High-density calcium fluoride photoelectric ceramic and ultralow-temperature preparation method thereof

Abstract

The invention belongs to the technical field of photoelectric ceramic material manufacturing, and relates to high-density calcium fluoride photoelectric ceramic and an ultralow-temperature preparation method thereof. The method comprises the following steps: S1, wet mixing: weighing calcium hydroxide (Ca (OH) 2) powder and ammonium fluoride (NH4F) powder according to a molar ratio of 1: (1.5-2), and mixing by taking an organic solvent as a medium to form slurry; s2, rapid drying: rapidly drying the slurry obtained in the step (1) to obtain mixed precursor powder; and S3, reaction cold sintering: putting the mixed precursor powder into a mold, and carrying out reaction cold sintering. The sintering temperature used in the method is not higher than 350 DEG C, and the sintering temperature can be changed according to actual needs so as to improve the mechanical property of the ceramic, and the mechanical property is improved by 2-4 times compared with that of a conventional hot pressed sintering sample.

Description

Technical Field

[0001] The invention belongs to the technical field of photoelectric ceramic material manufacturing, and relates to a high-density calcium fluoride photoelectric ceramic and an ultra-low temperature preparation method thereof. Background Art

[0002] Calcium fluoride (CaF2) ceramics have broad application prospects in the field of optoelectronics due to their excellent optical properties. CaF2 has high transmittance, covering a wide spectral range from vacuum ultraviolet (VUV, about 125nm) to mid-infrared (about 8μm), and has a low refractive index and small dispersion, making it an ideal broadband optical window material. In addition, its excellent laser damage threshold and low birefringence properties enable it to play a key role in high-end optoelectronic systems such as high-power laser systems, ultraviolet lithography, infrared imaging, and space optical communications. Compared with traditional optical glass, CaF2 ceramics also have higher chemical stability and radiation resistance, and are particularly suitable for the manufacture of optical detectors and laser lens elements in extreme environments. However, CaF2 ceramics need to be sintered at high temperatures to achieve density. The required temperature is usually higher than 1000°C, and oxygen defects are easily introduced into the ceramic during the sintering process. The process cost is high and the performance of the resulting samples is poor.

[0003] Cold sintering is a new technique that uses liquid phase and pressure as the densification driving force to produce densified ceramics at low temperatures. Due to its advantages such as ultra-low sintering temperature, strong controllability, and simple equipment and operation, it has attracted numerous researchers to study and expand its applications. Currently, some researchers have achieved cold sintering densification of CaF2 ceramics by adding acidic solvents such as HCl. However, this technique has a low success rate and is prone to damage in large-scale industrial production due to the violent reaction between the acidic solvent and the metal molds and equipment. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing high-density calcium fluoride photoelectric ceramics at ultra-low temperature. The sintering temperature used in this method is not higher than 350°C and the sintering temperature can be changed according to actual needs to improve the mechanical properties of the ceramics. Compared with conventional hot-pressed sintered samples, the mechanical properties are improved by 2-4 times.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] A method for preparing high-density calcium fluoride photoelectric ceramics at ultralow temperature, the method comprising the following steps:

[0007] S1 wet mixing: calcium hydroxide (Ca(OH)2) powder and ammonium fluoride (NH4F) powder are weighed in a molar ratio of 1:1.5-2 and mixed with an organic solvent to form a slurry;

[0008] S2 Rapid drying: Rapidly dry the slurry obtained in step (1) to obtain a mixed precursor powder; S3 Reaction cold sintering: Place the mixed precursor powder in a mold and perform reaction cold sintering, specifically including: S3.1 Reaction activation: Before applying the sintering pressure, heat the mold to 90 - 110 °C and keep it warm for 3 - 10 minutes to activate the chemical reaction between the precursors;

[0009] S3.2 Pressurization and temperature increase: After the heat preservation ends, apply a uniaxial pressure to the mold, and after the pressure stabilizes, raise the temperature to the preset sintering temperature;

[0010] S3.3 Isothermal sintering: Keep the preset time at the preset sintering temperature and uniaxial pressure for cold sintering to densify the ceramic. The preset sintering temperature is 150 - 350 °C, the uniaxial pressure is 400 - 1000 MPa, and the time is 0 h < t < 5 h, and then cool to obtain the calcium fluoride optoelectronic ceramic.

