Preparation method of high light-transmittance magnesium aluminate spinel transparent ceramic

Abstract

The present invention relates to a method for preparing a high-transparency magnesium aluminate spinel transparent ceramic. The method for preparing the high-transparency magnesium aluminate spinel transparent ceramic comprises: using an aluminum source and a Mg source as raw materials, weighing the raw materials according to the aluminum-magnesium ratio, adding calcium fluoride as a sintering aid and mixing, then forming a green body, and finally sintering to prepare the high-transparency magnesium aluminate spinel transparent ceramic; the calcium fluoride is selected from at least one of calcium fluoride powder and calcium fluoride single crystal particles; the chemical formula of the magnesium aluminate spinel transparent ceramic is MgO﹒nAl2O3, where 1≤n≤2.5.

Description

Technical Field

[0001] The present invention relates to a preparation method of magnesium aluminate spinel transparent ceramics, belonging to the field of transparent ceramics. Background Art

[0002] Since the advent of magnesium aluminate spinel transparent ceramics, they have received extensive attention due to their excellent optical and mechanical properties. Magnesium aluminate spinel belongs to the cubic crystal system, has optical isotropy, its light transmission range covers the ultraviolet to mid-infrared bands, and has excellent mechanical properties, such as high hardness, high flexural strength, etc. In addition, magnesium aluminate spinel also has characteristics such as low density, wear resistance, chemical corrosion resistance, sand erosion and rain erosion resistance, and is widely used in dual-use fields such as transparent armor, infrared seeker fairings, high-temperature observation windows, and precision instrument windows.

[0003] The main difficulty in the preparation of magnesium aluminate spinel transparent ceramics mainly focuses on the difficult sintering densification caused by the slow diffusion rate of closely packed oxygen ions. However, preparing magnesium aluminate spinel ceramics with high optical quality requires the porosity in the sample to be lower than 100 ppm and the pore size to be lower than 40 nm. Therefore, extreme methods such as high temperature combined with high pressure are usually used to prepare magnesium aluminate spinel transparent ceramics, which poses a huge challenge to the sintering equipment. In order to reduce the sintering temperature, currently, appropriate sintering aids are mainly added, such as LiF, CaO, B2O3, Y2O3, etc. Among them, LiF is the most mature sintering aid at present and has been applied to the preparation of large-size magnesium aluminate spinel transparent ceramics. The advantage of LiF is that it has both the functions of liquid-phase sintering and increasing the defect concentration, and promotes the densification process through these two ways together. In addition, LiF also has the function of removing impurities in the raw material powder. However, the abnormal grain growth caused by the LiF sintering aid and the second phase of LiAlO2 produced by the reaction with MgAl2O4 lead to microcracks at the grain boundaries, etc., which reduce the mechanical properties of the ceramics, seriously limiting the application of magnesium aluminate spinel transparent ceramics as a protective material. In addition, due to the characteristics of low melting point and low boiling point of LiF, hot pressing sintering is usually required. However, the graphite mold used in hot pressing sintering will contaminate the sample. Although the addition of LiF can play a role in carbon removal, it cannot be eradicated, resulting in the final sample still turning black. In addition, the uneven volatilization of LiF will lead to differential sintering, and the sintered sample will have a foggy center, affecting the optical quality of the sample, which seriously limits the preparation of large-size magnesium aluminate spinel transparent ceramic samples.

[0004] CaO is another sintering aid commonly used in the preparation of magnesium aluminate spinel transparent ceramics. Its advantage lies in that CaO can react with MgAl2O4 to form calcium aluminate with a low melting point. During the heating process, the calcium aluminate melts to form a liquid phase to promote sintering, which can significantly reduce the sintering temperature by about 100 °C and improve the transmittance of the sample in the ultraviolet band. However, when using CaO as a sintering aid, the temperature of hot isostatic pressing sintering needs to be strictly controlled. Excessive temperature will reduce the optical quality of the ceramic sample. In addition, at high temperatures, it will cause the deposition of the second phase of radioactive calcium aluminate, affecting the uniformity of the microstructure.

