A glass material, method of making and use thereof

Abstract

The present application relates to a kind of glass materials and its preparation method and application.The composition of the glass material includes: 53-60wt% SiO2, 20-26wt% Al2O3, 3-4wt% Li2O, 1-4wt% ZnO, 0.5-3wt% MgO, 1-2wt% TiO2, 1-2wt% ZrO2, 3-5wt% P2O5, 0.5-3wt% M2O5, 0.5-3wt% Ln2O3 and 0-2wt% clarifying agent;Wherein, R=at least one of Sr, Ca, Ba;M=at least one of Ta, Nb;Ln=at least one of Ce, Sc, Pr, Y, La, Nd, Sm, Gd, Tb, Dy, Er, Tm, Yb, Lu;The clarifying agent is selected from at least one of Sb2O3, CeO2 and combination.

Description

TECHNICAL FIELD

[0001] The present application relates to a glass material and a preparation method thereof, in particular to an ultra-low microcrystalline glass material for an optical system of an EUV lithography machine and a workpiece table and a mask table and a preparation method thereof. BACKGROUND

[0002] Transparent ultra-low expansion glass materials have been widely used in workpiece tables, mask tables and optical objective systems in lithography machines. In particular, the ultra-low expansion glass material in the optical system has very high requirements, in addition to the requirement of very low thermal expansion coefficient ≤ 10 ppb / K, the requirements for internal defects and processability are also very high. Extreme ultraviolet lithography (EUVL) is a microelectronic lithography technology using EUV rays with a wavelength of 11-14 nm as an exposure light source, which is suitable for mass production of integrated circuits with a feature size of 32 nm and finer line width. Therefore, different i-line to DUV lithography machine transmission type optical system design schemes, EUV lithography machine adopts 6 or 8 mirror reflection type exposure system to realize 3 nm and below chip product production, all optical parts use multilayer film coated aspherical reflective optical elements. Moreover, in order to meet the quality requirements of lithography imaging, the wavefront aberration of EUVL optical system needs to be controlled within 1 nm. The wavefront aberration needs to be carefully distributed to each detail factor affecting the imaging quality, such as mirror substrate, film thickness, etc. Since the medium and high frequency roughness of the working surface of the element directly affects the contrast of the image surface and the system energy transmission, the surface shape precision and roughness of the element need to reach deep sub-nanometer level. Germany Zeiss company has developed for 20 years under the demand of EUV lithography machine of ASML company in the Netherlands, with the improvement and improvement of the requirements of wavefront aberration, element surface roughness and multilayer film thickness, the optical processing, adjustment and coating technology of EUVL is becoming mature. The optical element surface error and medium and high frequency roughness processing precision of large aperture EUVL element reaches 0.1 nm rms, and the wavefront aberration of EUV optical system reaches the diffraction limit.

[0003] At present, high-quality ultra-low expansion transparent glass materials used in lithography machine systems are divided into two categories: microcrystalline ultra-low expansion transparent glass and amorphous ultra-low expansion microcrystalline glass.

[0004] The microcrystalline ultra-low expansion glass material is a Li2O-Al2O3-SiO2 system ultra-low expansion transparent microcrystalline glass with nano β-quartz solid solution as a main crystal phase. The grain size of the precipitated β-quartz solid solution phase is 50-80 nm, which is 1 / 10 of the wavelength of visible light. The refractive index of the crystal phase is close to the refractive index of the glass, so the light transmittance in the visible light and infrared light range is high. The volume fraction (70% or more) of the negative expansion β-quartz solid solution and the volume fraction of the remaining glass liquid with positive expansion can be well matched to form a near ultra-low expansion coefficient (7-10 ppb / K). Due to the characteristics of nearly zero thermal expansion, excellent three-dimensional overall uniformity, good processing performance, polishing to extremely high precision, good film plating performance, low chemical helium permeability, excellent chemical stability, etc., the ultra-low expansion transparent microcrystalline glass material is the core substrate material of the mask frame system of the DUV, EUV photoetching machine, and carries out the work of wafer pretreatment and exposure. At present, the microcrystalline ultra-low expansion microcrystalline glass material for photoetching machine adopts the ZERODUR® brand of Germany Schott Company Expansion Class 0SPECIAL brand and ZERODU The thermal expansion coefficients of the ultra-low expansion microcrystalline glass materials of EXTREME brand can be 7 ppb / K and 10 ppb / K (0-50℃) respectively (related patent numbers WO2015124710(A1), DE102010002188(A1)).

[0005] Table 1 is a performance comparison table of ultra-low expansion transparent microcrystalline glass materials of different companies

[0006]

[0007] Amorphous ultra-low expansion glass (TiO2-SiO2) is a titanium silicate low-expansion glass (related patent number WO20141085529 A1), produced using the same vapor deposition process as Corning's ULE system. Its thermal expansion coefficient is very close to 0 ppb / K. This glass is specifically designed to meet the mask requirements of EUVL applications and serve as an optical substrate for ultraviolet lithography. Both Asahi Glass and Nikon have related patent portfolios in this area (CN 104395248 B and CN102421713A). The shift in lithography technology from 193nm to 13.4nm requires a significant design shift from refractive to reflective stepper optics. In reflective optics, the substrate material should be purely passive. Incident light should be reflected from the optical device and the multilayer coating of the photomask without introducing any mechanical or optical distortion caused by the underlying substrate. In order to minimize deformation caused by small temperature changes and meet the strict EUVL specifications, the substrate must have a near-zero coefficient of thermal expansion (CTE, ppb / K level) and low peak-to-valley (PV) CTE variation. This is currently successfully applied in the optical system designed by Zeiss for the new generation of ASML EUV lithography machines. 3400 in.

[0008] Table 2 is the performance table of Corning's ultra-low expansion glass materials

[0009]

[0010] Research shows that there are two main reasons why microcrystalline ultra-low expansion microcrystalline glass materials, mainly produced by Schott in Germany, cannot be used in optical reflective components in EUV lithography machines: first, the mechanical properties of microcrystalline glass materials, such as elastic modulus and Poisson's ratio, are better than those of ULE glass, so the progress of ion beam polishing is slow; second, microcrystalline glass is composed of two phases: a 50-80nm β-quartz solid solution phase and a residual glass phase. Due to the different processing rates of the ion beam on the two phases, its high-frequency surface roughness is difficult to achieve the EUVL requirement of 0.12nm rms, and is as high as 0.5-0.7 0.12nm rms; third, most ultra-low expansion microcrystalline glass contains components such as B2O3, Na2O and K2O that are not conducive to the coating process. Summary of the Invention

[0011] The present application aims to provide an ultra-fine crystal extremely low expansion transparent microcrystalline glass material for EUVL lithography machine optical reflection element, which has extremely low thermal expansion coefficient of ±(3-10)ppb / K(-50-150℃), high optical properties and excellent performance uniformity, and can meet the application requirements of the basic material for the optical reflection element of the EUVL lithography machine.

