High-purity anhydrous composite rare earth halide, preparation method thereof, scintillation crystal, scintillation ceramic and scintillation film material

Abstract

The invention discloses a high-purity anhydrous composite rare earth halide and a preparation method thereof, a scintillation crystal, scintillation ceramic and a scintillation thin film material, the general formula of the composite rare earth halide is AxREyXx + 3y, A is an alkali metal element, RE is a rare earth element, X is a halogen element, and y is a rare earth element. The preparation method comprises the following steps: uniformly mixing alkali carbonate or hydroxide, rare earth metal oxide or carbonate or hydroxide and a first part of ammonium halide according to a first preset proportion to obtain a first mixture; carrying out primary heating halogenation reaction on the first mixture in an inert atmosphere to obtain a composite rare earth halide primary material; uniformly mixing the composite rare earth halide primary material with a second part of ammonium halide according to a second preset proportion to obtain a second mixture; and carrying out secondary heating halogenation reaction on the second mixture in an inert atmosphere to obtain the high-purity anhydrous rare earth composite halide. The deep purification of the composite rare earth halide is realized through a two-step halogenation process, and residual trace water and oxygen impurities are thoroughly removed.

Description

Technical Field

[0001] This invention relates to the field of rare earth luminescent materials, and particularly to a high-purity anhydrous composite rare earth halide and its preparation method, scintillation crystals, scintillation ceramics, and scintillation thin film materials. Background Technology

[0002] Scintillation materials are a class of optical functional materials that can convert the energy of high-energy rays or particles such as X-rays, gamma rays, and neutrons into ultraviolet or visible pulsed light. These materials play a crucial role in high-energy physics, nuclear medicine, industrial non-destructive testing, and even homeland security. In the past two decades, rare-earth halide scintillation materials have developed rapidly due to their advantages such as high light output and fast decay time, becoming a research hotspot in novel scintillation materials. Rare-earth halide scintillation materials are usually applied in single-crystal form, but under certain conditions, they can also be in ceramic, glass, or other forms. In the research and development system of rare-earth scintillation crystals, composite rare-earth halide scintillation crystals (such as Cs₂LiYCl₆:Ce, Cs₂LiLaBr₆:Ce, etc.) typically possess excellent properties such as high light output, high energy resolution, and the ability to achieve dual-mode detection, thus attracting widespread attention and showing promising application prospects in high-energy physics, security detection, oil well logging, and medical imaging.

[0003] In the growth or preparation of such scintillation crystal materials, high-purity anhydrous alkali metal halides and single rare earth halides are typically used as raw materials. For example, patents CN117385461A and CN105102693B use single-element halides as raw materials, weighing them according to a specific ratio and adding them to a crystal growth crucible for melting and mixing. However, due to the extremely strong oxygen affinity and deliquescent nature of rare earth elements, oxygen and water of crystallization impurities are easily introduced during the preparation of rare earth halides, making the preparation of high-purity anhydrous rare earth halides very difficult and costly, severely restricting the development and application of composite halide scintillation crystals. To directly prepare pure-phase high-purity anhydrous composite rare earth halides, existing technologies such as CN106753378A and CN106745163B employ a liquid-phase synthesis method using ammonium halides as a dehydrating agent to obtain high-purity composite rare earth halides free of water of crystallization and oxide impurities. However, this liquid-phase synthesis process requires multiple steps, including solution preparation, concentration, dehydration, and deammoniation. The entire process carries the risk of incomplete water molecule removal and the introduction of oxygen, making environmental control challenging and increasing the difficulty of preparing halides with low water and oxygen content. Therefore, developing a simple, efficient, and environmentally controllable preparation method for deep purification of complex rare earth halides, capable of stably controlling water and oxygen content at extremely low levels, is of great significance for promoting the domestic production of high-end scintillation crystal materials, scintillation ceramics, or scintillation thin film materials. Summary of the Invention

[0004] The purpose of this invention is to provide a high-purity anhydrous composite rare earth halide and its preparation method, as well as scintillation crystals, scintillation ceramics, and scintillation thin film materials. A primary composite rare earth halide material with uniform composition is obtained through a single heating halogenation reaction. A secondary halogenation process is then used to deeply purify the primary composite rare earth halide material, completely removing residual trace amounts of water and oxygen impurities. This effectively avoids the formation of water of crystallization during the synthesis process, facilitating the creation of an anhydrous and oxygen-free synthesis environment, minimizing the content of water and oxygen impurities, and resulting in a more pure phase and more uniform and accurate chemical composition of the obtained composite rare earth halide.

[0005] To address the aforementioned technical problems, a first aspect of this invention provides a method for preparing high-purity anhydrous composite rare earth halides, wherein the composite rare earth halide has the general formula A. x RE y X x+3y Where A is an alkali metal element, RE is a rare earth element, X is a halogen element, 1≤x≤3, 1≤y≤2, and the preparation method includes the following steps:

[0006] Alkali metal carbonates or hydroxides, rare earth metal oxides or carbonates or hydroxides, and a first portion of ammonium halide are uniformly mixed in a first preset ratio to obtain a first mixture.

[0007] The first mixture is subjected to a halogenation reaction under an inert atmosphere to obtain a primary composite rare earth halide material.

[0008] The composite rare earth halide primary material is uniformly mixed with the second part of ammonium halide in a second preset ratio to obtain the second mixture.

[0009] The second mixture was subjected to a secondary heating and halogenation reaction in an inert atmosphere to obtain a high-purity anhydrous rare earth composite halide.

[0010] Further, the first preset ratio is: the molar ratio of the alkali metal carbonate or hydroxide, the rare earth metal oxide or carbonate or hydroxide, and the first part of ammonium halide is A:RE:NH4X=x / y:1:q, where x+3y<q≤3(x+3y).

[0011] Further, the step of subjecting the first mixture to a single heating halogenation reaction in an inert atmosphere includes:

[0012] The first mixture is placed in a quartz or ceramic container and subjected to a heating halogenation reaction under an inert atmosphere according to the first preset heating conditions.

