Composite yttrium fluoride coating material and preparation method thereof

Abstract

The invention belongs to the field of optical materials, and discloses a composite yttrium fluoride coating material and a preparation method thereof.The composite yttrium fluoride coating material comprises yttrium fluoride, calcium fluoride and lead fluoride, the yttrium fluoride, the calcium fluoride and the lead fluoride form a ternary composite structure, and the yttrium element, the calcium element and the lead element are evenly distributed; the mass ratio of yttrium fluoride to calcium fluoride to lead fluoride in the composite yttrium fluoride coating material is (80-98): (15-1): (5-1). The calcium fluoride and the lead fluoride are introduced into the yttrium fluoride coating material, so that the thermal stability and the mechanical property of the coating material can be remarkably improved, and the problem that the yttrium fluoride coating material is splashed due to the fact that the outgassing amount is too large in the preheating stage is solved; meanwhile, the ternary composite structure is favorable for improving the uniformity and compactness of the film layer, so that the coating film is more flat and smoother, defects and pores in the film layer are reduced, the quality and performance of the coating film are improved, and the conditions of cracking and scattering of the film layer are reduced.

Description

Technical Field

[0001] The present invention belongs to the field of optical materials, relates to a material for optical coating, and particularly relates to a composite yttrium fluoride coating material and a preparation method thereof. Background Art

[0002] Yttrium fluoride (YF 3 ) material is widely used in the infrared band due to its excellent optical properties. In particular, its wide bandgap enables it to have high transmittance in the wide wavelength range from ultraviolet to infrared. Therefore, yttrium fluoride material is commonly used as a low refractive index material in interference filters and infrared optical coating elements.

[0003] In the prior art, when using yttrium fluoride material for coating, it is usually carried out by electron beam / crucible heating evaporation. When evaporating yttrium fluoride material by electron beam / crucible heating, sputtering is likely to occur, which will lead to the appearance of large particle film material points. These sputtered large particle film material points will cause fatal damage to the optical imaging effect of the lens. And even if a higher purity fluoride film material is selected to reduce sputtering, the production cost will be greatly increased. Summary of the Invention

[0004] Aiming at the defects and deficiencies existing in the prior art, on the first aspect, the present invention provides a composite yttrium fluoride coating material; on the second aspect, the present invention provides a preparation method of a yttrium fluoride coating material.

[0005] On the first aspect, the present invention provides a composite yttrium fluoride coating material, including yttrium fluoride, calcium fluoride and lead fluoride. The yttrium fluoride, calcium fluoride and lead fluoride form a ternary composite structure, wherein yttrium element, calcium element and lead element are evenly distributed; the mass ratio of yttrium fluoride, calcium fluoride and lead fluoride in the composite yttrium fluoride coating material is 80-98:15-1:5-1.

[0006] On the second aspect, the present invention provides a preparation method of a composite yttrium fluoride coating material, including the following steps: Step 1, ball-milling yttrium fluoride, calcium fluoride and lead fluoride in a vacuum environment to obtain a mixed powder; Step 2, pressing the mixed powder into a green body in a vacuum environment, and then roasting the green body in a vacuum atmosphere for a certain time, and cooling to obtain a crystalline block; Step 3, crushing and sieving the crystalline block, and the obtained particles are the composite yttrium fluoride coating material; In Step 1, the mass ratio of yttrium fluoride, calcium fluoride and lead fluoride is 80-98:15-1:5-1.

[0007] Preferably, before step 1, there is also a pretreatment process for yttrium fluoride, and the steps are as follows: Place yttrium fluoride in a quartz tube, introduce hydrogen fluoride gas into the quartz tube to displace the air in the quartz tube, then heat yttrium fluoride for a certain period of time to obtain fluorinated yttrium fluoride, and store the fluorinated yttrium fluoride in a vacuum environment.

[0008] Further preferably, in the pretreatment process, the heating temperature is 800 - 1100 °C, and the heating time is 30 - 240 min.

[0009] Preferably, in step 2, the density of the green body is 2.1 - 4.0 g / cm 3 .

[0010] Preferably, in step 2, the roasting temperature is 1200 - 1500 °C, and the roasting time is 1 - 5 h.

[0011] Preferably, in step 2, during cooling, first cool down to 800 - 1000 °C at a cooling rate of 0.1 - 5 °C / min, and then cool with the furnace.

[0012] Preferably, in step 2, when roasting the green body, place the green body in a crucible, then seal the crucible, and then place the crucible in a vacuum atmosphere for roasting.

