Transparent glass ceramic with low thermal expansion coefficient and preparation method thereof

Abstract

The invention belongs to the technical field of transparent ceramics and electronic packaging materials, and particularly relates to a low-thermal-expansion-coefficient transparent glass ceramic and a preparation method thereof. The base glass is prepared from the following components in percentage by mass: 60 to 65 percent of SiO2, 20 to 25 percent of Al2O3 and 4 to 10 percent of Li2O, the mass ratio of Li2O to Al2O3 is 0.22 to 0.3, the mass ratio of Li2O to SiO2 is 0.08 to 0.1, and the mass ratio of Al2O3 to SiO2 is 0.33 to 0.5; 2%-5% of a sintering aid B2O3; the nucleating agent at least comprises ZrO2, and the proportion of the components in the total raw materials is as follows: 1%-5% of ZrO2, 0%-3% of ZnO, 0%-3% of TiO2, 0%-1% of P2O5, 0%-4% of Al2TiO5 and 0%-3% of (BaO + CaO + SrO); the Al2TiO5 and the TiO2 are not used at the same time; the doping substance is a mixture of La2O3 and CeO2 and accounts for 0.5%-1% in total; and the clarifying agent is a mixture of SnO2 and CaF2 and accounts for 0.5%-1% in total. The preparation method comprises the steps of raw material melting and water quenching, grinding and sieving, granulation forming, sintering by a three-step sintering method, ion exchange treatment and the like, and finally the transparent glass ceramic with low thermal expansion coefficient, high light transmittance and high bending strength can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of transparent ceramics and electronic packaging materials, and in particular relates to a transparent glass ceramic with a low thermal expansion coefficient and a preparation method thereof. Background Art

[0002] With the development of electronic science and technology, electronic packaging materials are facing higher and higher requirements. Traditional metal, polymer and ceramic materials have their own advantages and disadvantages in the field of electronic packaging: metals have good electrical and thermal conductivity, but the thermal expansion coefficient is greatly mismatched with electronic devices and has high density; polymer-based electronic packaging materials have simple processes, low costs, and light weight, but often cannot meet the requirements in terms of thermodynamic properties; ceramic-based electronic packaging materials have excellent performance in mechanical properties, thermodynamic properties, dielectric properties, chemical stability, etc., but the preparation process is complex and the cost is high.

[0003] In recent years, glass ceramics, as a new type of electronic packaging material, have begun to show unique advantages because they have both the optical properties of glass and the excellent properties of ceramics such as mechanics, thermodynamics, and chemical stability. Li2O-Al2O3-SiO2 (LAS) system glass ceramics have attracted widespread attention due to their special thermodynamic properties and high flexural strength. By adjusting the components of the base glass, adding nucleating agents, doping with rare earth oxides and other measures, the type and content of the precipitated phase can be effectively adjusted, and through the interaction between the precipitated phase and the glass matrix, a lower thermal expansion coefficient, high transparency and higher flexural strength can be achieved. However, the glass ceramics prepared by the existing technology still have room for improvement in terms of thermal expansion coefficient, light transmittance and flexural strength, and cannot fully meet the stringent requirements for materials in the field of electronic packaging.

[0004] In summary, there is an urgent need for a glass-ceramic electronic packaging material with high bending strength and low thermal expansion coefficient. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a transparent glass-ceramic with a low thermal expansion coefficient and a preparation method thereof. By reasonably adjusting the formula components, the type and content of the added substances, and coordinating ion exchange to assist strengthening, transparent glass-ceramics with a low thermal expansion coefficient, high light transmittance and high bending strength can be finally obtained.

