CaLa2S4 transparent ceramic material as well as preparation method and application thereof

Abstract

The invention relates to a CaLa2S4 transparent ceramic material as well as a preparation method and application thereof. The method comprises the following steps: carrying out ball milling on CaLa2S4 powder in a sealed environment, and drying; heating the ball-milled CaLa2S4 powder at a rate of 5-10 DEG C / min under the protection of argon, introducing a mixed gas of carbon disulfide and argon when the temperature rises to 500 DEG C, then continuously heating to 750-850 DEG C, carrying out heat preservation for 2-4 hours, naturally cooling, removing the carbon disulfide when the temperature is lower than 500 DEG C, continuously introducing argon for protection until the temperature is reduced to room temperature, washing and drying to obtain the CaLa2S4 powder. The purified CaLa2S4 powder is obtained; the purified CaLa2S4 powder is evenly laid under the protection of argon and kept for 0.5 h; heating, boosting and preserving heat according to stages; and after the heat preservation is finished, releasing the pressure, naturally cooling to room temperature, and carrying out coarse grinding and polishing treatment on the obtained CaLa2S4 ceramic block to obtain the CaLa2S4 transparent ceramic material. According to the invention, CaLa2S4 powder is used as a raw material, and is subjected to refining, purification and hot pressed sintering treatment, so that the density and optical transmittance of the ceramic are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic materials, and specifically relates to a CaLa2S4 transparent ceramic material and a preparation method and application thereof. Background Art

[0002] Faced with the increasing complexity of future battlefields, infrared detection technology with the advantages of high precision, strong concealment, and low susceptibility to interference has been widely used in various new hypersonic aircraft and ultra-high-speed weapons to assist them in infrared guidance, infrared reconnaissance and infrared countermeasures. The infrared window is a key component of the infrared detection system, which can play the role of signal transmission, maintaining aerodynamic shape and protecting the precision components inside the system. However, aircraft and weapons will be accompanied by strong aerodynamic thermal effects and erosion by sand and raindrops during high Mach flight. Existing infrared window materials have the disadvantages of low optical transmittance, enhanced infrared radiation, poor corrosion resistance, and low hardness when dealing with such harsh environments. Therefore, it is urgent to develop high-performance infrared window materials that can adapt to high-speed flight environments.

[0003] CaLa2S4 is an alkaline earth metal-rare earth sulfide with a cubic phase crystal structure, good transmittance in the wavelength range of 0.5-14μm, and a hardness of up to 600kgf / mm 2, Young's modulus is 96GPa. Therefore, CaLa2S4 has unique advantages in infrared optical transmittance, withstanding harsh environments, and resisting environmental erosion, and is the preferred window material for ultra-high-speed aircraft infrared detection systems. Powder purification and dense sintering process are the key to obtaining good optical properties of CaLa2S4 transparent ceramics. In addition, while improving optical transmittance, combining simple manufacturing processes to improve the sintering activity of powders is a necessary condition for promoting the industrial production and commercial application of CaLa2S4 transparent ceramics. The preparation methods of CaLa2S4 powder mainly include precursor sulfidation method, evaporation thermal decomposition method, carbonate co-precipitation method, solution combustion method, etc. These methods have complex process and cannot guarantee batch stability, which is not conducive to the industrial production of transparent ceramics. In contrast, the use of commercially available CaLa2S4 powder reduces the discharge of chemical waste in the preparation process of transparent ceramics, shortens the powder synthesis cycle, and is easier to achieve engineering preparation, but the commercially available powder has the disadvantages of large particle size and low sintering activity, which will affect the density of the sintered ceramics and requires further treatment and purification. The main preparation methods of CaLa2S4 transparent ceramics include atmosphere hot pressureless sintering, atmosphere hot pressing sintering, hot isostatic pressing sintering and electric field assisted sintering. Among them, atmosphere hot pressing sintering helps the contact diffusion flow of powder particles and is conducive to the mass transfer process. It can also reduce the sintering temperature and shorten the sintering time to inhibit grain growth and obtain products with high density and high mechanical and mechanical properties. However, since CaLa2S4 powder contains a certain amount of gas, if the exhaust is not smooth during the hot pressing process, it will cause sulfur oxide impurities formed by oxidation in the CaLa2S4 ceramic phase, resulting in the appearance of SO3 in the 8-14μm infrared band. 2- and SO4 2- The strong absorption of CaLa2S4 affects its optical transmittance. In summary, the existing technology cannot meet the high performance and high stability engineering production requirements of CaLa2S4 transparent ceramics. Summary of the invention

[0004] In view of this, the main purpose of the present invention is to provide a CaLa2S4 transparent ceramic material and its preparation method and application. The problem to be solved is to use CaLa2S4 powder as raw material, refine it, purify it and hot-press sinter it, so as to improve the density and optical transmittance of the ceramic.

[0005] The purpose of the present invention and the technical problem to be solved are achieved by adopting the following technical solutions. A method for preparing a CaLa2S4 transparent ceramic material proposed in the present invention comprises the following steps:

[0006] S1 powder refinement: ball mill the CaLa2S4 powder in a sealed environment and dry it;

[0007] Purification of S2 powder: The ball-milled CaLa2S4 powder is heated at a rate of 5-10°C / min under the protection of argon. When the temperature reaches 500°C, a mixed gas of carbon disulfide and argon is introduced, and then the temperature is continued to be raised to 750-850°C, and naturally cooled after being kept at this temperature for 2-4 hours. When the temperature is lower than 500°C, the carbon disulfide gas is removed, and argon is continued to be introduced for protection until the temperature drops to room temperature, washed, and dried to obtain the purified CaLa2S4 powder;

[0008] S3 hot pressing sintering: the purified CaLa2S4 powder is evenly spread under the protection of argon and maintained for 0.5h; then the temperature and pressure are increased in stages and the temperature is kept warm; after the insulation is completed, the pressure is released and the temperature is naturally lowered to room temperature, and the obtained CaLa2S4 ceramic block is roughly ground and polished to obtain the CaLa2S4 transparent ceramic material.

[0009] The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

[0010] Preferably, in the aforementioned method for preparing the CaLa2S4 transparent ceramic material, in step S1, the purity of the CaLa2S4 powder is 99.9%.

[0011] Preferably, in the aforementioned method for preparing the CaLa2S4 transparent ceramic material, in step S1, the ball-to-material ratio of the ball milling is 5:1 to 10:1; the abrasive of the ball milling is zirconium oxide; and the medium of the ball milling is anhydrous ethanol.

[0012] Preferably, in the aforementioned method for preparing the CaLa2S4 transparent ceramic material, in step S1, the rotation speed of the ball mill is 100 to 500 r / min, and the time is 2 to 10 h.