[0011] Reaction-activated cold sintering technology (Reaction Cold Sintering, RCS) is based on the traditional cold sintering process. By introducing a chemical reaction as the driving force in the ceramic densification process, it is an effective way to achieve the densification and performance optimization of insoluble ceramics. The present invention innovatively prepares CaF2 ceramics for the first time based on reaction-activated cold sintering technology, and obtains CaF2 ceramics with high density and mechanical strength through controlling the cold sintering process in one step.

[0012] Preferably, in S1, the organic solvent is anhydrous alcohol. The mixed raw materials need to use high-purity (>98%) anhydrous alcohol as the medium to inhibit the premature occurrence of the reaction, so that the reactants are fully mixed but do not react.

[0013] Preferably, before S1, it further includes sieving the calcium hydroxide powder and ammonium fluoride powder to a particle size not greater than 120 mesh.

[0014] Preferably, in S2, a hot air gun is used to rapidly dry the slurry.

[0015] Preferably, in S3.1, the mold is heated to 100 °C and kept warm for 5 minutes. Before the formal cold sintering pressurization, the mold needs to be heated to 100 °C and kept warm for 5 min to activate the chemical reaction, and then a uniaxial pressure is applied. After the pressure stabilizes, the formal cold sintering procedure is carried out.

[0016] Preferably, in S3.3, the preset sintering temperature is 250 - 350 °C, and the uniaxial pressure is 600 MPa.

[0017] Preferably, in S3.3, the sintering time is 30 to 90 minutes. When the sintering time is greater than or equal to 30 minutes, the relative density of the obtained ceramic changes relatively stably and is greater than 94%. The process for preparing CaF2 ceramics by reaction-activated cold sintering provided by the present invention can achieve densification in a relatively short time.

[0018] A high-density calcium fluoride photoelectric ceramic prepared by the method of the invention.

[0019] A high mechanical property ceramic produced by the method has a relative density of CaF2 greater than 96% under sintering conditions of 350°C, 600 MPa, and 1 h, and its Vickers hardness and elastic modulus are higher than 6.66 GPa and 300 GPa, respectively. Compared with conventional hot-pressed sintered samples, the mechanical properties are improved by 2-4 times.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention uses relatively inexpensive ammonium fluoride and calcium hydroxide as raw materials, and the preparation process is reaction-activated cold sintering. Compared with common solid-phase sintered ceramics, it does not require complex mixing, calcination, multiple ball milling and other processes. The preparation process is simple, the stoichiometric ratio is accurately controlled, the repeatability is good, and the synthesized phase is stable and single, without the presence of a second phase.

[0022] (2) Compared with cold sintering by adding an acidic solvent (such as HCl) to CaF2, the reaction activation cold sintering process adopted in the present invention can effectively avoid problems such as the residue of the acidic solvent and the corrosion of metal molds and equipment.

[0023] (3) The sintering temperature used in the present invention is not higher than 350°C and the sintering temperature can be changed according to actual needs to improve the mechanical properties of the ceramic. Compared with conventional hot-pressed sintered samples, the mechanical properties are improved by 2-4 times.

[0024] (4) The samples prepared by the ceramic preparation method provided by the present invention have excellent performance in hardness, compressive strength and wear resistance, and can meet the needs of various high-end optoelectronic applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 XRD patterns of CaF2 ceramics with high density and mechanical strength according to Examples 1-5 of the present invention;

[0026] Figure 2 The relative density variation graph of CaF2 ceramics with high density and mechanical strength according to Examples 1-5 of the present invention is shown;

[0027] Figure 3Variation diagrams of the mechanical properties (Vickers hardness H, Young's modulus E) of the CaF₂ ceramics with high density and mechanical strength in Embodiments 1-5 of the present invention versus temperature;

[0028] Figure 4 Ashby diagram for comparing the mechanical properties of the high-density and high-strength CaF₂ ceramics of the present invention with those of other materials and sintering process materials;

[0029] Figure 5 XRD patterns of the CaF₂ ceramics prepared at sintering times t = 0 min, 30 min, and 90 min;

[0030] Figure 6 Relative density results of the CaF₂ ceramics prepared at sintering times t = 0 min, 30 min, and 90 min;

[0031] Figure 7 Vickers hardness and Young's modulus results of the CaF₂ ceramics prepared at sintering times t = 0 min, 30 min, and 90 min. Detailed implementation mode

[0032] The technical solution of the present invention will be further specifically described below through specific embodiments. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any formal modification and / or change made to the present invention will fall within the protection scope of the present invention.