[0012] Another object of the present application is to solve the above problems and provide a microcrystalline glass with extremely low expansion characteristics and a manufacturing method of the microcrystalline glass element.

[0013] In a first aspect, the present application provides a glass material, the composition of the glass material comprising: 53-60wt% SiO2, 20-26wt% Al2O3, 3-4wt% Li2O, 1-4wt% ZnO, 0.5-3wt% MgO, 0.2-3wt% RO, 1-2wt% TiO2, 1-2wt% ZrO2, 3-5wt% P2O5, 0.5-3wt% M2O5, 0.5-3wt% Ln2O3 and 0-3wt% fining agent; wherein R=at least one of Sr, Ca, Ba; M=at least one of Ta, Nb; Ln=at least one of Ce, Pr, Y, La, Sc, Nd, Sm, Gd, Tb, Dy, Er, Tm, Yb, Lu; the fining agent is selected from at least one of Sb2O3, CeO2 and a combination thereof.

[0014] Preferably, the composition of the glass material comprises: 55-60wt% SiO2, 20-25wt% Al2O3, 3-4wt% Li2O, 1-4wt% ZnO, 1-3wt% MgO, 0.2-2wt% RO, 1-2wt% TiO2, 1-2wt% ZrO2, 3-5wt% P2O5, 0.5-3wt% M2O5, 0.5-3wt% Ln2O3 and 0.5-3wt% fining agent. Preferably, Al2O3+SiO2=78-83wt%, SiO2 / Al2O3=2.3-2.7; SiO2+Al2O3+Li2O+MgO+ZnO=85-90wt%; Li2O+MgO+ZnO=6-8wt%, and Li2O / (MgO+ZnO)=1.1-1.5; the glass material does not contain B2O3, Na2O, K2O.

[0015] In a second aspect, the present application provides an ultra-low expansion transparent microcrystalline glass material, which is obtained by subjecting the above-mentioned glass material to microcrystallization treatment to obtain an ultra-low expansion transparent microcrystalline glass material, wherein the crystallized phase in the ultra-low expansion transparent microcrystalline glass material contains a β-quartz solid solution phase.

[0016] In order to realize the ultra-low expansion transparent microcrystalline glass material for EUV mirror material with excellent ultra-low expansion performance and ion beam processability, the present application repeatedly carries out in-depth experimental research, and adopts the following glass components: the base component is 55-60wt% SiO2, 20-25wt% Al2O3, 3-4wt% Li2O, 1-4wt% ZnO, 1-3wt% MgO, the fluxing agent is 0.2-2wt% RO (R=Sr, Ca, Ba), the nucleating agent is 1-2wt% TiO2, 1-2wt% ZrO2, 3-5wt% P2O5, the fine crystal control agent is 0.5-3wt% M2O5 (M=Ta, Nb) and 0.5-3wt% Ln2O3 (M=Y, La, Nd, Sm, Gd, Tb, Dy, Er, Tm, Yb, Lu) one or two kinds. The present application does not contain B2O3, R”2O (R”=Na, K) and other components which are not conducive to the coating process.

[0017] Preferably, the crystal grain size of the crystallization phase is 5-10nm, and the content of the crystallization phase is 70-80vol%.

[0018] Preferably, the average thermal expansion coefficient of the ultra-low expansion transparent microcrystalline glass material is 3-10ppb / ℃, the elastic modulus is 87-92GPa, and the Poisson's ratio is 0.245-0.255.

[0019] Preferably, the system of the microcrystallization treatment includes: the temperature is 680-740℃, and the holding time is 9-24 hours; preferably, the heating rate and the cooling rate of the microcrystallization treatment are both 0.1-3℃ / min; preferably, rotation is accompanied during the microcrystallization treatment, and the speed of the rotation is 0.05-1 revolutions / minute. Preferably, the system of the microcrystallization treatment includes: first holding at 300-400℃ for 6-24h, then holding at 500-600℃ for 6-24h, then holding at 680-740℃ for 9-24 hours, and finally cooling to 150-250℃, then power off and cooling to room temperature in the furnace.

[0020] In a third aspect, the present application provides a preparation method of the glass material, comprising:

[0021] (1) mixing Si source, Al source, Li source, Zn source, Mg source, Ti source, Zr source, P source, R source, M source, Ln source and fining agent, and then melting, homogenizing and cold leaching to obtain glass slag;

[0022] (2) melting, homogenizing, fining and annealing the obtained glass slag to obtain the glass material.

[0023] In order to realize the melting and forming of the homogeneous, defect-free (porosity, solidification, forming stripe) base glass of the ultra-low expansion transparent microcrystalline glass material for the EUV mirror material, the present application repeatedly carries out in-depth forming process test research, and obtains a preparation method of the ultra-low expansion transparent microcrystalline glass material in a gradient melting process, that is, the melting, stirring homogenization and clarification three stages in the glass melting process are carried out in different temperature furnaces.

[0024] Preferably, the Si source is silicon oxide or / and quartz glass, and the purity of the Si source is ≥ 99.9%;

[0025] The Al source is at least one of AlPO4 and Al(OH)3, and the purity of the Al source is ≥ 99.9%;

[0026] The Li source is Li2O or / and lithium carbonate, and the purity of the Li source is ≥ 99.9%;

[0027] The Zn source is ZnO, and the purity is ≥ 99.9%;

[0028] The Mg source is MgO, and the purity is ≥ 99.9%;

[0029] The Ti source is TiO2, and the purity is ≥ 99.9%;

[0030] The Zr source is ZrO2, and the purity is ≥ 99.9%;

[0031] The P source is P2O5 or / and AlPO4, and the purity of the P source is ≥ 99.9%;

[0032] The R source is at least one of the oxide of R, the carbonate of R, and the nitrate of R, and the purity of the R source is ≥ 99.9%;

[0033] The M source is at least one of the oxide of M, the carbonate of M, and the nitrate of M, and the purity of the M source is ≥ 99.9%;

[0034] The Ln source is at least one of the oxide of Ln, the carbonate of Ln, and the nitrate of Ln, and the purity of the Ln source is ≥ 99.9%.