[0013] Preferably, in the aforementioned method for preparing the CaLa2S4 transparent ceramic material, in step S1, the drying temperature is 60-80°C and the drying time is 8-10 hours.

[0014] Preferably, in the aforementioned method for preparing the CaLa2S4 transparent ceramic material, in step S1, the particle size of the CaLa2S4 powder is 2 to 3 μm; in step S2, the particle size of the CaLa2S4 after ball milling is 0.5 to 1.5 μm.

[0015] Preferably, in the aforementioned method for preparing the CaLa2S4 transparent ceramic material, in step S2, the flow rate of the argon gas is 20 to 40 mL / min.

[0016] Preferably, in the aforementioned method for preparing the CaLa2S4 transparent ceramic material, in step S2, the volume ratio of carbon disulfide to argon in the mixed gas of carbon disulfide and argon is 1:1 to 2:1.

[0017] Preferably, in the aforementioned method for preparing the CaLa2S4 transparent ceramic material, in step S2, the washing is carried out using anhydrous ethanol; the drying temperature is 60-80°C, and the drying time is 8-10 hours.

[0018] Preferably, in the aforementioned method for preparing the CaLa2S4 transparent ceramic material, in step S2, the impurity concentration of the purified CaLa2S4 powder is less than 100 ppm.

[0019] Preferably, in the aforementioned method for preparing the CaLa2S4 transparent ceramic material, in step S3, the flow rate of the argon gas is 30 to 50 mL / min.

[0020] Preferably, in the aforementioned method for preparing the CaLa2S4 transparent ceramic material, in step S3, the staged heating and pressure increasing include: in the first stage, slowly heating to 600-800°C at a rate of 10-20°C / min and keeping warm for 1 hour; in the second stage, continuing to heat to 1000-1200°C while applying a sintering pressure of 20-60MPa and keeping warm for 2-6 hours.

[0021] Preferably, in the aforementioned method for preparing the CaLa2S4 transparent ceramic material, in step S3, the maximum transmittance of the CaLa2S4 transparent ceramic material in the 8-14 μm long-wave infrared band is greater than or equal to 46%.

[0022] The purpose of the present invention and the technical problem solved are achieved by adopting the following technical solutions. The present invention proposes a CaLa2S4 transparent ceramic material, the maximum transmittance of which in the 8-14 μm long-wave infrared band is greater than or equal to 46%; the CaLa2S4 transparent ceramic material is prepared by the above method.

[0023] The purpose of the present invention and the technical problem solved are achieved by adopting the following technical solutions: The present invention proposes an infrared window, which is made of CaLa2S4 transparent ceramic material; the maximum transmittance of the CaLa2S4 transparent ceramic material in the 8-14μm long-wave infrared band is greater than or equal to 46%.

[0024] The purpose of the invention and the technical problem to be solved are achieved by adopting the following technical solutions. The present invention proposes an infrared detection system, which includes an infrared window, which is made of CaLa2S4 transparent ceramic material; the maximum transmittance of the CaLa2S4 transparent ceramic material in the 8-14 μm long-wave infrared band is greater than or equal to 46%.

[0025] By means of the above technical solution, the present invention provides a CaLa2S4 transparent ceramic material and a preparation method and application thereof, which have at least the following advantages:

[0026] The present invention adopts commercially available CaLa2S4 powder as raw material, refines and purifies it, does not require a complex synthesis process, simplifies the process flow, shortens the preparation cycle, and helps to reduce production cost investment; at the same time, it ensures the batch stability of ceramic powder, improves the reliability of product quality, and is conducive to the industrial production of CaLa2S4 ceramics; the ball milling refinement method proposed in the present invention can reduce the powder particle size, improve the powder dispersibility, and then improve the powder sintering activity, which means that the ceramic sintering process can be completed at a relatively low temperature and in a shorter time, reducing energy consumption and improving production efficiency; the powder purification process helps to remove trace impurities contained in the commercially available CaLa2S4 powder, promotes diffusion and bonding between powder particles, avoids the formation of internal defects, reduces light scattering centers, and thus improves the optical properties of the ceramic; the present invention optimizes the hot pressing sintering process, increases the exhaust time through a two-stage sintering process, promotes the exhaust of gas between powders, prevents sulfur oxide impurities formed by oxidation of CaLa2S4 ceramics, and improves the density and optical transmittance of the ceramic.

[0027] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a scanning electron microscope image of the commercially available CaLa2S4 powder used in the present invention;

[0029] Figure 2 is an energy dispersive X-ray spectrum of the commercially available CaLa2S4 powder used in the present invention;

[0030] Figure 3 This is the particle size distribution diagram of the powder after ball milling in Example 5 of the present invention;

[0031] Figure 4 This is a particle size distribution diagram of the powder after purification in Example 5 of the present invention;

[0032] Figure 5This is a transmittance diagram of the CaLa2S4 transparent ceramic material of Example 5 of the present invention. DETAILED DESCRIPTION

[0033] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of a CaLa2S4 transparent ceramic and its preparation method and application according to the present invention, its specific implementation, structure, characteristics and effects in combination with the preferred embodiment. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0034] The following materials or reagents, unless otherwise specified, were commercially available.

[0035] Some embodiments of the present invention provide a method for preparing a CaLa2S4 transparent ceramic material, comprising the following steps:

[0036] S1 powder refinement: Zirconia balls are used as abrasives, and zirconia abrasives are added according to a ball-to-material ratio of 5:1 to 10:1. A ball-to-material ratio higher than 10:1 will introduce too many impurities, affecting the subsequent purification process, while a ball-to-material ratio lower than 5:1 cannot form sufficient coverage and impact on the powder, and the material cannot be fully ground; take commercially available CaLa2S4 powder with a purity of 99.9% and put it into a high-energy ball mill and seal it. Use anhydrous ethanol as the ball milling medium and ball mill the sample at a speed of 100 to 500 r / min for 2 to 10 hours. If the speed exceeds 500 r / min, the surface energy of the refined powder increases due to the violent collision, the attraction between the powders increases, and agglomeration is easy to occur. If the speed is lower than 100 r / min, the impact and grinding effect on the powder is weak, which is not conducive to powder refinement; if the ball milling time is greater than 10 hours, it will cause powder agglomeration and impurities to mix in. If the ball milling time is less than 2 hours, it will cause insufficient powder refinement and the particle size will not meet the requirements. After the ball milling is completed, the obtained powder is placed in a vacuum drying oven at 60-80°C and dried for 8-10 hours; Figure 1 is a scanning electron microscope image of the commercially available CaLa2S4 powder used in the present invention; Figure 2 is an energy dispersive X-ray spectrum of the commercially available CaLa2S4 powder used in the present invention; Figure 1 It can be seen that the average particle size of the commercially available CaLa2S4 powder used is about 8μm, the particle size is large and there is agglomeration, which is not conducive to powder sintering. Figure 2 It can be seen that the commercially available CaLa2S4 powder used contains a small amount of oxygen, indicating that the commercially available CaLa2S4 powder contains oxide impurities and should be purified.

