimal and a matching transformer (3) to the electrodes (5). The thyristor power controller (11) is connected via a matching transformer (3) to electrodes (5). The matching transformer (3) also serves for galvanic isolation of the heating circuits.

[0234] The heating circuit without inverter uses the phase of the power grid. Besides varying the power output, the inverters (1) can furthermore impose a phase shift to their heating circuits relative to the other heating circuits. The inverters (1) are connected via a power factor correction (2) for keeping the phase difference between current and voltage minimal and a matching transformer (3) to the electrodes (5). According to this embodiment, the power grid frequency of 50 or 60 Hz is preferably used.

[0235] In other embodiments, in which all heating circuits comprise inverters, the inverters can furthermore convert the power grid frequency of 50 / 60 Hz to a medium range frequency of from 20 Hz to 25,000 Hz.

[0236] In the melting vessel (6) which is shown in a top view, three pairs of electrodes (5) are arranged extending horizontally from the wall. As indicated in the figure, in this example, the three heating circuits formed by the three pairs of electrodes (5) are shifted in their phase angle of the current by Aq>i and Aq , respectively. In each heating circuit, in the electrical lines connecting the matching transformers (3) with the electrodes (5) a phase detector (10) is installed in close proximity to one of the electrodes (5). These three phase detectors (10) measure the actual current signal at the electrodes (5) and provide this information via the further signal lines (7) to the common controller (8). The common controller (8) is connected to the global clock and acts as a clock generator generating a clock signal for the two heating circuits comprising inverters (1) in a defined phase angle to the heating circuit with the thyristor power controller (11). The two delay generators (9) installed in the signal lines (7) between the common controller (8) and the inverters (1) provide a shift of the phase angle of the current provided by them to the heating circuits by independently applying an individual delay Ah and At2to the trigger signal for its associated inverter (1).February 17, 2026

[0237] - 27 -

[0238] Process for producing a precision component - Ceramization

[0239] The above-described process for producing a green glass block of a glass-ceramic is essential to provide for a homogeneous distribution of the various chemical compounds in a glassceramic component. However, it is also advisable to carefully control the ceramization conditions so that ceramization, meaning nucleation and growth of crystals in the glass matrix of the glass-ceramic happen as controlled and as homogeneously as possible in the complete volume of the glass-ceramic component. The inventors have found that the below described method improves the absolute mean CTE of the glass-ceramic component as well as the spatial CTE homogeneity.

[0240] It is known that during the transformation of a green glass to a glass-ceramic an exothermic reaction takes place, in particular the transformation of the matrix glass to a high quartz solid solution (HQSS). This effect is easily detectable in samples in measurement devices, however, during ceramization in particular during ceramization of larger glass-ceramic blocks it was until now not possible to use this information to improve the ceramization process in actual production of glass-ceramic components.

[0241] The inventors have thoroughly investigated the ceramization process and found that the following method yields precision components with improved thermal expansion properties. In particular, it is necessary to determine a characteristic temperature for each set of green glass blocks and to use this characteristic temperature to control the ceramization program in a way that glass-ceramic components with improved thermal expansion properties can be achieved.

[0242] The inventors have found that the size and the shape of the green glass components influence said characteristic temperature. This is particularly the case for lager green glass blocks e.g. blocks having a weight of more than 100 kg or 200 kg or 500 kg.

[0243] Surprisingly, it was furthermore found that even very small compositional variations in the green glass influence the exothermic peak of the ceramization and thus the characteristic temperature. Very small variations of the composition can e.g. be found in different production batches or even, if the melt in a batch is not sufficiently homogenized. The above-described improved melting process yielding a very homogeneous green glass melt and green glass blocks was therefore also important for the further development of the ceramization process.

[0244] The invention further relates to a method of ceramizing a green glass component into a glassceramic, comprising the steps:February 17, 2026

[0245] - 28 - providing a set of green glass blocks,

[0246] determining the characteristic temperature for ceramizing a first green glass block of said set of green glass blocks to a glass-ceramic, whereas said characteristic temperature is determined by measuring the temperature on the glass block and the oven temperature and determining the difference of these temperatures,

[0247] applying the so determined characteristic temperature to (a) control the oven temperature and / or (b) the holding time during the ceramization of further blocks of the set of green glass blocks.