[0035] Preferably, in step (1), the temperature of the melting-homogenization is 1500-1600℃, and the holding time is 1-4 hours;

[0036] The cold extraction system is to pour the glass melt into a roller gate machine for cold extraction treatment,

[0037] Preferably, the heating rate and the cooling rate of the melting are both 2-20℃ / min.

[0038] Preferably, the number of operations of the melting-homogenizing and cold extraction is 1-4.

[0039] Preferably, in step (2), the temperature of the melting is 1450-1500 DEG C, the holding time is 4-24 hours; the temperature of the homogenizing is 1550-1600 DEG C and stirring is simultaneously performed during the homogenizing, the stirring system comprises high-speed stirring at 30-60 rpm and low-speed stirring at 15-25 rpm; the total time of the homogenizing and stirring is 4-24 hours, the ratio of the high-speed stirring time to the low-speed stirring time is 1:(0.2-0.5).

[0040] The temperature of the clarifying is 1400-1500 DEG C, the holding time is 4-12 hours.

[0041] The temperature system of the annealing is 600-700 DEG C, the holding time is 12-48 hours.

[0042] Preferably, in step (2), the melting, homogenizing, clarifying and annealing are respectively performed in 4 crucibles.

[0043] The crucible used for the melting is a platinum-rhodium crucible or a quartz crucible.

[0044] The crucible used for the homogenizing is a platinum-rhodium crucible or a quartz crucible.

[0045] The crucible used for the clarifying is a quartz crucible or a graphite crucible.

[0046] The crucible used for the annealing is a quartz crucible or a graphite crucible, and the structure design can realize no machining or less machining of the element.

[0047] In the fourth aspect, the application provides a glass material used in an optical reflecting element of an EUVL photolithography machine.

[0048] In the fifth aspect, the application provides an application of an ultra-low expansion transparent microcrystalline glass material in an optical reflecting element of an EUVL photolithography machine. The ultra-fine crystal ultra-low expansion transparent microcrystalline glass takes an ultra-fine crystal 1-10 nm beta-quartz solid phase as the main Li2O-Al2O3-SiO2 system microcrystalline glass, has an ultra-low expansion coefficient z±(3-10) ppb / ℃, and can control the surface error roughness to ≤0.20 nm rms through machining processes such as a small grinding head polishing (CCP), a magnetorheological polishing (MRF) and an ion beam polishing (IBF), can be used as an optical element in an extreme ultraviolet photolithography (EUVL) optical system, and can also be used as a basic material of a workpiece table and a mask table in a photolithography machine.

[0049] The application has the following beneficial effects:

[0050] The present application is according to the application requirement of EUV photoetching machine optical material, designs a kind of with ppb / K level with 5-10nm β-quartz solid solution phase as main crystal phase ultra-low expansion transparent glass-ceramics material and its element preparation method, its average linear expansion coefficient is ± (3-10) ppb / K (0-50 DEG C), and thermal expansion uniformity is also controlled in ± (3-10) ppb / K (0-50 DEG C) range, can realize to the substitution of Germany Schott company's Expansion Class 0SPECIAL brand and ZERODU Expansion Class 0EXTREME brand ultra-low expansion glass-ceramics material.And, according to the preferred mode of the present application, ultra-low expansion transparent glass-ceramics material can be obtained, which is composed of β-quartz solid solution phase crystal particles with a particle size in the range of 5-10 nm and residual glass phase, with a crystal phase content of ≥70 vol%, an elastic modulus of 87-92 GPa, a Poisson's ratio of 0.245-0.255, a microcrystallization system of 690-720°C for 9-15 hours, a thermal expansion coefficient of ± (3-10) ppb / K (0-50 DEG C), a surface error roughness of ≤0.20 nm rms controlled by ion beam polishing (IBF) and other processing technologies, a transmittance of more than 85% in the wavelength range of 500-1500 nm, and a strong adhesion between the glass-ceramic surface and the film layer after coating, which can fully meet the requirements of the basic material for optical elements in EUVL optical systems and worktable and mask table in all series of photoetching machines.

[0051] The present application has obvious advantages in formula design, melting and forming process, microcrystallization process, and compatibility of formula design and preparation process, and has the following specific beneficial effects:

[0052] 1. Firstly, to solve the problems of high thermal expansion coefficient, poor processability, and easy diffusion of coating ions, the content of alkaline earth metal oxides (CaO, BaO, SrO) in the base glass is reduced as much as possible, there are no alkali metal oxides (K2O, Na2O) and B2O3 components, and large ion oxides (Ta2O5, Nb2O5, and rare earth oxides) are introduced to compress the glass network structure, which can control the glass crystallization behavior, improve the compactness of the residual glass network structure, reduce the temperature sensitivity of the residual glass network structure, and thus obtain ultra-low expansion glass-ceramic material.

[0053] 2、The present application optimizes the traditional center / eccentric stirring + casting forming process in melting and forming process, designs gradient melting process: the glass melting-stirring homogenization-clearing stage is carried out in different crucibles respectively to form homogeneous, defect-free matrix glass, which meets the stringent requirements of manufacturing EUV optical device of lithography machine;

[0054] 3、The present application also optimizes the microcrystallization process, selects TiO2+ZrO2+P2O5 ternary system as nucleating agent, and controls its content, and there is no nucleation process in the microcrystallization process, and through ultra-low heating rate and low temperature crystallization temperature, the microcrystalline glass material has ultra-low thermal expansion coefficient 0.5-2×10 -8 / K (0-50℃) in the range of 690-720℃ holding for 9-15 hours, so that the microcrystalline glass element has high thermal expansion coefficient uniformity;

[0055] 4、The present application designs melting-forming-annealing-crystallization process and corresponding equipment according to the basic properties of glass formula, high-temperature glass melt viscosity characteristics, etc., and breaks through the whole chain of raw material-component design-key process and equipment design of ultra-low expansion microcrystalline glass material;

[0056] 5、The present application designs process and equipment according to the characteristics of the material, simplifies the process, shortens the production cycle, and produces high-quality ultra-low expansion microcrystalline glass material. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 TEM image of the ultra-low expansion transparent microcrystalline glass material of Example 1 after microcrystallization at 700℃ for 12h (scale 200nm);