[0033] In the present invention, unless otherwise specified, all parts and percentages are in weight units, and the equipment and raw materials used can be purchased from the market or are commonly used in the art. The methods in the following embodiments are conventional methods in the art unless otherwise specified.

[0034] The reagents used in the following embodiments can be purchased from a conventional biochemical reagent store unless otherwise specified.

[0035] The purity of the Ca(OH)₂ and NH₄F is 99.99%.

[0036] Cold sintering temperature (150 °C < T < 350 °C), pressure (P = 600 MPa), time (t = 1 h)

[0037] Embodiment 1

[0038] A method for preparing high-density optoelectronic ceramics at ultra-low temperature, the specific steps are as follows:

[0039] (1) Mixing materials: Weigh high-purity Ca(OH)₂ and NH₄F raw materials according to a molar ratio of 1:2 and quickly mix them with high-purity (>98%) absolute alcohol as the mixing medium.

[0040] (2) Drying: Rapidly dry the slurry in step (1). Use a hot air gun to quickly dry the mixed slurry in step (1).

[0041] (3) Cold sintering: The obtained mixed powder is placed in a cylindrical mold. Before the formal cold sintering and pressurization, the mold needs to be heated to 100℃ and kept warm for 5 minutes to activate the chemical reaction. Then, uniaxial pressure is applied. After the pressure (working pressure P = 600MPa) stabilizes, the temperature is quickly raised to 150℃ for the formal cold sintering procedure. After the sintering time t = 1h, it is naturally cooled to room temperature to obtain CaF2 ceramics.

[0042] like Figure 1 As shown, by comparing the XRD pattern of the ceramic in Example 1 with the standard PDF card of CaF2, it can be seen that the ceramic component obtained in this example is CaF2.

[0043] like Figure 2 As shown, the relative density of the CaF2 ceramic obtained in this Example 1 is 86.6%.

[0044] like Figure 3 As shown, the Vickers hardness and Young's modulus of the CaF2 ceramic obtained in this Example 1 are 1.41 GPa and 96.4 GPa, respectively.

[0045] like Figure 4 As shown in the figure, the wear resistance parameters (H 3 / E 2 ) distribution.

[0046] Example 2

[0047] A method for preparing high-density optoelectronic ceramics at ultra-low temperature, comprising the following steps:

[0048] (1) Mixing: High-purity Ca(OH)2 and NH4F raw materials were weighed in a molar ratio of 1:2 and quickly mixed with high-purity (>98%) anhydrous alcohol as a mixing medium.

[0049] (2) Drying: Rapidly dry the slurry in step (1). Use a hot air gun to quickly dry the mixed slurry in step (1).

[0050] (3) Cold sintering: The obtained mixed powder is placed in a cylindrical mold. Before the formal cold sintering and pressurization, the mold needs to be heated to 100℃ and kept warm for 5 minutes to activate the chemical reaction. Then, uniaxial pressure is applied. After the pressure (working pressure P = 600MPa) stabilizes, the temperature is quickly raised to 200℃ for the formal cold sintering procedure. After the sintering time t = 1h, it is naturally cooled to room temperature to obtain CaF2 ceramics.

[0051] like Figure 1As shown, by comparing the XRD pattern of the ceramic in Example 2 with the standard PDF card of CaF2, it can be seen that the ceramic component obtained in this example is CaF2.

[0052] like Figure 2 As shown, the relative density of the CaF2 ceramic obtained in Example 2 is 92.7%.

[0053] like Figure 3 As shown, the Vickers hardness and Young's modulus of the CaF2 ceramic obtained in Example 2 are 3.26 GPa and 168 GPa, respectively.

[0054] like Figure 4 As shown in the figure, the wear resistance parameters (H 3 / E 2 ) distribution.

[0055] Example 3

[0056] A method for preparing high-density optoelectronic ceramics at ultra-low temperature, comprising the following steps:

[0057] (1) Mixing: High-purity Ca(OH)2 and NH4F raw materials were weighed in a molar ratio of 1:2 and quickly mixed with high-purity (>98%) anhydrous alcohol as a mixing medium.

[0058] (2) Drying: Rapidly dry the slurry in step (1). Use a hot air gun to quickly dry the mixed slurry in step (1).

[0059] (3) Cold sintering: The obtained mixed powder is placed in a cylindrical mold. Before the formal cold sintering and pressurization, the mold needs to be heated to 100℃ and kept warm for 5 minutes to activate the chemical reaction. Then, uniaxial pressure is applied. After the pressure (working pressure P = 600MPa) stabilizes, the temperature is quickly raised to 250℃ for the formal cold sintering procedure. After the sintering time t = 1h, it is naturally cooled to room temperature to obtain CaF2 ceramics.