[0013] The first preset heating conditions are: first heat to 200℃~500℃ and then keep warm for 1 hour~10 hours, then heat to 500℃~800℃ and then keep warm for 1 hour~5 hours.

[0014] Furthermore, the first preset heating conditions are: heating to 300℃~450℃ and holding for 3 to 5 hours, then heating to 650℃~750℃ and holding for 2 to 3 hours.

[0015] Furthermore, the second preset ratio is: the mass of the second part of ammonium halide is 10% to 50% of the mass of the primary material of the composite rare earth halide.

[0016] Further, the second mixture undergoes a secondary heating halogenation reaction in an inert atmosphere, comprising:

[0017] The second mixture is placed in a quartz or ceramic container and subjected to a secondary heating halogenation reaction under an inert atmosphere according to the second preset heating conditions.

[0018] The second preset heating conditions are: first heat to 300℃~450℃ and then keep warm for 2 hours~4 hours, then heat to 650℃~750℃ and keep warm for 2 hours~5 hours.

[0019] Furthermore, the inert atmosphere includes nitrogen or argon.

[0020] Furthermore, the purity of the high-purity anhydrous composite rare earth halide is ≥99.9%, the water content is ≤10ppm, and the oxygen content is ≤50ppm.

[0021] Accordingly, a second aspect of the present invention provides a high-purity anhydrous composite rare earth halide, prepared based on the above-described method for preparing high-purity anhydrous composite rare earth halides, wherein the general formula of the composite rare earth halide is A. x RE y X x+3y Where A is one or more of the alkali metal elements Li, Na, K, Rb, and Cs; RE is one or more of the rare earth elements La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, and Y; and X is one of the halogen elements Cl, Br, and I.

[0022] Where 1≤x≤3, 1≤y≤2;

[0023] The purity of the high-purity anhydrous composite rare earth halide is ≥99.9%, the water content is ≤10ppm, and the oxygen content is ≤50ppm.

[0024] Accordingly, a third aspect of the present invention provides a scintillation crystal, scintillation ceramic, or scintillation thin film material comprising the above-mentioned high-purity anhydrous composite rare earth halide.

[0025] The above-described technical solutions of the embodiments of the present invention have the following beneficial technical effects:

[0026] 1. A solid-state heating halogenation process is used to synthesize composite rare earth halide raw materials. The resulting samples have uniform phase purity and composition and can be directly used for the growth of composite rare earth halide scintillation crystals or the preparation of scintillation ceramics. This avoids the problems of high cost, complicated operation, and component segregation caused by using single rare earth halides and alkali metal halides as raw materials.

[0027] 2. Through a two-step halogenation process, especially the second halogenation step, trace oxygen impurities that are difficult to eliminate by a single halogenation can be targeted and removed, and the oxygen content of the final sample can be stably controlled below 50 ppm.

[0028] 3. By adopting a solid-phase heating halogenation process, the influence of environmental water is eliminated, which is conducive to creating an anhydrous and oxygen-free environment throughout the synthesis process. This allows the bound water in the product to be completely removed and its reabsorption to be inhibited, resulting in a sample with a water content of less than 10 ppm.

[0029] 4. The process involved is simple. The reactant ammonium halide can be completely removed by heating and sublimation, which can effectively reduce the risk of introducing impurities during the synthesis process and finally obtain a high-purity product. Furthermore, the halogenation process is divided into two steps, which facilitates independent optimization and control of each step, improves the stability and repeatability of the process, and can be widely used in the deep purification of various complex rare earth halides. Attached Figure Description

[0030] Figure 1 This is a flowchart of the method for preparing high-purity anhydrous composite rare earth halides provided in the embodiments of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0032] Please refer to Figure 1 The first aspect of this invention provides a method for preparing high-purity anhydrous composite rare earth halides, wherein the general formula of the composite rare earth halides is A. x RE y X x+3y Where A is an alkali metal element, RE is a rare earth element, X is a halogen element, 1≤x≤3, 1≤y≤2, and the preparation method includes the following steps:

[0033] Step S100: Alkali metal carbonate or hydroxide, rare earth metal oxide or carbonate or hydroxide, and the first part of ammonium halide are uniformly mixed in a first preset ratio to obtain the first mixture.

[0034] Specifically, the first preset ratio is: the molar ratio of alkali metal carbonate or hydroxide, rare earth metal oxide or carbonate or hydroxide, and the first ammonium halide is A:RE:NH4X=x / y:1:q, where x+3y<q≤3(x+3y). To ensure the halogenation reaction proceeds fully, an excess of ammonium halide needs to be added; however, excessive ammonium halide addition will also affect the synthesis efficiency. Setting the raw material ratio to x+3y<q≤3(x+3y) yields better reaction results.

[0035] Step S200: The first mixture is subjected to a primary heating halogenation reaction in an inert atmosphere to obtain a primary composite rare earth halide material.

[0036] Specifically, the first mixture is placed in a quartz or ceramic container and subjected to a heating halogenation reaction under pre-set heating conditions in an inert atmosphere. The inert gas ensures that no external water or oxygen impurities affect the purity of the product during the heating halogenation reaction.

[0037] Optionally, the first preset heating conditions are: first heat to 200℃~500℃ and then keep warm for 1 hour~10 hours, then heat to 500℃~800℃ and then keep warm for 1 hour~5 hours.

[0038] Preferably, the first preset heating conditions are: heating to 300℃~450℃ and holding for 3 to 5 hours, then heating to 650℃~750℃ and holding for 2 to 3 hours. Setting the first stage heating temperature between 300℃ and 450℃ allows the added ammonium halide to undergo a full halogenation reaction under conditions below its boiling point, improving the halogenation efficiency of synthesizing composite rare earth halides. Setting the second stage heating temperature between 650℃ and 750℃ allows for the complete decomposition of the intermediate products generated in the first stage reaction, while simultaneously allowing the remaining ammonium halide to completely volatilize at high temperatures, yielding a primary composite rare earth halide material with an oxygen content of less than 500ppm.