[0037] S2 powder purification: The ball-milled CaLa2S4 powder is placed in a tube furnace, and argon is introduced as a protective gas at a flow rate of 20-40 mL / min. When the gas flow rate is greater than 40 mL / min, it is too fast, which will cause uneven heating of the sample and local overcooling and overheating. When the flow rate is less than 20 mL / min, it is too slow, which may cause residual air in the tube furnace and incomplete removal of impurities. The temperature is raised at a rate of 5-10 ° C / min. If the heating rate is greater than 10 ° C / min, the grain growth of the sample will be uneven and defects will appear at the grain boundaries. If the heating rate is less than 5 ℃ / min, the slow heating rate will make the sample stay at a lower temperature for a longer time, which may promote the growth and coarsening of grains and affect the optical properties of CaLa2S4 transparent ceramics; when the furnace temperature rises to 400-600℃, the gas introduced is changed to a mixed gas of carbon disulfide and argon (the mixed volume ratio of carbon disulfide and argon is 1:1-2:1), and then the temperature is continued to rise to 750-850℃. When it is higher than 850℃, the excessively high temperature will cause the powder grains to grow, the grain boundaries to disappear or lattice defects to appear, thereby affecting the physical and chemical properties of CaLa2S4. If it is lower than 750℃, the temperature is too low, the impurities are difficult to decompose and volatilize, the reaction is not complete, and it is not conducive to the purification of the powder; and after keeping warm for 2-4h, the furnace is naturally cooled. When the furnace temperature is lower than 400-600℃, the carbon disulfide gas is removed, and argon protection is continued at a flow rate of 20-40mL / min until the tubular furnace cools down to room temperature. After the powder is taken out, it is washed with anhydrous ethanol for 3 to 5 times and placed in a vacuum drying oven at 60 to 80°C to dry for 8 to 10 hours;

[0038] S3 hot pressing sintering: Graphite paper coated with BN powder is placed in the graphite mold to isolate the powder from the mold for easy demolding, and then 4.0g of purified CaLa2S4 powder is evenly spread in a mold with a diameter of 20mm and placed in a hot pressing furnace; before starting to heat up, argon gas is introduced into the hot pressing furnace at a flow rate of 30-50mL / min and maintained for 0.5-1h to exclude air. When the gas flow rate is greater than 50mL / min, the excessively fast gas flow rate will disrupt the temperature field distribution in the furnace and reduce the temperature uniformity in the furnace. When the gas flow rate is less than 30mL / min, the oxygen-free environment cannot be created due to the slow gas flow rate, which makes it easy for CaLa2S4 to undergo oxidation reaction during the sintering process; then the temperature is set according to the stage heating method. The first stage: slowly heat up to 600-800℃ at a rate of 10-20℃ / min and keep warm for 1-1.5h. No pressure is applied in this stage; the second stage: continue to heat up to 1000-1200℃ while applying a sintering pressure of 20-60MPa, keep warm for 2-6h, and above When the sintering temperature is too high at 1200℃, it will cause excessive growth of ceramic grains, increase the grain size, and induce secondary crystallization in the crystal. The pores are wrapped inside the grains, reducing the density of the ceramic; when it is below 1000℃, the sintering temperature is too low, the diffusion and bonding between the CaLa2S4 ceramic powder particles are insufficient, the pores in the green body cannot be effectively eliminated, and the S element will be volatilized, affecting the optical transmittance; when the sintering pressure is greater than 60MPa, it will lead to uneven internal structure of the ceramic, form internal stress, and reduce the mechanical properties of the ceramic; when the sintering pressure is less than 20MPa, it will not effectively promote the close stacking and bonding between the ceramic powder particles, making it difficult to completely eliminate the pores in the green body; when the holding time is greater than 6h, the hot pressing time is too long, which will cause the lack of sulfur element, resulting in the deviation of the CaLa2S4 stoichiometric ratio and the reduction of transmittance; if the holding time is less than 2h, the sintering time is too short, the bonding between the CaLa2S4 powder particles is not sufficient, and a good sintering neck cannot be formed, resulting in a low density of the ceramic. After the insulation time is over, the pressure is released, and the mold is cooled to room temperature naturally. The CaLa2S4 ceramic block is taken out, roughly ground with sandpaper, and then polished on a polishing machine to obtain the CaLa2S4 transparent ceramic material.

[0039] In some optional embodiments, in step S1, the particle size of the CaLa2S4 powder after ball milling can be reduced from an initial 2 to 3 μm to 0.5 to 1.5 μm.

[0040] In some optional embodiments, in step S2, the impurity concentration of the purified powder is less than 100 ppm.

[0041] In some optional embodiments, in step S2, the maximum transmittance of the CaLa2S4 transparent ceramic material in the 8-14 μm long-wave infrared band is not less than 46%.

[0042] In the above technical scheme, the present invention uses purified commercially available CaLa2S4 powder as raw material to prepare a method for CaLa2S4 transparent ceramics with high stability, high density and high transmittance through hot pressing sintering technology. The present invention has important potential application value in the field of infrared detection system window materials for ultra-high-speed aircraft, and the process involved is simple, the conditions are stable and controllable, and the existing preparation process of CaLa2S4 transparent ceramics is optimized, which is suitable for promotion and application.

[0043] Some embodiments of the present invention further provide a CaLa2S4 transparent ceramic material, wherein the maximum transmittance of the CaLa2S4 transparent ceramic material in the long-wave infrared band of 8 to 14 μm is greater than or equal to 46%; the CaLa2S4 transparent ceramic material is prepared by the above method.

[0044] Specifically, the CaLa2S4 transparent ceramic material uses commercially available CaLa2S4 powder with a purity of 99.9% as raw material, controls the powder particle size to be below 2 μm through a ball milling process, and removes residual oxide impurities in the powder by passing carbon disulfide gas through high-temperature heating, and then hot-presses the purified powder for densification and sintering in a staged heating manner.

[0045] Some embodiments of the present invention also provide an infrared window, which is composed of the above-mentioned CaLa2S4 transparent ceramic material; the CaLa2S4 transparent ceramic material has a maximum transmittance of ≥46% in the 8-14μm band, and has good mechanical properties and can resist external force impact, and can be used as a window material for the infrared detection system of high-speed aircraft.