[0006] Therefore, one of the objects of the present invention is to provide a low thermal expansion coefficient transparent glass ceramic, the raw material composition of which comprises the following components by mass percentage:

[0007] Basic glass formula: SiO2: 60%-65%, Al2O3: 20%-25%, Li2O: 4%-10%; the mass ratio of Li2O to Al2O3 is 0.22-0.3, the mass ratio of Li2O to SiO2 is 0.08-0.1, and the mass ratio of Al2O3 to SiO2 is 0.33-0.5;

[0008] Sintering aid: B2O3: 2%-5%;

[0009] Nucleating agent: at least contains ZrO2, and its components account for ZrO2 1%-5%, ZnO 0%-3%, TiO2 0%-3%, P2O5 0%-1%, Al2TiO5 0%-4%, (BaO+CaO+SrO) 0%-3% in the total raw materials; and Al2TiO5 and TiO2 are not used at the same time;

[0010] Doping material: a mixture of La2O3 and CeO2, accounting for 0.5%-1%;

[0011] Clarifying agent: A mixture of SnO2 and CaF2, accounting for 0.5%-1%.

[0012] By adjusting the content of SiO2, the glass network matrix can be made denser, thereby improving the bending strength of the system. 3+ and Ce 4+ Under high temperature conditions, it can fully diffuse and enter the lattice gaps of the main crystal phases such as eucryptite and quartz to produce solid solution strengthening. On the other hand, the addition of excess oxygen will increase the content of free oxygen in the system, reduce the number of bridging oxygen, induce the disintegration of the glass matrix, and thus reduce the melting temperature of the glass. The addition of nucleating agents provides nucleation sites, reduces the crystallization activation energy required for crystallization, promotes the precipitation of eucryptite, and uses multi-component nucleating agents to jointly regulate the nucleation process, and reasonably regulates the content of the main crystal phase and the glass matrix, thereby achieving low thermal expansion coefficient, high light transmittance and high bending strength.

[0013] Furthermore, the nucleating agent satisfies the following ratio:

[0014] 1) When TiO2 and ZrO2 are used simultaneously, the mass ratio of TiO2 / ZrO2 is 0.5-0.8;

[0015] 2) When ZnO and P2O5 are used simultaneously, the mass ratio of ZnO / P2O5 is 0.9-2.1;

[0016] 3) The mass ratio of (BaO+CaO) to SrO is ≤0.8.

[0017] The high strength and high refractive index of ZrO2 are used to improve the bending strength and transmittance of the sample; limiting the mass ratio of TiO2 / ZrO2 can avoid the problem of color and reduced transmittance of glass ceramic samples due to excessive TiO2 content, and avoid the problem of excessive melting temperature of the system due to excessive ZrO2 content. The addition of ZnO can promote the crystallization of the system and improve the high temperature stability and thermal shock resistance of the system; after adding P2O5 and melting operation, the system can produce excess free oxygen and [PO5], which can combine with free cations in the system to improve the chemical stability of the system; [PO5] as a constituent unit of the glass network can improve the density of the glass and thus improve the bending strength of the system. Limiting the mass ratio of ZnO / P2O5 can avoid excessive free oxygen generated by excessive addition of P2O5, thereby avoiding the problem of reduced stability of the glass network. Considering the existence of electric fields in the working environment of electronic devices, BaO, SrO and TiO2 themselves have relatively high dielectric constants, and their addition and reasonable mass ratio can ensure the normal operation of electronic devices.

[0018] Furthermore, in the doping material, the total mass of the rare earth oxides La2O3 and CeO2 is less than or equal to 5% of the total mass of the raw materials used, and the La2O3 / CeO2 mass ratio is 0.5-1.3. The high field strength, high chemical stability and small ion radius of the rare earth oxides themselves are used to improve the final performance of the glass ceramic sample.

[0019] Furthermore, the main crystal phase of the transparent glass-ceramic includes one or more of eucryptite, quartz, spodumene and solid solutions thereof, and the grain morphology is long strip, granular or lath-shaped and is evenly distributed.

[0020] Furthermore, the thermal expansion coefficient of the glass ceramic is 1×10 -7 / K -1 ~8×10 -7 / K -1 The transmittance in the visible light range is 85% to 92%.