[0039] Step S300: The primary material of composite rare earth halide is uniformly mixed with the second part of ammonium halide according to the second preset ratio to obtain the second mixture.

[0040] Specifically, the second preset ratio is: the mass of the second ammonium halide is 10% to 50% of the mass of the primary composite rare earth halide material. After one heating halogenation reaction, the residual oxygen impurities in the primary composite rare earth halide material are already low. Adding another 10% to 50% proportion of ammonium halide can further halogenate the residual oxygen impurities.

[0041] In step S400, the second mixture is subjected to a secondary heating halogenation reaction in an inert atmosphere to obtain a high-purity anhydrous rare earth composite halide.

[0042] Specifically, the second mixture is placed in a quartz or ceramic container and subjected to a secondary heating halogenation reaction under an inert atmosphere according to the second preset heating conditions.

[0043] Optionally, the second preset heating conditions are: first heating to 300℃~450℃ and holding for 2 to 4 hours, then heating to 650℃~750℃ and holding for 2 to 5 hours. The two-stage heating halogenation reaction fully halogenates the oxygen impurities in the primary composite rare earth halide material, while simultaneously decomposing the remaining ammonium halide at high temperature, ultimately obtaining high-purity anhydrous composite rare earth halides.

[0044] The inert atmosphere used in the above preparation method includes nitrogen or argon.

[0045] Through the above preparation method, the composite rare earth halide can be any of the following: Cs₂YCl₅, Cs₂LaBr₅, K₂LaCl₅, LiCeCl₄, K₂LaBr₅, K₂LaI₅, K₂LaBr₄I, K₂LaBr₃I₂, RbGd₂Br₇, Cs₂LiLaCl₆, Cs₂LiLaBr₆, Cs₂LiYCl₆, Cs₂LiYBr₆, Cs₃GdBr₆, Cs₃NaGdBr₆, Cs₂NaGdBr₆, Cs₃GdCl₆, Cs₂NaGdCl₆, LiGdCl₄, NaGdCl₄, LiGd 0.8 Ce 0.2 Cl4, NaCeCl4, NaGd 0.8 Ce 0.2 Cl4, RbCe2Br7, RbGd 1.8 Ce 0.2 Br7, K2CeCl5, K2La 0.9 Ce 0.1 Cl5, K2CeBr5, K2La 0.9 Ce 0.1 Br5, K2CeI5, K2La 0.9 Ce 0.1 I5, Ce3CeCl6, Cs3Gd 0.95 Ce 0.05 Cl6, Cs3CeBr6, Cs3Gd 0.95 Ce 0.05 Br6, Cs3CeI6, Cs3Gd 0.95 Ce 0.05 I6, Cs3CeCl6, Cs3La 0.95 Ce 0.05 Cl6, Cs3LaBr6, Cs3CeBr6, Cs3La 0.95 Ce 0.05Br6, Cs3CeI6, Cs3La 0.95 Ce 0.05 I6, Cs3Ce2I9, Cs3Gd 1.9 Ce 0.1 I9, Cs2LiY 0.96 Ce 0.04 Cl6, Cs3Lu2I9, Cs3Lu 1.9 Ce 0.1 I9, Cs2LiLa 0.96 Ce 0.04 Br6,Cs2LiLa 0.988 Pr 0.002 Ce 0.01 Br6.

[0046] Through the above preparation method, the purity of the high-purity anhydrous composite rare earth halide is ≥99.9%, the water content is ≤10ppm, and the oxygen content is ≤50ppm.

[0047] As can be seen from the above process, by adding excess ammonium halide during the primary heating halogenation reaction in this invention, the primary halogenation reaction can be promoted, allowing the oxides / carbonates / hydroxides of alkali metals and rare earth metals to be better halogenated, forming a composite rare earth halide phase. Simultaneously, the excess ammonium halide can act as a barrier to water and oxygen components in the environment, inhibiting the contact between the small amount of reaction-generated water and the products, thus improving the halogenation effect. During subsequent heating, the excess ammonium halide can be completely volatilized and recovered after high-temperature treatment. After the sample cools, the primary reaction material of the composite rare earth halide is obtained. However, because trace amounts of unreacted raw materials remain in the primary composite rare earth halide material, the water and oxygen content of the primary material is insufficient to meet the performance requirements of high-purity anhydrous raw materials.

[0048] Therefore, the present invention employs a secondary heating halogenation process after mixing the obtained composite rare earth halide primary material with ammonium halide again. This process allows the oxygen elements that did not react during the primary heating halogenation reaction to be fully halogenated, resulting in a final sample with extremely low water and oxygen content.

[0049] Since only ammonium halide sublimates during the entire reaction process, and excess ammonium halide is recovered and reused, alkali metals and rare earth metals are not lost. Therefore, this invention can control the stoichiometric ratio of the final product by accurately weighing the raw materials of each element component, thereby achieving the efficient preparation of different high-purity anhydrous composite rare earth halides.

[0050] The study also found that existing composite rare earth halide scintillation crystals generally use Ce as the base metal. 3+ or Pr 3+As an activating ion, this invention can also directly synthesize single-phase anhydrous composite rare earth halides containing precise activator components. The activator concentration in the rare earth halide raw materials in the final scintillation crystal, scintillation ceramic, or thin film can be adjusted by modifying the raw material ratio as needed. For example, this invention can obtain a composition similar to Cs₂LiY by adding the required molar amounts of cerium salt or praseodymium salt (oxide, carbonate, or hydroxide) to the initial mixture according to the stoichiometric ratio of the final scintillation material through the entire synthesis process. 0.96 Ce 0.04 Cl6 or Cs2LiLa 0.988 Pr 0.002 Ce 0.01 A single-phase high-purity anhydrous composite rare earth halide of Br6. Compared to conventional methods that add each individual halide and activator separately to the ingredients, the method of this invention can directly incorporate the activator component during the synthesis of the composite raw material. This avoids the segregation of the final material composition caused by the inconsistent melting of the halide components during the high-temperature treatment stage (such as the crystal melting process). This has a positive promoting effect on improving the consistency of material performance and batch stability.