[0046] Some embodiments of the present invention further provide an infrared detection system, comprising an infrared window, wherein the infrared window is made of a CaLa2S4 transparent ceramic material; the maximum transmittance of the CaLa2S4 transparent ceramic material in the 8-14 μm long-wave infrared band is greater than or equal to 46%.

[0047] The specific implementation methods of the present invention are further described in detail below in conjunction with the embodiments, but it should not be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by technicians in this field based on the above-mentioned contents of the present invention still fall within the scope of protection of the present invention.

[0048] Unless otherwise specified, the materials, reagents, etc. involved below are all commercially available products well known to those skilled in the art; unless otherwise specified, the methods described are all methods well known in the art. Unless otherwise defined, the technical terms or scientific terms used should have the common meanings understood by ordinary technicians in the field to which the present invention belongs.

[0049] Example 1

[0050] This embodiment provides a method for preparing a CaLa2S4 transparent ceramic material, comprising the following steps:

[0051] Step 1: Powder refinement: Weigh 5.0g of commercially available CaLa2S4 powder with a purity of 99.9% and a particle size of about 8μm, put it into a high-energy ball mill, add zirconium oxide abrasive at a ball-to-material ratio of 5:1, and add 5mL of anhydrous ethanol as a solvent for ball milling. Seal the high-energy ball mill and ball mill the sample at a speed of 200r / min for 4h. After the ball milling, place the obtained powder in a vacuum drying oven at 80℃ and dry it for 10h. Test the particle size of the obtained CaLa2S4 powder, and the average particle size is about 0.8μm.

[0052] Step 2: Powder purification: The CaLa2S4 powder obtained in step 1 is placed in a tube furnace, and argon gas with a purity of 99.99% is introduced as a protective gas at a flow rate of 20 mL / min, and the temperature is increased at a rate of 5°C / min. When the furnace temperature rises to 500°C, the gas introduced is changed to a mixed gas of carbon disulfide and argon (the volume ratio of carbon disulfide to argon in the mixed gas is 2:1), and then the temperature is continued to rise to 750°C, and after keeping warm for 2 hours, the furnace is naturally cooled. After the furnace temperature drops to 500°C, the carbon disulfide gas is removed, and argon gas with a purity of 99.99% is continued to be introduced at a rate of 20 mL / min until the tube furnace cools to room temperature. After the powder is taken out, it is washed 3 times with anhydrous ethanol and placed in a vacuum drying oven at 80°C for 10 hours. The average particle size of the purified CaLa2S4 powder is about 0.8μm.

[0053] Step 3: Hot pressing sintering: Use a graphite paper pad (the thickness of the graphite paper pad is 0.03mm) uniformly coated with 0.1g of boron nitride powder to isolate the powder from the mold in the graphite mold for demoulding, and then take 4.0g of purified CaLa2S4 powder and evenly spread it in a graphite mold with a diameter of 20mm, and put it into a hot pressing furnace. Before starting to heat up, introduce argon gas with a purity of 99.99% into the hot pressing furnace at a flow rate of 30mL / min and keep it for 0.5h to exclude air. Then set the temperature according to the stage heating method. The first stage: slowly heat up to 600℃ at a rate of 10℃ / min and keep it warm for 1h. No pressure is applied in this stage; the second stage: continue to heat up to 1000℃ while applying a sintering pressure of 30MPa and keep it warm for 3h. After the insulation time is over, the pressure is released, and the mold is cooled down to room temperature naturally. The CaLa2S4 ceramic block is taken out, roughly ground with sandpaper, and polished on a polishing machine at a speed of 1000r / min until both sides are flat and smooth. After polishing, the maximum transmittance of the sample in the 8-14μm long-wave infrared band can reach 49.3%.

[0054] Example 2

[0055] This embodiment provides a method for preparing a CaLa2S4 transparent ceramic material, comprising the following steps:

[0056] Step 1: Powder refinement: Weigh 5.0g of commercially available CaLa2S4 powder with a purity of 99.9% and a particle size of about 8μm, put it into a high-energy ball mill, add zirconium oxide abrasive according to a ball-to-material ratio of 10:1, and add 5mL of anhydrous ethanol as a solvent for ball milling. Seal the high-energy ball mill and ball mill the sample at a speed of 400r / min for 8h. After the ball milling, place the obtained powder in a vacuum drying oven at 80℃ and dry it for 10h. Test the particle size of the CaLa2S4 powder, and the average particle size is about 0.5μm.

[0057] Step 2: Powder purification: The CaLa2S4 powder obtained in step 1 is placed in a tubular furnace, and argon gas with a purity of 99.99% is introduced as a protective gas at a flow rate of 20 mL / min, and the temperature is increased at a rate of 5°C / min. When the furnace temperature rises to 500°C, the gas introduced is changed to a mixed gas of carbon disulfide and argon (mixing ratio volume ratio carbon disulfide: argon = 2:1), and then the temperature is continued to rise to 750°C, and after keeping warm for 2 hours, the furnace is naturally cooled. After the furnace temperature drops to 500°C, the carbon disulfide gas is removed, and argon gas with a purity of 99.99% is continued to be introduced at a rate of 20 mL / min until the tubular furnace cools to room temperature. After the powder is taken out, it is washed 3 times with anhydrous ethanol and placed in a vacuum drying oven at 80°C for 10 hours. The particle size of the purified CaLa2S4 powder is about 0.5μm.

[0058] Step 3: Hot pressing sintering: Use a graphite paper pad (the thickness of the graphite paper pad is 0.03mm) uniformly coated with 0.1g of boron nitride powder to isolate the powder from the mold in the graphite mold for easy demoulding, and then take 4.0g of purified CaLa2S4 powder and evenly spread it in a mold with a diameter of 20mm, and put it into a hot pressing furnace. Before starting to heat up, introduce argon gas with a purity of 99.99% into the hot pressing furnace at a flow rate of 30mL / min and keep it for 0.5h to exclude air. Then set the temperature according to the stage heating method. The first stage: slowly heat up to 600℃ at a rate of 10℃ / min and keep it warm for 1h. No pressure is applied in this stage; the second stage: continue to heat up to 1000℃ while applying a sintering pressure of 30MPa and keep it warm for 3h. After the insulation time is over, the pressure is released, and the mold is cooled down to room temperature naturally. The CaLa2S4 ceramic block is taken out, roughly ground with sandpaper, and polished on a polishing machine at a speed of 1000r / min until both sides are flat and smooth. After polishing, the maximum transmittance of the sample in the 8-14μm long-wave infrared band can reach 46.1%.

