Method for synthesizing fluor-carbon thorianite single crystal under high temperature and high pressure

Abstract

The application discloses a method for synthesizing fluorocarnotite monocrystal under high temperature and high pressure, and relates to the technical field of rare earth minerals.The method uses TmCl3*6H2O, NaF and Na2CO3 as raw materials, and performs a stage type temperature rising reaction under a predetermined pressure, so that the obtained fluorocarnotite monocrystal is a pure substance and has good chemical stability, and the technical problem of difficult growth of fluorocarnotite monocrystal at present is solved.In addition, the method has the advantages of simple operation process, easy control of conditions and the like.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of rare earth ore, in particular to a method for synthesizing monocrystal of fluorcarbonate monazite under high temperature and high pressure. BACKGROUND

[0002] Rare earth elements are the general term of 17 elements in the periodic table, including lanthanum series elements and scandium and yttrium. Due to the special physical properties such as light, electricity and magnetism, the rare earth elements are often used as additives of other compounds and / or metal alloys, and are used to form new materials with different properties and various types, which are widely applied to many fields such as national defense and military industry, aerospace, clean energy, information technology, industrial catalysis, special materials, energy and agriculture, and have important strategic significance for national economy, national security and scientific and technological development.

[0003] In today's world, one out of every six new technologies invented is related to rare earth elements. Since the rare earth elements have very important applications in high-tech industries, only a small amount is needed to improve or enhance the performance of the final product, and they are called industrial "vitamins" and are also known as the "hope of the earth" of human beings. As the use of rare earth elements in various industries is becoming more and more extensive, their importance is growing, and they have become a key and strategic mineral resource for global economic development and social progress.

[0004] At present, more than 250 kinds of rare earth minerals have been found in nature, among which more than 60 kinds of minerals have high content of rare earth metal elements, and more than 20 kinds of the most important rare earth minerals include monazite, bastnaesite, parisite, xenotime, gadoelite, and fergusonite. However, with the continuous exploitation of rare earth deposits, the amount of rare earth resources shows a significant downward trend, and strengthening the research on rare earth ore is an important way to maintain rare earth resources.

[0005] Rare earth fluorocarbonate minerals are a very important class of rare earth minerals, and in many large rare earth deposits, rare earth fluorocarbonate minerals are the main ore minerals. Among the rare earth fluorocarbonate minerals, bastnaesite is one of the most widely distributed rare earth minerals.

[0006] At present, for common light rare earth bastnaesite such as bastnaesite (cerium), bastnaesite (lanthanum), bastnaesite (praseodymium), bastnaesite (neodymium) and the like, people have carried out relatively detailed research on their chemical synthesis, crystal structure, thermodynamic properties and solubility. However, the crystal structure and thermodynamic properties of most heavy rare earth bastnaesite (such as bastnaesite (holmium), bastnaesite (erbium), bastnaesite (thulium), bastnaesite (ytterbium), bastnaesite (yttrium), bastnaesite (lutetium) and the like) have not been well studied, which greatly hinders people's understanding of the enrichment, migration and mineralization of rare earth elements in nature, as well as the differentiation mechanism of light and heavy rare earths.

[0007] Thulium: atomic number 69, relative atomic mass 168.9, appearance is silver-white, melting point 1545℃, density 9.32g / cm 3 Stable in air, with certain ductility, the use includes medical X-ray machine ray source, fluorescent powder activator, metal halogen lamp additive, and can also be used for clinical diagnosis and treatment of tumors. Thulium is two hundred thousandth in the crust, is one of the rare earth elements with the least content, widely used in high-strength power light source, laser, high-temperature superconductor and other fields.

[0008] Thulium can be applied to clinical diagnosis and treatment of tumors because it has high affinity for tumor tissue, and heavy rare earth has greater affinity than light rare earth, especially thulium has the greatest affinity. Thulium is used as an activator in the fluorescent powder of the X-ray intensifying screen to enhance the optical sensitivity, thereby reducing the irradiation and harm of X-rays to humans. Compared with the previous calcium tungstate intensifying screen, the X-ray dose can be reduced by 50%, which has important practical significance in medical applications.