[0051] In summary, the embodiments of this invention effectively reduce trace amounts of water and oxygen by employing a primary heating halogenation reaction followed by a secondary halogenation process during the synthesis of raw materials, resulting in high-purity anhydrous composite rare earth halide samples. Compared to the liquid-phase synthesis method under ammonium halide protection, this invention is carried out entirely in an anhydrous inert atmosphere, which facilitates the control of the water and oxygen environment during the synthesis process, effectively suppressing the adsorption and hydrolysis reactions of halides with water molecules in the environment, and yielding samples with ultra-low water content. Simultaneously, the secondary halogenation process can thoroughly remove unreacted oxygen elements from the primary heating halogenation process, further improving the purity of the composite rare earth halide and significantly reducing the water and oxygen content of the material. The high-purity anhydrous composite rare earth halide obtained by this invention not only possesses extremely low water and oxygen content but also extremely high phase purity and compositional uniformity, and can be directly used in the preparation of scintillation crystals, scintillation ceramics, or scintillation films in composite halide systems, contributing to improved batching efficiency and product quality. The high-purity anhydrous composite rare earth halide prepared by this invention has significantly lower water and oxygen content than products obtained by conventional processes. It also features simple preparation process, controllable environmental conditions, and ease of large-scale preparation, providing a good foundation for effectively reducing the production cost of composite scintillation materials and realizing large-scale applications.

[0052] The preparation method of the present invention will be further explained and illustrated below with several embodiments:

[0053] Comparative Example 1: 325.8 g of Cs₂CO₃ (99.99%), 36.9 g of Li₂CO₃ (99.99%), 112.9 g of Y₂O₃ (99.99%), and 642 g of NH₄Br (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for heating and halogenation. The entire reaction process and subsequent operations were carried out under high-purity Ar gas. The reaction temperature was raised from room temperature to 320℃ and held for 4 hours, then raised to 700℃ and held for 3 hours, with a heating rate of 2℃ / min. After cooling, the material was removed to obtain the composite rare earth halide material Cs₂LiYCl₆. The water content of the obtained sample was 25 ppm, and the oxygen content was 260 ppm.

[0054] Comparative Example 2: 325.8 g of Cs₂CO₃ (99.99%), 36.9 g of Li₂CO₃ (99.99%), 162.9 g of La₂O₃ (99.99%), and 1172 g of NH₄Br (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for heating and halogenation. The entire reaction process and subsequent operations were carried out under high-purity Ar gas. The reaction temperature was raised from room temperature to 320 °C and held for 4 hours, then raised to 700 °C and held for 3 hours, with a heating rate of 2 °C / min. After cooling, the material was removed to obtain the composite rare earth halide Cs₂LiLaBr₆. The water content of the obtained sample was 21 ppm, and the oxygen content was 180 ppm.

[0055] Comparative Example 3: 325.8 g of Cs₂CO₃ (99.99%), 112.9 g of Li₂CO₃ (99.99%), and 401 g of NH₄Cl (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for heating and halogenation. The entire reaction process and subsequent operations were carried out under high-purity Ar gas conditions. The reaction temperature was raised from room temperature to 160 °C and held for 10 hours, then raised to 500 °C and held for 5 hours, with a heating rate of 3 °C / min, to obtain a primary composite rare earth halide. The cooled primary mixture was then uniformly mixed with 106 g of NH₄Cl (99.9%) and placed in a tube furnace for a secondary heating and halogenation reaction. The reaction temperature was raised from room temperature to 250 °C and held for 2 hours, then raised to 640 °C and held for 3 hours, with a heating rate of 2 °C / min. After the material is cooled, it is removed, and the remaining product is the high-purity composite rare earth halide Cs₂YCl₅. The tested sample showed a water content of 18 ppm and an oxygen content of 130 ppm.

[0056] Comparative Example 4: 325.8 g of Cs₂CO₃ (99.99%), 162.9 g of La₂O₃ (99.99%), and 732 g of NH₄Br (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for heating and halogenation. The entire reaction process and subsequent operations were carried out under high-purity N₂ gas. The reaction temperature was raised from room temperature to 550 °C and held for 1 hour, then raised to 850 °C and held for 1 hour, with a heating rate of 3 °C / min, to obtain a primary composite rare earth halide. The cooled primary mixture was then uniformly mixed with 161 g of NH₄Br (99.9%) and placed in a tube furnace for a secondary heating and halogenation reaction. The reaction temperature was raised from room temperature to 480 °C and held for 3 hours, then raised to 780 °C and held for 2 hours, with a heating rate of 2 °C / min. After the material is cooled, it is removed, and the remaining product is the high-purity composite rare earth halide Cs2LaBr6. The tested sample had a water content of 13 ppm and an oxygen content of 120 ppm.

[0057] Example 1: 325.8g of Cs₂CO₃ (99.99%), 36.9g of Li₂CO₃ (99.99%), 112.9g of Y₂O₃ (99.99%), and 642g of NH₄Cl (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for a primary heating halogenation reaction. The entire reaction process and subsequent operations were carried out under high-purity Ar gas conditions. The reaction temperature was raised from room temperature to 320°C and held for 4 hours, then raised to 700°C and held for 3 hours, with a heating rate of 2°C / min, to obtain a primary composite rare earth halide. The cooled primary mixture was then uniformly mixed with 172g of NH₄Cl (99.9%) and placed in a tube furnace for a secondary heating halogenation reaction. The reaction temperature was raised from room temperature to 320°C and held for 4 hours, then raised to 700°C and held for 3 hours, with a heating rate of 2°C / min. After the material was cooled, it was removed, and the remaining product was the high-purity composite rare earth halide Cs₂LiYCl₆. The tested sample contained 5 ppm of water and 28 ppm of oxygen.