[0060] like Figure 1 As shown, by comparing the XRD pattern of the ceramic in Example 3 with the standard PDF card of CaF2, it can be seen that the ceramic component obtained in this example is CaF2.

[0061] like Figure 2 As shown, the relative density of the CaF2 ceramic obtained in Example 3 is 95.2%.

[0062] like Figure 3 As shown, the Vickers hardness and Young's modulus of the CaF2 ceramic obtained in Example 3 are 6.08 GPa and 193 GPa, respectively.

[0063] like Figure 4 As shown in the figure, the wear resistance parameters (H3 / E 2 ) distribution.

[0064] Example 4

[0065] A method for preparing high-density optoelectronic ceramics at ultra-low temperature, comprising the following steps:

[0066] (1) Mixing: High-purity Ca(OH)2 and NH4F raw materials were weighed in a molar ratio of 1:2 and quickly mixed with high-purity (>98%) anhydrous alcohol as a mixing medium.

[0067] (2) Drying: Rapidly dry the slurry in step (1). Use a hot air gun to quickly dry the mixed slurry in step (1).

[0068] (3) Cold sintering: The obtained mixed powder is placed in a cylindrical mold. Before the formal cold sintering and pressurization, the mold needs to be heated to 100℃ and kept warm for 5 minutes to activate the chemical reaction. Then, uniaxial pressure is applied. After the pressure (working pressure P = 600MPa) stabilizes, the temperature is quickly raised to 300℃ for the formal cold sintering procedure. After the sintering time t = 1h, it is naturally cooled to room temperature to obtain CaF2 ceramics.

[0069] like Figure 1 As shown, by comparing the XRD pattern of the ceramic of Example 4 with the standard PDF card of CaF2, it can be seen that the ceramic component obtained in this example is CaF2.

[0070] like Figure 2 As shown, the relative density of the CaF2 ceramic obtained in Example 4 is 96.4%.

[0071] like Figure 3 As shown, the Vickers hardness and Young's modulus of the CaF2 ceramic obtained in Example 4 are 6.67 GPa and 264 GPa, respectively.

[0072] like Figure 4 As shown in the figure, the wear resistance parameters (H 3 / E 2 ) distribution.

[0073] Example 5

[0074] A method for preparing high-density optoelectronic ceramics at ultra-low temperature, comprising the following steps:

[0075] (1) Mixing: High-purity Ca(OH)2 and NH4F raw materials were weighed in a molar ratio of 1:2 and quickly mixed with high-purity (>98%) anhydrous alcohol as a mixing medium.

[0076] (2) Drying: Rapidly dry the slurry in step (1). Use a hot air gun to quickly dry the mixed slurry in step (1).

[0077] (3) Cold sintering: The obtained mixed powder is placed in a cylindrical mold. Before the formal cold sintering and pressurization, the mold needs to be heated to 100℃ and kept warm for 5 minutes to activate the chemical reaction. Then, uniaxial pressure is applied. After the pressure (working pressure P = 600MPa) stabilizes, the temperature is quickly raised to 350℃ for the formal cold sintering procedure. After the sintering time t = 1h, it is naturally cooled to room temperature to obtain CaF2 ceramics.

[0078] like Figure 1 As shown, by comparing the XRD pattern of the ceramic in Example 5 with the standard PDF card of CaF2, it can be seen that the ceramic component obtained in this example is CaF2.

[0079] like Figure 2 As shown, the relative density of the CaF2 ceramic obtained in Example 5 is 95.3%.

[0080] like Figure 3 As shown, the Vickers hardness and Young's modulus of the CaF2 ceramic obtained in Example 5 are 6.66 GPa and 300 GPa, respectively.

[0081] like Figure 4 As shown in the figure, the wear resistance parameters (H 3 / E 2 ) distribution.

[0082] The performance parameters of the CaF2 ceramics were tested using the Archimedes drainage method and nanoindentation instrument. The specific performance parameters are shown in Table 1.

