High infrared-visible transmittance transparent ceramic and method of making same

Abstract

The application relates to the technical field of transparent ceramics, and particularly discloses a high-visible-infrared-transmittance transparent ceramic, a chemical general formula of which is MgAl x Ga2O 4+1.5x , and the value range of x is 0 < x <= 1.5, and a preparation method thereof comprises the following steps: performing molding on raw material powder based on MgAl x Ga2O 4+1.5x , sintering and annealing, and finally obtaining the transparent ceramic. The series of transparent ceramics disclosed by the application not only exhibit high transmittance in the visible-infrared wave band, but also successfully solve the problem that the optical uniformity of Mg(Al x Ga 1‑x )2O4-based transparent ceramics is poor due to white point aggregation in the sintering process, and meanwhile overcome the difficulty of a narrow infrared cutoff edge of magnesium-aluminum spinel transparent ceramics; and the preparation process is simple, raw materials are easy to obtain, and the cost is low, so the transparent ceramic can be applied to the fields of transparent armor, infrared windows, fairing covers and protective windows of aircraft and the like.

Description

Technical Field

[0001] This invention belongs to the field of transparent ceramics technology, specifically relating to a transparent ceramic with high visible-infrared transmittance and its preparation method. Background Technology

[0002] Materials used in transparent armor, infrared windows, aircraft fairings, and protective windows require high linear transmittance in the visible light (380–760 nm) and mid-infrared (3–6 μm) bands. Furthermore, they must possess sufficiently superior mechanical and thermal properties to withstand impacts from foreign objects such as missiles, sand, air friction, and high temperatures. Transparent ceramic materials are considered ideal candidates for these applications.

[0003] In recent years, transparent ceramic materials such as AlON, MgF2, and MgAl2O4 have developed rapidly, and their preparation technologies are relatively mature. AlON transparent ceramics have excellent mechanical properties, comparable to sapphire, and are low in preparation cost, but their transmission range in the infrared band is narrow, and their stability at high temperatures is not good enough. MgF2 transparent ceramics have a sufficiently wide optical transmission range, but their mechanical properties are relatively poor. MgAl2O4 transparent ceramics have excellent overall performance, but high-transmittance samples are difficult to prepare, often relying on sintering aids to improve optical quality, which to some extent affects mechanical properties and optical uniformity. Further development of novel transparent ceramics to meet the needs of transparent armor, infrared windows, aircraft fairings, and protective windows has become an urgent technical problem to be solved.

[0004] Previous studies have indicated that spinel-type Mg-Al-Ga-O solid solutions can be rapidly obtained at high temperatures through solid-state reactions of three oxides: MgO, Al₂O₃, and Ga₂O₃, with a wide solid solution range, potentially making them a promising transparent ceramic material. Patent CN 114773049A discloses a stoichiometric Mg(Al)O₂O₃ solid solution... x Ga 1-x 2O4 transparent ceramic material possesses excellent optical quality in the visible-infrared band, meeting the material performance requirements for transparent armor, infrared windows, aircraft fairings, and protective windows. While this approach achieves broad-band transmission from visible to infrared light, the sintering process is prone to the formation of locally aggregated pores (a problem particularly pronounced during ceramic size scaling), resulting in visible white spots and affecting the optical quality of the sample. Summary of the Invention

[0005] The main objective of this invention is to provide a spinel-type transparent ceramic with high visible-infrared transmittance, a wide light transmission range, and high hardness, which can effectively improve the performance of existing Mg(Al)2O3 ceramics. x Ga1-x This paper addresses issues such as localized pore aggregation in 2O4-based transparent ceramics and narrow permeability in magnesium aluminum spinel transparent ceramics. Furthermore, the preparation process involved is simple, the raw materials are readily available and the cost is low, making it suitable for widespread use.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A transparent ceramic with high visible-infrared transmittance, wherein the general chemical formula of the transparent ceramic is MgAl. x Ga2O 4+1.5x The range of x is 0 < x ≤ 1.5.