[0058] Example 2: 325.8g of Cs₂CO₃ (99.99%), 36.9g of Li₂CO₃ (99.99%), 162.9g of La₂O₃ (99.99%), and 1172g of NH₄Br (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for a single-stage halogenation reaction. The entire reaction process and subsequent operations were carried out under high-purity Ar gas. The reaction temperature was raised from room temperature to 400℃ and held for 4 hours, then raised to 720℃ and held for 4 hours, with a heating rate of 2℃ / min, to obtain a primary composite rare earth halide material. The cooled primary material was then uniformly mixed with 267g of NH4Br (99.9%), and then placed in a tube furnace for a secondary heating halogenation reaction. The reaction temperature was raised from room temperature to 420℃ and held for 3 hours, then raised to 720℃ and held for 3 hours, with a heating rate of 2℃ / min. After cooling, the material was removed, and the remaining product was the high-purity composite rare earth halide Cs2LiLaBr6. The sample was tested and found to contain 4 ppm of water and 25 ppm of oxygen.

[0059] Example 3: 325.8g of Cs₂CO₃ (99.99%), 112.9g of Li₂CO₃ (99.99%), and 401g of NH₄Cl (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for a primary heating halogenation reaction. The entire reaction process and subsequent operations were carried out under high-purity Ar gas conditions. The reaction temperature was raised from room temperature to 200℃ and held for 10 hours, then raised to 500℃ and held for 5 hours, with a heating rate of 3℃ / min, to obtain a primary composite rare earth halide. The cooled primary material was then uniformly mixed with 106g of NH₄Cl (99.9%) and placed in a tube furnace for a secondary heating halogenation reaction. The reaction temperature was raised from room temperature to 350℃ and held for 2 hours, then raised to 650℃ and held for 3 hours, with a heating rate of 3℃ / min. After the material is cooled, it is removed, and the remaining product is the high-purity composite rare earth halide Cs₂YCl₅. The tested sample had a water content of 10 ppm and an oxygen content of 49 ppm.

[0060] Example 4: 325.8g of Cs₂CO₃ (99.99%), 162.9g of La₂O₃ (99.99%), and 732g of NH₄Br (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for a primary heating halogenation reaction. The entire reaction process and subsequent operations were carried out under high-purity N₂ gas. The reaction temperature was raised from room temperature to 350°C and held for 6 hours, then raised to 650°C and held for 4 hours, with a heating rate of 3°C / min, to obtain a primary composite rare earth halide. The cooled primary mixture was then uniformly mixed with 161g of NH₄Br (99.9%) and placed in a tube furnace for a secondary heating halogenation reaction. The reaction temperature was raised from room temperature to 450°C and held for 2 hours, then raised to 750°C and held for 2 hours, with a heating rate of 3°C / min. After the material is cooled, it is removed, and the remaining product is the high-purity composite rare earth halide Cs₂LaBr₆. The tested sample showed a water content of 4 ppm and an oxygen content of 45 ppm.

[0061] Example 5: 138.2g of K2CO3 (99.99%), 162.9g of La2O3 (99.99%), and 1221g of NH4Br (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for a primary heating halogenation reaction. The entire reaction process and subsequent operations were carried out under high-purity Ar gas conditions. The reaction temperature was raised from room temperature to 500℃ and held for 1 hour, then raised to 750℃ and held for 1 hour, with a heating rate of 3℃ / min, to obtain a primary composite rare earth halide. The cooled primary material was then uniformly mixed with 62g of NH4Br (99.9%) and placed in a tube furnace for a secondary heating halogenation reaction. The reaction temperature was raised from room temperature to 320℃ and held for 3 hours, then raised to 710℃ and held for 2 hours, with a heating rate of 3℃ / min. After the material is cooled, it is removed, and the remaining product is the high-purity composite rare earth halide K2LaBr5. The tested sample had a water content of 5 ppm and an oxygen content of 50 ppm.

[0062] Example 6: 138.2g of K2CO3 (99.99%), 162.9g of La2O3 (99.99%), and 1666g of NH4I (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for a primary heating halogenation reaction. The entire reaction process and subsequent operations were carried out under high-purity Ar gas conditions. The reaction temperature was raised from room temperature to 340℃ and held for 7 hours, then raised to 760℃ and held for 2 hours, with a heating rate of 3℃ / min, to obtain a primary composite rare earth halide. The cooled primary material was then uniformly mixed with 170g of NH4Br (99.9%) and placed in a tube furnace for a secondary heating halogenation reaction. The reaction temperature was raised from room temperature to 380℃ and held for 3.5 hours, then raised to 720℃ and held for 3 hours, with a heating rate of 2℃ / min. After the material is cooled, it is removed, and the remaining product is the high-purity composite rare earth halide K2LaI5. The tested sample had a water content of 8 ppm and an oxygen content of 43 ppm.

[0063] Example 7: 36.9g of Li₂CO₃ (99.99%), 187.3g of Gd₂O₃ (99.99%), and 1172g of NH₄Cl (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for a primary heating halogenation reaction. The entire reaction process and subsequent operations were carried out under high-purity Ar gas conditions. The reaction temperature was raised from room temperature to 320°C and held for 5 hours, then raised to 580°C and held for 5 hours, with a heating rate of 2.5°C / min, to obtain a primary composite rare earth halide. The cooled primary mixture was then uniformly mixed with 153g of NH₄Cl (99.9%) and placed in a tube furnace for a secondary heating halogenation reaction. The reaction temperature was raised from room temperature to 300°C and held for 4 hours, then raised to 660°C and held for 2 hours, with a heating rate of 2°C / min. After the material is cooled, it is removed, and the remaining product is the high-purity composite rare earth halide LiGdCl4. The sample was tested and found to have a water content of 9 ppm and an oxygen content of 40 ppm.