[0005] Currently, several commonly used sintering aids cannot meet the application requirements for preparing large-sized and high-optical-quality magnesium aluminate spinel transparent ceramics. To get rid of the dependence on LiF sintering aids, it is crucial to explore new sintering aid systems for their practical applications. Summary of the Invention

[0006] For this reason, the purpose of the present invention is to provide a preparation method for magnesium aluminate spinel transparent ceramics with a simple process. The chemical formula of the magnesium aluminate spinel transparent ceramics is MgO﹒nAl2O3, where 1 ≤ n ≤ 2.5. The present invention selects high-purity magnesium and aluminum sources (oxides or hydroxides of magnesium and aluminum) with wide sources or commercial magnesium aluminate spinel powders as raw materials, adds calcium fluoride as a sintering aid that can melt into a liquid phase at high temperatures, and through the liquid phase formed during the sintering heating process, fully wets the particle surface, promotes particle rearrangement, reduces the sintering temperature, promotes the discharge of nano-pores, and prevents abnormal grain growth, so as to prepare magnesium aluminate spinel transparent ceramics with high optical quality.

[0007] On the one hand, the present invention provides a preparation method for high-transparency magnesium aluminate spinel transparent ceramics. The chemical formula of the magnesium aluminate spinel transparent ceramics is MgO﹒nAl2O3, where 1 ≤ n ≤ 2.5;

[0008] The preparation method for the high-transparency magnesium aluminate spinel transparent ceramics includes: using an aluminum source and a Mg source as raw materials, weighing the raw materials according to the aluminum-magnesium ratio, adding calcium fluoride as a sintering aid and mixing, then forming a green body, and finally sintering to prepare high-transparency magnesium aluminate spinel transparent ceramics; the calcium fluoride is selected from at least one of calcium fluoride powder and calcium fluoride single crystal particles. The invention point of the present invention is that by using the CaF2 aid that can melt into a liquid phase at high temperatures, through the liquid phase formed during the sintering heating process, fully wet the particle surface, promote particle rearrangement, reduce the sintering temperature, promote the discharge of nano-pores, and prevent abnormal grain growth, high-optical-quality magnesium aluminate spinel transparent ceramics are prepared, belonging to the field of transparent ceramics.

[0009] Preferably, the aluminum source and the magnesium source are at least one of aluminum and magnesium oxides / hydroxides or magnesium aluminate spinel powder. In the present invention, the aluminum source is an aluminum oxide / hydroxide. The magnesium source is a magnesium oxide / hydroxide. The aluminum source and the magnesium source can also be magnesium aluminate spinel powder.

[0010] Preferably, the purity of the aluminum oxide Al2O3 powder is ≥99.9% and the particle size is 50 - 1000 nm; the purity of the magnesium oxide MgO powder is ≥99.9% and the particle size is 100 - 1000 nm.

[0011] Preferably, the purity of the aluminum hydroxide Al(OH)3 is ≥99.9% and the particle size is 10 - 20 μm; the purity of the magnesium hydroxide Mg(OH)2 powder is ≥99.9% and the particle size is 5 - 7 μm.

[0012] On the other hand, the present invention provides a method for preparing a highly transparent magnesium aluminate spinel transparent ceramic, and the chemical formula of the magnesium aluminate spinel transparent ceramic is MgO﹒nAl2O3, where 1 ≤ n ≤ 2.5;

[0013] The method for preparing the highly transparent magnesium aluminate spinel transparent ceramic includes: using magnesium aluminate spinel MgO﹒nAl2O3 powder as a raw material, adding calcium fluoride as a sintering aid and mixing, then forming a green body, and finally sintering to prepare the highly transparent magnesium aluminate spinel transparent ceramic; the calcium fluoride is selected from at least one of calcium fluoride powder and calcium fluoride single crystal particles.