[0248] A “set of green glass blocks” means that all green glass blocks have the same or approximately the same shape and size and that all green glass blocks originate from the same highly homogeneous melting batch.

[0249] In this context green, glass blocks “having the same size” means green glass blocks the weight of which differs at most 5 % or at most 3 % or at most 1 % and / or “having the same shape” means green glass blocks either (a) the diameter and height of a round green glass block differ by at most 5 % or at most 3 % or at most 1 % or (b) the edge lengths of a cubic or cuboid green glass blocks differ by at most 5 % or at most 3 % or at most 1 %.

[0250] Green glass blocks “originating from the same highly homogenized melting batch” means in case of a discontinuous melting process that all blocks originate from the same melting batch and having the same chemical composition e.g. compositional fluctuations of one or more or all components in a melt should be less than 0.5 wt.-% or less than 0.1 wt.-% or less than 0.05 wt.%. According to specific embodiments, “originating from the same melting batch” can also mean, originating from certain sections of the same melting batch, e.g. blocks cast during the first half of the melting batch or during the second half of the melting batch or during an otherwise specifically defined part of the melting batch.

[0251] At least one thermometer with an accuracy of at least ±1 Kelvin is placed on the surface of the green glass block to be ceramized. In particular, in case of large or very large green glass blocks, it is advantageous to use more than one thermometer, e.g. 2 or 4 or 6 or even more thermometers.

[0252] At least one further thermometer with an accuracy of at least ±1 Kelvin is placed in the oven to measure the oven temperature. More than one, e.g. 2 or 4 or 6 or even more thermometers, can be used to measure the oven temperature.February 17, 2026

[0253] - 29 - The difference between the thermometers on the surface of the green glass block and the thermometers in the oven atmosphere is closely monitored. During the phase transition, the difference between temperature on the blank and the oven temperature has a peak-like shape, and the characteristic temperature can be determined from this peak-like shape. According to one embodiment, a master peak shape can be fitted to the measurement of the thermometer.

[0254] When a characteristic temperature for a set of green glass blocks has been determined, this characteristic temperature is assigned to the standard ceramization program. Then this adapted ceramization program is used together with the measured blank temperature during ceramization to control the ceramization program of the further blocks from the set of green glass blocks. In particular, when detecting a deviation of the blank temperature from the calculated ceramiz-ing program for the set of green glass blocks, it is possible to control and adapt (a) the oven temperature and / or (b) the holding time during the ceramization of such further block of the set of green glass blocks and thus compensating the deviation of the ceramization program and / or the small deviation in chemical composition.

[0255] The determination of the characteristic temperature and / or the controlling of the oven temperature and / or holding time using the characteristic temperature can be supported by artificial intelligence and / or machine learning programs in particular for compensation of noise.

[0256] Although determining the characteristic temperature for each set of green glass blocks seems meticulous, it nevertheless is of great advantage in mass production of high precision components. The above-mentioned improved ceramization process not only serves to improve the homogeneity of the thermal expansion properties, it also assures that e.g. the zero-crossing temperature can be set with high accuracy within the set of produced glass-ceramic blocks.

[0257] Use of the precision component

[0258] The invention also relates to the use of a precision component.

[0259] The precision component can advantageously be used in metrology, lithography, spectroscopy, astronomy, earth observation from space, for example as mirrors or mirror substrates for segmented or monolithic astronomical telescopes or as lightweight or (ultra)light mirror substrates for space-based telescopes, measurement technology, for example, as high-precision structural components for distance measurement, e.g. in space or optics for earth observation, as mirrors and prisms in LCD lithography, microlithography and / or EUV lithography, for example, as mask holders, wafer stages, reference plates, reference frames and grating plates in microlithography or additionally, mirrors or mask blanks in EUV lithography, or as mirrors or mirror substrates for range finders, directed energy weapons (DEW), laser fusion or particle accelerators. AnotherFebruary 17, 2026

[0260] - 30 -possible application is thermal insulation for cryogenic storage and transportation of liquid hydrogen or other liquid gases.