[0083] Table 1 Comparison of parameters of high mechanical performance CaF2 ceramics of Examples 1-5

[0084]

[0085]

[0086] The five examples described above show a significant increase in relative density with increasing sintering temperature. When the sintering temperature is greater than or equal to 200°C, the relative density of the resulting ceramic is greater than 90%, and in particular, a high density of 96.4% is achieved at 300°C. This indicates that the process for producing CaF2 ceramics by reaction-activated cold sintering provided by the present invention can achieve densification at relatively low temperatures. In the experiment, when the temperature was further increased from 300°C to 350°C, the Young's modulus of the material continued to increase, which may be related to the further growth of grain size or changes in grain boundary structure. The slight decrease in relative density and hardness may be due to abnormal grain growth at high temperatures.

[0087] The present invention can regulate the mechanical properties of ceramics by controlling the sintering temperature. For example, sintering at 300°C can achieve the highest density and Vickers hardness; while sintering at 250°C can achieve the optimal wear resistance index.

[0088] Furthermore, the influence of sintering time on the density and performance of ceramics is analyzed through the following examples.

[0089] Cold sintering temperature (T = 300 ° C), pressure (P = 600 MPa), time (t = 0 min, 30 min, 90 min)

[0090] Example 6

[0091] A method for preparing high-density optoelectronic ceramics at ultra-low temperature, comprising the following steps:

[0092] (1) Mixing: High-purity Ca(OH)2 and NH4F raw materials were weighed in a molar ratio of 1:2 and quickly mixed with high-purity (>98%) anhydrous alcohol as a mixing medium.

[0093] (2) Drying: Rapidly dry the slurry in step (1). Use a hot air gun to quickly dry the mixed slurry in step (1).

[0094] (3) Cold sintering: The obtained mixed powder is placed in a cylindrical mold. Before the formal cold sintering and pressurization, the mold needs to be heated to 100℃ and kept warm for 5 minutes to activate the chemical reaction. Then, uniaxial pressure is applied. After the pressure (working pressure P = 600MPa) stabilizes, the temperature is quickly raised to 300℃ for the formal cold sintering procedure. After the sintering time t = 0min, it is naturally cooled to room temperature to obtain CaF2 ceramics.

[0095] like Figure 5 As shown, by comparing the XRD pattern of the ceramic of Example 6 with the standard PDF card of CaF2, it can be seen that the ceramic component obtained in this example is CaF2.

[0096] like Figure 6 As shown, the relative density of the CaF2 ceramic obtained in Example 6 is 92.3%.

[0097] like Figure 7 As shown, the Vickers hardness and Young's modulus of the CaF2 ceramic obtained in Example 6 are 1.41 GPa and 63 GPa, respectively.

[0098] Example 7

[0099] A method for preparing high-density optoelectronic ceramics at ultra-low temperature, comprising the following steps:

[0100] (1) Mixing: High-purity Ca(OH)2 and NH4F raw materials were weighed in a molar ratio of 1:2 and quickly mixed with high-purity (>98%) anhydrous alcohol as a mixing medium.

[0101] (2) Drying: Rapidly dry the slurry in step (1). Use a hot air gun to quickly dry the mixed slurry in step (1).

[0102] (3) Cold sintering: The obtained mixed powder is placed in a cylindrical mold. Before the formal cold sintering and pressurization, the mold needs to be heated to 100℃ and kept warm for 5 minutes to activate the chemical reaction. Then, uniaxial pressure is applied. After the pressure (working pressure P = 600MPa) stabilizes, the temperature is quickly raised to 300℃ for the formal cold sintering procedure. After the sintering time t = 30 minutes, it is naturally cooled to room temperature to obtain CaF2 ceramics.

[0103] like Figure 5 As shown, by comparing the XRD pattern of the ceramic in Example 7 with the standard PDF card of CaF2, it can be seen that the ceramic component obtained in this example is CaF2.

[0104] like Figure 6 As shown, the relative density of the CaF2 ceramic obtained in Example 7 is 96.4%.

[0105] like Figure 7 As shown, the Vickers hardness and Young's modulus of the CaF2 ceramic obtained in Example 7 are 5.53 GPa and 163 GPa, respectively.

[0106] Example 8

[0107] A method for preparing high-density optoelectronic ceramics at ultra-low temperature, comprising the following steps:

[0108] (1) Mixing: High-purity Ca(OH)2 and NH4F raw materials were weighed in a molar ratio of 1:2 and quickly mixed with high-purity (>98%) anhydrous alcohol as a mixing medium.

[0109] (2) Drying: Rapidly dry the slurry in step (1). Use a hot air gun to quickly dry the mixed slurry in step (1).