[0009] Tm 3+ When added to glass, it can be made into rare earth glass laser material, which is currently the solid laser material with the largest output pulse and the highest output power. Tm 3+ It can also be used as an active ion of rare earth up-conversion laser material.

[0010] Previous studies on the formation mechanism of fluorcarbonate cerium (thulium) are relatively few, and there is no report on the growth of artificial fluorcarbonate cerium (thulium) single crystal and its crystal structure data. Therefore, exploring the method for synthesizing high-purity fluorcarbonate cerium (thulium) single crystal is an important prerequisite and foundation for further studying the crystal structure characteristics and formation mechanism of fluorcarbonate cerium (thulium). SUMMARY

[0011] The purpose of the present application is to provide a method for synthesizing fluorcarbonate thulium single crystal under high temperature and high pressure, to solve the technical problem of difficult growth of heavy rare earth fluorcarbonate cerium single crystal at present, and the method has the advantages of simple operation, easy control of conditions, etc.

[0012] To achieve the above-mentioned purpose, the present application provides the following scheme:

[0013] The present application provides a method for synthesizing fluorcarbonate thulium single crystal, comprising the following steps:

[0014] TmCl3·6H2O, NaF and Na2CO3 are mixed in a chemical reaction molar dosage ratio, and the obtained mixture is kept at a first temperature, a second temperature and a third temperature for 45 min respectively under pressure conditions, and then kept at a fourth temperature for 100 h to obtain the fluorcarbonate thulium single crystal;

[0015] The first temperature is 100-150 DEG C, the second temperature is 300-350 DEG C, the third temperature is 500-550 DEG C, and the fourth temperature is 650-850 DEG C.

[0016] Further, the pressure value of the pressure condition is 1.2-1.8 GPa.

[0017] Further, the pressure is increased to the preset pressure value at a pressure increasing rate of 0.2 GPa / 30 min under normal pressure.

[0018] Further, the molar ratio of TmCl3.6H2O, NaF and Na2CO3 is 1:1:1.

[0019] Further, the purity grade of TmCl3.6H2O, NaF and Na2CO3 is analytical pure or above.

[0020] Further, the purity of TmCl3.6H2O, NaF and Na2CO3 is all greater than 99.99%.

[0021] Further, the temperature increasing rate is controlled to be 15 DEG C / min, so that the temperature is sequentially increased from the first temperature to the second temperature, the third temperature and the fourth temperature.

[0022] Further, the heat preservation process of the mixture is carried out in a large cavity press.

[0023] Further, the mixture is placed in a high temperature and high pressure synthesis assembly block; the high temperature and high pressure synthesis assembly block comprises pyrophyllite as a pressure transmission medium, a graphite tube as a heating furnace and a thermocouple for temperature control.

[0024] Further, the thermocouple is an S-type thermocouple.

[0025] In the application, fluorcarboniite is heavy rare earth fluorcarbonate (thulium).

[0026] The application combines the related disciplines of rare earth mineralogy, crystal chemistry, rare earth element geochemistry, crystallography and mineralogy, crystal optics, optical mineralogy and crystal materials, and simulates the formation process of fluorcarbonate (thulium) single crystal under high temperature and high pressure conditions based on the principle that fluorcarbonate (thulium) is slowly formed under the oxidation and reduction conditions in the earth interior.

[0027] The application adopts a large cavity press equipment, and the main chemical reaction equation involved is as follows:

[0028] TmCl3.6H2O+NaF+Na2CO3→Tm(CO3)F+3NaCl+6H2O

[0029] The present application provides thulium element indispensable for synthesizing fluorcarbonate (thulium) single crystal under high temperature and high pressure conditions, in which the selected initial raw material is solid thulium (III) chloride hexahydrate [molecular formula: TmCl3·6H2O]. The initial raw material solid sodium fluoride [molecular formula: NaF] provides fluorine element indispensable for synthesizing fluorcarbonate (thulium) single crystal. The initial raw material solid anhydrous sodium carbonate [molecular formula: Na2CO3] provides carbonate radical indispensable for synthesizing fluorcarbonate (thulium) single crystal.

