Ultra-pure calcium fluoride crystal raw material and preparation method thereof

Abstract

The invention relates to an ultra-pure calcium fluoride crystal raw material and a preparation method thereof. The preparation method of the hyperpure calcium fluoride CaF2 crystal raw material comprises the following steps: (1) respectively weighing a calcium source and a fluorine source according to the stoichiometric ratio of elements in CaF2, and carrying out vacuum drying to remove adsorbed water and bound water so as to obtain a dehydrated calcium source and a dehydrated fluorine source; (2) mixing the dehydrated calcium source, the dehydrated fluorine source and absolute ethyl alcohol, and carrying out ball milling to obtain a white pasty mixed raw material; and (3) carrying out vacuum high-temperature heat treatment on the white pasty mixed raw material, carrying out solid-phase reaction on calcium ions and fluorine ions to generate calcium fluoride, cooling after the reaction is finished to obtain white powder, and grinding and crushing to obtain the ultra-pure calcium fluoride crystal raw material.

Description

Technical Field

[0001] This invention belongs to the field of calcium fluoride crystal technology, specifically relating to a method for preparing ultrapure calcium fluoride crystal raw materials through solid-phase reaction under high vacuum conditions. Background Technology

[0002] Calcium fluoride (CaF2) crystals possess advantages such as a wide transmission wavelength range (continuously covering the deep ultraviolet to mid-far infrared), uniform refractive index, stable thermodynamic properties, low hygroscopicity, and strong resistance to radiation damage, making them one of the best-performing optical materials currently available. Calcium fluoride crystals are typical cubic crystals, lacking natural birefringence and other optical anisotropies. Therefore, they are suitable for use as optical materials such as deep ultraviolet lenses, windows and prisms, and laser gain media. Furthermore, calcium fluoride has a moderate melting point (1418℃), is easy to crystallize, and can achieve the fabrication of large-size, high-quality crystals, thus finding wide application in the optical field.

[0003] Improving the purity of calcium fluoride raw materials and enhancing the performance stability of different batches of raw materials are crucial for preparing high-optical-quality, high-transmittance calcium fluoride crystals. In particular, under specific application scenarios, calcium fluoride crystal optical components need to withstand continuous irradiation by high-energy-density lasers. Trace amounts of impurity elements in the raw materials, such as oxygen (O), hydroxyl groups (OH-), iron (Fe), cerium (Ce), and europium (Eu), can generate strong absorption at different wavelengths, affecting the stability of the optical system. Furthermore, impurity elements can remain within the calcium fluoride crystal during its growth process, causing a sharp decline in optical quality and potentially inducing laser damage under high-energy laser irradiation. Therefore, obtaining ultrapure calcium fluoride crystal raw materials to achieve the growth of high-optical-quality calcium fluoride crystals is a pressing technical challenge that needs to be addressed.

[0004] Currently, high-purity calcium fluoride crystal raw materials are mainly obtained through liquid-phase precipitation reactions. For example, Chinese patent CN110372025A discloses a method for preparing flake-shaped nano-calcium fluoride powder, which involves dissolving calcium nitrate and ammonium fluoride in anhydrous ethanol and distilled water, respectively, and adding polyethylene glycol during ultrasonication. The powder is then synthesized using a precipitation reaction to produce flake-shaped calcium fluoride powder with uniform particle size distribution. Chinese patent CN116332216B discloses a method for preparing high-purity calcium fluoride raw materials, which also involves dissolving inorganic calcium salts and fluoride ion precipitants in deionized water, where calcium and fluoride ions react in the aqueous solution to obtain calcium fluoride powder. In other words, most existing high-purity calcium fluoride raw material preparation techniques involve dissolving calcium-containing compounds and fluoride-containing compounds in deionized water or ethanol solvents, and then obtaining calcium fluoride gel through a precipitation reaction. This calcium fluoride gel inevitably requires repeated washing and centrifugation to remove excess nitrate and other impurity ions from the solution. This method requires multiple washing and centrifugation processes, making the experimental procedure complex and cumbersome, and unsuitable for large-scale production of calcium fluoride raw materials. In particular, because calcium fluoride raw materials synthesized by precipitation methods generally have small particle sizes, large specific surface areas, and strong adsorption capacity, the deionized water, ethanol, and other solvents used in the above process, or their hydroxyl components, inevitably remain or are adsorbed into the prepared raw material product. Furthermore, calcium fluoride raw materials prepared in aqueous solutions or ethanol solvents easily adsorb impurity ions from deionized water or ethanol solvents, which are often difficult to remove during subsequent high-temperature heat treatment. In addition, calcium fluoride readily undergoes the following chemical reaction with water molecules or hydroxyl groups adsorbed on the powder surface at high temperatures: CaF₂ + H₂O → CaO + 2HF The generated calcium oxide will remain in the calcium fluoride raw material as a second phase and is extremely difficult to remove, leading to a decrease in the purity of the calcium fluoride powder. This impurity phase will further cause defects in the calcium fluoride crystals during growth, adversely affecting the optical properties of the calcium fluoride crystals, such as transmittance, optical uniformity, and scattering loss.