[0261] Precision components can be, for example, optical components, more specifically a "normal incidence mirror", i.e. a mirror which is operated close to the vertical incidence of radiation, or a "grazing incidence mirror", i.e. a mirror which is operated with a grazing incidence of radiation. In addition to the substrate, such a mirror comprises a coating which reflects the incident radiation. Particularly in the case of a mirror for X-rays, the reflective coating is, for example, a multilayer system or multilayer having a multiplicity of layers with a high reflectivity in the X-ray range in the case of non-grazing incidence. Such a multilayer system of a normal incidence mirror preferably comprises 40 to 200 layer pairs, consisting of alternating layers, for example one of the material pairs Mo / Si, Mo / Bi, Ru / Si and / or MoRu / Be.

[0262] In particular, the optical elements according to the invention can be X-ray optical elements, i.e. optical elements which are used in conjunction with X-rays, in particular soft X-rays or EUV radiation, in particular reticle masks or photomasks operated in reflection, in particular for EUV microlithography. They can advantageously be mask blanks. Furthermore, the precision component can advantageously be used as a mirror or as a substrate for a mirror for EUV lithography.

[0263] Furthermore, the precision component according to the invention can be a component, in particular a mirror for astronomical applications. Such components can be used for astronomical applications both terrestrially and in space. High-precision structural components for distance measurements, for example in space, are another advantageous field of application.

[0264] The precision component according to the invention can be a lightweight structure. The component according to the invention can furthermore comprise a lightweight structure. This means that, in some regions of the component, cavities are provided for weight reduction. Lightweight machining is preferably used to reduce the weight of a component by at least 80%, more preferably at least 90%, in comparison with the unmachined component.

[0265] The present invention will be illustrated below by a series of examples. However, the present invention is not limited to the examples mentioned.

[0266] Examples

[0267] Glass-ceramic components with the compositions described in Table 1 were produced according to standard procedures, as described in WO 2015 / 124710 for Comparative Examples. ExFebruary 17, 2026

[0268] - 31 - amples 1 and 2 were prepared by augmenting the standard procedures with the novel procedures (additional electric heating and improved ceramization process) as described above. Precision components having a dimension of 500 mm x 500 mm x 100 mm were prepared from the resulting glass-ceramic blocks. The results are shown in Table 1.

[0269] Table 1: Examples and Comparative Examples

[0270] < < <

[0271]

[0272] Comparative Examples 1 to 4 do not show a sufficiently low CTE homogeneity. The values for mean CTE of Comparative Examples 2 and 3 were not sufficiently low, therefore, more detailed experiments were not conducted. In case of Comp. Ex. 2 this was attributed to the high SiO2content and, therefore, the high viscosity of the melt rendering a highly homogeneous melt and green glass impossible. The CTE of Comparative Example 2 was better yet still insufficient and it was not possible to tailor further the CTE in the desired range.

[0273] Thermal Shock Resistance Experiments

[0274] For the experimental results displayed in Table 2, glass-ceramic test specimen with a length of 100 mm and 6 mm diameter were cut from the precision components of Example 1 and submit-February 17, 2026

[0275] - 32 -ted to a thermal shock treatment, i.e. heating to a temperature TE with a heating rate of 100K / h, held at this temperature for 16 h and cooled with a cooling rate of 900 K / h to ambient temperature. The mean CTE(0;50) was measured bevor and after this procedure and the difference in the mean CTE(0;50) before and after heating and rapid cooling ACTE(0;50) is also displayed in Table 2.

[0276] Table 2: Overall CTE(0;50) change after heating and thermal shock procedure

[0277]

[0278] The thermal shock resistance of Ex. 1 vs. Comp. Ex. 1 is also shown in Figure 3. Whereas Comp. Ex. 1 shows a substantial change in CTE after being heated to 200°C or more and cooled rapidly, the CTE of Ex. 1 does not change substantially. This is of great advantage when the precision component is heated during further processing, e.g. when a metal coating is sputtered on the surface of the precision component.

[0279] CTE(0;50) homogeneity of Ex. 1, Ex. 2 and Comp. Ex. 1 were determined by submitting three test specimens for each Example and Comp. Ex., respectively, to heating to TE = 320°C and rapid cooling. Whereas the CTE homogeneity for Ex. 1 and 2 was still excellent, the CTE homogeneity for the Comparative Example was substantially impaired.