[0059] Increasing the ball-to-material ratio and extending the ball milling rate and time can make the powder particle size finer, but a small amount of impurities will be introduced into the powder, resulting in a decrease in the infrared transmittance of the ceramic after sintering.

[0060] Example 3

[0061] This embodiment provides a method for preparing a CaLa2S4 transparent ceramic material, comprising the following steps:

[0062] Step 1: Powder refinement: Weigh 5.0g of commercially available CaLa2S4 powder with a purity of 99.9% and a particle size of about 8μm, put it into a high-energy ball mill, add zirconium oxide abrasive at a ball-to-material ratio of 5:1, and add 5mL of anhydrous ethanol as a solvent for ball milling. Seal the high-energy ball mill and ball mill the sample at a speed of 200r / min for 4h. After the ball milling, place the obtained powder in a vacuum drying oven at 80℃ and dry it for 10h. Test the particle size of the CaLa2S4 powder, and the average particle size is about 0.8μm.

[0063] Step 2: Powder purification: The CaLa2S4 powder obtained in step 1 is placed in a tube furnace, and argon gas with a purity of 99.99% is introduced as a protective gas at a flow rate of 40 mL / min, and the temperature is increased at a rate of 10°C / min. When the furnace temperature rises to 600°C, the gas introduced is changed to a mixed gas of carbon disulfide and argon (mixing ratio volume ratio carbon disulfide: argon = 1:1), and then the temperature is continued to rise to 850°C, and after keeping warm for 4 hours, the furnace is naturally cooled. After the furnace temperature drops to 600°C, the carbon disulfide gas is removed, and argon gas with a purity of 99.99% is continued to be introduced at a rate of 40 mL / min until the tube furnace cools to room temperature. After the powder is taken out, it is washed 3 times with anhydrous ethanol and placed in a vacuum drying oven at 80°C for 10 hours. The average particle size of the purified CaLa2S4 powder is about 1.5μm.

[0064] Step 3: Hot pressing sintering: Use a graphite paper pad (the thickness of the graphite paper pad is 0.03mm) uniformly coated with 0.1g of boron nitride powder to isolate the powder from the mold in the graphite mold for easy demoulding, and then take 4.0g of purified CaLa2S4 powder and evenly spread it in a mold with a diameter of 20mm, and put it into a hot pressing furnace. Before starting to heat up, introduce argon gas with a purity of 99.99% into the hot pressing furnace at a flow rate of 30mL and keep it for 0.5h to exclude air. Then set the temperature according to the stage heating method. The first stage: slowly heat up to 600℃ at a rate of 10℃ / min and keep warm for 1h. No pressure is applied in this stage; the second stage: continue to heat up to 1000℃ while applying a sintering pressure of 30MPa and keep warm for 3h. After the holding time is over, the pressure is released, and the mold is cooled to room temperature naturally. The CaLa2S4 ceramic block is taken out, and it is roughly ground with sandpaper, and then polished on a polishing machine at a speed of 1000r / min until both sides are flat and smooth. After polishing, the maximum transmittance of the sample in the 8-14μm long-wave infrared band can reach 46.7%. Reducing the proportion of carbon disulfide gas is not conducive to the removal of impurities in the CaLa2S4 powder, resulting in incomplete powder purification.

[0065] Example 4

[0066] This embodiment provides a method for preparing a CaLa2S4 transparent ceramic material, comprising the following steps:

[0067] Step 1: Powder refinement: Weigh 5.0g of commercially available CaLa2S4 powder with a purity of 99.9% and a particle size of about 8μm, put it into a high-energy ball mill, add zirconium oxide abrasive at a ball-to-material ratio of 5:1, and add 5mL of anhydrous ethanol as a solvent for ball milling. Seal the high-energy ball mill and ball mill the sample at a speed of 200r / min for 4h. After the ball milling, place the obtained powder in a vacuum drying oven at 80℃ and dry it for 10h. Test the particle size of the obtained CaLa2S4 powder, and the average particle size is about 0.8μm.

[0068] Step 2: Powder purification: The CaLa2S4 powder obtained in step 1 is placed in a tube furnace, and argon gas with a purity of 99.99% is introduced as a protective gas at a flow rate of 30 mL / min, and the temperature is increased at a rate of 5°C / min. When the furnace temperature rises to 500°C, the gas introduced is changed to a mixed gas of carbon disulfide and argon (the volume ratio of carbon disulfide to argon in the mixed gas is 2:1), and then the temperature is continued to rise to 800°C, and after being kept warm for 3 hours, the furnace is naturally cooled. After the furnace temperature drops to 500°C, the carbon disulfide gas is removed, and argon gas with a purity of 99.99% is continued to be introduced at a rate of 30 mL / min until the tube furnace cools to room temperature. After the powder is taken out, it is washed 5 times with anhydrous ethanol and placed in a vacuum drying oven at 80°C for 10 hours. The average particle size of the purified CaLa2S4 powder is about 1.0 μm.

[0069] Step 3: Hot pressing sintering: Use a graphite paper pad (the thickness of the graphite paper pad is 0.03mm) uniformly coated with 0.1g of boron nitride powder to isolate the powder from the mold in the graphite mold for easy demoulding, and then take 4.0g of purified CaLa2S4 powder and evenly spread it in a graphite mold with a diameter of 20mm, and put it into a hot pressing furnace. Before starting to heat up, introduce argon gas with a purity of 99.99% into the hot pressing furnace at a flow rate of 30mL / min and keep it for 0.5h to exclude air. Then set the temperature according to the stage heating method. The first stage: slowly heat up to 600℃ at a rate of 10℃ / min and keep it warm for 1h. No pressure is applied in this stage; the second stage: continue to heat up to 1000℃ while applying a sintering pressure of 30MPa and keep it warm for 3h. After the insulation time is over, the pressure is released, and the mold is cooled down to room temperature naturally. The CaLa2S4 ceramic block is taken out, roughly ground with sandpaper, and polished on a polishing machine at a speed of 1000r / min until both sides are flat and smooth. After polishing, the maximum transmittance of the sample in the 8-14μm long-wave infrared band can reach 50.2%.