[0005] Therefore, it is particularly important to develop a method for preparing calcium fluoride crystal raw material powder that does not require reaction in solution, has extremely low water molecule and hydroxyl content on the powder surface, and has a simple process. Summary of the Invention

[0006] To address the technical problem of how to eliminate water molecules, hydroxyl groups, and other residual impurity ions from other reaction reagents adsorbed on the surface of calcium fluoride raw materials to the greatest extent possible, so as to avoid the chemical reaction between calcium fluoride and water during crystal growth to generate impurities such as calcium oxide, the present invention aims to provide a method for preparing ultrapure calcium fluoride crystal raw materials through solid-phase reaction under high vacuum conditions.

[0007] In a first aspect, the present invention provides a method for preparing ultrapure calcium fluoride (CaF2) crystal raw material, the preparation method comprising the following steps: (1) Weigh the calcium source and fluorine source according to the stoichiometric ratio of the elements in CaF2, and dry them under vacuum to remove adsorbed water and bound water to obtain dehydrated calcium source and dehydrated fluorine source. (2) The dehydrated calcium source, the dehydrated fluorine source and anhydrous ethanol are mixed and ball-milled to obtain a white paste-like mixed raw material; (3) The white paste-like mixed raw material is subjected to vacuum high-temperature heat treatment to generate calcium fluoride by solid-phase reaction between calcium ions and fluoride ions. After the reaction is completed, the mixture is cooled to obtain white powder, which is then ground and crushed to obtain the ultrapure calcium fluoride crystal raw material.

[0008] Preferably, in step (1), the calcium source includes at least one of calcium nitrate, calcium carbonate, calcium acetate, and the hydrate of the calcium salt, with a purity ≥99%; the fluorine source includes ammonium fluoride, with a purity ≥99.9%.

[0009] Preferably, in step (1), the vacuum drying temperature is 100–200°C, the drying time is 12–48 hours, and the vacuum degree is 1×10⁻⁶. -3 Pa ~ 5 × 10 -3 Pa.

[0010] Preferably, in step (2), the ratio of the amount of anhydrous ethanol added to the total mass of the dehydrated calcium source and fluorine source is 100-500 mL: 27.1-44.5 g.

[0011] Preferably, in step (2), the grinding and mixing time is 12 to 24 hours, and the ball milling speed is 100 to 500 revolutions per minute.

[0012] Preferably, in step (3), the parameters of the vacuum high-temperature heat treatment are: reaction temperature 700–900°C, holding time 2–6 hours, and vacuum degree 1×10⁻⁶. -3 ~1×10 -2 Pa; preferably, during the heating stage, a constant temperature period of 10 to 20 hours is set at 200°C.

[0013] Preferably, in step (3), the grinding and crushing are carried out in an agate mortar for 5 to 30 minutes; the particle size of the ultrapure calcium fluoride crystal raw material obtained after grinding and crushing is 1 to 10 micrometers.

[0014] Secondly, the present invention provides an ultrapure calcium fluoride crystal raw material obtained according to the above preparation method, wherein the purity of the ultrapure calcium fluoride crystal raw material can reach 99.9969-99.999%, the yield can reach 90-99%, and the content of impurity elements is O<30ppm, Fe<1ppm, Y<0.01ppm, Ce<0.01ppm, Eu<0.01ppm.