[0021] Another object of the present invention is to provide a method for preparing the above-mentioned low thermal expansion coefficient transparent glass-ceramic, comprising the following steps:

[0022] S1, weigh the raw materials in proportion, ball-mill them once, dry them and sieve them;

[0023] S2, melting the sieved powder at 1350-1450° C. for 2-4 hours to obtain glass liquid, and quenching the glass liquid with water to obtain glass particles;

[0024] S3, ball-milling the glass particles for a second time and drying them, and then mixing them with a binder to form granules;

[0025] S4, sintering the granulated sample by a three-step sintering method of "annealing-nucleation-crystallization" to obtain transparent glass ceramics;

[0026] S5. Completely immerse the transparent glass ceramics prepared in S4 in the mixed molten salt and perform ion exchange at 400-500° C. for 2.5-3 hours to obtain ion exchange-assisted strengthened transparent glass ceramics.

[0027] Furthermore, the parameters used in the first ball milling and the second ball milling are the same, a planetary ball mill is used, the ball mill speed is set to 600 r / min, and the ball milling time is greater than or equal to 4 hours;

[0028] And / or, the mass percentage of the sample, deionized water and grinding balls is 1:1:1.5.

[0029] Furthermore, before the three-step sintering method is performed, the glass powder after secondary ball milling and drying needs to be tested by differential scanning calorimetry. The glass transition temperature T g and crystallization peak temperature T c2 .

[0030] Further, the steps of the three-step sintering method in S4 are as follows: first, annealing and debinding treatment is performed in the temperature range of 500-650°C, the heating rate is 5°C / min, the treatment time is 2-4 hours, and then the heating rate reaches T at 20°C / min. g The nucleation was carried out at a temperature of ±10°C and kept for 5 hours, and then at T c2 After reaching the temperature point, crystallization is carried out and kept warm for 30 minutes; then it is cooled to room temperature at a cooling rate of 5℃ / min. The three-step sintering method of "annealing-nucleation-crystallization" is adopted. On the one hand, annealing can ensure that the stress inside the glass-ceramic sample is completely removed before sintering to avoid cracking during sintering; the longer nucleation time (5 hours) ensures that the parent phase glass is fully crystallized under the joint action of the multi-component nucleating agent to produce a large number of crystal nuclei; the shorter crystallization time (30 minutes) makes it impossible for the crystal nucleus to grow fully, thereby ensuring the small grain size of the crystalline phase and avoiding abnormal grain growth, which can play a role in fine grain strengthening and enhancement.

[0031] Furthermore, the mixed molten salt in S5 uses NaNO3, Ca(NO3)2, and Mg(NO3)2 as the salts used for ion exchange, and the masses of different molten salts are equal when used; and when the salt used contains Ca(NO3)2, CaO is not used as the nucleating agent. The mixed molten salt NaNO3, Ca(NO3)2, and Mg(NO3)2 used in the ion exchange process can be used to convert Na + Mg 2+ , Ca 2+When plasma is introduced into the glass-ceramic system, the new cations can, on the one hand, enter the original crystalline functional phase of the system to produce solid solution strengthening and enhance the strength of the system; on the other hand, the excess free oxygen and unutilized non-bridging oxygen in the system can combine with the new cations to enhance the connectivity and density of the glass network, thereby enhancing the flexural strength of the glass-ceramic sample.

[0032] Another object of the present invention is to provide the application of the low thermal expansion coefficient transparent glass ceramic in electronic equipment, optical instruments or aerospace fields.

[0033] The advantages and positive effects of the present invention are:

[0034] 1) Innovation in formula design: The present invention limits the mass percentage of two of Li2O, Al2O3 and SiO2, and uses a multi-component nucleating agent to synergistically modify the performance of glass ceramics; ZrO2 and ZnO are used to improve the transparency and bending strength of glass ceramics; the lower thermal expansion coefficient of Al2TiO5 itself offsets the adverse effects of the crystalline phase with a higher thermal expansion coefficient in glass ceramics, reducing the thermal expansion coefficient by 40%-60%; at the same time, rare earth oxides La2O3 and CeO2 are doped, on the one hand, La 3+ and Ce 4+ Under high temperature conditions, it can fully diffuse and enter the lattice gaps of the main crystal phases such as eucryptite and quartz to produce solid solution strengthening. On the other hand, the addition of excess oxygen will increase the content of free oxygen in the system, reduce the number of bridging oxygen, induce the disintegration of the glass matrix, and thus reduce the melting temperature of the glass.