[0058] Figure 2 TEM image of the ultra-low expansion transparent microcrystalline glass material of Example 1 after microcrystallization at 700℃ for 12h (scale 5nm), from the figure, it can be known that the crystal grains are uniformly distributed, and the particle size is about 5nm;

[0059] Figure 3 The transmission optical diagram of the ultra-low expansion transparent microcrystalline glass material of Comparative Example 1, from the figure, it can be known that no low-temperature homogenization process in the stirring process will cause a large number of stripes in the glass, causing the mechanical properties to decrease and the thermal expansion coefficient to be large;

[0060] Figure 4 The macroscopic photo of the ultra-low expansion transparent microcrystalline glass material of Comparative Example 2, from the figure, it can be known that no high-temperature defoaming process in the stirring process will cause a large number of bubbles in the glass, causing the mechanical properties to decrease and the thermal expansion coefficient to be large. DETAILED DESCRIPTION

[0061] The present application is further illustrated by the following examples, which should not be construed as limiting the present application.

[0062] In the present application, the glass component of the glass material is: the base component is 55-60wt% SiO2, 20-25wt% Al2O3, 3-4wt% Li2O, 1-4wt% ZnO, 1-3wt% MgO, the fluxing agent is 0.2-2wt% RO (R=Sr, Ca, Ba), the nucleating agent is 1-2wt% TiO2, 1-2wt% ZrO2, 3-5wt% P2O5, the fine crystal control agent is 0.5-3wt% M2O5 (M=Ta, Nb) and 0.5-3wt% Ln2O3 (M=Y, La, Sc, Nd, Sm, Gd, Tb, Dy, Er, Tm, Yb, Lu, one or two of which) and 0-3wt% clarifying agent (Sb2O3, CeO2 and combinations). The present application does not contain B2O3, R"2O (R"=Na, K and other components that are not conducive to the plating process).

[0063] In the optional embodiment, the following explanation is made regarding the composition design:

[0064] In the Li2O-Al2O3-SiO2 system ultralow expansion transparent glass ceramic composition, Li2O-Al2O3-SiO2 is the main component of the β-quartz solid solution phase, and therefore the composition ratio of the three is the core of the glass ceramic having an ultralow expansion coefficient and optical performance. In the present application, the β-quartz solid solution refers to the introduction of Al 3+ ion into the β-quartz phase 4+ and the introduction of interstitial ions Li + (occupying the tetrahedral vacancy in the β-quartz phase structure), Mg 2+ (occupying the octahedral vacancy in the β-quartz phase structure), and Zn 2+ (occupying the tetrahedral vacancy in the β-quartz phase structure) to balance the charge. Therefore, the main components of the glass in the present application are SiO2, Al2O3, Li2O, MgO and ZnO, wherein SiO2+Al2O3+Li2O+MgO+ZnO=85-90wt%; Li2O+MgO+ZnO=6-8wt%, and Li2O / (MgO+ZnO)=1.1-1.5.

[0065] SiO2 as a glass network former oxide, if its content is less than 50wt%, on the one hand, the mechanical strength of the base glass will be reduced, the crystal size will be coarse after crystallization, and the SiO2 component in the residual glass phase will be too low, on the other hand, the content is too low, which will also lead to the decrease of the transparency of the glass, and the parent glass is easy to be devitrified; but when the content of SiO2 is more than 60wt%, it will increase the high temperature viscosity of the glass melt, leading to the fact that the stripes, bubbles and stones cannot disappear in the glass. Therefore, the content of SiO2 in the application is preferably 53-60wt%, more preferably 55-59wt%.

[0066] Al2O3 as a glass network intermediate oxide, can reduce the crystallization tendency of the glass, improve the chemical stability, thermal stability, mechanical strength, hardness and refractive index of the glass. When its amount is ≥20wt% or more, the melting of the base glass becomes easy, so the homogeneity of the obtained microcrystalline glass is improved, and the chemical durability of the microcrystalline glass is also good. And when its amount is ≤26wt% or less, the devitrification resistance of the base glass is improved, and the organization of the product in the crystallization stage caused by the decrease of the devitrification resistance does not appear to be coarse, and the mechanical strength is improved. Therefore, the content of Al2O3 in the application is preferably 20-26wt%, more preferably 22-24wt%.

[0067] The total content of SiO2 and Al2O3 directly affects the melting property of the glass, considering the requirements of the main crystal phase components and the properties of the residual glass phase after crystallization. Therefore, in the application, Al2O3+SiO2=78-83wt%, SiO2 / Al2O3=2.3-2.7.

[0068] Li2O, MgO and ZnO as one of the necessary components of the beta-quartz solid solution phase, can also play a fluxing effect, and MgO and ZnO can improve the mechanical properties and chemical stability of the glass. But if the content is too high, on the one hand, it will lead to the increase of the crystallization ability of the parent glass, and the grain size will be too large, which will affect the transparency of the material. Therefore, in the application, Li2O+MgO+ZnO=6-8wt%, Li2O / (MgO+ZnO)=1.1-1.5.

[0069] In the application, alkaline earth metal oxides CaO, BaO and SrO as glass structure network outer oxides have good fluxing effect, and the introduction of glass can reduce the melting temperature and significantly improve the refining effect, and reduce the crystallization ability. In the microcrystalline glass, they remain in the residual glass phase, but in order to ensure the hardness of the microcrystalline glass, the content should not be too high. Therefore, in the application, CaO+BaO+SrO=0-2wt%.

[0070] In the present application, TiO2-ZrO2-P2O5 ternary system oxide is selected as the crystal nucleus agent, which plays a very important role in the microcrystallization heat treatment process of the glass-ceramics. If the content is insufficient, the crystallization degree of the β-quartz solid solution is not enough, the content of the negative expansion phase is insufficient, and the thermal expansion coefficient of the product is too high, or the β-quartz solid solution grain grows too large, thereby causing the optical decline of the glass-ceramics. If the content of the crystal nucleus agent is too high, the grains grow too fast, which leads to optical decline, and even more, the β-quartz solid solution is converted into β-spodumene phase, which leads to the increase of the thermal expansion. Similarly, if the composition of the three is not reasonable, the above problems will occur. In the present application, in order to expand the microcrystallization temperature and time interval of the ultra-low expansion glass-ceramics, the content of the nucleating agent is relatively low compared with other patents, which is: TiO2: 1-2%, ZrO2: 1-2%, and P2O5: 4-5%.