[0015] Beneficial effects (1) The present invention directly uses a high-temperature solid-phase reaction method to prepare ultrapure calcium fluoride raw material. Impurity ions are directly removed after high-temperature decomposition, without the need for cumbersome steps such as washing and centrifugation. The process is simple, the reaction is easy to control, and the energy consumption is low. It can provide high-quality raw materials for the growth of high-optical-quality calcium fluoride crystals in batches. (2) Compared with the existing methods for synthesizing calcium fluoride raw materials, the calcium fluoride raw material synthesized by the present invention is carried out in a vacuum-sealed environment throughout the process, and will not come into contact with water. This avoids the formation of impurities such as calcium oxide by chemical reaction between calcium fluoride and water at high temperatures, and maximizes the purity of the calcium fluoride raw material. Attached Figure Description

[0016] Figure 1 The image shows the XRD pattern of the calcium fluoride crystal raw material synthesized in Example 1 of this invention. Figure 2 The infrared spectrum of the calcium fluoride crystal raw material prepared in Example 1 of this invention; Figure 3 This is a scanning electron microscope image of the calcium fluoride raw material prepared in Example 1 of the present invention. Detailed Implementation

[0017] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0018] The following is an exemplary description of a method for preparing ultrapure calcium fluoride crystal raw materials provided by the present invention. The preparation method may include the following steps: (1) Weigh the calcium source and fluorine source according to the stoichiometric ratio of the elements in CaF2, and dry them under vacuum to remove adsorbed water and bound water to obtain dehydrated calcium source and dehydrated fluorine source. (2) The dehydrated calcium source, the dehydrated fluorine source and anhydrous ethanol are mixed and ball-milled to obtain a white paste-like mixed raw material; (3) The white paste-like mixed raw material is subjected to vacuum high-temperature heat treatment to generate calcium fluoride by solid-phase reaction between calcium ions and fluoride ions. After the reaction is completed, the mixture is cooled to obtain white powder, which is then ground and crushed to obtain the ultrapure calcium fluoride crystal raw material.

[0019] In some embodiments, in step (1), the calcium source may include at least one of calcium nitrate, calcium carbonate, calcium acetate, and the hydrate of the calcium salt, with a purity ≥99%; the fluorine source may include ammonium fluoride with a purity ≥99.9%. Using ammonium fluoride as the fluorine source allows for the direct removal of the ammonium salt generated after the reaction by heating, leaving no cation residue.

[0020] In some embodiments, in step (1), the vacuum drying temperature can be 100–200°C, the drying time can be 12–48 hours, and the vacuum degree can be 1×10⁻⁶. -3 Pa ~ 5 × 10 -3 Pa. Too low a temperature or too short a time will result in incomplete drying; while too high a temperature may cause some impurities to react with calcium fluoride during the drying process, thus forming impurities that are difficult to remove; 10 -3 A vacuum level in the Pa range ensures that oxygen-containing impurities generated during the drying process can be removed in a timely manner.

[0021] In some embodiments, in step (2), the ratio of the amount of anhydrous ethanol added to the total mass of the dehydrated calcium source and fluorine source is preferably 100-500 mL: 27.1-44.5 g, to ensure that the mixture can be completely and evenly mixed after grinding following the addition of anhydrous ethanol. If the order of steps 1 and 2 is reversed, i.e., mixing first and then drying, the already mixed paste mixture will precipitate or separate during the drying process, resulting in a decrease in uniformity.

[0022] In some embodiments, in step (2), the grinding and mixing time can be 12 to 24 hours, and the ball milling speed can be 100 to 500 revolutions per minute.

[0023] In some embodiments, the parameters for the vacuum high-temperature heat treatment in step (3) can be: reaction temperature 700–900°C, holding time 2–6 hours, and vacuum degree 1×10⁻⁶. -3 ~1×10 -2 Pa, preferably 1×10 -3 ~5×10 -3 Pa; preferably, during the heating stage, a constant temperature period of 200°C for 10 to 20 hours can be set to remove ethanol from the reactants.

[0024] In some embodiments, in step (3), the grinding and crushing can be carried out in an agate mortar, and the grinding and crushing time can be 5 minutes to 30 minutes; preferably, the particle size of the ultrapure calcium fluoride crystal raw material obtained after grinding and crushing can be 1 to 10 micrometers.