[0008] Preferably, the value of x is in the range of 0.8 to 1.2.

[0009] In the above scheme, the average grain size of the transparent ceramic is no higher than 50 μm, the size distribution is uniform and the range does not exceed 10 μm, and there is no abnormal grain growth or local pore aggregation.

[0010] In the above scheme, under the same process conditions, compared with the stoichiometric Mg(Al) x Ga 1-x The 2O4-based transparent ceramic produced samples with no obvious pore aggregation, resulting in significantly improved optical uniformity. Compared to magnesium aluminum spinel transparent ceramics, the infrared cutoff edge was broadened by approximately 0.7–1.1 μm. This transparent ceramic exhibits excellent optical and mechanical properties, displaying high transmittance in both the visible and infrared bands, with an optical transmission range of 250–7500 nm and a Vickers hardness of 12–13 GPa.

[0011] Preferably, the above-mentioned transparent ceramic material has a maximum transmittance of 82% in the visible light band of 400-800nm, a maximum transmittance of 85% in the infrared band of 2.5-5.5μm, and a Vickers hardness of 13GPa.

[0012] The above-mentioned MgAl x Ga2O 4+1.5x The preparation method of transparent ceramics includes the following steps:

[0013] 1) Using single-phase MgAl x Ga2O 4+1.5x Powder or according to the chemical formula MgAl x Ga2O 4+1.5x Weigh out the stoichiometric ratio of Mg, Al and Ga source powders as raw material powder, mix with ball milling media and dispersant, ball mill, dry, calcine, and sieve to obtain the target powder;

[0014] 2) Press the powder obtained in step 1) into shape and sinter it to obtain a ceramic sintered body with a density >99%;

[0015] 3) The obtained ceramic sintered body is annealed in an oxidizing atmosphere, cooled, and polished to obtain the transparent ceramic with high visible-infrared transmittance.

[0016] In the above scheme, the raw material powder can be MgAl. x Ga2O 4+1.5x Powder or according to the chemical formula MgAl x Ga2O 4+1.5x A mixture of Mg source, Al source and Ga source powders weighed in a stoichiometric ratio of 0 < x ≤ 1.5.

[0017] Furthermore, the purity of the Mg source, Al source, and Ga source is all above 99.9%; MgAl x Ga2O 4+1.5x The purity of the powder is greater than 99.9%.

[0018] Optionally, the Mg source is at least one of compounds containing Mg oxides, Mg hydroxides, Mg inorganic salts and their crystalline hydrates; the Al source is at least one of compounds containing Al oxides, Al hydroxides, Al inorganic salts and their crystalline hydrates; and the Ga source is at least one of compounds containing Ga oxides, Ga hydroxides, Ga inorganic salts and their crystalline hydrates.

[0019] Optionally, the dispersant is polyethyleneimine, polyvinylidene fluoride, polyacrylic acid, or polyvinyl alcohol, and its dosage is 0.025-3% of the raw material powder mass; preferably, it is polyethyleneimine or polyacrylic acid, and the dosage is 0.1%.

[0020] Preferably, the Mg source, Al source, and Ga source are MgO, Al2O3, and Ga2O3 powders with a purity greater than 99.9% and a particle size of 50–2000 nm. Preferably, MgAl x Ga2O 4+1.5x The powder has a purity greater than 99.9%, is spherical in shape, and has a particle size of 100–1000 nm.

[0021] Optionally, the grinding balls used in the ball milling step can be one of corundum balls, silicon nitride balls, or zirconium oxide balls with a diameter of 2–10 mm. The ball-to-material ratio is (3–5):1; wet milling dispersion is used, and the dispersion solvent is one of small molecule organic solvents such as ethanol or acetone; the rotation speed is 100–350 r / min, and the ball milling time is not less than 6 hours.

[0022] Preferably, in step 1), the milling balls are corundum balls with a diameter of 5 mm, the ball-to-material ratio is 4:1, the dispersing solvent is anhydrous ethanol, the rotation speed is 280 r / min, and the milling time is 24 h.