[0071] In the present application, B2O3, Na2O and K2O are selected as the fluxing agent, which can effectively reduce the glass melting temperature. However, B2O3, Na2O and K2O are not contained in the present project because they are easy to ionize during the Si and Mo plating process.

[0072] In an optional embodiment, the glass transition temperature of the ultra-low expansion transparent glass-ceramics material is 700-850℃, and the initial crystallization temperature is 800-1000℃.

[0073] In the present application, the main crystal phase of the ultra-low expansion transparent glass-ceramics material is β-quartz solid solution phase with a grain size of 5-10 nm and a crystal phase content of ≥80%.

[0074] In an optional embodiment, the average linear expansion coefficient of the ultra-low expansion transparent glass-ceramics is ±(3-10) ppb / K (0-50℃), and the thermal expansion uniformity of the medium cavity is also controlled to be ±(3-10) ppb / K (0-50℃). The ultra-low expansion transparent glass-ceramics material has an elastic modulus of 87-92 GPa, a Poisson's ratio of 0.245-0.255, and a microcrystallization system of 690-720℃ for 9-15 hours, which has an ultra-low thermal expansion coefficient of ±(3-10) ppb / K (0-50℃). The surface error roughness can be controlled to be ≤0.20 nm rms through ion beam polishing (IBF) and other processing technologies, and the transmittance in the 500-1500 nm wavelength band is higher than 85%.

[0075] The preparation method of the ultra-low expansion transparent glass-ceramics material is exemplarily described below.

[0076] The raw materials are calculated according to the composition of the oxide mass percentage, accurately weighed by an electronic balance, and then mixed uniformly in a three-dimensional mixer with iron removal function;

[0077] In an alternative embodiment, the base glass melting raw materials of the microcrystalline glass are selected as follows: SiO2 is introduced by one or more of silica with a purity of ≥ 99.9% or quartz glass;

[0078] Al2O3 is introduced by one or more of AlPO4 and Al(OH)3 with a purity of ≥ 99.9%, wherein AlPO4 can both act as a flux and increase the reactivity of AlPO4 and Al(OH)3 during melting, thereby reducing the melting temperature;

[0079] Li2O is introduced by one or more of carbonates or oxides with a purity of ≥ 99.9%;

[0080] R'O (R' = Sr, Ca) and R"2O (R" = Na, K) are introduced by one or more of carbonates / nitrates with a purity of ≥ 99.0%, wherein the carbonates / nitrates are controlled at a ratio of 1 : (0-0.5);

[0081] BaO is introduced by one or more of barium nitrates with a purity of ≥ 99.0%, because barium carbonate decomposes too high at ≥ 1400°C, which is not conducive to gas removal, resulting in too high gas content in the glass matrix, leading to bubble precipitation during fining, thereby affecting the quality of the matrix glass, while barium nitrate decomposes at 600°C;

[0082] ZnO / MgO / TiO2 / ZrO2 are introduced by oxides with a purity of ≥ 99.9%;

[0083] P2O5 is introduced by AlPO4 with a purity of ≥ 99.9%;

[0084] The fining agent is introduced by at least one of Sb2O3, CeO2, and combinations thereof with a purity of ≥ 99.9%.

[0085] In the glass high-temperature melting furnace, platinum-rhodium crucible or quartz crucible is used to melt at 1550-1600°C for 2-6 hours, and the glass is rapidly cooled and extracted into glass fragments (which can be referred to as glass clinker hereinafter) by a pair of rollers.

[0086] In an alternative embodiment, in the preparation method of the microcrystalline glass, the glass clinker melting system is 1550-1600°C for 2-6 hours, the glass clinker melting process is operated 1-4 times, and the glass component uniformity is improved and the dissolved gas bubbles in the glass matrix are eliminated through the extrusion pressure in the forming process.

[0087] In an alternative embodiment, in the preparation method of the microcrystalline glass, the glass clinker melting process uses platinum-rhodium crucible or quartz crucible, and a high-temperature glass melting furnace is used.

[0088] After initial crushing, the glass frit is added to a self-designed multi-layer platinum-rhodium or quartz crucible at room temperature or 1400-1500°C, and heated to 1550-1600°C at a heating rate of 1-5°C / min for 2-8h of melting-homogenization of the ingredients, and then decreased to 1500-1400°C at a rate of 1-5°C / min for 4-10h of fining, and then decreased to 600-700°C at a rate of 2-10°C / min for 24-96h of annealing treatment, and then decreased to 150°C at a rate of 0.5-2°C / min and then air-cooled to room temperature after the electric current is turned off, without stirring process during the glass melting-homogenization process.

[0089] In an alternative embodiment, the preparation method of the microcrystalline glass, the charging temperature and melting regime are 1450-1500°C for 4-24h, the homogenization regime is 1550-1650°C for 4-24h, the fining regime is 1400-1500°C for 4-12h, and the annealing regime is 600-700°C for 12-48h. Stirring is performed simultaneously during the homogenization process, and the stirring regime comprises: stirring at 30-60rpm for 2-12h, and then stirring at 15-25rpm for 2-6h; the total time of the homogenization and stirring is 4-24h.

[0090] In an alternative embodiment, the preparation method of the microcrystalline glass, the melting-added material can be a glass raw material mixture and a glass frit.

[0091] In an alternative embodiment, the glass stirring process in the preparation method of the microcrystalline glass uses an eccentric stirring process, and the stirring process is divided into a high-speed process at 30-60r / min and a low-speed process at 15-25r / min, wherein the high-speed stirring time and the low-speed stirring time ratio is 1:(0.2-0.5).

[0092] In an alternative embodiment, the preparation method of the ultra-low expansion transparent microcrystalline glass material, the glass melting-stirring homogenization-fining, the melting and stirring process can be a platinum-rhodium crucible or a quartz crucible, the fining crucible can be a platinum-rhodium crucible, and the stirring paddle can be made of reinforced platinum-rhodium or quartz material.

[0093] The homogeneous and defect-free glass blank is placed in a self-developed rotary crystallization furnace and heated to 680-750°C at a rate of 0.5-2°C / min for microcrystallization treatment.

[0094] In an alternative embodiment, the microcrystallization regime in the preparation method of the microcrystalline glass is 680-750°C for 6-24h, and 350 and 500°C for 24h, and the heating and cooling rates are 0.1-3°C / min. In an alternative embodiment, the microcrystallization process in the preparation method of the microcrystalline glass uses a rotary crystallization furnace, the temperature control accuracy is ±1°C, and the rotation speed is -0.05-1r / min.