[0035] 2) Innovation in preparation process: The three-step sintering method of "annealing, debinding, nucleation and crystallization" is adopted to avoid the energy waste caused by the traditional sintering after annealing, debinding and cooling; by extending the nucleation time (extending the nucleation time to 5 hours to promote the precipitation of crystal nuclei) and shortening the crystallization time (shortened to 30 minutes), a lithium aluminum silicate crystalline functional phase with a lower thermal expansion coefficient is precipitated, thereby reducing the thermal expansion coefficient of the system;

[0036] 3) Ion exchange strengthening: The ions on the surface of the glass ceramic are fully exchanged with the ions in the mixed molten salt to achieve surface strengthening. During the ion exchange process, stress is generated and the compressive toughness of the glass ceramic is enhanced, its crack resistance is enhanced, and the bending strength is increased to more than 160MPa, which is better than the traditional process (<120MPa);

[0037] In summary, the present invention can prepare glass ceramics with excellent performance. The samples have high flexural strength and low thermal expansion coefficient, which can better serve the field of electronic packaging materials. The preparation process is simplified, the energy consumption is low, and it is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a process flow chart of the preparation method of the present invention. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field without creative work based on the embodiments of the present invention are within the scope of protection of the present invention.

[0040] The invention discloses a transparent glass ceramic with low thermal expansion coefficient, which comprises the following mass components: basic glass formula: SiO2 accounts for 60%-65%, Al2O3 accounts for 20%-25%, and Li2O accounts for 4-10%; sintering aid is B2O3, which accounts for 2-5%; nucleating agent is: ZrO21-5%, ZnO 0-3%, TiO2 0-3%, P2O5 0-1%, Al2TiO5 0-4%, (BaO+CaO+SrO) 0-3%; doping material: (La2O3+CeO2) 0.5-1%; clarifier: (SnO2+CaF2) 0.5-1%.

[0041] The specific formula of the above components is shown in Table 1:

[0042] Table 1 Raw material ratio of each component glass ceramic (mass percentage)

[0043]

[0044]

[0045] The method for preparing the transparent glass-ceramic with low thermal expansion coefficient comprises the following steps:

[0046] S1, weigh the raw materials in proportion, ball-mill them once, dry them and sieve them;

[0047] S2, melting the sieved powder at 1350-1450° C. for 2-4 hours to obtain glass liquid, and quenching the glass liquid with water to obtain glass particles;

[0048] S3, ball-milling the glass particles for a second time and drying them, and then mixing them with a binder to form granules;

[0049] S4, sintering the granulated sample by a three-step sintering method of "annealing-nucleation-crystallization" to obtain transparent glass ceramics;

[0050] S5. The prepared transparent glass-ceramics are subjected to ion exchange treatment to obtain ion exchange-assisted strengthened transparent glass-ceramics.

[0051] The specific embodiments are as follows:

[0052] Example 1

[0053] According to the chemical composition of the samples listed in Table 1, [BaO+CaO]:SrO is 0.8, the mass ratio of rare earth oxides La2O3 and CeO2 is 1, and the mass ratio of clarifiers CaF2 and SnO2 is 1.

[0054] S1. Weigh each raw material using an electronic balance, use deionized water as the ball milling medium, use zirconium oxide balls as grinding balls, and the mass ratio of the material, deionized water, and grinding balls is 1:1:1.5. Place the raw materials in a planetary ball mill and mill for 4 hours (600r / min). Pour the milled slurry into a drying plate, place it in a drying oven and dry it at 70°C for 12 hours, and pass it through a 200-mesh sieve;

[0055] S2, placing the sieved powder in a platinum crucible and melting it at 1400° C. for 3 hours, then pouring the melt into deionized water for quenching to obtain glass particles;

[0056] S3, ball milling the glass particles for a second time, the ball milling conditions are the same as the first time, after drying, the glass particles are sieved through a 200 mesh sieve, mixed with 5% by mass of acrylic acid for granulation, and prepared into shapes of 120 mm×20 mm×20 mm, 10 mm×50 mm×1 mm, and 10 mm×10 mm×50 mm;

[0057] S4. According to the data obtained from the DSC curve, the glass sample was annealed at 520°C for 3.5 hours to remove binder, nucleated at 700°C for 5 hours, crystallized at 800°C for 30 minutes, and then cooled to room temperature at a cooling rate of 5°C / min to obtain a transparent glass ceramic.