[0014] Preferably, the purity of the magnesium aluminate spinel powder is ≥99.9% and the particle size is 50 - 500 nm.

[0015] Preferably, the particle size of the calcium fluoride powder is 100 - 1000 nm, and the particle size of the calcium fluoride single crystal particles is 100 μm - 300 μm.

[0016] Preferably, the mass concentration of the sintering aid is 100 - 5000 ppm, preferably 100 - 3000 ppm;

[0017] Preferably, when the sintering aid is calcium fluoride powder, the mass concentration is 500 - 2000 ppm;

[0018] Preferably, when the sintering aid is calcium fluoride single crystal particles, the mass concentration is 500 - 3000 ppm. In the present invention, unless otherwise specified, calcium fluoride powder generally refers to calcium fluoride polycrystalline powder.

[0019] Preferably, the forming method is dry forming or wet forming. Dry forming includes dry pressing forming or / and cold isostatic pressing forming. Wet forming includes slip casting forming and injection molding.

[0020] Preferably, before sintering, the formed green body is pre-sintered;

[0021] The pre-sintering is pressureless sintering, including: the temperature of pressureless sintering is 1400 - 1700 °C, and the sintering atmosphere is one of air or vacuum;

[0022] Preferably, under air atmosphere, using the pressureless sintering process, the sintering temperature is 1400 - 1600 °C, and the holding time is 3 - 6 hours;

[0023] Preferably, under vacuum atmosphere, the sintering temperature of the pressureless sintering process is 1500 - 1700 °C, and the holding time is 4 - 6 hours.

[0024] Preferably, when the green body contains a binder, the green body is first degummed and then pre-sintered; the temperature of the degumming treatment is 600 - 800 °C, and the holding time is 3 - 6 hours to remove organic substances.

[0025] Preferably, the sintering method is hot isostatic pressing sintering; the process parameters of the hot isostatic pressing sintering are: the sintering temperature is 1500 - 1700 °C; the holding time is 1 - 6 hours; the pressurizing medium is argon or nitrogen, and the pressure is 120 - 200 MPa.

[0026] Beneficial effects:

[0027] The preparation method provided by the present invention can realize low-temperature sintering of magnesium aluminate spinel transparent ceramics, and prepare magnesium aluminate spinel transparent ceramics with high optical quality. The transmittance of the sample (5 mm thick) after double-sided polishing in the near-infrared region (760 - 1100 nm) can reach 87%, realizing the theoretical transmittance of magnesium aluminate spinel. The transmittance at 400 nm in the visible light band can reach more than 82%, which can meet the requirements of optical and mechanical properties for the application of magnesium aluminate spinel transparent ceramics in fields such as optical seeker fairings and transparent armors. In addition, compared with the prior art, the preparation method of the present invention has the advantages of simple process, easy control of material composition, and low cost. Description of the Drawings

[0028] Figure 1 It is a physical picture of a magnesium aluminate spinel transparent ceramic sample with a thickness of 5 mm after grinding and double-sided polishing for the sample prepared in Example 1;

[0029] Figure 2 It is the transmittance curve of a magnesium aluminate spinel transparent ceramic sample with a thickness of 5 mm after grinding and double-sided polishing for the sample prepared in Example 1;

[0030] Figure 3 It is the transmittance curve of a magnesium aluminate spinel transparent ceramic sample with a thickness of 5 mm after grinding and double-sided polishing for the sample prepared in Example 2;

[0031] Figure 4 Transmittance curve of a magnesium aluminate spinel transparent ceramic sample with a thickness of 5 mm after grinding and double-sided polishing for the sample prepared in Example 3;

[0032] Figure 5 Photo of a magnesium aluminate spinel transparent ceramic sample with a thickness of 5 mm after grinding and double-sided polishing for the sample prepared in Example 4;

[0033] Figure 6 Transmittance curve of a magnesium aluminate spinel transparent ceramic sample with a thickness of 5 mm after grinding and double-sided polishing for the sample prepared in Example 5;

[0034] Figure 7 Transmittance curve of a magnesium aluminate spinel transparent ceramic sample with a thickness of 5 mm after grinding and double-sided polishing for the sample prepared in Comparative Example 1. Detailed implementation manners

[0035] The present invention will be further described by the following implementation manners. It should be understood that the following implementation manners are only used to illustrate the present invention and do not limit the present invention.