[0095] Test method:

[0096] (1) Thermal expansion analysis test: thermal expansion test adopts a thermal expansion analyzer of type DIL 402 of Netzsch, Germany, and the temperature is raised from -50 to 100℃ at a rate of 5℃ / min, and the reference standard is GB / T 7962.16-2010 Optical Glass Test Methods Part 16: Linear Expansion Coefficient, Transition Temperature and Sag Temperature;

[0097] (2) Optical performance test: the test of the Young's modulus of the glass-ceramics in the application is based on the standard GB / T 7962.12-2010 Optical Glass Test Methods Part 12: In-Spectrum Transmittance

[0098] (3) Mechanical property test: the test of the Young's modulus of the glass-ceramics in the application is based on the standard GBT 7962 6-2010 Optical Glass Test Methods Part 6: Young's Modulus, Shear Modulus and Poisson's Ratio; the test standard of Knoop hardness is GB / T 7962.18-2010 Optical Glass Test Methods Part 18: Knoop Hardness; and the test standard of bending strength is GBT 6569-2006 Fine Ceramic Bending Strength Test Method.

[0099] The following further examples are used to illustrate the application in detail. It should also be understood that the following examples are only used to further illustrate the application, and cannot be understood as limiting the protection scope of the application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the application all belong to the protection scope of the application. The specific process parameters in the following examples are only one example in the appropriate range, i.e. those skilled in the art can make appropriate selection within the range through the description herein, and are not limited to the specific values in the following examples.

[0100] Example 1:

[0101] (1) Proportioning: the glass mass fractions in Example 1 in Table 1 are proportioned, the total mass is 3000 grams, and each corresponding raw material is calculated and weighed: SiO2 1463.63 grams, Al(OH)3 774.75 grams, Li2CO3 233.22 grams, CaCO3 57.32 grams, AlPO4 165.56 grams, ZnO 56.33 grams, ZrO2 44.35 grams, TiO2 44.35 grams, Sb2O3 25.49 grams, MgO 17.33 grams, Ba(NO3)3 44.75 grams, Sc2O3 37.22 grams, Ta2O5 35.69 grams, and the mixture is obtained after the three-dimensional mixer with iron removal function is rotated for 8 hours and the material is discharged;

[0102] (2) clinker melting system: the mixture in step (1) is placed in a 1500 °C platinum crucible for melting and homogenization for 3 hours to obtain a glass melt; then the glass melt is poured into a roller gate machine to realize cold extraction to obtain glass slag;

[0103] (3) melting, homogenization and clarification system of glass slag: the mixture in step (2) is placed in a 1550 °C furnace for melting and holding for 2 hours to obtain a glass melt; the obtained glass melt is introduced into a 1620 °C furnace through a microflow pipe for homogenization while stirring at 40 r / min for 4 hours, and then the stirring speed is reduced to 20 r / min for 2 hours to obtain a glass liquid; the homogeneous glass liquid is introduced into a 1450 °C furnace for clarification and holding for 4 hours, and then poured into a forming mold;

[0104] (4) annealing process: the glass in step (3) is placed in a 660 °C rotary annealing furnace for holding for 48 hours, then the temperature is reduced to 100 °C at a rate of 2 °C / min, and the furnace is turned off and cooled to room temperature;

[0105] (5) crystallization process: the glass obtained in step (4) is placed in a rotary crystallization furnace (rotation speed is 0.1 r / min) and heated to 350 °C at a rate of 1 °C / min, held for 24 h, then heated to 500 °C at a rate of 1 °C / min, held for 24 h, and finally heated to 700 °C at a rate of 1 °C / min, held for 12 h, then cooled to 100 °C at a rate of 2 °C / min, the power is turned off and the furnace is cooled to room temperature, to obtain an ultra-low expansion glass-ceramic material.

[0106] Example 2:

[0107] The preparation process of the ultra-low expansion transparent glass-ceramic material in this example 2 is as in example 1, the only difference is that: step (1) batching: the glass mass fractions in example 1 in table 1 are proportioned, the total mass is 3000 grams, and each corresponding raw material is calculated and weighed: SiO2 1463.63 grams, Al(OH)3 774.75 grams, Li2CO3 233.22 grams, CaCO3 57.32 grams, AlPO4 165.56 grams, ZnO 56.33 grams, ZrO2 44.35 grams, TiO2 44.35 grams, Sb2O3 25.49 grams, MgO 17.33 grams, Ba(NO3)3 44.75 grams, Y2O3 37.22 grams, Ta2O5 35.69 grams, the mixture is obtained after rotating the three-dimensional mixer with iron removal function for 8 hours, and the mixture is obtained.

[0108] Example 3:

[0109] The preparation process of the ultra-low expansion transparent microcrystalline glass material in this embodiment 3 refers to embodiment 1, the only difference is that: step (1) batching: according to the glass mass fraction of embodiment 1 in table 1, calculate and take the corresponding raw materials with a total mass of 3000 grams: SiO2 1463.63 grams, Al(OH)3 774.75 grams, Li2CO3 233.22 grams, CaCO3 57.32 grams, AlPO4 165.56 grams, ZnO 56.33 grams, ZrO2 44.35 grams, TiO2 44.35 grams, Sb2O3 25.49 grams, MgO 17.33 grams, Ba(NO3)3 44.75 grams, Er2O3 37.22 grams, Ta2O5 35.69 grams, and the mixture is obtained after rotating for 8 hours by using a three-dimensional mixer with iron removal function.

[0110] Embodiment 4:

[0111] The preparation process of the ultra-low expansion transparent microcrystalline glass material in this embodiment 4 refers to embodiment 1, the only difference is that: step (1) batching: according to the glass mass fraction of embodiment 4 in table 1, calculate and take the corresponding raw materials with a total mass of 5000 grams: SiO2 2496.38 grams, Al(OH)3 1197.89 grams, Li2CO3 395.42 grams, CaCO3 71.16 grams, AlPO4 306.45 grams, ZnO 82.31 grams, ZrO2 62.59 grams, TiO2 62.59 grams, Sb2O3 42.87 grams, MgO 61.31 grams, Ba(NO3)3 75.26 grams, Dy2O3 85.74 grams, Nb2O5 55.73 grams, and the mixture is obtained after rotating for 8 hours by using a three-dimensional mixer with iron removal function.