[0110] (3) Cold sintering: The obtained mixed powder is placed in a cylindrical mold. Before the formal cold sintering and pressurization, the mold needs to be heated to 100℃ and kept warm for 5 minutes to activate the chemical reaction. Then, uniaxial pressure is applied. After the pressure (working pressure P = 600MPa) stabilizes, the temperature is quickly raised to 300℃ for the formal cold sintering procedure. After the sintering time t = 90min, it is naturally cooled to room temperature to obtain CaF2 ceramics.

[0111] like Figure 5As shown, by comparing the XRD pattern of the ceramic in Example 8 with the standard PDF card of CaF2, it can be seen that the ceramic component obtained in this example is CaF2.

[0112] like Figure 6 As shown, the relative density of the CaF2 ceramic obtained in Example 8 is 95.2%.

[0113] like Figure 7 As shown, the Vickers hardness and Young's modulus of the CaF2 ceramic obtained in Example 8 are 6.36 GPa and 253 GPa, respectively.

[0114] The above-mentioned Examples 6-8 show that as the sintering time increases, the relative density is significantly improved from 0 min to 30 min. When the time is greater than or equal to 30 min, the relative density of the obtained ceramic changes relatively stably and is greater than 94%, indicating that the process method for preparing CaF2 ceramics by reaction activation cold sintering provided by the present invention can achieve densification in a shorter time.

[0115] In addition, the Vickers hardness and Young's modulus values ​​of the ceramic materials obtained in the above-mentioned embodiments are 1.41-6.67GPa and 96-300GPa, respectively. The optimal values ​​are much higher than the mechanical properties of conventional hot-pressed sintered CaF2 ceramics. These high-quality CaF2 ceramics have important application value for realizing large-scale optoelectronic applications. The results fully demonstrate that the reaction activated cold sintering (RCS) technology, as an environmentally friendly preparation method with low energy consumption and high efficiency, shows important application potential in the preparation of high-density, excellent mechanical properties optoelectronic ceramics.

Claims

1. A method for preparing high-density calcium fluoride photoelectric ceramics at ultra-low temperature, characterized in that: The method comprises the following steps: S1 Wet mixing: Weigh calcium hydroxide (Ca(OH)2) powder and ammonium fluoride (NH4F) powder according to a molar ratio of 1:1.5 - 2, and mix them with an organic solvent as the medium to form a slurry. S2 Rapid drying: Rapidly dry the slurry obtained in step (1) to obtain a mixed precursor powder; S3 Reaction cold sintering: Place the mixed precursor powder in a mold and conduct reaction cold sintering, specifically including: S3.1 Reaction activation: Before applying the sintering pressure, heat the mold to 90 - 110 °C and keep it warm for 3 - 10 minutes to activate the chemical reaction between the precursors. S3.2 Pressurizing and heating: After the heat preservation ends, apply a uniaxial pressure to the mold, and increase the temperature to the preset sintering temperature after the pressure stabilizes. S3.3 Isothermal sintering: Keep it for a preset time at the preset sintering temperature and uniaxial pressure for cold sintering to densify the ceramic. The preset sintering temperature is 150 - 350 °C, the uniaxial pressure is 400 - 1000 MPa, the time is 0h < t < 5h, and then cool to obtain the calcium fluoride optoelectronic ceramic.

2. The method according to claim 1, wherein: In S1, the organic solvent is anhydrous alcohol. The mixed raw materials need to use high - purity (>98%) anhydrous alcohol as the medium to inhibit the premature occurrence of the reaction, so that the reactants are fully mixed but do not react.

3. The method according to claim 1, wherein: Before S1, it also includes sieving the calcium hydroxide powder and ammonium fluoride powder to a particle size not greater than 120 mesh respectively.

4. The method according to claim 1, wherein: In S2, a hot air gun is used to rapidly dry the slurry.

5. The method according to claim 1, wherein: In S3.1, heat the mold to 100 °C and keep it warm for 5 minutes.

6. The method according to claim 1, wherein: In S3.3, the preset sintering temperature is 250 - 350 °C, and the uniaxial pressure is 600 MPa.

7. The method according to claim 1, wherein: In S3.3, the sintering time is 30 min to 90 min.

8. A high - density calcium fluoride optoelectronic ceramic prepared by the method according to any one of claims 1 - 7.

9. The high-density calcium fluoride photoelectric ceramic according to claim 1, characterized in that: Under the sintering conditions of 350 °C, 600 MPa, and 1 h, the relative density of CaF2 is greater than 96%, and at the same time its Vickers hardness and elastic modulus are higher than 6.66 GPa and 300 GPa respectively.

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