[0036] In the present invention, commercial high-purity magnesium sources and aluminum sources (including but not limited to oxides or hydroxides of magnesium and aluminum) or commercial powders of high-purity magnesium aluminate spinel are used as raw materials, and calcium fluoride as a sintering aid (including but not limited to calcium fluoride powder or calcium fluoride single crystal particles) is added to prepare magnesium aluminate spinel transparent ceramics with different magnesium-aluminum ratios. The main technological process of this method includes three steps: raw material powder mixing, powder forming, and densification. First, weigh the magnesium source, aluminum source or commercial powder of magnesium aluminate spinel and the sintering aid according to the ratio of the required sample, uniformly mix and deagglomerate the powder by wet ball milling, obtain a ceramic green body by dry / wet forming (including but not limited to dry pressing, slip casting, gel casting, etc.), and then pre-sinter the ceramic green body to remove open pores, and combine hot isostatic pressing sintering to remove residual closed pores, so as to obtain a ceramic sample with optical transparency.

[0037] The preparation method of the magnesium aluminate spinel transparent ceramic in the present invention will be exemplarily described below.

[0038] Powder mixing and deagglomeration: Weigh the magnesium source, aluminum source or commercial magnesium aluminate spinel powder and sintering aids in proportion (if the wet forming process is adopted, appropriate dispersants and curing agents, etc. also need to be added when preparing the slurry). Use deionized water / anhydrous ethanol as the dispersion medium and high-purity alumina milling beads as the milling medium for uniform mixing. When the mixing method is planetary ball milling, the ball milling process is 200 - 300 revolutions per minute and the ball milling time is 10 - 12 hours. The mixing methods include but are not limited to planetary ball milling. Any method that can achieve uniform mixing of raw materials is applicable to the present invention. If the powder processing amount is too large, any equipment that can achieve powder deagglomeration and uniform mixing (such as stirred mills, sand mills, etc.) is applicable to the present invention. Using high-purity aluminum and magnesium oxides as raw materials, the purity of Al2O3 powder is ≥99.9% and the particle size is 50 - 1000 nm, the purity of MgO powder is ≥99.9% and the particle size is 100 - 1000 nm. Using high-purity aluminum and magnesium hydroxides as raw materials, the purity of Al(OH)3 is ≥99.9% and the particle size is 10 - 20 μm. The purity of Mg(OH)2 powder is ≥99.9% and the particle size is 5 - 7 μm. Using commercial high-purity magnesium aluminate spinel powder, the powder purity is ≥99.9% and the particle size is 20 - 500 nm. The mass concentration of the added calcium fluoride sintering aid is 100 - 5000 ppm, preferably 100 - 3000 ppm. Preferably, when the sintering aid is calcium fluoride powder, the mass concentration is 500 - 2000 ppm and the particle size of the calcium fluoride powder is 100 - 500 nm. If the addition amount of calcium fluoride powder is higher, it is easier to generate a second phase during sintering, thereby affecting the optical quality of the transparent ceramic sample. Preferably, when the sintering aid is calcium fluoride single crystal particles, the mass concentration is 500 - 3000 ppm and the particle size of the single crystal calcium fluoride is 0.1 - 0.3 mm. If the addition amount of calcium fluoride single crystal particles is too high, similar to the case of adding calcium fluoride powder, it is easy to generate a second phase, thus affecting the optical quality of the transparent ceramic sample.