[0030] The temperature and pressure conditions and the corresponding stepwise heating mode of the present application can promote the dehydration of TmCl3·6H2O, so as to form a fluid environment in the sample cavity, and promote the growth of single crystal samples.

[0031] The present application discloses the following technical effects:

[0032] Compared with natural fluorcarbonate (thulium), the purity of natural fluorcarbonate (thulium) is difficult to reach 70% due to the presence of other impurities. The fluorcarbonate (thulium) single crystal obtained in the process of growing fluorcarbonate (thulium) single crystal of the present application is a pure substance and has good chemical stability, which solves the technical problem of the difficulty in growing fluorcarbonate (thulium) single crystal at present. In addition, the method of the present application has the advantages of simple operation process and easy control of conditions. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0034] Figure 1 A schematic diagram of a case of high temperature and high pressure sample synthesis assembly of the present application;

[0035] Figure 2 A microscopic photograph of the heavy rare earth fluorcarbonate (thulium) single crystal sample synthesized in Example 1;

[0036] Figure 3 A Raman spectrum of the heavy rare earth fluorcarbonate (thulium) single crystal sample synthesized in Example 1;

[0037] Figure 4 A synchrotron single crystal diffraction spectrum of the heavy rare earth fluorcarbonate (thulium) single crystal sample synthesized in Example 1. DETAILED DESCRIPTION

[0038] The following detailed description of various exemplary embodiments of the application will not be considered limiting of the application, but rather a description of certain aspects, features, and embodiments of the application.

[0039] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Additionally, for a range of values of a parameter, unless otherwise stated, each intervening value of the parameter is also specifically included within the scope of the application. The intervening values of the parameter are combined with a stated value of the parameter in range form. These are only exemplary of the various preferred embodiments and are not intended to be limiting of the application. Additionally, other variations that are within the spirit of the application will be apparent to those skilled in the art and can be made without departing from the scope or spirit of the application.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All publications mentioned in this specification are herein incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. The citation of any reference is not construed as an admission that it is prior art with respect to the present application.

[0041] Many modifications and variations of this application can be made in the light of the above teachings without departing from the spirit and scope thereof. Other implementations of this application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The examples and embodiments described herein are exemplary only and are not intended to be limiting.

[0042] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional, unrecited elements or method steps.

[0043] The high-temperature and high-pressure synthesis fluorocarnotite of the present application comprises the following steps:

[0044] Step 1, using TmCl3·6H2O, NaF, Na2CO3 powder as starting material, grinding in a sufficient amount in a marver mortar according to the stoichiometric molar ratio of 1:1:1;

[0045] Step 2, using a tablet press to press the mixture powder into a shape, then filling the sample after pressing into a platinum sample tube, and sealing both ends using a welding gun;

[0046] Step 3, assembling the platinum sample tube in a high-temperature and high-pressure synthesis assembly block;

[0047] Step 4, placing the high-temperature and high-pressure synthesis assembly block in a six-surface top press to perform high-temperature and high-pressure reaction, and the high-temperature and high-pressure reaction process is:

[0048] The pressure is increased to the preset maximum pressure (1.2-1.8 GPa) at a pressure increasing rate of 0.2 GPa / 30 min under normal pressure, and then stepwise heating is performed: the temperature is increased to 100 DEG C, 300 DEG C, 500 DEG C and the maximum temperature (650-850 DEG C) at a temperature increasing rate of 15 DEG C / min, respectively, and the temperature is maintained at 100 DEG C, 300 DEG C and 500 DEG C for 45 min, respectively, and the reaction is performed at the maximum temperature for 100 h.

[0049] Step 5: the platinum-gold sample tube after the reaction is taken out, and a diamond cutter is used to open the platinum-gold sample tube to obtain a fluorcarbonatite (thulium) single crystal.

[0050] The fluorcarbonatite (thulium) single crystal obtained in step 5 is a single phase without impurity phases.

[0051] The fluorcarbonatite (thulium) single crystal prepared by the method has a hexagonal crystal structure, a space group of P-62c, and cell parameters of a = 0.5 nm, c = 1.2 nm, and V = 0.3 nm3. The crystal has a hexagonal plate shape, and the average size is 50-100 mu m, and the maximum size is 150 mu m.