[0058] The main crystal phases of the obtained transparent glass ceramics are eucryptite, quartz, spodumene and their solid solutions. The grain morphology is long strips and granules, and the distribution is uniform. The thermal expansion coefficient of the sample is 6×10 -7 / K -1 , the transmittance in the visible light range reaches 92%;

[0059] S5. The transparent glass ceramic sample was then completely immersed in a mixed molten salt of NaNO3 and Mg(NO3)2 in a mass ratio of 1:1, and ion exchange was performed at 450°C for 2.5 hours. The sample was then rinsed with deionized water for a flexural strength test, and the flexural strength reached 188MPa.

[0060] Embodiment 2:

[0061] According to the chemical composition of the samples listed in Table 1, the mass ratio of BaO to SrO is 0.8, the mass ratio of rare earth oxides La2O3 and CeO2 is 0.9, and the mass ratio of clarifiers CaF2 and SnO2 is 1.

[0062] S1. Weigh each raw material using an electronic balance, use deionized water as the ball milling medium, use zirconium oxide balls as grinding balls, and the mass ratio of the material, deionized water, and grinding balls is 1:1:1.5. Place the raw materials in a planetary ball mill and mill for 4 hours (600r / min). Pour the milled slurry into a drying plate, place it in a drying oven and dry it at 70°C for 12 hours, and pass it through a 200-mesh sieve;

[0063] S2, placing the sieved powder in a platinum crucible and melting it at 1420° C. for 2.5 hours, then pouring the melt into deionized water for quenching to obtain glass particles;

[0064] S3, ball milling the glass particles for a second time, the ball milling conditions are the same as the first time, after drying, the glass particles are sieved through a 200 mesh sieve, mixed with 5% by mass of acrylic acid for granulation, and prepared into shapes of 120 mm×20 mm×20 mm, 10 mm×50 mm×1 mm, and 10 mm×10 mm×50 mm;

[0065] S4. According to the data obtained from the DSC curve, the glass sample was annealed at 550°C for 3 hours, nucleated at 710°C for 5 hours, crystallized at 840°C for 30 minutes, and then cooled to room temperature at a cooling rate of 5°C / min to obtain a transparent glass ceramic.

[0066] The main crystal phase of the obtained transparent glass ceramic is eucryptite and its solid solution. The grain morphology is long and uniformly distributed. The thermal expansion coefficient of the sample is 3×10 -7 / K -1 , the transmittance in the visible light range reaches 85%;

[0067] S5. The transparent glass ceramic sample was then completely immersed in a mixed molten salt of NaNO3, Mg(NO3)2, and Ca(NO3)2 in a mass ratio of 1:1:1, and ion exchange was carried out at 450°C for 2.5 hours. The sample was then rinsed with deionized water for a flexural strength test, and the flexural strength reached 177MPa.

[0068] Embodiment 3:

[0069] According to the chemical composition of the samples listed in Table 1, [BaO+CaO]:SrO is 0.8, the mass ratio of rare earth oxides La2O3 and CeO2 is 0.8, and the mass ratio of clarifiers CaF2 and SnO2 is 1.

[0070] S1. Weigh each raw material using an electronic balance, use deionized water as the ball milling medium, use zirconium oxide balls as grinding balls, and the mass ratio of the material, deionized water, and grinding balls is 1:1:1.5. Place the raw material in a planetary ball mill and mill for 4 hours (600r / min). Pour the milled slurry into a drying plate, place it in a drying oven and dry it at 70°C for 12 hours, and pass it through a 200-mesh sieve;

[0071] S2, placing the sieved powder in a platinum crucible and melting it at 1350° C. for 3.5 hours, then pouring the melt into deionized water for quenching to obtain glass particles;

[0072] S3, ball milling the glass particles for a second time, the ball milling conditions are the same as the first time, after drying, the glass particles are sieved through a 200 mesh sieve, mixed with 5% by mass of acrylic acid for granulation, and prepared into shapes of 120 mm×20 mm×20 mm, 10 mm×50 mm×1 mm, and 10 mm×10 mm×50 mm;

[0073] S4. According to the data obtained from the DSC curve, the glass sample was annealed at 550°C for 3.5 hours to remove binder, nucleated at 710°C for 5 hours, crystallized at 815°C for 30 minutes, and then cooled to room temperature at a cooling rate of 5°C / min to obtain a transparent glass ceramic.