[0013] Preferably, the particles obtained in step 3 are formulated into a composite yttrium fluoride coating material with a loose packing density of 2.0 - 2.8 g / cm 3 .

[0014] Compared with the prior art, the present invention has at least one of the following beneficial effects: By introducing calcium fluoride and lead fluoride into the yttrium fluoride coating material, the present invention prepares a yttrium fluoride coating material with a ternary composite structure, which can significantly improve the thermal stability and mechanical properties of the coating material, endow it with more excellent film-forming properties, solve the problem of excessive gas evolution during the preheating stage of the yttrium fluoride coating material resulting in sputtering, and reduce the difficulty and cost of the coating process; at the same time, the ternary composite structure helps to improve the uniformity and denseness of the film layer, make the coating more flat and smooth, reduce the defects and pores in the film layer, improve the quality and performance of the coating, and reduce the occurrence of cracking and scattering in the film layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 SEM image of the composite yttrium fluoride coating material prepared in Example 1; Figure 2 XRD pattern of the composite yttrium fluoride coating material prepared in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention provides the following specific technical solutions.

[0017] In a first aspect, the present invention provides a composite yttrium fluoride coating material, comprising yttrium fluoride, calcium fluoride, and lead fluoride, wherein the yttrium fluoride, calcium fluoride, and lead fluoride form a ternary composite structure, and the yttrium element, calcium element, and lead element are uniformly distributed; the mass ratio of yttrium fluoride, calcium fluoride, and lead fluoride in the composite yttrium fluoride coating material is 80-98:15-1:5-1.

[0018] Through research, the inventors found that by introducing calcium fluoride and lead fluoride into the yttrium fluoride coating material to obtain a yttrium fluoride coating material with a ternary composite structure, the thermal stability and mechanical properties of the coating material can be significantly improved, enabling it to have more excellent film-forming properties, solving the problem of splashing caused by excessive gas evolution during the pre-melting stage of the yttrium fluoride coating material, and reducing the difficulty and cost of the coating process; at the same time, the ternary composite structure helps to improve the uniformity and denseness of the coating, making the coating more flat and smooth, reducing defects and pores in the coating, improving the quality and performance of the coating, and reducing the occurrence of cracking and scattering in the coating.

[0019] Furthermore, the inventors found that by controlling the mass ratio of yttrium fluoride, calcium fluoride, and lead fluoride in the composite yttrium fluoride coating material to 80-98:15-1:5-1, the transmittance of the film layer of the yttrium fluoride coating material can be improved on the premise of meeting the requirements of most yttrium fluoride film layers on the market, and the antioxidant performance of the yttrium fluoride coating material is greatly enhanced, further improving the stability of the coating.

[0020] In a second aspect, the present invention provides a preparation method for a composite yttrium fluoride coating material, comprising the following steps: Step 1, ball-mill yttrium fluoride, calcium fluoride, and lead fluoride in a vacuum environment to obtain a mixed powder; Step 2, press the mixed powder into a green body in a vacuum environment, then bake the green body in a vacuum atmosphere for a certain time, and cool to obtain a crystalline block; Step 3, crush and screen the crystalline block, and the obtained particles are the composite yttrium fluoride coating material; In Step 1, the mass ratio of yttrium fluoride, calcium fluoride, and lead fluoride is 80-98:15-1:5-1.

[0021] Through research, the inventors found that through the above preparation method of the composite yttrium fluoride coating material, a coating material with a ternary composite structure can be obtained, which has a more stable structure, and can significantly improve the uniformity and transmittance of the film layer after coating, and the film layer grows uniformly and densely.

[0022] Preferably, before Step 1, there is also a pre-treatment process for yttrium fluoride, and the steps are as follows: place yttrium fluoride in a quartz tube, introduce hydrogen fluoride gas into the quartz tube to displace the air in the quartz tube, then heat yttrium fluoride for a certain time to obtain fluorinated yttrium fluoride, and store the fluorinated yttrium fluoride in a vacuum environment.

[0023] The inventor further optimized the preparation process. By pre-treating yttrium fluoride, oxygen impurities in the yttrium fluoride raw material were removed, uncontrollable factors during the film coating process were reduced, and in combination with the subsequent calcination process, the stability of the thin film material was further improved.

[0024] More preferably, in the pre-treatment process, the heating temperature is 800 - 1100 °C and the heating time is 30 - 240 min.