[0112] Embodiment 5:

[0113] The preparation process of the ultra-low expansion transparent microcrystalline glass material in this embodiment 5 refers to embodiment 1, the only difference is that: step (1) batching: according to the glass mass fraction of embodiment 4 in table 1, calculate and take the corresponding raw materials with a total mass of 5000 grams: SiO2 2496.38 grams, Al(OH)3 1197.89 grams, Li2CO3 395.42 grams, CaCO3 71.16 grams, AlPO4 306.45 grams, ZnO 82.31 grams, ZrO2 62.59 grams, TiO2 62.59 grams, Sb2O3 42.87 grams, MgO 61.31 grams, Ba(NO3)3 75.26 grams, Dy2O3 42.87 grams, Dy2O3 42.87 grams, Nb2O5 55.73 grams, and the mixture is obtained after rotating for 8 hours by using a three-dimensional mixer with iron removal function.

[0114] Example 6:

[0115] The preparation process of the ultra-low expansion transparent glass-ceramic material in this example 6 refers to example 1, the difference is only in step (5) crystallization process: the glass obtained in step (4) is placed in a rotating crystallization furnace (rotation speed is 0.1 r / min) and heated to 350℃ at a heating rate of 1℃ / min for 24h, then heated to 500℃ at a heating rate of 1℃ / min for 24h, finally heated to 680℃ at a heating rate of 1℃ / min for 12h, and then cooled to 100℃ at a cooling rate of 2℃ / min, and the furnace is cooled to room temperature, to obtain the ultra-low expansion glass-ceramic material.

[0116] Example 7:

[0117] The preparation process of the ultra-low expansion transparent glass-ceramic material in this example 7 refers to example 1, the difference is only in step (5) crystallization process: the glass obtained in step (4) is placed in a rotating crystallization furnace (rotation speed is 0.1 r / min) and heated to 350℃ at a heating rate of 1℃ / min for 24h, then heated to 500℃ at a heating rate of 1℃ / min for 24h, finally heated to 740℃ at a heating rate of 1℃ / min for 12h, and then cooled to 100℃ at a cooling rate of 2℃ / min, and the furnace is cooled to room temperature, to obtain the ultra-low expansion glass-ceramic material.

[0118] Comparative Example 1:

[0119] The preparation process of the ultra-low expansion transparent glass-ceramic material in this comparative example 1 refers to example 1, the difference is only in step (3) melting, homogenizing and fining of glass slag: the mixture in step (2) is placed in a 1550℃ furnace for melting and heat preservation for 2 hours to obtain a glass melt; the obtained glass melt is introduced into a 1620℃ furnace through a microflow pipe for homogenization while stirring at a speed of 40r / min for 6 hours to obtain a glass liquid; the uniform glass liquid is introduced into a 1450℃ furnace for fining and heat preservation for 4 hours, and then poured into a forming mold.

[0120] Comparative Example 2:

[0121] The preparation process of the ultra-low expansion transparent glass-ceramic material in this comparative example 2 refers to example 1, the difference is only in step (3) melting, homogenizing and fining of glass slag: the mixture in step (2) is placed in a 1550℃ furnace for melting and heat preservation for 2 hours to obtain a glass melt; the obtained glass melt is introduced into a 1620℃ furnace through a microflow pipe for homogenization while stirring at a speed of 20r / min for 6 hours to obtain a glass liquid; the uniform glass liquid is introduced into a 1450℃ furnace for fining and heat preservation for 4 hours, and then poured into a forming mold.

[0122] Comparative Example 3:

[0123] The preparation process of the ultra-low expansion transparent microcrystalline glass material in the present comparative example 3 is referred to the preparation process of the example 1, the only difference is that: the glass mass fraction of the comparative example 3 in table 1 is used for proportioning, the total mass is 3000 grams, the corresponding raw materials are calculated and weighed: SiO2 1499.32 grams, Al(OH)3 774.75 grams, Li2CO3 233.22 grams, CaCO3 57.32 grams, AlPO4 165.56 grams, ZnO 56.33 grams, ZrO2 44.35 grams, TiO2 44.35 grams, Sb2O3 25.49 grams, MgO 17.33 grams, Ba(NO3)3 44.75 grams, Sc2O3 37.22 grams, Ta2O5 0 grams, the mixture is obtained after the three-dimensional mixer with iron removal function is rotated for 8 hours.

[0124] Comparative example 4:

[0125] The preparation process of the ultra-low expansion transparent microcrystalline glass material in the present comparative example 4 is referred to the preparation process of the example 1, the only difference is that: the crystallization process of step (5) is that the glass obtained in step (4) is placed in a rotary crystallization furnace (rotation speed is 0.1 r / min) and heated to 350℃ at a heating rate of 1℃ / min for 24h, then heated to 500℃ at a heating rate of 1℃ / min for 24h, finally heated to 660℃ at a heating rate of 1℃ / min for 12h, and then cooled to 100℃ at a cooling rate of 2℃ / min, and then the power is turned off and the furnace is cooled to room temperature, to obtain the ultra-low expansion microcrystalline glass material.

[0126] Comparative example 5:

[0127] The preparation process of the ultra-low expansion transparent microcrystalline glass material in the present example 7 is referred to the preparation process of the example 1, the only difference is that: the crystallization process of step (5) is that the glass obtained in step (4) is placed in a rotary crystallization furnace (rotation speed is 0.1 r / min) and heated to 350℃ at a heating rate of 1℃ / min for 24h, then heated to 500℃ at a heating rate of 1℃ / min for 24h, finally heated to 760℃ at a heating rate of 1℃ / min for 12h, and then cooled to 100℃ at a cooling rate of 2℃ / min, and then the power is turned off and the furnace is cooled to room temperature, to obtain the ultra-low expansion microcrystalline glass material.