[0074] The main crystal phase of the obtained transparent glass ceramic is quartz and its solid solution. The grain morphology is lath-shaped and evenly distributed. The thermal expansion coefficient of the sample is 8×10 -7 / K -1 , the transmittance in the visible light range reaches 86%;

[0075] S5. The transparent glass ceramic sample was then completely immersed in a mixed molten salt of NaNO3 and Mg(NO3)2 in a mass ratio of 1:1, and ion exchange was performed at 450°C for 2.5 hours. The sample was then rinsed with deionized water for a flexural strength test, and the flexural strength reached 175MPa.

[0076] Embodiment 4:

[0077] According to the chemical composition of the samples listed in Table 1, [BaO+CaO]:SrO is 0.8, the mass ratio of rare earth oxides La2O3 and CeO2 is 0.7, and the mass ratio of clarifiers CaF2 and SnO2 is 1.

[0078] S1. Weigh each raw material using an electronic balance, use deionized water as the ball milling medium, use zirconium oxide balls as grinding balls, and place the raw materials in a planetary ball mill for 4 hours (600r / min). Pour the milled slurry into a drying plate, place it in a drying oven and dry it at 70°C for 12 hours, and pass it through a 200-mesh sieve;

[0079] S2, placing the sieved powder in a platinum crucible and melting it at 1400° C. for 2.5 hours, then pouring the melt into deionized water for quenching to obtain glass particles;

[0080] S3, ball milling the glass particles for a second time, the ball milling conditions are the same as the first time, after drying, the glass particles are sieved through a 200 mesh sieve, mixed with 5% by mass of acrylic acid for granulation, and prepared into shapes of 120 mm×20 mm×20 mm, 10 mm×50 mm×1 mm, and 10 mm×10 mm×50 mm;

[0081] S4. Then, according to the data obtained from the DSC curve, the glass sample was annealed at 600°C for 3 hours to remove binder, nucleated at 715°C for 5 hours, crystallized at 825°C for 30 minutes, and then cooled to room temperature at a cooling rate of 5°C / min to obtain a transparent glass ceramic.

[0082] The main crystal phase of the obtained transparent glass ceramic is spodumene, quartz and its solid solution. The grain morphology is granular and evenly distributed. The thermal expansion coefficient of the sample is 3×10 -7 / K -1 , the transmittance in the visible light range reaches 91%;

[0083] S5. The transparent glass ceramic sample was then completely immersed in a mixed molten salt of NaNO3 and Mg(NO3)2 in a mass ratio of 1:1, and ion exchange was performed at 450°C for 3 hours. The sample was then rinsed with deionized water for a flexural strength test, and the flexural strength reached 160MPa.

[0084] Embodiment 5:

[0085] According to the chemical composition of the samples listed in Table 1, the mass ratio of BaO to SrO is 0.8, the mass ratio of rare earth oxides La2O3 and CeO2 is 0.6, and the mass ratio of clarifiers CaF2 and SnO2 is 1.

[0086] S1. Weigh each raw material using an electronic balance, use deionized water as the ball milling medium, use zirconium oxide balls as grinding balls, and place the raw materials in a planetary ball mill for 4 hours (600r / min). Pour the milled slurry into a drying plate, place it in a drying oven and dry it at 70°C for 12 hours, and pass it through a 200-mesh sieve;

[0087] S2, placing the sieved powder in a platinum crucible and melting it at 1400° C. for 3 hours, then pouring the melt into deionized water for quenching to obtain glass particles;

[0088] S3, ball milling the glass particles for a second time, the ball milling conditions are the same as the first time, after drying, the glass particles are sieved through a 200 mesh sieve, mixed with 5% by mass of acrylic acid for granulation, and prepared into shapes of 120 mm×20 mm×20 mm, 10 mm×50 mm×1 mm, and 10 mm×10 mm×50 mm;

[0089] S4. Then, according to the data obtained from the DSC curve, the glass sample was annealed at 650°C for 2.5 hours to remove binder, nucleated at 700°C for 5 hours, crystallized at 830°C for 30 minutes, and then cooled to room temperature at a cooling rate of 5°C / min to obtain a transparent glass ceramic.