[0025] This invention removes adsorbed and bound water from the calcium and fluoride ion chemical reagents through vacuum calcination. Then, calcium and fluoride ions undergo a solid-phase reaction under high temperature and high vacuum conditions to prepare calcium fluoride raw material. The entire preparation process of calcium fluoride raw material is carried out under sealed high vacuum conditions, avoiding direct contact with water. Furthermore, under high temperature conditions, other ions in the chemical reagents will undergo decomposition reactions and will not remain on the powder surface, thus maximizing the purity of the calcium fluoride raw material.

[0026] The calcium fluoride raw material synthesized using this method can meet the stringent purity requirements for the growth of high-optical-quality calcium fluoride crystals. Furthermore, the synthesis process of this method is simple and is very suitable for the large-scale production of ultrapure calcium fluoride raw materials.

[0027] In some embodiments, the purity of the ultrapure calcium fluoride crystal raw material can reach 99.9969–99.999%, the yield (the ratio of the actual mass of calcium fluoride raw material to the theoretical mass of calcium fluoride calculated according to the theoretical feed amount) can reach 90–99%, and the content of impurity elements is O < 30 ppm, Fe < 1 ppm, Y < 0.01 ppm, Ce < 0.01 ppm, Eu < 0.01 ppm.

[0028] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0029] Example 1

[0030] The preparation method of ultrapure calcium fluoride crystal raw material provided in this embodiment includes the following steps: (1) Weigh out calcium nitrate dihydrate (Ca(NO3)2·2H2O) and ammonium fluoride (NH4F) with a purity of 99% according to the stoichiometric ratio of the elements in CaF2; put the weighed calcium nitrate dihydrate and ammonium fluoride into an alumina crucible and place it in a vacuum drying oven at 120℃. Use a vacuum pump to evacuate the drying oven and dry the calcium nitrate dihydrate and ammonium fluoride in the vacuum drying oven for 48 hours to remove the adsorbed water and bound water in the chemical reagents, and obtain dehydrated calcium nitrate and dehydrated ammonium fluoride. (2) Pour the dehydrated calcium nitrate and ammonium fluoride obtained in step (1) into a polytetrafluoroethylene ball mill jar, add 100 mL of anhydrous ethanol to ensure that the two reagents containing calcium ions and fluoride ions are mixed evenly. The speed of the ball mill is 100 rpm. After ball milling for 12 hours, it becomes a white paste and a white paste mixed raw material is obtained. (3) Transfer the white paste-like mixture obtained in step (2) to a graphite crucible and treat it at a high temperature of 700°C for 2 hours in a vacuum furnace to allow calcium nitrate and ammonium fluoride to undergo the following chemical reaction: Ca(NO3)2+2NH4F→CaF2↓+2NH3↑+2NO2↑+2H2O↑ The added calcium nitrate and ammonium fluoride undergo a solid-phase reaction at high temperature to generate calcium fluoride raw material. Simultaneously, the nitrate ions in the calcium nitrate reagent react with the ammonium ions in the ammonium fluoride under high temperature conditions, decomposing to generate ammonia, nitrogen dioxide, and water vapor. These three gases are rapidly expelled from the vacuum furnace by continuous operation of diffusion pumps and mechanical pumps, leaving no residue in the calcium fluoride and ensuring the ultra-high purity of the calcium fluoride raw material. Throughout the entire reaction process, the vacuum in the vacuum furnace is maintained at 6.0 × 10⁻⁶. -3 Pa; After the calcium nitrate and ammonium fluoride have reacted completely, the vacuum furnace heating is turned off, and the furnace is naturally cooled to room temperature by the cooling effect of circulating water. The white powder in the graphite crucible is taken out and ground and crushed in an agate mortar for 5 minutes to obtain the ultrapure calcium fluoride crystal raw material (yield 99%).