[0023] In the above scheme, the drying temperature in step 1) is 50-100℃, and the sieve used for sieving is larger than 50 mesh.

[0024] Preferably, the drying temperature in step 1) is 60-80°C, and the mesh size of the sieve selected is 100-200 mesh.

[0025] Optionally, the pressing process described in step 2) is either dry molding or wet molding. Dry molding includes dry pressing and / or cold isostatic pressing; wet molding includes slip casting or injection molding.

[0026] In the above scheme, the sintering method of the dense material is pressureless sintering or a combination of pressure sintering and hot isostatic pressing. Before pressureless sintering, the powder is first subjected to cold isostatic pressing treatment at a pressure of 150-300 MPa and a holding time of 5-20 min.

[0027] Furthermore, the pressureless sintering process involves a sintering temperature of 900–1500°C, a holding time of not less than 1 hour, and an atmosphere of one of vacuum, air, oxygen, hydrogen, nitrogen, or argon; a hot-pressing sintering process involves a temperature of 700–1400°C, a pressure of 10–90 MPa, a holding time of not less than 0.2 hours, and an atmosphere of one of vacuum, hydrogen, nitrogen, or argon; a spark plasma sintering process involves a temperature of 700–1400°C, a pressure of 10–90 MPa, a holding time of not less than 0.2 hours, and an atmosphere of one of vacuum, hydrogen, nitrogen, or argon; and a post-hot isostatic pressing process involves a post-treatment temperature of 1200–1600°C, a pressure of 100–300 MPa, a holding time of not less than 1 hour, and a pressurizing medium of one of argon or nitrogen.

[0028] Furthermore, the pressure sintering employs hot-press sintering and spark plasma sintering processes, which include a pressure process without requiring an additional pressing step. Preferably, when using MgO, Al2O3, and Ga2O3 powders as raw materials, the hot-press sintering process uses a sintering temperature of 900–1300℃, a pressure of 40–90 MPa, a holding time of 0.2–5 h, and an atmosphere of either vacuum or nitrogen. The spark plasma sintering process uses a sintering temperature of 800–1300℃, a pressure of 50–90 MPa, a holding time of 0.2–1 h, and an atmosphere of either nitrogen or argon. The pressureless sintering process uses a sintering temperature of 1000–1500℃, a holding time of 4–10 h, and an atmosphere of either vacuum or air. The post-treatment temperature of hot isostatic pressing is 1300-1500℃, the pressure is 100-300MPa, the holding time is 4-8h, and the pressurizing medium is either argon or nitrogen.

[0029] Preferably, MgAl is used. x Ga2O 4+1.5xWhen powder is used as raw material, the hot pressing sintering process uses a sintering temperature of 900–1400℃, a pressure of 50–90 MPa, a holding time of 1–8 h, and an atmosphere of either vacuum or nitrogen. The discharge plasma sintering process uses a sintering temperature of 900–1400℃, a pressure of 50–80 MPa, a holding time of 0.5–1 h, and an atmosphere of either nitrogen or argon. The pressureless sintering process uses a sintering temperature of 1000–1600℃, a holding time of 4–10 h, and an atmosphere of either vacuum or air. The hot isostatic pressing post-treatment temperature is 1300–1600℃, a pressure of 100–300 MPa, a holding time of 4–10 h, and the pressurizing medium is either argon or nitrogen.

[0030] In the above scheme, the annealing temperature is 700-1200℃, and the holding time is more than 2 hours.