[0025] Preferably, in step 2, the density of the green body is 2.1 - 4.0 g / cm 3 。

[0026] The inventor found through research that by controlling the density of the green body, the crucible loading capacity can be increased, while the sintering activity between the powders is higher, the sintered sample is denser, which is beneficial to increasing the loose packing density and reducing the gaps and internal pores between the particles.

[0027] Preferably, in step 2, the calcination temperature is 1200 - 1500 °C and the calcination time is 1 - 5 h.

[0028] Preferably, in step 2, during cooling, first cool at a cooling rate of 0.1 - 5 °C / min to 800 - 1000 °C, and then cool with the furnace.

[0029] The inventor found through research that by controlling the cooling rate, lattice distortion of the composite yttrium fluoride coating material can be avoided, the structural stability of the composite coating material is improved, and the stability of the coating can be further improved.

[0030] In step 2, when calcining the green body, place the green body in a crucible, then seal the crucible, and then place the crucible in a vacuum atmosphere for calcination.

[0031] The inventor found through research that there is a saturated vapor pressure in a closed container. Placing the intermediate product A in a crucible for calcination treatment can prevent the decomposition of the fluorinated material, and placing the closed container in a vacuum or inert atmosphere for calcination can further reduce the possibility of decomposition of the fluorinated material, reduce raw material loss, and reduce production costs.

[0032] Preferably, the particles obtained in step 3 are formulated into a composite yttrium fluoride coating material with a loose packing density of 2.0 - 2.8 g / cm 3 of.

[0033] The inventor found through research that by controlling the apparent density of the composite yttrium fluoride coating material, during evaporation coating, the coating material can be heated more uniformly during coating, the evaporation rate of molecules or atoms is relatively stable, so that a more uniform thin film can be formed on the substrate, reducing defects such as uneven film thickness and spots, improving the quality and consistency of the coating, making the evaporation process more stable, enabling a higher deposition rate, shortening the coating time, and improving production efficiency. During the actual production process, different-sized particles are obtained by screening with sieves of different specifications, and then the particles of different sizes are mixed according to actual needs to obtain a composite yttrium fluoride coating material with an apparent density of 2.0~2.8 g / cm 3 ³.

[0034] To make the technical problems, technical solutions, and technical advantages to be solved by the present invention clearer, the following will be described in detail with specific examples, but the protection scope of the present invention is not limited to the following specific embodiments.

[0035] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0036] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0037] Example 1: A preparation method of a composite yttrium fluoride coating material, comprising the following steps: Step 1, weigh 2000 g of yttrium fluoride and place it in a quartz tube, introduce hydrogen fluoride gas to displace the air in the quartz tube, and then heat the yttrium fluoride to 950 °C for fluorination for 60 min. After natural cooling, take out the fluorinated yttrium and store it in vacuum packaging.

[0038] Step 2, place a ball milling tank in a vacuum glove box, take 300 g of fluorinated yttrium, 26.67 g of calcium fluoride, and 6.67 g of lead fluoride powder and put them into the ball milling tank, seal and evacuate, set the ball milling frequency at 31 Hz, and ball mill for 90 min to mix evenly to obtain a mixed powder.

[0039] Step 3, add 2 wt% of water to the mixed powder and stir evenly, add the mixed powder into a press mold for pressing and forming, and the green density after forming is 2.35 g / cm 3 ³.

[0040] Step 4: Place the pressed green body inside the crucible, seal the crucible, then transfer the crucible to a vacuum drying oven and dry it at 100 °C for 24 h. After that, transfer the crucible to a vacuum atmosphere heating furnace and heat it at 1250 °C for 3 h. Then, cool it down to 800 °C at a cooling rate of 1 °C / min, and then cool it in the furnace to obtain the crystalline block.

[0041] Step 5: Crush and screen the crystalline block, and divide the particles into three groups: >3 mm, 1 - 3 mm, and <1 mm.

[0042] Step 6: According to the particle size, prepare a composite yttrium fluoride coating material with a loose packing density of 2.5 g / cm 3 ±0.05.

[0043] Figure 1 SEM image of the composite yttrium fluoride coating material prepared in Example 1. It can be Figure 1 seen that it is completely solid - solved, the surface shows porcelain - like characteristics, there are no obvious pores, and the density is high.