[0031] Example 2

[0032] The preparation method of the ultrapure calcium fluoride crystal raw material provided in this embodiment is the same as that in the embodiment, with the main difference being: In step (1), the raw materials are calcium carbonate (Ca(CO3)2) and ammonium fluoride (NH4F), which are dried at 100°C for 12 hours; In step (2), the amount of anhydrous ethanol added is 300 mL, the ball milling speed is 500 rpm, and the ball milling time is 24 hours; In step (3), the calcium carbonate is treated at a high temperature of 850°C for 4 hours in a vacuum furnace to cause the following chemical reaction between calcium carbonate and ammonium fluoride: CaCO3+2NH4F→CaF2↓+2NH3↑+CO2↑+H2O↑ The added calcium carbonate and ammonium fluoride undergo a solid-phase reaction at high temperature to produce calcium fluoride raw material. Simultaneously, the carbonate ions in the calcium carbonate reagent react chemically with the ammonium ions in the ammonium fluoride under high temperature conditions, decomposing to produce ammonia, carbon dioxide, and water vapor. These three gases are immediately expelled from the vacuum furnace by continuous evacuation pumps and mechanical pumps, leaving no residue in the calcium fluoride and ensuring the ultra-high purity of the calcium fluoride raw material. Throughout the entire reaction process, the vacuum in the vacuum furnace is maintained at 5.0 × 10⁻⁶. -3 Pa; After the calcium carbonate and ammonium fluoride have reacted completely, the vacuum furnace heating is turned off, and the furnace is naturally cooled to room temperature by the cooling effect of circulating water. The white powder in the graphite crucible is taken out and ground and crushed in an agate mortar for 20 minutes to obtain the ultrapure calcium fluoride crystal raw material (yield 97%).

[0033] Example 3

[0034] The preparation method of the ultrapure calcium fluoride crystal raw material provided in this embodiment is the same as that in the embodiment, with the main difference being: In step (1), the raw materials are calcium acetate monohydrate (Ca(CH3COO)2·H2O) and ammonium fluoride (NH4F), and the drying time is 24 hours; In step (2), the amount of anhydrous ethanol added is 500 mL, and the ball milling speed is 300 rpm; In step (3), the high-temperature treatment time is 6 hours, causing calcium acetate and ammonium fluoride to undergo the following chemical reaction: Ca(CH3COO)2+2NH4F→CaF2↓+NH3↑+CH4↑+CO2↑ The added calcium acetate and ammonium fluoride undergo a solid-phase reaction at high temperature to generate calcium fluoride raw material. Simultaneously, the acetate ions in the calcium acetate reagent also react chemically with the ammonium ions in the ammonium fluoride under high temperature conditions, decomposing to generate ammonia, methane, and carbon dioxide. These three gases are immediately expelled from the vacuum furnace by continuous evacuation pumps and mechanical pumps, leaving no residue in the calcium fluoride and ensuring the ultra-high purity of the calcium fluoride raw material. Throughout the entire reaction process, the vacuum in the vacuum furnace is maintained at 6.4 × 10⁻⁶. -3 Pa; After the calcium acetate and ammonium fluoride have reacted completely, the vacuum furnace heating is turned off, and the furnace is naturally cooled to room temperature by the cooling effect of circulating water. The white powder in the graphite crucible is taken out and ground and crushed in an agate mortar for 30 minutes to obtain the ultrapure calcium fluoride crystal raw material (yield 98.8%).

[0035] Comparative Example 1

[0036] The preparation method of the calcium fluoride raw material provided in this comparative example is the same as that in Example 1. The main difference is that in step (1), vacuum calcination was not used to remove the adsorbed water and bound water in the dihydrate calcium nitrate and ammonium fluoride chemical reagents.

[0037] Comparative Example 2

[0038] The preparation method of the calcium fluoride raw material provided in this comparative example is the same as that in Example 1. The main difference is that step (2) is not carried out. Instead, the dried calcium nitrate and ammonium fluoride are directly put into a vacuum furnace for solid-phase reaction.

[0039] Table 1 below compares the impurity element content and yield of the calcium fluoride raw material (sample 1) prepared in Embodiment 1 of the present invention with those of the calcium fluoride raw materials (sample 2, sample 3) obtained in Comparative Examples 1 and 2: Table 1. Detection results and yield of impurity elements in calcium fluoride crystal raw materials (unit: ppm) As can be seen from the table, the content of impurity elements, especially oxygen content, in the calcium fluoride raw material synthesized by the preparation method provided by the present invention is significantly lower than that in the calcium fluoride raw material that has not undergone vacuum drying and ball milling.