[0031] Preferably, the annealing temperature is 800–1000°C, the holding time is 12–36 h, and the atmosphere is oxygen.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The non-stoichiometric MgAl proposed in this invention x Ga2O 4+1.5x The composition contains a large number of cation vacancies, which can promote the elimination of pores and prevent pore aggregation to a certain extent; the introduction of high molar mass Ga can effectively broaden the visible-infrared transmission domain; in addition, this invention further optimizes the wet milling process and introduces a dispersant to refine the powder particle size, improve powder uniformity and activity, promote the elimination of pores in the subsequent sintering process, and effectively solve the problem of light loss caused by pore scattering; the prepared non-stoichiometric MgAl x Ga2O 4+1.5x Transparent ceramics and stoichiometry of Mg(Al) x Ga 1- Compared with x)2O4-based transparent ceramics, the pore aggregation phenomenon is greatly improved, the optical uniformity is significantly enhanced, and it exhibits high transmittance in the visible-infrared band (0.5-6μm) while also possessing good mechanical properties. At the same time, it can effectively solve the problem of narrow visible-infrared transmission range of magnesium aluminum spinel transparent ceramics, and the infrared cutoff edge is widened by about 0.7-1.1μm.

[0034] (2) The MgAl of the present invention x Ga2O 4+1.5xThe composition and properties of transparent ceramics can be customized. By adjusting the x-value, their optical and mechanical properties can be controlled. In particular, when x = 0.8 to 1.2, their mechanical properties are excellent, and their Vickers hardness can reach 12.6 to 13 GPa. When x = 0.1 to 0.3, they have a wide infrared transmission range, and their infrared cutoff wavelength is 7400 to 7500 nm. The composition and properties of transparent ceramics can be designed and controlled as needed according to the service environment, effectively meeting the application requirements for optical and mechanical properties in fields such as transparent armor, infrared windows, and aircraft fairings.

[0035] (3) The MgAl of the present invention x Ga2O 4+1.5x The preparation methods for transparent ceramics are simple to operate, low in cost, and the raw materials are readily available. The conditions are stable and controllable, making them suitable for large-scale industrial production. Attached Figure Description

[0036] Figure 1 The XRD patterns are of the transparent ceramics prepared in Example 2 and Comparative Examples 1-3 of this invention.

[0037] Figure 2 The images show actual photos of the transparent ceramics prepared in Example 2 and Comparative Examples 1-3 of this invention.

[0038] Figure 3 Microstructure images of the transparent ceramics prepared in Example 2 and Comparative Examples 1-3 of this invention;

[0039] Figure 4 The transmittance spectra of the transparent ceramics prepared in Example 2 and Comparative Examples 1-3 of this invention in the ultraviolet-mid infrared. Detailed Implementation

[0040] The technical solutions in the embodiments of this invention will be described in detail and clearly below with specific examples. It should be noted that the embodiments described herein are only a part of this invention, not all of it. Any other implementation methods that can be conceived by those skilled in the art without inventive effort based on this invention should be considered to fall within the protection scope of this invention.

[0041] Example 1

[0042] A transparent ceramic with high visible-infrared transmittance is prepared by the following steps:

[0043] 1) According to the chemical formula MgAl 0.88 Ga2O 5.32200g of MgO, Al2O3, and Ga2O3 powders with a purity greater than 99.9% were weighed out according to the stoichiometric ratio of each element and placed together with 800g of corundum balls and 2g of PEI in a ball mill jar. Anhydrous ethanol was used as the ball milling medium, and the mixture was ball milled at 180r / min for 24h to obtain a mixed powder slurry. The mixed slurry was then dried in an oven at 70℃ for 24h. After drying, the powder was sieved through a 100-mesh sieve. The sieved powder was then calcined in a muffle furnace at 600℃ to remove organic matter for 12h.

[0044] 2) The mixed powder is dry-pressed at a pressure of 20 MPa for 2 min, and then cold isostatic pressing is performed at a pressure of 180 MPa for 10 min to obtain a ceramic blank.

[0045] 3) The ceramic blank was placed in a high-temperature furnace for pressureless sintering in an air atmosphere at a temperature of 1350℃ for 4 hours, with a heating rate of 5℃ / min and a cooling method of natural cooling with the furnace. Subsequently, the ceramic obtained by pressureless sintering was subjected to hot isostatic pressing at a temperature of 1600℃ for 5 hours, a pressure of 200MPa, and nitrogen as the pressurizing medium.