[0044] Figure 2 XRD pattern of the composite yttrium fluoride coating material prepared in Example 1. It can be Figure 2 known that the main phase is YF 3 phase, and there is a very small amount of Y 5 O 4 F 7 phase. The oxygen content is extremely low, indicating that the deoxidation effect is very obvious. The peak intensity of the YF 3 phase is high, showing an obvious polycrystalline structure.

[0045] Comparative Example 1: A preparation method of a composite yttrium fluoride coating material, which is different from Example 1 in that in Step 2, place a ball - milling tank in a vacuum glove box, take 300 g of fluorinated yttrium fluoride and load it into the ball - milling tank, seal and evacuate it, set the ball - milling frequency at 31 Hz, and ball - mill for 90 min to mix evenly to obtain a mixed powder.

[0046] Comparative Example 2: A preparation method of a composite yttrium fluoride coating material, which is different from Example 1 in that in Step 2, place a ball - milling tank in a vacuum glove box, take 300 g of fluorinated yttrium fluoride and 26.67 g of calcium fluoride and load them into the ball - milling tank, seal and evacuate it, set the ball - milling frequency at 31 Hz, and ball - mill for 90 min to mix evenly to obtain a mixed powder.

[0047] Comparative Example 3: A preparation method of a composite yttrium fluoride coating material, which is different from Example 1. In step 2, place a ball milling jar in a vacuum glove box. Take 300 g of fluorinated yttrium fluoride and 6.67 g of lead fluoride powder and put them into the ball milling jar, seal it and evacuate it. Set the ball milling frequency at 31 Hz and ball mill for 90 min to mix evenly, obtaining a mixed powder.

[0048] Example 2: A preparation method of a composite yttrium fluoride coating material, comprising the following steps: Step 1, weigh 2000 g of yttrium fluoride and place it in a quartz tube. Pass hydrogen fluoride gas to displace the air in the quartz tube, and then heat the yttrium fluoride to 950 °C for fluorination for 60 min. After natural cooling, take out the fluorinated yttrium fluoride and store it in a vacuum package.

[0049] Step 2, place a ball milling jar in a vacuum glove box. Take 300 g of fluorinated yttrium fluoride, 9.47 g of calcium fluoride and 6.32 g of lead fluoride powder and put them into the ball milling jar, seal it and evacuate it. Set the ball milling frequency at 31 Hz and ball mill for 90 min to mix evenly, obtaining a mixed powder.

[0050] Step 3, add 2% of water to the mixed powder and stir evenly. Add the mixed powder into a press mold for molding. The density of the green compact after molding is 2.31 g / cm 3 。

[0051] Step 4, place the pressed green compact inside a crucible, seal the crucible, and then transfer the crucible to a vacuum drying oven for drying at 100 °C for 24 h. Then transfer the crucible to a vacuum atmosphere heating furnace and heat it at 1350 °C for 2.5 h. Then cool it at a rate of 2 °C / min to 850 °C, and then cool it with the furnace to obtain the crystal block.

[0052] Step 5, crush and screen the crystal block, and divide the particles into three groups of >3 mm, 1 - 3 mm, and <1 mm.

[0053] Step 6, according to the particle size, prepare a composite yttrium fluoride coating material with a loose packing density of 2.65 g / cm 3 ±0.05.

[0054] Example 3: A preparation method of a composite yttrium fluoride coating material, comprising the following steps: Step 1, weigh 2000 g of yttrium fluoride and place it in a quartz tube. Pass hydrogen fluoride gas to displace the air in the quartz tube, and then heat the yttrium fluoride to 800 °C for fluorination for 30 min. After natural cooling, take out the fluorinated yttrium fluoride and store it in a vacuum package.

[0055] Step 2, place the ball milling jar in a vacuum glove box. Take 300 g of fluorinated yttrium fluoride, 56.25 g of calcium fluoride, and 18.75 g of lead fluoride powder, put them into the ball milling jar, seal it, and evacuate it. Set the ball milling frequency at 31 Hz and ball mill for 90 min to mix evenly, obtaining a mixed powder.

[0056] Step 3, add 2% water to the mixed powder and stir evenly. Put the mixed powder into a press mold for pressing and forming. The green density after forming is 2.0 g / cm 3 .

[0057] Step 4, place the pressed green body inside the crucible, seal the crucible, then transfer the crucible to a vacuum drying oven and dry at 100 °C for 24 h. After that, transfer the crucible to a vacuum atmosphere heating furnace and heat at 1200 °C for 5 h. Then, cool it at a rate of 3 °C / min to 900 °C, and then cool it with the furnace to obtain the crystalline block.