[0040] Figure 1 The image shows the XRD pattern of the calcium fluoride crystal raw material synthesized in Example 1 of this invention. As can be seen from the image, the diffraction peaks in the XRD pattern perfectly match the standard card for calcium fluoride, indicating that the calcium fluoride crystal raw material prepared in Example 1 is pure calcium fluoride without any other impurities. Furthermore, the high intensity and very narrow full width at half maximum (FWHM) of the XRD diffraction peaks of the calcium fluoride raw material indicate that the prepared calcium fluoride raw material has excellent crystallinity and large grain size.

[0041] Figure 2 The infrared spectrum of the calcium fluoride crystal raw material prepared in Example 1 of this invention was obtained using the potassium bromide pellet method. As can be seen from the figure, apart from the extremely low OH- characteristic peak introduced by the addition of potassium bromide, no other infrared peaks were observed. This indicates that the surface of the calcium fluoride crystal raw material prepared in Example 1 did not adsorb other impurity ions and groups. Therefore, the preparation method of this invention can yield ultrapure calcium fluoride raw material.

[0042] Figure 3 This is a scanning electron microscope (SEM) image of the calcium fluoride raw material prepared in Example 1 of this invention. As can be seen from the image, the calcium fluoride crystal raw material prepared in Example 1 has a relatively large particle size, approximately 1–2 micrometers.

[0043] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing ultrapure calcium fluoride (CaF2) crystal raw material, characterized in that, The preparation method includes the following steps: (1) Weigh the calcium source and fluorine source according to the stoichiometric ratio of the elements in CaF2, and dry them under vacuum to remove adsorbed water and bound water to obtain dehydrated calcium source and dehydrated fluorine source. (2) The dehydrated calcium source, the dehydrated fluorine source and anhydrous ethanol are mixed and ball-milled to obtain a white paste-like mixed raw material; (3) The white paste-like mixed raw material is subjected to vacuum high-temperature heat treatment to generate calcium fluoride by solid-phase reaction between calcium ions and fluoride ions. After the reaction is completed, the mixture is cooled to obtain white powder, which is then ground and crushed to obtain the ultrapure calcium fluoride crystal raw material.

2. The preparation method according to claim 1, characterized in that, In step (1), the calcium source includes at least one of calcium nitrate, calcium carbonate, calcium acetate, and the hydrate of the calcium salt, with a purity ≥99%; the fluorine source includes ammonium fluoride with a purity ≥99.9%.

3. The preparation method according to claim 1, characterized in that, In step (1), the vacuum drying temperature is 100–200°C, the drying time is 12–48 hours, and the vacuum degree is 1×10⁻⁶. -3 Pa ~ 5 × 10 -3 Pa.

4. The preparation method according to claim 1, characterized in that, In step (2), the ratio of the amount of anhydrous ethanol added to the total mass of the dehydrated calcium source and fluorine source is 100-500 mL: 27.1-44.5 g.

5. The preparation method according to claim 1, characterized in that, In step (2), the grinding and mixing time is 12 to 24 hours, and the ball milling speed is 100 to 500 revolutions per minute.

6. The preparation method according to claim 1, characterized in that, In step (3), the parameters for the vacuum high-temperature heat treatment are: reaction temperature 700–900℃, holding time 2–6 hours, and vacuum degree 1×10⁻⁶. -3 ~1×10 -2 Pa; preferably, during the heating stage, a constant temperature period of 10 to 20 hours is set at 200°C.

7. The preparation method according to claim 1, characterized in that, In step (3), the grinding and crushing are carried out in an agate mortar for 5 to 30 minutes; the particle size of the ultrapure calcium fluoride crystal raw material obtained after grinding and crushing is 1 to 10 micrometers.

8. An ultrapure calcium fluoride crystal raw material obtained by the preparation method according to claim 1, characterized in that, The purity of the ultrapure calcium fluoride crystal raw material can reach 99.9969-99.999%, the yield can reach 90-99%, and the content of impurity elements is O < 30 ppm, Fe < 1 ppm, Y < 0.01 ppm, Ce < 0.01 ppm, Eu < 0.01 ppm.

Images