[0039] Forming: The ceramic green body is obtained by using the dry / wet forming process. When the forming process is the dry forming process, the above-mentioned slurry needs to be dried. The drying conditions are drying at 50 - 60 °C for 8 - 12 hours and passing through a 100-mesh sieve. The powder is pressed into shape by using dry pressing forming or / and cold isostatic pressing forming methods. When using dry pressing forming combined with cold isostatic pressing forming, the treated slurry is dried and passed through a 100-mesh sieve, calcined at 600 - 800 °C for 4 - 6 hours to remove residual organic impurities, the treated raw material powder is loaded into a mold, and dry pressing forming is carried out under a pressure of 10 - 20 MPa for 1 - 3 minutes. The dry-pressed green body is subjected to cold isostatic pressing treatment, with a pressure of 200 MPa and a holding time of 5 - 10 minutes. When the forming process is the wet forming process, it includes but is not limited to injection molding, slip casting, etc. When using the injection molding process, 0.3 - 2.0 wt% dispersant (CE64 or Dolapix) and 0.2 - 0.3 wt% gel curing agent (ISOBAM AF600 or ISOBAM 104) need to be added during the preparation of the slurry. The solid content of the slurry is 35 - 56 vol%, and it is cured and dried at room temperature, and kept at 600 - 800 °C for 3 - 6 hours to discharge organic substances, obtaining a green body with higher strength.

[0040] Pre-sintering the ceramic green body to completely discharge the open pores and obtain a pre-sintered body. The pre-sintering process is as follows: pressureless sintering at 1400 - 1700 °C, and the sintering atmosphere is one of air or vacuum. Preferably, in an air atmosphere, the sintering temperature of the pressureless sintering process is 1400 - 1600 °C, the holding time is 3 - 6 hours, and the relative density of the obtained sintered body is not less than 96%. Preferably, in a vacuum atmosphere, the sintering temperature of the pressureless sintering process is 1500 - 1700 °C, and the holding time is 4 - 6 hours.

[0041] Hot isostatic pressing sintering. The pre-sintered body is subjected to hot isostatic pressing sintering treatment. The hot isostatic pressing sintering process is as follows: the sintering temperature is 1500 - 1700 °C, the holding time is 1 - 6 hours, the pressurizing medium is argon or nitrogen, and the pressure is 120 - 200 MPa.

[0042] The sample after hot isostatic pressing sintering is preferably subjected to annealing treatment. After polishing treatment, magnesium aluminate spinel transparent ceramic is obtained. Among them, the temperature of the annealing treatment can be 1100 - 1350 °C, the time is 6 - 30 hours, and the atmosphere is air or oxygen atmosphere.

[0043] The transmittance of the double-sided polished 5-mm-thick magnesium aluminate spinel transparent ceramic prepared by the present invention can reach 87% in the near-infrared region (760 - 1100 nm), reaching the theoretical transmittance, and the transmittance at 400 nm in the visible light band can reach over 82%. In addition, the manufacturing process of this method is simple, and it can realize the preparation of magnesium aluminate spinel transparent ceramics with complex shapes, meeting the application requirements of this material in fields such as transparent armor, spacecraft optical seeker fairings, and optical windows. Moreover, the sintering aid system selected in the preparation method of the present invention can significantly reduce the sintering temperature of magnesium aluminate spinel transparent ceramics and lower the production cost.

[0044] The following further gives examples to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the protection scope of the present invention. The specific process parameters and the like in the following examples are also only an example within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description herein, rather than being limited to the specific values in the following examples.