[0090] The main crystal phase of the obtained transparent glass ceramic is eucryptite, quartz and its solid solution. The grain morphology is long and uniformly distributed. The thermal expansion coefficient of the sample is 5×10 -7 / K -1 , the transmittance in the visible light range is 88%;

[0091] S5. The transparent glass ceramic sample was then completely immersed in a mixed molten salt of NaNO3, Ca(NO3)2, and Mg(NO3)2 in a mass ratio of 1:1:1, and ion exchange was carried out at 460°C for 2.5 hours. The sample was then rinsed with deionized water for a flexural strength test, and the flexural strength reached 178MPa.

[0092] Embodiment 6:

[0093] According to the chemical composition of the samples listed in Table 1, the mass ratio of BaO to SrO is 0.8, CaO is not used, the mass ratio of rare earth oxides La2O3 and CeO2 is 0.5, and the mass ratio of clarifiers CaF2 and SnO2 is 1.

[0094] S1. Weigh each raw material using an electronic balance, use deionized water as the ball milling medium, use zirconium oxide balls as grinding balls, and place the raw materials in a planetary ball mill for 4 hours (600r / min). Pour the milled slurry into a drying plate, place it in a drying oven and dry it at 70°C for 12 hours, and pass it through a 200-mesh sieve;

[0095] S2, placing the sieved powder in a platinum crucible and melting it at 1450° C. for 2 hours, then pouring the melt into deionized water for quenching to obtain glass particles;

[0096] S3, ball milling the glass particles for a second time, the ball milling conditions are the same as the first time, after drying, the glass particles are sieved through a 200 mesh sieve, mixed with 5% by mass of acrylic acid for granulation, and prepared into shapes of 120 mm×20 mm×20 mm, 10 mm×50 mm×1 mm, and 10 mm×10 mm×50 mm;

[0097] S4. According to the data obtained from the DSC curve, the glass sample was annealed at 600°C for 3 hours, nucleated at 758°C for 5 hours, crystallized at 835°C for 30 minutes, and then cooled to room temperature at a cooling rate of 5°C / min to obtain a transparent glass ceramic.

[0098] The main crystal phase of the obtained transparent glass ceramic is eucryptite, quartz and its solid solution. The grain morphology is long and uniformly distributed. The thermal expansion coefficient of the sample is 1×10 -7 / K -1 , the transmittance in the visible light range reaches 90%;

[0099] S5. The transparent glass ceramic sample was then completely immersed in a mixed molten salt of NaNO3, Ca(NO3)2, and Mg(NO3)2 in a mass ratio of 1:1:1, and ion exchange was carried out at 450°C for 3 hours. The sample was then rinsed with deionized water for a flexural strength test, and the flexural strength reached 180MPa.

[0100] It should be noted that the above contents are further detailed descriptions of the present invention in combination with specific implementation methods, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions; the dimensional data of this embodiment does not limit the technical solution, but only shows one of the specific working conditions. For ordinary technicians in the technical field to which the present invention belongs, several simple improvements and modifications can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A transparent glass ceramic with low thermal expansion coefficient, characterized in that: The raw material composition, calculated by mass percentage, includes the following components: Basic glass formula: SiO2: 60%-65%, Al2O3: 20%-25%, Li2O: 4%-10%; the mass ratio of Li2O to Al2O3 is 0.22-0.3, the mass ratio of Li2O to SiO2 is 0.08-0.1, and the mass ratio of Al2O3 to SiO2 is 0.33-0.5; Sintering aid: B2O3: 2%-5%; Nucleating agent: at least contains ZrO2, and its components account for ZrO2 1%-5%, ZnO 0%-3%, TiO20%-3%, P2O5 0%-1%, Al2TiO5 0%-4%, (BaO+CaO+SrO) 0%-3% in the total raw materials; and Al2TiO5 and TiO2 are not used at the same time; Doping material: a mixture of La2O3 and CeO2, accounting for 0.5%-1%; Clarifying agent: A mixture of SnO2 and CaF2, accounting for 0.5%-1%.