[0128] Table 1 is the composition and performance comparison of the microcrystalline glass materials obtained in examples 1-6 (mass percentage)

[0129]

[0130]

[0131] Table 2 is the composition and performance comparison of the microcrystalline glass materials obtained in examples 7 and comparative examples 1-8 (mass percentage)

[0132]

[0133]

Claims

1. A method for preparing an ultra-low expansion transparent glass-ceramic material, characterized in that: The glass material comprises: 53-60 wt% SiO2, 20-26 wt% Al2O3, 3-4 wt% Li2O, 1-4 wt% ZnO, 0.5-3 wt% MgO, 0.2-3 wt% RO, 1-2 wt% TiO2, 1-2 wt% ZrO2, 3-4.16 wt% P2O5, 0.5-3 wt% M2O5, 0.5-3 wt% Ln2O3, and 0-2 wt% of a fining agent; wherein R = at least one of Sr, Ca, and Ba; M = at least one of Ta and Nb; and Ln = at least one of Ce, Sc, Pr, Y, La, Nd, Sm, Gd, Tb, Dy, Er, Tm, Yb, and Lu; and the fining agent is selected from at least one of Sb2O3, CeO2, and a combination thereof. The preparation method comprises: (1) Si source, Al source, Li source, Zn source, Mg source, Ti source, Zr source, P source, R source, M source, Ln source and clarifier are mixed, and then melted, homogenized and quenched to obtain glass slag; (2) melting, homogenizing, clarifying and annealing the obtained glass slag to obtain the glass material; (3) The glass material is subjected to microcrystallization treatment to obtain an ultra-low expansion transparent microcrystalline glass material, wherein the microcrystallization treatment system includes: a temperature of 680 to 740°C, a heat preservation time of 9 to 24 hours, and a heating rate and a cooling rate of the microcrystallization treatment are both 0.1 to 3°C / min.

2. The preparation method according to claim 1, wherein The glass material comprises: 55-59wt% SiO2, 20-25wt% Al2O3, 3-4wt% Li2O, 1-4wt% ZnO, 1-3wt% MgO, 0.2-2wt% RO, 1-2wt% TiO2, 1-2wt% ZrO2, 3-4.16wt% P2O5, 0.5-3wt% M2O5, 0.5-3wt% Ln2O3 and 0.5-2wt% clarifier.

3. The preparation method according to claim 1, characterized in that in, Al2O3+SiO2=78~83wt%, SiO2 / Al2O3=2.3~2.7; Among them, SiO2+Al2O3+Li2O+MgO+ZnO=85~90wt%; Among them, Li2O+MgO+ZnO=6~8wt%, and Li2O / (MgO+ZnO)=1.1~1.5; The glass material does not contain B2O3, Na2O, or K2O.

4. The preparation method according to claim 1, characterized in that The microcrystallization process is accompanied by rotation, and the rotation speed is 0.05 to 1 revolutions per minute.

5. The preparation method according to claim 1, characterized in that The microcrystallization treatment system includes: first keeping the temperature at 300-400°C for 6-24 hours, then keeping the temperature at 500-600°C for 6-24 hours, then keeping the temperature at 680-740°C for 9-24 hours, and finally cooling to 150-250°C, then turning off the power and cooling to room temperature along with the furnace.

6. The preparation method according to claim 1, characterized in that The Si source is silicon oxide and / or quartz glass, and the purity of the Si source is ≥99.9%; The Al source is at least one of AlPO4 and Al(OH)3, and the purity of the Al source is ≥99.9%; The Li source is Li2O and / or lithium carbonate, and the purity of the Li source is ≥99.9%; The Zn source is ZnO with a purity of ≥99.9%; The Mg source is MgO with a purity of ≥99.9%; The Ti source is TiO2 with a purity of ≥99.9%; The Zr source is ZrO2 with a purity of ≥99.9%; The P source is P2O5 or / and AlPO4, and the purity of the P source is ≥99.9%; The R source is at least one of an oxide of R, a carbonate of R, and a nitrate of R, and the purity of the R source is ≥99.9%; The M source is at least one of an oxide of M, a carbonate of M, and a nitrate of M, and the purity of the M source is ≥99.9%; The Ln source is at least one of Ln oxide, Ln carbonate, and Ln nitrate, and the purity of the Ln source is ≥99.9%.

7. The preparation method according to claim 1, characterized in that In step (1), the melting-homogenizing temperature is 1500-1600° C., and the holding time is 1-4 hours; The quenching system is to pour the molten glass into a roller mill for quenching treatment.

8. The preparation method according to claim 7, characterized in that The heating rate and cooling rate of the melting are both 2-20°C / min.

9. The preparation method according to claim 1, characterized in that The melting-homogenizing and quenching operations are performed 1 to 4 times.

10. The preparation method according to claim 1, characterized in that In step (2): The melting temperature is 1450-1500°C and the holding time is 4-24 hours; The homogenization temperature is 1550-1600°C and stirring is performed simultaneously during the homogenization process. The stirring system includes: first high-speed stirring at 30-60 rpm, and then low-speed stirring at 15-25 rpm; the total time of the homogenization and stirring is 4-24 hours, and the ratio of high-speed stirring time to low-speed stirring time is 1:(0.2-0.5); The clarification temperature is 1400-1500°C and the holding time is 4-12 hours; The annealing temperature is 600-700° C., and the heat preservation time is 12-48 hours.

11. The preparation method according to claim 10, characterized in that: In step (2): the melting, homogenization, clarification and annealing are carried out in four crucibles respectively; The crucible used for melting is a platinum-rhodium crucible or a quartz crucible; The crucible used for homogenization is a platinum-rhodium crucible or a quartz crucible; The crucible used for clarification is a quartz crucible or a graphite crucible; The crucible used for annealing is a quartz crucible or a graphite crucible, and the components used can be free of processing or require minimal processing through structural design.

12. An ultra-low expansion transparent glass-ceramic material prepared by the preparation method according to any one of claims 1 to 11, characterized in that: The crystallization phase in the ultra-low expansion transparent glass-ceramics material contains a β-quartz solid solution phase.

13. The ultra-low expansion transparent glass-ceramic material according to claim 12, characterized in that: The ultra-low expansion transparent glass-ceramic material does not contain B2O3, Na2O, or K2O.

14. The ultra-low expansion transparent glass-ceramic material according to claim 12 or 13, characterized in that: The crystal particle size of the crystallized phase is 5 to 10 nm, and the content of the crystallized phase is 70 to 80 vol%.

15. The ultra-low expansion transparent glass-ceramic material according to claim 12 or 13, characterized in that: The ultra-low expansion transparent glass-ceramics material has an average thermal expansion coefficient of 3 to 10 ppb / °C, an elastic modulus of 87 to 92 GPa, and a Poisson's ratio of 0.245 to 0.

255.

16. Use of the ultra-low expansion transparent glass-ceramic material according to any one of claims 12 to 15 in an optical reflective element of an EUVL lithography machine.

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