[0064] Example 8: 488.7g of Cs₂CO₃ (99.99%), 154.8g of La₂O₃ (99.99%), 8.5g of Ce₂O₃ (99.99%), and 578g of NH₄Cl (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for a single-stage halogenation reaction. The entire reaction process and subsequent operations were carried out under high-purity Ar gas conditions. The reaction temperature was raised from room temperature to 330℃ and held for 7 hours, then raised to 650℃ and held for 3 hours, with a heating rate of 2℃ / min, to obtain a primary composite rare earth halide material. The cooled primary material was then uniformly mixed with 300g of NH4Br (99.9%), and then placed in a tube furnace for a secondary heating halogenation reaction. The reaction temperature was raised from room temperature to 330℃ and held for 3 hours, then raised to 670℃ and held for 2.5 hours, with a heating rate of 2℃ / min. After cooling, the material was removed, and the remaining product was the high-purity complex rare earth halide Cs3La. 0.95 Ce 0.05 Cl6. The tested sample contained 7 ppm of water and 46 ppm of oxygen.

[0065] Example 9: 488.7g of Cs₂CO₃ (99.99%), 154.8g of La₂O₃ (99.99%), 8.5g of Ce₂O₃ (99.99%), and 1114g of NH₄Br (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for a single-stage halogenation reaction. The entire reaction process and subsequent operations were carried out under high-purity Ar gas. The reaction temperature was raised from room temperature to 450℃ and held for 3 hours, then raised to 710℃ and held for 4 hours, with a heating rate of 2℃ / min, to obtain a primary composite rare earth halide material. The cooled primary material was then uniformly mixed with 305g of NH4Br (99.9%), and then placed in a tube furnace for a secondary heating halogenation reaction. The reaction temperature was raised from room temperature to 440℃ and held for 4 hours, then raised to 750℃ and held for 5 hours, with a heating rate of 3℃ / min. After cooling, the material was removed, and the remaining product was the high-purity complex rare earth halide Cs3La. 0.95 Ce 0.05 Br6. The tested sample contained 4 ppm of water and 24 ppm of oxygen.

[0066] Example 10: 488.7g of Cs₂CO₃ (99.99%), 389.4g of Lu₂CO₃ (99.99%), 17g of Ce₂O₃ (99.99%), and 1695g of NH₄I (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for a single-stage halogenation reaction. The entire reaction process and subsequent operations were carried out under high-purity N₂ gas. The reaction temperature was raised from room temperature to 450°C and held for 5 hours, then raised to 800°C and held for 1 hour, with a heating rate of 3°C / min, to obtain a primary composite rare earth halide material. The cooled primary material was then uniformly mixed with 566g of NH4I (99.9%), and then placed in a tube furnace for a secondary heating halogenation reaction. The reaction temperature was raised from room temperature to 450℃ and held for 3 hours, then raised to 750℃ and held for 2 hours, with a heating rate of 2℃ / min. After cooling, the material was removed, and the remaining product was the high-purity composite rare earth halide Cs3Lu. 1.9 Ce 0.1 I9. The tested sample contained 6 ppm of water and 35 ppm of oxygen.

[0067] Example 11: 325.8g of Cs₂CO₃ (99.99%), 36.9g of Li₂CO₃ (99.99%), 108.4g of Y₂O₃ (99.99%), 6.8g of Ce₂O₃ (99.99%), and 834g of NH₄Cl (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for a single-stage halogenation reaction. The entire reaction process and subsequent operations were carried out under high-purity Ar gas conditions. The reaction temperature was raised from room temperature to 350°C and held for 9 hours, then raised to 780°C and held for 3 hours, with a heating rate of 2°C / min, to obtain a primary composite rare earth halide material. The cooled primary material was then uniformly mixed with 288g of NH4Cl (99.9%), and then placed in a tube furnace for a secondary heating halogenation reaction. The reaction temperature was raised from room temperature to 350℃ and held for 3 hours, then raised to 680℃ and held for 4 hours, with a heating rate of 2℃ / min. After cooling, the material was removed, and the remaining product was the high-purity composite rare earth halide Cs2LiY. 0.96 Ce 0.04 Cl6. The tested sample contained 8 ppm of water and 30 ppm of oxygen.

[0068] Example 12: 325.8g of Cs₂CO₃ (99.99%), 36.9g of Li₂CO₃ (99.99%), 156.4g of La₂O₃ (99.99%), 6.8g of Ce₂O₃ (99.99%), and 1114g of NH₄Br (99.9%) were accurately weighed and uniformly mixed. The mixture was then transferred to a quartz crucible and placed in a tube furnace for a single-stage halogenation reaction. The entire reaction process and subsequent operations were carried out under high-purity Ar gas conditions. The reaction temperature was raised from room temperature to 380℃ and held for 8 hours, then raised to 750℃ and held for 2 hours, with a heating rate of 3℃ / min, to obtain a primary composite rare earth halide material. The cooled primary material was then uniformly mixed with 356g of NH4Br (99.9%), and then placed in a tube furnace for a secondary heating halogenation reaction. The reaction temperature was raised from room temperature to 440℃ and held for 4 hours, then raised to 740℃ and held for 5 hours, with a heating rate of 2℃ / min. After cooling, the material was removed, and the remaining product was the high-purity complex rare earth halide Cs2LiLa. 0.96 Ce 0.04 Br6. The tested sample contained 5 ppm of water and 29 ppm of oxygen.