[0046] 4) The ceramic after hot isostatic pressing is annealed at 800℃ for 12 hours in air atmosphere. After cooling to room temperature, the surface is polished to obtain the transparent ceramic. The specific process parameters and sample properties are shown in Table 1.

[0047] Example 2

[0048] A transparent ceramic with high visible-infrared transmittance is prepared by the following steps:

[0049] 1) Weigh out MgAl with a purity greater than 99.9%. 0.88 Ga2O 5.32 200g of powder, along with 750g of corundum balls and 2g of PEI, were placed in a ball mill jar and milled at 200r / min for 36h using anhydrous ethanol as the milling medium to obtain a powder slurry. The powder slurry was then dried in an oven at 70℃ for 24h. After drying, the powder was sieved through a 200-mesh sieve. The sieved powder was then calcined in a muffle furnace at 600℃ for 12h to remove organic matter.

[0050] 2) The ceramic powder is dry-pressed at a pressure of 25 MPa and a holding time of 2 min. Then it is subjected to cold isostatic pressing at a pressure of 180 MPa and a holding time of 10 min to obtain a ceramic blank. The ceramic blank is then placed in a muffle furnace for calcination to remove organic matter. The calcination temperature is 600℃ and the holding time is 12 h to obtain a ceramic green body.

[0051] 3) The ceramic green body was placed in a high-temperature furnace for pressureless sintering in an air atmosphere at a temperature of 1400℃ for 6 hours, with a heating rate of 10℃ / min and a cooling method of natural cooling with the furnace. Subsequently, the ceramic obtained by pressureless sintering was subjected to hot isostatic pressing at a temperature of 1600℃ for 5 hours, a pressure of 250MPa, and nitrogen as the pressurizing medium.

[0052] 4) The ceramic after hot isostatic pressing is annealed at 850℃ for 12 hours in air atmosphere. After cooling to room temperature, the surface is polished to obtain the transparent ceramic. The specific process parameters and sample properties are shown in Table 1.

[0053] Example 3

[0054] A transparent ceramic with high visible-infrared transmittance is prepared by the following steps:

[0055] 1) According to the chemical formula MgAl 0.02 Ga2O 4.03 200g of MgO, Al2O3, and Ga2O3 powders with a purity greater than 99.9% were weighed out according to the stoichiometric ratio of each element and placed together with 800g of corundum balls and 2g of PEI in a ball mill jar. Anhydrous ethanol was used as the ball milling medium, and the mixture was ball milled at 200r / min for 24h to obtain a mixed powder slurry. The mixed slurry was then placed in an oven to dry at 70℃ for 24h. After drying, the mixture was sieved through a 100-mesh sieve to obtain a uniformly mixed powder. The powder was then placed in a muffle furnace to calcine to remove organic matter at 600℃ for 12h.

[0056] 2) Take 40-50g of powder and place it in a hot press mold for hot pressing sintering. The sintering temperature is 1000℃, the pressure is 60MPa, the holding time is 2h, and the atmosphere is nitrogen. The ceramic obtained by hot pressing sintering is then subjected to hot isostatic pressing treatment. The hot isostatic pressing temperature is 1400℃, the holding time is 5h, the pressure is 200MPa, and the pressurizing medium is nitrogen.

[0057] 3) The ceramic after hot isostatic pressing is annealed at 750℃ for 36 hours in air atmosphere. After cooling to room temperature, the surface is polished to obtain the transparent ceramic. The specific process parameters and sample properties are shown in Table 1.

[0058] Example 4

[0059] A transparent ceramic with high visible-infrared transmittance is prepared by the following steps:

[0060] 1) Weigh out MgAl with a purity greater than 99.9%. 0.26 Ga2O 4.39 200g of powder, along with 750g of corundum balls and 2g of PEI, were placed in a ball mill jar and milled at 250r / min for 18h using anhydrous ethanol as the milling medium to obtain a powder slurry. The powder slurry was then dried in an oven at 70℃ for 24h. After drying, the powder was sieved through a 200-mesh sieve. Subsequently, the powder was calcined in a muffle furnace at 600℃ to remove organic matter for 12h.