[0058] Step 5, crush and screen the crystalline block, and divide the particles into three groups: >3 mm, 1 - 3 mm, and <1 mm.

[0059] Step 6, according to the particle size, prepare a composite yttrium fluoride coating material with a loose density of 2.1 g / cm 3 ±0.05.

[0060] Example 4: A preparation method of a composite yttrium fluoride coating material, comprising the following steps: Step 1, weigh 2000 g of yttrium fluoride and place it in a quartz tube. Pass hydrogen fluoride gas to displace the air in the quartz tube, then heat the yttrium fluoride to 1100 °C for fluorination for 240 min. After natural cooling, take out the fluorinated yttrium fluoride and store it in vacuum packaging.

[0061] Step 2, place the ball milling jar in a vacuum glove box. Take 300 g of fluorinated yttrium fluoride, 3.06 g of calcium fluoride, and 3.06 g of lead fluoride powder, put them into the ball milling jar, seal it, and evacuate it. Set the ball milling frequency at 31 Hz and ball mill for 90 min to mix evenly, obtaining a mixed powder.

[0062] Step 3, add 2% water to the mixed powder and stir evenly. Put the mixed powder into a press mold for pressing and forming. The green density after forming is 2.5 g / cm 3 .

[0063] Step 4, place the pressed green body inside the crucible, seal the crucible, then transfer the crucible to a vacuum drying oven and dry at 100 °C for 24 h. After that, transfer the crucible to a vacuum atmosphere heating furnace and heat at 1500 °C for 1 h. Then, cool it at a rate of 5 °C / min to 1000 °C, and then cool it with the furnace to obtain the crystalline block.

[0064] Step 5, crush and screen the crystalline blocks, and divide the particles into three groups of >3 mm, 1-3 mm, and <1 mm.

[0065] Step 6, according to the particle size, prepare a composite yttrium fluoride coating material with a loose packing density of 2.75 g / cm 3 ±0.05.

[0066] Example 5: A preparation method of a composite yttrium fluoride coating material, comprising the following steps: Step 1, place a ball milling tank in a vacuum glove box, take 300 g of yttrium fluoride, 26.67 g of calcium fluoride and 6.67 g of lead fluoride powders and put them into the ball milling tank, seal and evacuate, set the ball milling frequency at 31 Hz, and ball mill for 90 min to mix evenly to obtain a mixed powder.

[0067] Step 2, add 2% of water to the mixed powder and stir evenly, put the mixed powder into a press die for pressing and forming, the green density after forming is 2.8 g / cm 3 , the green density after forming is 2.35 g / cm 3 , repeat the operation 10 times to prepare 300 g of pellets.

[0068] Step 3, place the pressed green body inside a crucible, seal the crucible, then transfer the crucible to a vacuum drying oven and dry at 100 °C for 24 h, then transfer the crucible to a vacuum atmosphere heating furnace and heat at 1250 °C for 3 h, then cool at a rate of 1 °C / min to 800 °C, and then cool with the furnace to obtain the crystalline block.

[0069] Step 4, crush and screen the crystalline blocks, and divide the particles into three groups of >3 mm, 1-3 mm, and <1 mm.

[0070] Step 5, according to the particle size, prepare a composite yttrium fluoride coating material with a loose packing density of 2.6 g / cm 3 ±0.05.

[0071] Detect the oxygen content in the coating materials prepared in Examples 1-5 and Comparative Examples 1-3, and conduct coating experiments on the coating materials prepared in Examples 1-5 and Comparative Examples 1-3. Using sapphire as the coating substrate, test the transmittance of the film layer at a wavelength of 600-700 nm. The experimental phenomena and detection data are shown in Table 1.

[0072] Table 1 Oxygen content and coating conditions of the coating materials prepared in Examples 1-5 and Comparative Examples 1-3 The oxygen content of the yttrium fluoride raw materials used in Examples 1 to 5 and Comparative Examples 1 to 3 of the present invention is 476 ppm. As can be seen from Table 1, the preparation process provided by the present invention can greatly reduce the oxygen content in the yttrium fluoride material, which is beneficial to the subsequent film coating and helps to improve the film coating quality.

[0073] As can be seen from Table 1, by comparing the film coating situations of Example 1 and Comparative Example 1, it can be known that doping calcium fluoride and lead fluoride in the yttrium fluoride film coating material provided by the present invention can effectively reduce the oxygen content inside the film material, prevent sputtering phenomena, reduce the film layer stress after film coating to prevent cracking, and at the same time is beneficial to the red shift of the transmittance curve to increase the maximum transmittance, and the film coating performance is more excellent.