[0052] In step 3, the platinum-gold sample tube is assembled in the high-temperature and high-pressure synthesis assembly block as follows:

[0053] A hole is drilled in the center of the pyrophyllite block on a lathe, and then the graphite heating tube is inserted into the hole, and then the alumina insulation tube is inserted into the graphite heating tube, and then the platinum-gold sample tube is inserted into the middle of the alumina insulation tube, and finally the pyrophyllite plug is used to seal the upper and lower ends of the graphite heating tube.

[0054] The high-temperature and high-pressure synthesis assembly block is provided with thermocouples. The temperature in the sample cavity is calibrated by using S-type thermocouples during high temperature and high pressure. The S-type thermocouple is a platinum-rhodium 10-platinum thermocouple, which is a noble metal thermocouple. The nominal chemical composition of the positive electrode (SP) is a platinum-rhodium alloy, which contains 10% rhodium and 90% platinum. The negative electrode (SN) is pure platinum. The long-term maximum use temperature of the thermocouple is 1300 DEG C, and the short-term maximum use temperature is 1600 DEG C. The S-type thermocouple has the highest accuracy, the best stability, the widest temperature measurement range, and the longest service life in the thermocouple series. It has good physical and chemical properties, good thermoelectric potential stability and good oxidation resistance at high temperature, and is suitable for use in oxidizing and inert atmospheres. Each set of S-type thermocouples is symmetrically placed in the middle of the outer wall of the sample cavity (the outer wall of the alumina insulation tube), which realizes the temperature calibration in the sample cavity.

[0055] In the high-temperature and high-pressure assembly block of the present application, pyrophyllite is used as a pressure transmission medium, graphite tube is used as a heating furnace, and thermocouples are used as a temperature control device.

[0056] The size of the high-temperature and high-pressure assembly block can be determined according to the size of the sample loaded in the platinum sample tube, Figure 1 A schematic diagram of a case of the high-temperature and high-pressure sample synthesis assembly of the application.

[0057] The high-temperature and high-pressure assembly block has the following advantages: ①The thermocouple is used for temperature control, and the heating system adjusts the heating power through the temperature feedback of the thermocouple to change the temperature. This method can realize instant monitoring of the temperature and is suitable for experiments with high requirements for temperature measurement accuracy; ②The pyrophyllite has good pressure transmission, machinability, heat resistance, heat preservation and insulation; ③The graphite tube is used as a heating furnace, and the temperature uniformity is high.

[0058] The application will be further described in detail in combination with the embodiments.

[0059] In the embodiments of the application, the purity of TmCl3·6H2O powder is >99.99%, the purity of NaF powder is >99.99%, and the purity of Na2CO3 powder is >99.99%.

[0060] Embodiment 1

[0061] (1) TmCl3·6H2O, NaF and Na2CO3 powders are mixed and ground uniformly according to the stoichiometric molar ratio of 1:1:1 to serve as starting materials;

[0062] (2) The mixture powder (about 180 mg) is pressed into a cylinder (Φ4 mm×4 mm) using a powder tablet press, and the sample is inserted into a platinum tube with a diameter of Φ4 mm, a height of 4 mm and a wall thickness of 0.2 mm, and the two ends are sealed using a welding gun;

[0063] (3) The platinum sample tube is assembled in the high-temperature and high-pressure synthesis assembly block:

[0064] ①A circular through hole with a diameter of 14 mm is punched in the center of a 32.5 mm×32.5 mm×32.5 mm pyrophyllite block;

[0065] ②A graphite heating tube with an outer diameter of 14 mm and an inner diameter of 12 mm is sleeved in the circular through hole of the pyrophyllite block;

[0066] ③An alumina insulation tube with an outer diameter of 12 mm and an inner diameter of 4 mm is placed in the graphite heating tube;

[0067] ④The platinum sample tube is placed in the middle of the alumina insulation tube, and the upper and lower ends are sealed with pyrophyllite plugs with a diameter of 4 mm;

[0068] (4) Put the high temperature and high pressure synthesis assembly block into the six-surface top press machine to carry out high temperature and high pressure reaction (the reaction process is controlled by thermocouple): under normal pressure, increase the pressure to the preset maximum pressure (1.2 GPa) at a pressure increasing rate of 0.2 GPa / 30 min, and then increase the temperature in steps: increase the temperature to 100℃, 300℃, 500℃ and the maximum temperature (650℃) respectively at a temperature increasing rate of 15℃ / min, and keep the temperature at 100℃, 300℃, 500℃ for 45 min respectively, and keep the temperature at the maximum temperature for 100 h.