[0061] 2) Take 50-60g of powder and place it in a mold for spark plasma sintering. The sintering temperature is 1200℃, the pressure is 50MPa, the holding time is 0.4h, and the atmosphere is argon. The ceramic obtained by spark plasma sintering is then subjected to hot isostatic pressing (HIP) treatment. The HIP temperature is 1500℃, the holding time is 5h, the pressure is 250MPa, and the pressurizing medium is nitrogen.

[0062] 3) The ceramic after hot isostatic pressing is annealed at 900℃ for 24 hours in air atmosphere. After cooling to room temperature, the surface is polished to obtain the transparent ceramic. The specific process parameters and sample properties are shown in Table 1.

[0063] Example 5

[0064] A transparent ceramic with high visible-infrared transmittance is prepared by the following steps:

[0065] 1) According to the chemical formula MgAl 0.58 Ga2O 4.87200g of Mg(OH)₂, Al₂O₃, and Ga₂O₃ powders with a purity greater than 99.9% were weighed out according to the stoichiometric ratio of each element and placed together with 800g of corundum balls in a ball mill jar. Anhydrous ethanol was used as the ball milling medium, and the mixture was ball milled at 200 r / min for 24 h to obtain a mixed powder slurry. The mixed slurry was then dried in an oven at 70℃ for 24 h. After drying, it was sieved through a 100-mesh sieve to obtain a uniformly mixed powder. The mixed powder was then calcined in a muffle furnace for 3 h at 1100℃ at a heating rate of 10℃ / min. After the calcined powder cooled to room temperature, it was placed together with 700g of corundum balls and 2g of PEI in a ball mill jar. Anhydrous ethanol was used as the ball milling medium, and the mixture was ball-milled at 280 r / min for 24 h to obtain a ceramic powder slurry. The powder slurry was then dried in an oven at 70 °C for 24 h. After drying, the powder was sieved through a 200-mesh sieve to obtain ceramic powder. The sieved powder was then calcined in a muffle furnace to remove organic matter at 600 °C for 12 h.

[0066] 2) Take 50-60g of powder and place it in a mold for spark plasma sintering. The sintering temperature is 1300℃, the pressure is 60MPa, the holding time is 0.4h, and the atmosphere is argon. The ceramic obtained by spark plasma sintering is then subjected to hot isostatic pressing (HIP) treatment. The HIP temperature is 1500℃, the holding time is 5h, the pressure is 250MPa, and the pressurizing medium is nitrogen.

[0067] 3) The ceramic after hot isostatic pressing is annealed at a temperature of 925℃ for 24 hours in an air atmosphere. After cooling to room temperature, the surface is polished to obtain the transparent ceramic. The specific process parameters and sample properties are shown in Table 1.

[0068] Example 6

[0069] A transparent ceramic with high visible-infrared transmittance is prepared by the following steps:

[0070] 1) Weigh out MgAl with a purity greater than 99.9%. 1.16 Ga2O 6.9 200g of powder, 750g of corundum balls, and 2g of PEI were placed together in a ball mill jar and milled at 260r / min for 24h using anhydrous ethanol as the milling medium to obtain a powder slurry. The powder slurry was then dried in an oven at 70℃ for 24h. After drying, the powder was sieved through a 200-mesh sieve. The sieved powder was then calcined in a muffle furnace at 600℃ for 12h to remove organic matter.

[0071] 2) Weigh 50-60g of powder and place it in a mold for hot pressing and sintering. The sintering temperature is 1300℃, the pressure is 90MPa, the holding time is 5h, and the atmosphere is nitrogen.

[0072] 3) The hot-pressed sintered ceramic is annealed at a temperature of 900℃ for 36 hours in an air atmosphere. After cooling to room temperature, the surface is polished to obtain the transparent ceramic. The specific process parameters and sample properties are shown in Table 1.