[0069] Example 13: Accurately weigh 325.8g Cs2CO3 (99.99%), 36.9g Li2CO3 (99.99%), 161.1g La2O3 (99.99%), 1.7g Ce2O3 (99.99%), 1.7g Ce2O3 (99.99%), and 0.4g Pr6O 11 1231g of NH4Br (99.99%) and 1231g of NH4Br (99.9%) were uniformly mixed, and then the mixture was transferred to a quartz crucible and placed in a tube furnace for a primary heating halogenation reaction. The entire reaction process and subsequent operations were carried out under high-purity Ar gas conditions. The reaction temperature was raised from room temperature to 480℃ and held for 2 hours, and then raised to 680℃ and held for 5 hours, with a heating rate of 2℃ / min, to obtain the primary material of the composite rare earth halide. The cooled primary material was then uniformly mixed with 178g of NH4Br (99.9%), and then placed in a tube furnace for a secondary heating halogenation reaction. The reaction temperature was raised from room temperature to 350℃ and held for 3 hours, and then raised to 670℃ and held for 3 hours, with a heating rate of 2℃ / min. After the material cooled, it was removed, and the remaining product was the high-purity composite rare earth halide Cs2LiLa. 0.988 Pr 0.002 Ce 0.01 Br6. The tested sample contained 8 ppm of water and 46 ppm of oxygen.

[0070] By comparing the experimental results of Comparative Examples 1-4 with those of Examples 1-13, it is clear that the secondary halogenation process used in this application has significant technical effects in the preparation of high-purity composite rare earth halides. Comparative Examples 1-4, which only underwent a single halogenation reaction or used different reaction conditions, yielded products with high oxygen content, all above 100 ppm (up to 260 ppm), and relatively high water content, all above 10 ppm (up to 25 ppm). In contrast, Examples 1-13, after the initial halogenation reaction, all added a secondary halogenation step. By optimizing the reaction temperature, holding time, and ammonium halide addition, the final products showed significantly reduced oxygen and water content: oxygen content generally dropped below 50 ppm (minimum 24 ppm), and water content dropped below 10 ppm (minimum 4 ppm), far superior to the results of the comparative examples. This indicates that the secondary halogenation process can effectively remove residual oxygen and moisture from the intermediate products, improving the purity and stability of the products. Therefore, the preparation method of this application, by introducing and optimizing the secondary halogenation process, achieves precise control over the purity of the composite rare earth halide product, and has outstanding technical advantages and promising industrial application prospects.

[0071] Accordingly, a second aspect of the present invention provides a high-purity anhydrous composite rare earth halide, prepared based on the above-described method for preparing high-purity anhydrous composite rare earth halides, wherein the general formula of the composite rare earth halide is A. x RE y X x+3y Wherein A is one or more of the alkali metal elements Li, Na, K, Rb, and Cs; RE is one or more of the rare earth elements La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, and Y; and X is one of the halogen elements Cl, Br, and I; wherein 1≤x≤3 and 1≤y≤2; the purity of the high-purity anhydrous composite rare earth halide is ≥99.9%, the water content is ≤10ppm, and the oxygen content is ≤50ppm.

[0072] The aforementioned high-purity anhydrous composite rare earth halide was obtained using the preparation method described above, and it possesses a potassium cryolite structure. In terms of chemical composition alone, the general formula of the composite rare earth halide is A. x RE y X x+3y Where A is one or more of the alkali metal elements Li, Na, K, Rb, and Cs; RE is one or more of the rare earth elements La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, and Y; X is one of the halogen elements Cl, Br, and I; and x and y are both integers or non-integers, satisfying 1≤x≤3 and 1≤y≤2.

[0073] More specifically, the high-purity anhydrous composite rare earth halides obtained by the preparation method described above can be any of the following halides: Cs₂YCl₅, Cs₂LaBr₅, K₂LaCl₅, LiCeCl₄, K₂LaBr₅, K₂LaI₅, K₂LaBr₄I, K₂LaBr₃I₂, RbGd₂Br₇, Cs₂LiLaCl₆, Cs₂LiLaBr₆, Cs₂LiYCl₆, Cs₂LiLaBr₆, Rb₂LiYCl₆, Cs₂LiYBr₆, Cs₃GdBr₆, Cs₃NaGdBr₆, Cs₂NaGdBr₆, Cs₃GdCl₆, Cs₂NaGdCl₆, LiGdCl₄, NaGdCl₄, LiGd 0.8 Ce 0.2 Cl4, NaCeCl4, NaGd 0.8 Ce 0.2 Cl4, RbCe2Br7, RbGd 1.8 Ce 0.2 Br7, K2CeCl5, K2La 0.9 Ce 0.1 Cl5, K2CeBr5, K2La 0.9 Ce 0.1 Br5, K2CeI5, K2La 0.9 Ce 0.1 I5, Ce3CeCl6, Cs3Gd 0.95 Ce 0.05 Cl6, Cs3CeBr6, Cs3Gd 0.95 Ce 0.05 Br6, Cs3CeI6, Cs3Gd 0.95 Ce 0.05 I6, Cs3CeCl6, Cs3La 0.95 Ce 0.05 Cl6, Cs3LaBr6, Cs3CeBr6, Cs3La 0.95 Ce 0.05 Br6, Cs3CeI6, Cs3La 0.95 Ce 0.05 I6, Cs3Ce2I9, Cs3Gd 1.9 Ce 0.1 I9, Cs3Lu2I9, Cs3Lu 1.9 Ce 0.1 I9, Cs2LiY 0.96 Ce 0.04 Cl6, Cs2LiLa 0.96 Ce 0.04 Br6,Cs2LiLa 0.989 Pr 0.001 Ce 0.01Br6,Cs2LiLa 0.96 Ce 0.04 Br6,Cs2LiLa 0.988 Pr 0.002 Ce 0.01 Br6.

[0074] Furthermore, in terms of purity, the high-purity anhydrous composite rare earth halide obtained by the present invention has a purity ≥99.9%, a water content ≤10ppm, and an oxygen content ≤50ppm; preferably, the water content ≤8ppm and the oxygen content ≤40ppm; more preferably, the water content ≤4ppm and the oxygen content ≤30ppm; which can meet the raw material requirements for the preparation of scintillation crystals, scintillation ceramics or thin film materials.