[0070] Example 5

[0071] This embodiment provides a method for preparing a CaLa2S4 transparent ceramic material, comprising the following steps:

[0072] Step 1: Powder refinement: Weigh 5.0 g of commercially available CaLa2S4 powder with a purity of 99.9%, put it into a high-energy ball mill, add zirconium oxide abrasive at a ball-to-material ratio of 5:1, and then add 5 mL of anhydrous ethanol as a solvent for ball milling. Seal the high-energy ball mill and ball mill the sample at a speed of 200 r / min for 4 hours. After the ball milling is completed, place the obtained powder in a vacuum drying oven at 80°C and dry it for 10 hours. The particle size of the CaLa2S4 powder was tested, and the average particle size was about 0.8 μm. Figure 3 .from Figure 3 It can be seen that the particle size of the CaLa2S4 powder after ball milling is concentrated at 0.8μm, which is significantly smaller and more uniform than the particle size of the CaLa2S4 raw material, which helps to improve the sintering activity of the powder.

[0073] Step 2: Powder purification: Place the ball-milled CaLa2S4 powder in a tubular furnace, introduce argon with a purity of 99.99% as a protective gas at a flow rate of 30 mL / min, and heat it at a rate of 5°C / min. When the furnace temperature rises to 500°C, change the introduced gas to a mixture of carbon disulfide and argon (mixing ratio volume ratio carbon disulfide: argon = 2:1), then continue to heat to 800°C, and cool naturally with the furnace after keeping warm for 3 hours. After the furnace temperature is lower than 500°C, remove the carbon disulfide gas, and continue to introduce argon with a purity of 99.99% at a rate of 30 mL / min until the tubular furnace cools to room temperature. After the powder is taken out, wash it 5 times with anhydrous ethanol and place it in a vacuum drying oven at 80°C for 10 hours. Test the particle size of the CaLa2S4 powder. The average particle size of the purified CaLa2S4 powder is about 1.0 μm. Figure 4 .from Figure 4 It can be seen that the particle size of the purified CaLa2S4 powder has slightly increased compared to that before purification, and the particle size is concentrated at 1.0um. This is mainly because the purification process requires high-temperature treatment of the powder, and the powder grains grow slightly.

[0074] Step 3: Hot pressing sintering: Use a graphite paper pad (thickness of the graphite paper pad is 0.03mm) uniformly coated with 0.1g of boron nitride powder to isolate the powder from the mold in the graphite mold for demolding, and then take 4.0g of purified CaLa2S4 powder and evenly spread it in a graphite mold with a diameter of 20mm, and put it into a hot pressing furnace. Before starting to heat up, introduce argon gas with a purity of 99.99% into the hot pressing furnace at a flow rate of 50mL and keep it for 0.5h to exclude air. Then set the temperature according to the stage heating method. The first stage: slowly heat up to 700℃ at a rate of 10℃ / min and keep it warm for 1h. No pressure is applied in this stage; the second stage: continue to heat up to 1100℃ while applying a sintering pressure of 40MPa and keep it warm for 4h. After the holding time is over, the pressure is released, and the mold is cooled to room temperature naturally. The CaLa2S4 ceramic block is taken out, and it is roughly ground with sandpaper, and then polished on a polishing machine at a speed of 1000r / min until both sides are flat and smooth. After polishing, the maximum transmittance of the sample in the 8-14μm long-wave infrared band can reach 52.4%, as shown in FIG. Figure 5 .from Figure 5 It can be seen that the maximum transmittance of the CaLa2S4 ceramic material prepared in Example 5 reaches 52.4% at 8-14 μm, and has good optical properties.

[0075] Example 6

[0076] This embodiment provides a method for preparing a CaLa2S4 transparent ceramic material, comprising the following steps:

[0077] Step 1: Powder refinement: Weigh 5.0g of commercially available CaLa2S4 powder with a purity of 99.9% and a particle size of about 8μm, put it into a high-energy ball mill, add zirconium oxide abrasive according to a ball-to-material ratio of 5:1, and then add 5mL of anhydrous ethanol as a solvent for ball milling. Seal the high-energy ball mill and ball mill the sample at a speed of 200r / min for 4h. After the ball milling is completed, place the obtained powder in a vacuum drying oven at 80℃ and dry it for 10h. Test the particle size of the obtained CaLa2S4 powder, and the average particle size is about 0.8μm.

[0078] Step 2: Powder purification: The CaLa2S4 powder obtained in step 1 is placed in a tube furnace, and argon gas with a purity of 99.99% is introduced as a protective gas at a flow rate of 30 mL / min, and the temperature is increased at a rate of 5°C / min. When the furnace temperature rises to 500°C, the gas introduced is changed to a mixed gas of carbon disulfide and argon (the volume ratio of carbon disulfide to argon in the mixed gas is 2:1), and then the temperature is continued to rise to 800°C, and after being kept warm for 3 hours, the furnace is naturally cooled. After the furnace temperature drops to 500°C, the carbon disulfide gas is removed, and argon gas with a purity of 99.99% is continued to be introduced at a rate of 30 mL / min until the tube furnace cools to room temperature. After the powder is taken out, it is washed 5 times with anhydrous ethanol and placed in a vacuum drying oven at 80°C for 10 hours. The average particle size of the purified CaLa2S4 powder is about 1.0 μm.

[0079] Step 3: Hot pressing sintering: Use a graphite paper pad (thickness of the graphite paper pad is 0.03mm) uniformly coated with 0.1g of boron nitride powder to isolate the powder from the mold in the graphite mold for demolding, and then take 4.0g of purified CaLa2S4 powder and evenly spread it in a graphite mold with a diameter of 20mm, and put it into a hot pressing furnace. Before starting to heat up, argon is introduced into the hot pressing furnace at a flow rate of 50mL / min and maintained for 0.5h to exclude air. Then set the temperature according to the stage heating method. The first stage: slowly heat up to 800℃ at a rate of 20℃ / min and keep warm for 1h. No pressure is applied in this stage; the second stage: continue to heat up to 1200℃ while applying a sintering pressure of 60MPa and keep warm for 6h. After the insulation time is over, the pressure is released, and the mold is cooled down to room temperature naturally. The CaLa2S4 ceramic block is taken out, roughly ground with sandpaper, and polished on a polishing machine at a speed of 1000r / min until both sides are flat and smooth. After polishing, the maximum transmittance of the sample in the 8-14μm long-wave infrared band can reach 48.6%.

[0080] Comparative Example 1

[0081] This embodiment provides a method for preparing a CaLa2S4 transparent ceramic material, comprising the following steps:

[0082] Step 1: Powder refinement: Weigh 5.0g of commercially available CaLa2S4 powder with a purity of 99.9%, put it into a high-energy ball mill, add zirconium oxide abrasive at a ball-to-material ratio of 5:1, and then add 5mL of anhydrous ethanol as a solvent for ball milling. Seal the high-energy ball mill and ball mill the sample at a speed of 200r / min for 4h. After the ball milling, place the obtained powder in a vacuum drying oven at 80℃ and dry it for 10h. Test the particle size of the CaLa2S4 powder, and the average particle size is about 0.8μm.