[0073] Comparative Example 1

[0074] A transparent ceramic, the preparation method of which is largely the same as that in Example 2, except that:

[0075] In step 1), stoichiometric MgAl with a purity greater than 99.9% is used. 0.51 Ga 0.49 O4 powder;

[0076] Comparative Example 2

[0077] A transparent ceramic, the preparation method of which is largely the same as that in Example 2, except that:

[0078] In step 1), non-stoichiometric MgAl with a purity greater than 99.9% is used. 2.88 O 5.32 powder.

[0079] Comparative Example 3

[0080] The preparation method of a transparent ceramic is roughly the same as that of Example 2, except that no PEI dispersant is added.

[0081] Figure 1 The images show the XRD patterns of the transparent ceramics prepared in Example 2 and Comparative Examples 1-3. It can be seen that the product obtained in Example 2 has a significant deviation from the same diffraction peak positions compared with Comparative Examples 1 and 2.

[0082] The ceramic obtained in Comparative Example 1, after double-sided polishing, exhibited visible white spots inside. SEM images showed that these white spots were formed by the aggregation of numerous pores. In contrast, the stoichiometric MgAl prepared in Example 2... 0.88 Ga2O 5.32 No white spots are visible to the naked eye. This is due to the non-stoichiometric amount of MgAl. 0.88 Ga2O 5.32 The presence of numerous cation vacancies hinders pore aggregation and results in a more uniform microstructure. Therefore, MgAl 0.88 Ga2O 5.32 It exhibits better performance than MgAl in the visible-infrared band. 0.51 Ga0.49 O4 has higher transmittance.

[0083] Although Comparative Example 2 also has relatively high optical transmittance, its range in the visible-infrared band is narrower than that of Example 2 by about 0.5 μm; Figure 2 Although no white spots are visible to the naked eye, a small number of internal pores are still present in the crystal (see...). Figure 4 ).

[0084] Although the product obtained in Comparative Example 3 did not have any white spots visible to the naked eye, it had a lower optical transmittance and fewer internal pores in the crystal.

[0085] Table 1. Specific process parameters and sample properties of the transparent ceramic samples prepared in Examples 1-6 and Comparative Examples 1-3 of this invention.

[0086]

[0087]

[0088]

[0089] The preparation methods provided in Examples 1-6 successfully prepared MgAl with different compositions. x Ga2O 4+1.5x This patent describes a transparent ceramic with high optical transmittance, achieved through its uniform microstructure. Compared to Comparative Examples 1-3, the composition of this patent maintains high optical transmittance and uniformity while possessing a wider infrared cutoff edge. The average grain size of the prepared transparent ceramic is smaller than 5-50 μm, achieving a theoretical sintering density of over 99.5%, a transmittance range of 250-7500 nm, an elastic modulus of 250-300 MPa, and a hardness of 12-13 GPa. Notably, when x is around 0.88, the optical transmittance at 2-5 μm exceeds 80%, with a hardness of 12.8 GP and a Young's modulus of 275 GPa, balancing excellent optical transmittance and good mechanical properties. This transparent ceramic can meet the requirements for transparent armor, infrared windows, aircraft fairings, and protective windows.

[0090] The MgAl of the present invention x Ga2O 4+1.5x The method for preparing transparent ceramics can flexibly combine the powder processing and sintering processes mentioned above. The process parameters for each step can not only be reasonably selected within the range of conditions provided in the aforementioned methods, but can also be further optimized and screened by skilled personnel within the framework of the aforementioned process regime. These embodiments are for illustrative purposes only and do not constitute a limitation on the scope of the invention.

[0091] This specification details numerous specific aspects of the invention. However, it must be clear that these specific embodiments are not the only ways in which the invention can be implemented. In fact, even without these detailed specifications, embodiments of the invention can still be effectively implemented. The above embodiments represent only preferred solutions to the process system of the invention and do not constitute a limitation on other forms of the invention. Any person skilled in the art, such as those with expertise in inorganic non-metallic materials, ceramics, and glass, can make appropriate modifications based on the disclosed technical content, and these modifications should be considered equivalent embodiments. As long as these modifications do not depart from the core technical solution of the invention, that is, simple modifications, equivalent changes, and alterations to the embodiments based on the technical essence of the invention, they should be included within the scope of protection of the invention.