[0074] By comparing the film coating situations of Example 1 and Comparative Example 2, it can be known that only introducing calcium fluoride into the yttrium fluoride film coating material cannot completely and effectively remove the oxygen content inside the raw materials. It can reduce the film layer stress but does not reach the target effect, and there is a red shift phenomenon resulting in a relatively low maximum transmittance.

[0075] By comparing the film coating situations of Example 1 and Comparative Example 3, it can be known that only introducing lead fluoride into the yttrium fluoride film coating material, lead fluoride can effectively reduce the oxygen content inside the film material, but there is no obvious improvement in the overall performance of the film material, and it is also unable to eliminate the thermal stress of the film layer, resulting in a significant increase in the film layer cracking rate. Without adding calcium fluoride, the air holes caused by lead fluoride deoxidation cannot be completely eliminated, resulting in an increase in the gas release amount during pre-melting and sputtering phenomena.

[0076] Through the above comparison, it can be proved that the yttrium fluoride film coating material provided by the present invention has good thermal stability and mechanical properties, excellent film forming properties, solves the problem of excessive gas release during the pre-melting stage of the yttrium fluoride film coating material in the prior art, causing sputtering, and reduces the difficulty and cost of the film coating process.

[0077] By comparing Example 1 and Example 5, it can be known that fluorinating the lead fluoride raw material can further reduce the oxygen content of the film coating material, which is beneficial to improving the film coating quality.

[0078] The above-mentioned embodiments are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope of the present invention, according to the technical solution and its concept of the present invention, makes equivalent substitutions or changes, and all should be covered by the protection scope of the present invention.

Claims

1. A composite yttrium fluoride coating material, characterized in that: The composite yttrium fluoride coating material comprises yttrium fluoride, calcium fluoride and lead fluoride, wherein the yttrium fluoride, calcium fluoride and lead fluoride form a ternary composite structure, wherein the yttrium element, the calcium element and the lead element are evenly distributed; and the mass ratio of yttrium fluoride, calcium fluoride and lead fluoride in the composite yttrium fluoride coating material is 80-98:15-1:5-1.

2. A method for preparing a composite yttrium fluoride material, characterized in that: The steps include: Step 1, ball-milling yttrium fluoride, calcium fluoride and lead fluoride under vacuum to obtain a mixed powder; Step 2, pressing the mixed powder into a green body under vacuum, then calcining the green body under vacuum for a certain period of time, and obtaining a crystal block after cooling; Step 3, crushing and sieving the crystal block, and the obtained particles are the composite yttrium fluoride coating material; In step 1, the mass ratio of yttrium fluoride, calcium fluoride and lead fluoride is 80-98:15-1:5-1.

3. The method for preparing the composite yttrium fluoride material according to claim 2, characterized in that: Before step 1, a pretreatment process of yttrium fluoride is also included, the steps are: placing yttrium fluoride in a quartz tube, introducing hydrogen fluoride gas into the quartz tube to replace the air in the quartz tube, then heating the yttrium fluoride for a certain period of time to obtain fluorinated yttrium fluoride, and storing the fluorinated yttrium fluoride in a vacuum environment.

4. The method for preparing the composite yttrium fluoride material according to claim 3, characterized in that: In the pretreatment process, the heating temperature is 800~1100℃ and the heating time is 30~240min.

5. The method for preparing the composite yttrium fluoride material according to claim 2, characterized in that: In step 2, the density of the green body is 2.1~4.0g / cm 3 .

6. The method for preparing the composite yttrium fluoride material according to claim 2, characterized in that: In step 2, the calcination temperature is 1200-1500° C., and the calcination time is 1-5 hours.

7. The method for preparing the composite yttrium fluoride material according to claim 2, characterized in that: In step 2, during cooling, the temperature is first lowered to 800-1000°C at a rate of 0.1-5°C / min, and then cooled in the furnace.

8. The method for preparing the composite yttrium fluoride material according to claim 2, characterized in that: In step 2, when firing the green body, the green body is placed in a crucible, the crucible is sealed, and the crucible is placed in a vacuum atmosphere for firing.

9. The method for preparing the composite yttrium fluoride material according to claim 2, characterized in that: The particles obtained in step 3 are formulated to have a bulk density of 2.0-2.8 g / cm 3 Composite yttrium fluoride coating material.

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