[0069] (5) After the high temperature and high pressure reaction is completed, take out the obtained sample, open the platinum sample tube using a diamond cutter, and take out the fluorcarbonate cerite (thulium) single crystal under a stereomicroscope after the sample is naturally air-dried.

[0070] The fluorcarbonate cerite (thulium) single crystal obtained in Example 1 has a hexagonal crystal structure, a space group of P-62c, and cell parameters of a = 1.2 nm, c = 0.7 nm. The crystal has a hexagonal plate shape, an average size of 50-100 μm, and a maximum size of 150 μm.

[0071] Figure 2 A microscopic photograph of the heavy rare earth fluorcarbonate cerite (thulium) single crystal sample synthesized in Example 1 is shown in Figure 1.

[0072] Figure 3 A Raman spectrum of the heavy rare earth fluorcarbonate cerite (thulium) single crystal sample synthesized in Example 1 is shown in Figure 2.

[0073] Figure 4 A synchrotron single crystal diffraction spectrum of the heavy rare earth fluorcarbonate cerite (thulium) single crystal sample synthesized in Example 1 is shown in Figure 3.

[0074] Example 2

[0075] (1) TmCl3·6H2O, NaF and Na2CO3 powders are mixed in a stoichiometric molar ratio of 1:1:1 to prepare starting materials;

[0076] (2) The mixture powder (about 180 mg) is pressed into a cylinder (Φ4 mm×4 mm) using a powder tablet press, the sample is inserted into a platinum sample tube with a diameter of Φ4 mm and a height of 4 mm and a wall thickness of 0.2 mm, and the two ends are sealed using a welding gun;

[0077] (3) The platinum sample tube is assembled in a high temperature and high pressure synthesis assembly block:

[0078] ① A circular through hole with a diameter of 14 mm is punched in the center of a 32.5 mm×32.5 mm×32.5 mm pyrophyllite block;

[0079] ② A graphite heating tube with an outer diameter of 14 mm and an inner diameter of 12 mm is sleeved in the circular through hole of the pyrophyllite block;

[0080] (3) Put the graphite heating tube into the center of the pyrophyllite block, and then put the alumina insulation tube into the graphite heating tube;

[0081] (4) Put the platinum sample tube into the alumina insulation tube, and seal the top and bottom with pyrophyllite plugs with a diameter of 4 mm;

[0082] (4) Put the high-temperature and high-pressure synthesis assembly block into a six-surface top press machine for high-temperature and high-pressure reaction (the reaction process is controlled by a thermocouple): under normal pressure, increase the pressure to the preset maximum pressure (1.4 GPa) at a pressure increasing rate of 0.2 GPa / 30 min, and then increase the temperature in stages: increase the temperature to 100℃, 300℃, 500℃ and the maximum temperature (700℃) respectively at a temperature increasing rate of 15℃ / min, and keep the temperature at 100℃, 300℃, 500℃ for 45 min respectively, and react at the maximum temperature for 100 h.

[0083] Step 5: Take out the reacted sample, use a diamond cutter to open the platinum sample tube, and take out the fluorocarbon cerium ore (thulium) single crystal under a stereomicroscope.