Claims

1. A transparent ceramic with high visible-infrared transmittance, characterized in that, Its general chemical formula is MgAl x Ga2O 4+1.5x The range of x is 0 < x ≤ 1.5; The preparation method of the transparent ceramic with high visible-infrared transmittance includes the following steps: 1) Using single-phase MgAl x Ga2O 4+1.5x Powder or according to MgAl x Ga2O 4+1.5x Weigh out the stoichiometric ratio of Mg, Al and Ga source powders as raw material powder, mix with ball milling media and dispersant, ball mill, dry, calcine, and sieve to obtain the target powder; 2) Press the powder obtained in step 1) into shape and sinter it to obtain a ceramic sintered body with a density >99%; 3) The obtained ceramic sintered body is annealed in an oxidizing atmosphere, cooled, and polished to obtain the transparent ceramic with high visible-infrared transmittance.

2. The transparent ceramic according to claim 1, characterized in that, The average grain size of the transparent ceramic is no higher than 50 μm, the size distribution is uniform and the range does not exceed 10 μm, and there is no local pore aggregation.

3. The transparent ceramic according to claim 1, characterized in that, The optical transmittance range of the transparent ceramic is 250~7500nm; the highest transmittance is ≥82% in the visible light band of 400~800nm ​​and the highest transmittance is ≥83% in the infrared band of 2~5μm.

4. The method for preparing the high visible-infrared transmittance transparent ceramic according to any one of claims 1 to 3, characterized in that, Includes the following steps: 1) Using single-phase MgAl x Ga2O 4+1.5x Powder or according to MgAl x Ga2O 4+1.5x Weigh out the stoichiometric ratio of Mg, Al and Ga source powders as raw material powder, mix with ball milling media and dispersant, ball mill, dry, calcine, and sieve to obtain the target powder; 2) Press the powder obtained in step 1) into shape and sinter it to obtain a ceramic sintered body with a density >99%; 3) The obtained ceramic sintered body is annealed in an oxidizing atmosphere, cooled, and polished to obtain the transparent ceramic with high visible-infrared transmittance.

5. The preparation method according to claim 4, characterized in that, In step 1), the ball milling process uses a ball-to-material ratio of (3~5):1, a rotation speed of 100~350 r / min, and a milling time of not less than 6 hours.

6. The preparation method according to claim 4, characterized in that, In step 1), the dispersant is polyethyleneimine, polyvinylidene fluoride, polyacrylic acid, or polyvinyl alcohol.

7. The preparation method according to claim 4, characterized in that, Step 2) The dense sintering process adopts either pressureless sintering or pressure sintering. Before pressureless sintering, the powder is first pressed into shape and then subjected to cold isostatic pressing. Pressure sintering adopts either hot pressing sintering or spark plasma sintering, which does not require additional forming steps.

8. The preparation method according to claim 7, characterized in that, The pressureless sintering temperature is 900~1500℃, the holding time is more than 1 hour, and the atmosphere is one of vacuum, air, oxygen, hydrogen, nitrogen, and argon; the hot pressing sintering temperature is 700~1400℃, the pressure is 10~90MPa, the holding time is more than 0.2 hours, and the atmosphere is one of vacuum, hydrogen, nitrogen, and argon; the spark plasma sintering temperature is 700~1400℃, the pressure is 10~90MPa, the holding time is more than 0.2 hours, and the atmosphere is one of vacuum, hydrogen, nitrogen, and argon.

9. The preparation method according to claim 7, characterized in that, After pressureless or pressurized sintering, hot isostatic pressing is performed. The temperature of the hot isostatic pressing post-treatment is 1200~1600℃, the pressure is 100~300MPa, the holding time is more than 1 hour, and the pressurizing medium is either argon or nitrogen.

10. The preparation method according to claim 4, characterized in that, The annealing temperature mentioned in step 3) is 700~1200°C, and the holding time is more than 2 hours.

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