[0045] Example 1:

[0046] (1) Weigh MgO and Al2O3 powders respectively according to the molar ratio of MgO:Al2O3 of 1:1, and then weigh 500 ppm calcium fluoride powder by mass and place it in a ball mill tank. Using anhydrous ethanol as the dispersion medium and high-purity alumina ball mill beads as the ball mill medium, ball mill at a speed of 200 - 300 rpm / min for 12 hours. Place the ball-milled slurry in an oven at 60 °C and dry for 12 hours. Pass the dried powder through a 100-mesh sieve, and place the sieved powder in a muffle furnace and calcine at 800 °C for 6 hours to remove residual alcohol and organic impurities;

[0047] (2) Weigh 3 g of the above calcined powder into a mold with a diameter of 20 mm, and dry-press the powder into a shape at 20 MPa by means of double-sided pressing and hold the pressure for 1 minute. Subject the preformed green body to cold isostatic pressing at 200 MPa and hold the pressure for 5 minutes to obtain a green body with a density greater than 40%;

[0048] (3) Place the above green body in a muffle furnace and pre-burn at 1500 °C for 3 hours in an air atmosphere. After removing the open pores, obtain a pre-burned sample with a relative density greater than 96%;

[0049] (4) Subject the obtained pre-burned sample to hot isostatic pressing sintering. The sintering atmosphere is argon, the pressure is 200 MPa, the sintering temperature is 1550 °C, and the holding time is 3 hours;

[0050] (5) Grind and double-side polish the above hot isostatic pressing sintered sample to a thickness of 5 mm.

[0051] Figure 1 It is a physical picture of the sample prepared by the method described in Example 1. The sample has been subjected to double-sided polishing treatment and has a thickness of 5 mm. The sample has good light transmittance in the visible light range and no visible defects to the naked eye. Figure 2 It is the linear transmittance curve of the 5-mm-thick transparent ceramic prepared by the method described in Example 1. The transmittance of the sample in the near-infrared band (760 - 1100 nm) can reach more than 87%, achieving the theoretical transmittance. The linear transmittance at 400 nm in the visible light band can reach more than 82%, having a high transmittance.

[0052] Example 2:

[0053] The preparation process of the high-light-transmittance magnesium aluminate spinel transparent ceramic in this Example 2 is similar to that in Example 1. The differences are as follows: the addition amount of nano-calcium fluoride powder is 2000 ppm, and the pre-sintering temperature is 1455 °C.

[0054] Figure 3 It is the linear transmittance curve of the 5-mm-thick transparent ceramic prepared by the method described in Example 2. The transmittance of the sample in the near-infrared band (760 - 1100 nm) can reach 87%, achieving the theoretical transmittance. The linear transmittance at 400 nm in the visible light band can reach more than 78%.

[0055] Example 3:

[0056] The preparation process is similar to that in Example 1. The differences are as follows: the molar ratio of MgO:Al2O3 is 1:1.5, the addition amount of the sintering aid is 2000 ppm, and the pre-sintering temperature is 1485 °C.

[0057] Figure 4 It is the linear transmittance curve of the 5-mm-thick transparent ceramic prepared by the method described in Example 3. The transmittance of the sample in the near-infrared band (760 - 1100 nm) can reach more than 85%, approaching the theoretical transmittance. The linear transmittance at 400 nm in the visible light band can reach 76%.

[0058] Example 4:

[0059] The preparation process is similar to that in Example 1. The differences are as follows: pre-sintering in a vacuum atmosphere, with the pre-sintering temperature being 1550 °C; the hot isostatic pressing sintering temperature is 1600 °C; after hot isostatic pressing, the sample is annealed in an air atmosphere at 1300 °C for 10 hours.

[0060] Figure 5 It is a photo of the 5-mm-thick transparent ceramic prepared by the method described in Example 4. There are no visible defects in the sample. Its transmittance in the near-infrared band (760 - 1100 nm) can reach 84%, and the transmittance at 400 nm in the visible band can reach 75.2%.