[0083] Step 2: Powder purification: The CaLa2S4 powder obtained in step 1 is placed in a tubular furnace, and argon gas with a purity of 99.99% is introduced as a protective gas at a flow rate of 30 mL / min, and the temperature is increased at a rate of 5°C / min. When the furnace temperature rises to 500°C, the gas introduced is changed to a mixed gas of carbon disulfide and argon (the volume ratio of carbon disulfide to argon is 1:2), and then the temperature is continued to rise to 800°C, and after keeping warm for 1h, the furnace is naturally cooled with the furnace. After the furnace temperature is lower than 500°C, the carbon disulfide gas is removed, and argon gas with a purity of 99.99% is continued to be introduced at a rate of 30 mL / min until the tubular furnace cools to room temperature. After the powder is taken out, it is washed with anhydrous ethanol 5 times and placed in a vacuum drying oven at 80°C for 10h. The particle size of the CaLa2S4 powder is tested, and the average particle size is about 0.8μm. The average particle size of the purified CaLa2S4 powder is about 0.8μm.

[0084] Step 3: Hot pressing sintering: Use a graphite paper pad (thickness of the graphite paper pad is 0.03mm) uniformly coated with 0.1g of boron nitride powder to isolate the powder from the mold in the graphite mold for demolding, and then take 4.0g of purified CaLa2S4 powder and evenly spread it in a graphite mold with a diameter of 20mm, and put it into a hot pressing furnace. Before starting to heat up, introduce argon into the hot pressing furnace at a flow rate of 50mL and keep it for 0.5h to exclude air. Then set the temperature according to the stage heating method. The first stage: slowly heat up to 700℃ at a rate of 10℃ / min and keep it warm for 1h. No pressure is applied in this stage; the second stage: continue to heat up to 1100℃ while applying a sintering pressure of 40MPa and keep it warm for 4h. After the insulation time is over, the pressure is released, and the mold is cooled down to room temperature naturally. The CaLa2S4 ceramic block is taken out, roughly ground with sandpaper, and polished on a polishing machine at a speed of 1000r / min until both sides are flat and smooth. After polishing, the maximum transmittance of the sample in the 8-14μm long-wave infrared band can reach 40.5%.

[0085] Comparative Example 2

[0086] This comparative example provides a method for preparing a CaLa2S4 transparent ceramic material, comprising the following steps:

[0087] Step 1: Powder refinement: Weigh 5.0g of commercially available CaLa2S4 powder with a purity of 99.9%, put it into a high-energy ball mill, add zirconium oxide abrasive at a ball-to-material ratio of 5:1, and then add 5mL of anhydrous ethanol as a solvent for ball milling. Seal the high-energy ball mill and ball mill the sample at a speed of 200r / min for 4h. After the ball milling, place the obtained powder in a vacuum drying oven at 80℃ and dry it for 10h. Test the particle size of the CaLa2S4 powder, and the average particle size is about 0.8μm.

[0088] Step 2: Powder purification: The CaLa2S4 powder obtained in step 1 is placed in a tube furnace, and argon gas with a purity of 99.99% is introduced as a protective gas at a flow rate of 30 mL / min, and the temperature is increased at a rate of 5°C / min. When the furnace temperature rises to 500°C, the gas introduced is changed to a mixed gas of carbon disulfide and argon (the volume ratio of carbon disulfide to argon is 2:1), and then the temperature is continued to rise to 800°C, and after keeping warm for 3 hours, the furnace is naturally cooled with the furnace. After the furnace temperature is lower than 500°C, the carbon disulfide gas is removed, and argon gas with a purity of 99.99% is continued to be introduced at a rate of 30 mL / min until the tube furnace cools to room temperature. After the powder is taken out, it is washed with anhydrous ethanol 5 times and placed in a vacuum drying oven at 80°C for 10 hours. The particle size of the CaLa2S4 powder is tested, and the average particle size is about 0.8μm. The average particle size of the purified CaLa2S4 powder is about 1.0μm.

[0089] Step 3: hot pressing sintering: Use a graphite paper pad (thickness of the graphite paper pad is 0.03mm) uniformly coated with 0.1g of boron nitride powder to isolate the powder from the mold in the graphite mold for demolding, and then take 4.0g of purified CaLa2S4 powder and evenly spread it in a graphite mold with a diameter of 20mm, and put it into a hot pressing furnace. Before starting to heat up, introduce argon gas with a purity of 99.99% into the hot pressing furnace at a flow rate of 50mL and keep it for 0.5h to exclude air. Then heat it to 1100℃ at a rate of 10℃ / min and apply a sintering pressure of 40MPa at the same time, and keep it warm for 4h. After the insulation time, release the pressure, wait for the mold to cool down to room temperature naturally, take out the CaLa2S4 ceramic block, grind it with sandpaper, and polish it on a polishing machine at a speed of 1000r / min until both sides are flat and smooth. After polishing, the maximum transmittance of the sample in the 8-14μm long-wave infrared band can reach 42.3%. Insufficient introduction of carbon disulfide gas will affect the powder purification process, resulting in a small amount of impurities remaining in the CaLa2S4 powder.

[0090] Compared with Example 1, Example 2 increases the ball-to-material ratio, prolongs the ball milling rate and ball milling time to make the powder particle size finer, but introduces a small amount of impurities into the powder, resulting in a decrease in infrared transmittance after ceramic sintering. In Example 3, increasing the heating rate and temperature causes the grains to grow, and the growth is uneven, resulting in an increase and disorder of the grain boundaries, affecting the internal transmission of light in the CaLa2S4 ceramic, and reducing the optical transmittance; reducing the proportion of carbon disulfide gas is not conducive to the removal of impurities in the CaLa2S4 powder, resulting in incomplete powder purification. Example 4 helps to control the size of the CaLa2S4 grains and promote the reaction and volatilization of impurities by adjusting the purification temperature and time, thereby improving the light transmittance of the CaLa2S4 ceramic material.

[0091] Compared with Example 4, the increase in hot pressing time and pressure in Example 5 can improve the diffusion and sintering of the powder to increase the density of the ceramic material. Due to the long hot pressing time in Example 6, the sulfur element of the CaLa2S4 ceramic material is missing during the hot pressing process, the stoichiometric ratio deviates, and the optical transmittance decreases.