[0280] The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and / or operating conditions of this invention for those used in the preceding examples. From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

Claims

Applicant: SCHOTT AG February 17, 2026 Our File: P06243 WOAppl. No: - 33 -Claims1. Thermal shock resistant precision component,- having a CTE(0;50) of at most 0 ± 20 ppb / K or at most 10 ppb / K or at most 5 ppb / K and- having a ACTE(0;50) of at most 0 ± 10 ppb / K or at most 0 ± 5 ppb / K, after heating the component to a temperature TE of 150° or 300°C or 400°C and rapid cooling with a cooling rate of at least 100 K / h, whereasACTE(0;50) = CTE(0;50) (after rapid cooling) - CTE(0;50) (before heating to TE).

2. Precision component according to claim 1 , having a spatial CTE(0;50) homogeneity of at most 2 ppb / K or at most 1.5 ppb / K.

3. Precision component according to claim 1 or 2, having a spatial CTE(0;50) homogeneity of less than 3 ppb / K or at most 2 ppb / K or less than 2 ppb / K after heating to a temperature TEof 150° or 300°C or 400°C and rapid cooling with a cooling rate of at least 100 K / h.

4. Precision component according to any of the preceding claims, wherein the component comprises a LAS-glass-ceramic comprising the following composition (in wt.-% based on oxide)SiO235 - 72AI2O315- 33P2O50- 12Li2O 2 -6Na2O 0-2K2O 0-3MgO 0-0.5CaO 0-4BaO 0-5SrO 0-3ZnO 0 - 1TiO20-6ZrO20-5February 17, 2026- 34 - 5. Precision component according to any of the preceding claims, having a rectangular base with edge lengths of at least 100 mm or having a circular base with a diameter of at least 100 mm.

6. Precision component according to any of the preceding claims, having a thermal hysteresis in a temperature range of from 10°C to 35°C of at most 0,1 ppm.

7. Method of manufacturing precision components according to any of claims 1 to 6 comprising the steps ofmelting a batch of raw materials to form a green glass melt in a melting vessel (6) wherein the melting vessel (6) is heated using two or more heating circuits, each comprising a transformer (3) and at least two electrodes (5), wherein at least one heating circuit comprises an inverter (1) providing an alternating current (AC) to its heating circuit,- withdrawing the green glass melt from the melting vessel (6),- forming the green glass melt into a green glass,- ceramizing the green glass.

8. Method according to claim 7, wherein in at least one heating circuit comprising an inverter providing a current to its heating circuit, the amplitude and / or the phase angle of this current independently of the amplitudes and / or phase angles of the currents of the other heating circuits adjusted and a phase angle shift to its current relative to at least one other heating circuit is applied.

9. Method according to claim 7 or 8, wherein desired thermal zones are created within the glass melt in the melting vessel (6) by setting the amplitude and / or the phase of the current of each individual heating circuit.

10. Method according to any one of claims 7 to 9, wherein the electrodes (5) are operated at a current frequency of at least 20 Hz and at most 25,000 Hz, optionally of at least 50 Hz and at most 25,000 Hz, optionally of at least 50 Hz and at most 15,000 Hz, optionally of at least 100 Hz and at most 12,000 Hz, optionally of at least 1,000 Hz and at most 10,000 Hz, optionally of at least 1 ,000 Hz and at most 5,000 Hz.

11. Use of a precision component according to any of claims 1 to 6, in metrology, spectroscopy, measurement technology, lithography, astronomy or Earth observation from space, for example as mirror or mirror carrier for segmented or monolithic astronomical telescopes or else as weight-reduced or ultra-light mirror substrates for, for example, space-based telescopes or as high-precision structure components for measurementFebruary 17, 2026- 35 -of distance, for example in space, or optics for Earth observation, as precision components, such as standards for precision measurement technology, precision rules, reference plates in interferometers, as mechanical precision parts, for example for ring laser gyroscopes, spiral springs for the clock industry, as for example mirrors and prisms in LCD lithography, and for example as mask holders, wafer stages, reference plates, reference frames and grid plates in microlithography and in EUV microlithography, and as mirrors and / or photomask substrates, photomask carriers or reticle mask blanks in EUV microlithography.

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