[0075] Of course, the high-purity anhydrous composite rare earth halides obtained by the preparation method described above are not rare earth compounds with limited purity, but rather rare earth materials that can meet the application needs of fields such as high-energy physics, nuclear medicine, industrial non-destructive testing, and homeland security. This material not only has high purity and a clean phase, but also its stoichiometric composition is precisely controllable, significantly distinguishing it from other known materials in the prior art.

[0076] Accordingly, a third aspect of the present invention provides a scintillation crystal, scintillation ceramic, or scintillation thin film material comprising the above-mentioned high-purity anhydrous composite rare earth halide.

[0077] The embodiments of this invention aim to protect a high-purity anhydrous composite rare earth halide and its preparation method, which have the following effects:

[0078] 1. A solid-state heating halogenation method is used to synthesize composite rare earth halide raw materials. The resulting samples have uniform phase purity and composition and can be directly used for the growth of composite rare earth halide scintillation crystals or the preparation of scintillation ceramics. This avoids the problems of high cost, complicated operation, and component segregation caused by using single rare earth halides and alkali metal halides as raw materials.

[0079] 2. Through a two-step halogenation process, especially the second halogenation step, trace oxygen impurities that are difficult to eliminate by a single halogenation can be targeted and removed, and the oxygen content of the final sample can be stably controlled below 50 ppm.

[0080] 3. By adopting a solid-phase reaction synthesis system, the influence of environmental water is eliminated, which is conducive to creating an anhydrous and oxygen-free environment throughout the synthesis process. This allows the bound water in the product to be completely removed and its reabsorption to be inhibited, resulting in a sample with a water content of less than 10 ppm.

[0081] 4. The process involved is simple. The reactant ammonium halide can be completely removed by heating and sublimation, which can effectively reduce the risk of introducing impurities during the synthesis process and finally obtain a high-purity product. Furthermore, the halogenation process is divided into two steps, which facilitates independent optimization and control of each step, improves the stability and repeatability of the process, and can be widely used in the deep purification of various complex rare earth halides.

[0082] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for preparing high-purity anhydrous composite rare earth halides, characterized in that, The general formula of the composite rare earth halide is A x RE y X x+3y Where A is an alkali metal element, RE is a rare earth element, X is a halogen element, 1≤x≤3, 1≤y≤2, and the preparation method includes the following steps: Alkali metal carbonates or hydroxides, rare earth metal oxides or carbonates or hydroxides, and a first portion of ammonium halide are uniformly mixed in a first preset ratio to obtain a first mixture. The first mixture is subjected to a halogenation reaction under an inert atmosphere to obtain a primary composite rare earth halide material. The composite rare earth halide primary material is uniformly mixed with the second part of ammonium halide in a second preset ratio to obtain the second mixture. The second mixture was subjected to a secondary heating and halogenation reaction in an inert atmosphere to obtain a high-purity anhydrous rare earth composite halide.

2. The method for preparing high-purity anhydrous composite rare earth halides according to claim 1, characterized in that, The first preset ratio is: the molar ratio of the alkali metal carbonate or hydroxide, the rare earth metal oxide or carbonate or hydroxide, and the first part of ammonium halide is A:RE:NH4X=x / y:1:q, where x+3y<q≤3(x+3y).

3. The method for preparing high-purity anhydrous composite rare earth halides according to claim 1, characterized in that, The step of subjecting the first mixture to a single heating halogenation reaction in an inert atmosphere includes: The first mixture is placed in a quartz or ceramic container and subjected to a heating halogenation reaction under an inert atmosphere according to the first preset heating conditions. The first preset heating conditions are: first heat to 200℃~500℃ and then keep warm for 1 hour~10 hours, then heat to 500℃~800℃ and then keep warm for 1 hour~5 hours.

4. The method for preparing high-purity anhydrous composite rare earth halides according to claim 3, characterized in that, The first preset heating conditions are: heating to 300℃~450℃ and holding for 3 to 5 hours, then heating to 650℃~750℃ and holding for 2 to 3 hours.

5. The method for preparing high-purity anhydrous composite rare earth halides according to claim 1, characterized in that, The second preset ratio is: the mass of the second part of ammonium halide is 10% to 50% of the mass of the primary material of the composite rare earth halide.

6. The method for preparing high-purity anhydrous composite rare earth halides according to claim 1, characterized in that, The second mixture undergoes a secondary heating and halogenation reaction in an inert atmosphere, comprising: The second mixture is placed in a quartz or ceramic container and subjected to a secondary heating halogenation reaction under an inert atmosphere according to the second preset heating conditions. The second preset heating conditions are: first heat to 300℃~450℃ and then keep warm for 2 hours~4 hours, then heat to 650℃~750℃ and keep warm for 2 hours~5 hours.

7. The method for preparing high-purity anhydrous composite rare earth halides according to any one of claims 1-6, characterized in that, The inert atmosphere includes nitrogen or argon.

8. The method for preparing high-purity anhydrous composite rare earth halides according to any one of claims 1-6, characterized in that, The purity of the high-purity anhydrous composite rare earth halide is ≥99.9%, the water content is ≤10ppm, and the oxygen content is ≤50ppm.

9. A high-purity anhydrous composite rare earth halide, characterized in that, The high-purity anhydrous composite rare earth halide is prepared according to any one of the methods described in claims 1-8, and the general formula of the composite rare earth halide is A. x RE y X x+3y Where A is one or more of the alkali metal elements Li, Na, K, Rb, and Cs; RE is one or more of the rare earth elements La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, and Y; and X is one of the halogen elements Cl, Br, and I, wherein 1≤x≤3 and 1≤y≤2. The purity of the high-purity anhydrous composite rare earth halide is ≥99.9%, the water content is ≤10ppm, and the oxygen content is ≤50ppm.

10. A scintillation crystal, scintillation ceramic, or scintillation thin film material, characterized in that, It contains the high-purity anhydrous composite rare earth halide as described in claim 9.

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