[0092] Compared with Example 1, the step-by-step heating in Comparative Example 1 can increase the exhaust time, promote the exhaust of gas between powders, prevent sulfur oxide impurities formed by oxidation of CaLa2S4 ceramics, and the step-by-step heating can better control grain growth and promote uniform densification. The amount of carbon disulfide gas introduced in Comparative Example 2 is insufficient, which affects the powder purification process and results in a small amount of impurities remaining in the CaLa2S4 powder.

[0093] The X-ray fluorescence spectrum analysis results of the CaLa2S4 powders in Examples 1 to 6 of the present invention after the purification treatment in step 2 are summarized in Table 1. The average particle size results of the CaLa2S4 powders in Examples 1 to 6 of the present invention after the treatment in steps 1 and 2 are summarized in Table 2. The numerical results of the maximum transmittance of the CaLa2S4 transparent ceramics in the 8-14 μm infrared band of Examples 1 to 6 of the present invention and Comparative Examples 1 to 2 are summarized in Table 3.

[0094] Table 1 X-ray fluorescence spectroscopic analysis results of CaLa2S4 powder after purification in step 2 in Examples 1 to 6 of the present invention

[0095]

[0096] It can be seen from the data in Table 1 that the impurity content of the CaLa2S4 powder prepared in Examples 1-6 of the present invention is less than 0.1%, and the purity is relatively high; reducing the impurity content can avoid the absorption loss of light by impurities, reduce light scattering centers, and improve the optical transmittance of CaLa2S4 transparent ceramics.

[0097] Table 2 Average particle size of CaLa2S4 powder after treatment in step 1 and step 2 in Examples 1 to 6 of the present invention

[0098]

[0099] From the data in Table 2, it can be seen that after the ball milling treatment in step 1, the particle size of the powder is greatly reduced, which is conducive to grain refinement and improving the sintering activity of the powder. After the high-temperature purification process in step 2, the particle size of the powder increases slightly, but it is still smaller than the particle size of the CaLa2S4 raw material.

[0100] Table 3 Maximum transmittance values ​​of CaLa2S4 transparent ceramics in 8-14 μm infrared band of Examples 1-6 of the present invention and Comparative Examples 1-2

[0101]

[0102] It can be seen from the data in Table 3 that due to the control of powder particle size and purity and optimization adjustment of the sintering process in Examples 1 to 6 of the present invention, the CaLa2S4 ceramic samples prepared therefrom all show higher light transmittance, and are significantly better than the light transmittance of the CaLa2S4 ceramic samples prepared in Comparative Examples 1 to 2.

[0103] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0104] The numerical range described in the present invention includes all the numerical values ​​within the range, and includes the range value formed by any two numerical values ​​within the range. Different numerical values ​​of the same indicator appearing in all embodiments of the present invention can be arbitrarily combined to form a range value.

[0105] The technical features in the claims and / or the specification of the present invention may be combined, and the combination is not limited to the combination obtained by reference in the claims. The technical solution obtained by combining the technical features in the claims and / or the specification is also within the protection scope of the present invention.

[0106] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a CaLa2S4 transparent ceramic material, characterized in that: The following steps are involved: S1 powder refinement: ball mill the CaLa2S4 powder in a sealed environment and dry it; Purification of S2 powder: The ball-milled CaLa2S4 powder is heated at a rate of 5-10°C / min under the protection of argon. When the temperature reaches 500°C, a mixed gas of carbon disulfide and argon is introduced, and then the temperature is continued to be raised to 750-850°C, and naturally cooled after being kept at this temperature for 2-4 hours. When the temperature is lower than 500°C, the carbon disulfide gas is removed, and argon is continued to be introduced for protection until the temperature drops to room temperature, washed, and dried to obtain the purified CaLa2S4 powder; S3 hot pressing sintering: the purified CaLa2S4 powder is evenly spread under the protection of argon for 0.5h; then the temperature and pressure are increased in stages and kept warm; After the heat preservation is completed, the pressure is released, the temperature is naturally lowered to room temperature, and the obtained CaLa2S4 ceramic block is roughly ground and polished to obtain the CaLa2S4 transparent ceramic material.

2. The method for preparing the CaLa2S4 transparent ceramic material according to claim 1, characterized in that: In step S1, the purity of the CaLa2S4 powder is 99.9%.

3. The method for preparing the CaLa2S4 transparent ceramic material according to claim 1, characterized in that: In step S1, the ball-to-material ratio of the ball mill is 5:1-10:1; the abrasive of the ball mill is zirconium oxide; the medium of the ball mill is anhydrous ethanol; the rotation speed of the ball mill is 100-500 r / min, and the time is 2-10 h; the drying temperature is 60-80° C., and the time is 8-10 h.

4. The method for preparing the CaLa2S4 transparent ceramic material according to claim 1, characterized in that: In step S1, the particle size of the CaLa2S4 powder is 8 to 10 μm; in step S2, the particle size of the CaLa2S4 after ball milling is 0.5 to 1.5 μm.

5. The method for preparing the CaLa2S4 transparent ceramic material according to claim 1, characterized in that: In step S2, the flow rate of the argon gas is 20 to 40 mL / min; the volume ratio of carbon disulfide to argon in the mixed gas of carbon disulfide and argon is 1:1 to 2:1; the washing is carried out using anhydrous ethanol; the drying temperature is 60 to 80°C and the time is 8 to 10 hours.

6. The method for preparing the CaLa2S4 transparent ceramic material according to claim 1, characterized in that: In step S2, the impurity concentration of the purified CaLa2S4 powder is less than 100 ppm; the flow rate of the argon gas is 30 to 50 mL / min.

7. The method for preparing the CaLa2S4 transparent ceramic material according to claim 1, characterized in that: In step S3, the staged heating and pressure increase includes: in the first stage, slowly heating to 600-800°C at a rate of 10-20°C / min and keeping warm for 1 hour; in the second stage, continuing to heat to 1000-1200°C while applying a sintering pressure of 20-60MPa and keeping warm for 2-6 hours.

8. A CaLa2S4 transparent ceramic material, characterized in that: The maximum transmittance of the CaLa2S4 transparent ceramic material in the long-wave infrared band of 8 to 14 μm is greater than or equal to 46%; the CaLa2S4 transparent ceramic material is prepared by the method described in any one of claims 1 to 7.

9. An infrared window, characterized in that: The infrared window is made of CaLa2S4 transparent ceramic material; the maximum transmittance of the CaLa2S4 transparent ceramic material in the 8-14 μm long-wave infrared band is greater than or equal to 46%.

10. An infrared detection system, characterized in that: The infrared detection system comprises an infrared window, which is made of CaLa2S4 transparent ceramic material; the maximum transmittance of the CaLa2S4 transparent ceramic material in the 8-14 μm long-wave infrared band is greater than or equal to 46%.

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