[0084] Example 3

[0085] (1) TmCl3·6H2O, NaF and Na2CO3 powders were mixed in a stoichiometric molar ratio of 1:1:1 and ground uniformly as starting materials;

[0086] (2) The mixture powder (about 180 mg) was pressed into a cylinder (Φ4 mm×4 mm) using a powder tablet press, and the sample was inserted into a platinum sample tube with a diameter of Φ4 mm and a height of 4 mm, and the two ends were sealed using a welding gun;

[0087] (3) Assemble the platinum sample tube in the high-temperature and high-pressure synthesis assembly block:

[0088] (1) Drill a circular hole with a diameter of 14 mm in the center of a 32.5 mm×32.5 mm×32.5 mm pyrophyllite block;

[0089] (2) Put a graphite heating tube with an outer diameter of 14 mm and an inner diameter of 12 mm into the circular hole of the pyrophyllite block;

[0090] (3) Put an alumina insulation tube with an outer diameter of 12 mm and an inner diameter of 4 mm into the graphite heating tube;

[0091] (4) Put the platinum sample tube into the alumina insulation tube, and seal the top and bottom with pyrophyllite plugs with a diameter of 4 mm;

[0092] (4) Put the high temperature and high pressure synthesis assembly block into the six-surface big press machine to carry out high temperature and high pressure reaction (the reaction process is controlled by thermocouple): under normal pressure, the pressure is increased to the preset maximum pressure (1.6 GPa) at the pressure increasing rate of 0.2 GPa / 30 min, and then the temperature is increased in steps: the temperature is increased to 100℃, 300℃, 500℃ and the maximum temperature (750℃) respectively at the temperature increasing rate of 15℃ / min, and the temperature is kept at 100℃, 300℃ and 500℃ for 45 min respectively, and the reaction is carried out at the maximum temperature for 100 h.

[0093] Step 5: the reacted sample is taken out, the platinum sample tube is opened by using a diamond cutter, and the fluorcarbonatetm (thulium) single crystal is taken out under a stereomicroscope.

[0094] Example 4

[0095] (1) TmCl3·6H2O, NaF and Na2CO3 powders are mixed uniformly as starting raw materials in the stoichiometric molar ratio of 1:1:1;

[0096] (2) the mixture powder (about 180 mg) is pressed into a cylinder (Φ4 mm×4 mm) by using a powder tablet press, the sample is inserted into a platinum sample tube with a diameter of Φ4 mm and a height of 4 mm and a wall thickness of 0.2 mm, and the two ends are sealed by using a welding gun;

[0097] (3) the platinum sample tube is assembled in a high temperature and high pressure synthesis assembly block:

[0098] ① a circular through hole with a diameter of 14 mm is punched in the center of a 32.5 mm×32.5 mm×32.5 mm pyrophyllite block;

[0099] ② a graphite heating pipe with an outer diameter of 14 mm and an inner diameter of 12 mm is sleeved in the circular through hole of the pyrophyllite block;

[0100] ③ an alumina insulation pipe with an outer diameter of 12 mm and an inner diameter of 4 mm is placed in the graphite heating pipe;

[0101] ④ the platinum sample tube is placed in the middle of the alumina insulation pipe, and the upper and lower ends are sealed by using pyrophyllite plugs with a diameter of 4 mm;

[0102] (4) the high temperature and high pressure synthesis assembly block is put into the six-surface big press machine to carry out high temperature and high pressure reaction (the reaction process is controlled by thermocouple): under normal pressure, the pressure is increased to the preset maximum pressure (1.8 GPa) at the pressure increasing rate of 0.2 GPa / 30 min, and then the temperature is increased in steps: the temperature is increased to 100℃, 300℃, 500℃ and the maximum temperature (800℃) respectively at the temperature increasing rate of 15℃ / min, and the temperature is kept at 100℃, 300℃ and 500℃ for 45 min respectively, and the reaction is carried out at the maximum temperature for 100 h.

[0103] Step 5, the reacted sample was taken out, the platinum gold sample tube was opened using a diamond cutter, and the fluor carbon cerite (thulium) single crystal was taken out under a stereomicroscope.

[0104] Example 5

[0105] (1) TmCl3·6H2O, NaF and Na2CO3 powders were mixed uniformly as starting materials in a stoichiometric molar ratio of 1:1:1;

[0106] (2) The mixture powder (about 180 mg) was pressed into a cylinder (Φ4 mm x 4 mm) using a powder tablet press, the sample was inserted into a platinum gold sample tube with a Φ4 mm, 4 mm high, and 0.2 mm thick wall, and the two ends were sealed using a welding gun;

[0107] (3) The platinum gold sample tube was assembled in a high temperature and high pressure synthesis assembly block:

[0108] ① A circular through hole with a diameter of 14 mm was punched in the center of a 32.5 mm x 32.5 mm x 32.5 mm pyrophyllite block;

[0109] ② A graphite heating tube with an outer diameter of 14 mm and an inner diameter of 12 mm was sleeved in the circular through hole of the pyrophyllite block;

[0110] ③ An alumina insulation tube with an outer diameter of 12 mm and an inner diameter of 4 mm was placed in the graphite heating tube;

[0111] ④ The platinum gold sample tube was placed in the middle of the alumina insulation tube, and the upper and lower ends were sealed with pyrophyllite plugs with a diameter of 4 mm;

[0112] (4) The high temperature and high pressure synthesis assembly block was placed in a six-surface top press for high temperature and high pressure reaction (the reaction process was controlled by a thermocouple): under normal pressure, the pressure was increased to the preset maximum pressure (1.8 GPa) at a pressure increasing rate of 0.2 GPa / 30 min, and then the temperature was increased in stages: the temperature was increased to 100℃, 300℃, 500℃ and the maximum temperature (850℃) respectively at a temperature increasing rate of 15℃ / min, and the temperature was maintained at 100℃, 300℃, 500℃ for 45 min respectively, and the reaction was carried out at the maximum temperature for 100 h.

[0113] Step 5, the reacted sample was taken out, the platinum gold sample tube was opened using a diamond cutter, and the fluor carbon cerite (thulium) single crystal was taken out under a stereomicroscope.

[0114] Comparative Example 1

[0115] The difference between Example 1 and Comparative Example 1 is only that the stepwise temperature increasing method is not used, and the high temperature and high pressure reaction process of step (4) is:

[0116] The reaction was carried out at 650 DEG C under a pressure of 1.2 GPa for 100 h.

[0117] The results show that the powder sample in the platinum-gold sample tube is consolidated into a block, and a single crystal sample is not formed, and the block sample is not fluorcarbonate cerium (thulium) either, and the fluorcarbonate cerium (thulium) single crystal sample cannot be synthesized without using the staged heating mode.

[0118] The above-described embodiments are only to illustrate the preferred modes of the present application, and are not intended to limit the scope of the present application, and various modifications and improvements to the technical solutions of the present application made by those skilled in the art without departing from the design spirit of the present application shall fall within the protection scope defined by the claims of the present application.

Claims

1. A method of synthesizing a fluorocarnotite single crystal, characterized by, The method comprises the following steps: TmCl3·6H2O, NaF and Na2CO3 are mixed in a molar dosage ratio of a chemical reaction, and the obtained mixture is kept at a first temperature, a second temperature and a third temperature for 45 min respectively under a pressure of 1.2-1.8 GPa, and then kept at a fourth temperature for 100 h to obtain the fluorocarbondine single crystal; The first temperature is 100-150 ℃, the second temperature is 300-350 ℃, the third temperature is 500-550 ℃, and the fourth temperature is 650-850 ℃.

2. The method of synthesizing fluorocarnotite single crystals according to claim 1, characterized by, The pressure is increased to a preset pressure value at a pressure increasing rate of 0.2 GPa / 30 min under normal pressure.

3. The method of synthesizing fluorocarnotite single crystal according to claim 1, characterized in that, The purity of the TmCl3·6H2O, NaF and Na2CO3 is all greater than 99.99%.

4. The method of synthesizing fluorocarnotite single crystal according to claim 1, characterized in that, The temperature increasing rate is controlled to be 15 ℃ / min, and the temperature is sequentially increased from the first temperature to the second temperature, the third temperature and the fourth temperature.

5. The method of synthesizing fluorocarnotite single crystals according to claim 1, characterized by, The keeping process of the mixture is carried out in a large cavity press.

6. The method of synthesizing fluorocarnotite single crystals according to claim 5, characterized by, The mixture is placed in a high temperature and high pressure synthesis assembly block; the high temperature and high pressure synthesis assembly block comprises pyrophyllite as a pressure transmission medium, a graphite tube as a heating furnace and a thermocouple for temperature control.

7. The method of synthesizing fluorocarnotite single crystals according to claim 6, characterized by, The thermocouple is an S-type thermocouple.

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