2. The low thermal expansion coefficient transparent glass-ceramic according to claim 1, characterized in that: The nucleating agent satisfies the following ratio: 1) When TiO2 and ZrO2 are used simultaneously, the mass ratio of TiO2 / ZrO2 is 0.5-0.8; 2) When ZnO and P2O5 are used simultaneously, the mass ratio of ZnO / P2O5 is 0.9-2.1; 3) The mass ratio of (BaO+CaO) to SrO is ≤0.

8.

3. The low thermal expansion coefficient transparent glass-ceramic according to claim 1, characterized in that: In the doping material, the total mass of the rare earth oxides La2O3 and CeO2 is less than or equal to 5% of the total mass of the raw materials used, and the mass ratio of La2O3 / CeO2 is 0.5-1.

3.

4. The low thermal expansion coefficient transparent glass-ceramic according to claim 1, characterized in that: The main crystal phase of the transparent glass ceramic includes one or more of eucryptite, quartz, spodumene and solid solutions thereof, and the grain morphology is in the form of long strips, particles or laths and is evenly distributed.

5. The low thermal expansion coefficient transparent glass-ceramic according to claim 1, characterized in that: The thermal expansion coefficient of the glass ceramic is 1×10 -7 / K -1 ~8×10 -7 / K -1 The transmittance in the visible light range is 85% to 92%.

6. The method for preparing a transparent glass-ceramic with a low thermal expansion coefficient according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, weigh the raw materials in proportion, ball-mill them once, dry them and sieve them; S2, melting the sieved powder at 1350-1450° C. for 2-4 hours to obtain glass liquid, and quenching the glass liquid with water to obtain glass particles; S3, ball-milling the glass particles for a second time and drying them, and then mixing them with a binder to form granules; S4, sintering the granulated sample by a three-step sintering method of "annealing-nucleation-crystallization" to obtain transparent glass ceramics; S5. Completely immerse the transparent glass ceramics prepared in S4 in the mixed molten salt and perform ion exchange at 400-500° C. for 2.5-3 hours to obtain ion exchange-assisted strengthened transparent glass ceramics.

7. The method for preparing the transparent glass-ceramic with low thermal expansion coefficient according to claim 6, characterized in that: The parameters used in the first ball milling and the second ball milling are the same, a planetary ball mill is used, the ball mill speed is set to 600r / min, and the ball milling time is greater than or equal to 4 hours; And / or, the mass percentage of the sample, deionized water and grinding balls is 1:1:1.

5.

8. The method for preparing the transparent glass-ceramic with low thermal expansion coefficient according to claim 6, characterized in that: Before the three-step sintering method is carried out, the glass powder after secondary ball milling and drying needs to be subjected to differential scanning calorimetry analysis to obtain the glass transition temperature T g and crystallization peak temperature T c2 .

9. The method for preparing a transparent glass-ceramic with a low thermal expansion coefficient according to claim 8, characterized in that: The three-step sintering method in S4 is as follows: first, annealing and debinding treatment is performed in the temperature range of 500-650℃, the heating rate is 5℃ / min, and the treatment time is 2-4 hours. Then, the heating rate reaches T at 20℃ / min. g The nucleation was carried out at a temperature of ±10°C and kept for 5 hours, and then at T c2 The crystallization was carried out at the temperature point and kept warm for 30 minutes; then cooled to room temperature at a cooling rate of 5°C / min.

10. The method for preparing the transparent glass-ceramic with low thermal expansion coefficient according to claim 6, characterized in that: The mixed molten salt in S5 uses NaNO3, Ca(NO3)2, and Mg(NO3)2 as salts used for ion exchange, and the masses of different molten salts are equal when used; and when the salt used includes Ca(NO3)2, CaO is not used as the nucleating agent.

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