[0061] Example 5:

[0062] (1) Weigh 0.5 wt% dispersant (CE64) and 0.3 wt% gel curing agent (ISOBAM 600AF) according to the proportion and dissolve them in deionized water. Weigh commercial magnesium aluminate spinel powder, and then weigh calcium fluoride powder with a mass concentration of 500 ppm and place them in a ball milling tank. Using deionized water as the dispersion medium and high-purity alumina ball milling beads as the ball milling medium, prepare a slurry with a solid content of 45 Vol%. Ball mill at a speed of 200 - 300 rpm / min for 12 hours. After mixing evenly, pour the slurry into a mold, and carry out in-situ curing through cross-linking reaction, demold, dry at room temperature, and place it in a muffle furnace to calcine at 800 °C for 6 hours to remove residual alcohol and organic impurities;

[0063] (2) Place the above green body in a muffle furnace and pre-calcine it at 1475 °C for 3 hours in an air atmosphere. After removing the open pores, the hot isostatic pressing sintering process is similar to that in Example 1.

[0064] Figure 6 is the linear transmittance curve of the 5-mm-thick transparent ceramic prepared by the method described in Example 5. The transmittance of the sample in the near-infrared band (760 - 1100 nm) can reach more than 85%, approaching the theoretical transmittance, and the linear transmittance at 400 nm in the visible light band can reach 75%.

[0065] Comparative Example 1:

[0066] The preparation process is similar to that in Example 1, and the difference is that no sintering aid is added; Figure 7 is the linear transmittance curve of the 5-mm-thick transparent ceramic prepared in Comparative Example 1. The transmittance of the sample in the near-infrared band (760 - 1100 nm) can reach more than 84%, and the linear transmittance at 400 nm in the visible light band can reach 75%, with a relatively low transmittance.

Claims

1. A preparation method of a magnesium aluminate spinel transparent ceramic with high light transmittance, characterized in that, The chemical formula of the magnesium aluminate spinel transparent ceramic is MgO﹒nAl2O3, where n = 1; The preparation method of the high light transmittance magnesium aluminate spinel transparent ceramic includes: using an aluminum source and a magnesium source as raw materials, weighing the raw materials according to the aluminum-magnesium ratio, adding calcium fluoride as a sintering aid and mixing, and then forming to obtain a green body; the aluminum source and the magnesium source are at least one of oxides / hydroxides of aluminum and magnesium; Then pre-sinter the formed green body, and finally perform hot isostatic pressing sintering to prepare the high light transmittance magnesium aluminate spinel transparent ceramic; the calcium fluoride is calcium fluoride powder; the particle size of the calcium fluoride powder is 100 - 1000 nm, and the mass concentration of the calcium fluoride is 500 - 2000 ppm; The pre-sintering is pressureless sintering, including: the temperature of the pressureless sintering is 1455 - 1500 °C, and the sintering atmosphere is air; The process parameters of the hot isostatic pressing sintering are: the sintering temperature is 1500 - 1550 °C; the holding time is 1 - 3 hours; the pressure medium is argon or nitrogen, and the pressure is 120 - 200 MPa; The obtained high light transmittance magnesium aluminate spinel transparent ceramic has a transmittance of 87% in the near-infrared band.

2. The preparation method according to claim 1, wherein, The purity of the aluminum oxide Al2O3 powder is ≥99.9%, and the particle size is 50 - 1000 nm; the purity of the magnesium oxide MgO powder is ≥99.9%, and the particle size is 100 - 1000 nm; The purity of the aluminum hydroxide Al(OH)3 is ≥99.9%, and the particle size is 10 - 20 μm; the purity of the magnesium hydroxide Mg(OH)2 powder is ≥99.9%, and the particle size is 5 - 7 μm.

3. The preparation method according to claim 1, wherein, The forming method is dry forming or wet forming. Dry forming includes dry pressing forming or / and cold isostatic pressing forming, and wet forming includes slip casting forming and gel casting forming.

4. The preparation method according to claim 1, wherein When the green body contains a binder, the green body is first subjected to debinding treatment and then pre-sintered; The temperature of the debinding treatment is 600 - 800 °C, and the holding time is 3 - 6 hours to remove organic substances.

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