Method for synthesizing fluorocarbon loparite single crystal under high temperature and high pressure

Abstract

The application discloses a method for synthesizing fluorocarblucentite monocrystal under high temperature and high pressure, and relates to the technical field of rare earth minerals. The method uses LuCl3*6H2O, NaF and Na2CO3 as raw materials, and performs a stage type temperature rising reaction under a predetermined pressure, so that the obtained fluorocarblucentite monocrystal is a pure substance and has good chemical stability, and the technical problem of difficult growth of the fluorocarblucentite monocrystal is solved. In addition, the method has the advantages of simple operation process and easy control of conditions.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of rare earth minerals, in particular to a method for synthesizing fluorocarbcerinite single crystals under high temperature and high pressure. BACKGROUND

[0002] Rare earth elements are the "vitamins" of modern industry, important strategic resources in today's society, and are widely used in modern industry, having irreplaceable major uses in emerging industries such as new materials, new energy, information technology, etc. At present, more than 250 kinds of rare earth minerals have been found in nature, more than 60 kinds of which have high content of rare earth metal elements, and more than 20 kinds of which are the most important rare earth minerals, such as monazite, bastnaesite, parisite, xenotime, gadoelite, and fergusonite.

[0003] The industrial minerals of rare earths are mainly fluorocarbcerinite of fluorocarbcarbonate of rare earths and monazite and xenotime of phosphoric acid of rare earths. Rare earth fluorocarbonate minerals are a kind of very important 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, fluorocarbcerinite is one of the most widely distributed rare earth minerals and is the main mineral for extracting rare earth elements.

[0004] At present, for common light rare earth fluorocarbcerinite, such as fluorocarbcerinite (cerium), fluorocarbcerinite (lanthanum), fluorocarbcerinite (praseodymium), fluorocarbcerinite (neodymium), etc., people have carried out relatively detailed research work on their chemical synthesis, crystal structure, thermodynamic properties and solubility, etc. However, at present, the crystal structure and thermodynamic properties of most heavy rare earth fluorocarbcerinite (such as fluorocarbcerinite (holmium), fluorocarbcerinite (erbium), fluorocarbcerinite (lutetium), fluorocarbcerinite (ytterbium), fluorocarbcerinite (yttrium), fluorocarbcerinite (lutetium), etc.) have not been well studied, which greatly hinders people's understanding of the enrichment, migration and mineralization of rare earth elements in nature, and the differentiation mechanism of light and heavy rare earths.

[0005] Lutetium element: atomic number 71, relative atomic mass 174.96, luster between silver and iron, is the hardest and densest metal among rare earth elements, melting point 1663 DEG C, density 9.84 g / cm 3 , is relatively stable in air, and can be used as a catalyst for petroleum chemical industry, a raw material for magnetic bubble storage, a raw material for special alloy, etc.

[0006] Lutetium is the heaviest and largest molecule among all rare earth elements, and also the hardest and most corrosion-resistant. Lutetium can be used to manufacture certain special alloys; for example, lutetium-aluminum alloys are used for neutron activation analysis. It can also be used as a catalyst in petroleum cracking, alkylation, hydrogenation, and polymerization reactions. Furthermore, doping some laser crystals, such as yttrium aluminum garnet, with lutetium can improve their laser performance and optical uniformity. In addition, lutetium can be used in phosphors: lutetium tantalate is currently the densest white material known, making it an ideal material for X-ray phosphors. 177 Lu is a synthetically produced radioactive nuclide that can be used for radiotherapy of tumors.

[0007] Like other rare earth metals, lutetium is considered to have low toxicity, but its compounds should be handled with care. For example, inhalation of lutetium fluoride is dangerous, and the compounds are skin irritants. Luteinium nitrate is also dangerous because it can explode and burn. Luteinium oxide powder is a toxic substance and is dangerous if inhaled or ingested.

[0008] Previous studies on the formation mechanism of lutetium fluorocarbonate (Celastite) are limited, and there are currently no reports on the growth of artificial Celastium fluorocarbonate (Celastite) single crystals or their crystal structure data. Therefore, exploring methods for the artificial synthesis of high-purity Celastium fluorocarbonate (Celastite) single crystals is an important prerequisite and foundation for further in-depth research on the crystal structure characteristics and formation mechanism of Celastium fluorocarbonate (Celastite). Summary of the Invention

[0009] The purpose of this invention is to provide a method for synthesizing lutetium carbonate single crystals under high temperature and high pressure, so as to solve the technical problem of difficult growth of heavy rare earth lutetium carbonate single crystals. At the same time, the method has the characteristics of simple operation and easy control of conditions.

[0010] To achieve the above objectives, the present invention provides the following solution:

[0011] This invention provides a method for synthesizing lutetium fluorocarbonate single crystals, comprising the following steps:

[0012] LuCl3·6H2O, NaF and Na2CO3 were mixed in a chemical reaction molar ratio. Under pressure, the mixture was kept at a first temperature, a second temperature and a third temperature for 60 min, and then kept at a fourth temperature for 50-80 h to obtain the lutetium carbonate single crystal.

[0013] The first temperature is 200-300℃, the second temperature is 400-450℃, the third temperature is 600-650℃, and the fourth temperature is 800-950℃.

[0014] Furthermore, the pressure value of the pressure condition is 1.6-2.0 GPa.

[0015] Furthermore, under normal pressure, the pressure is increased to the preset pressure value at a pressurization rate of 0.2 GPa / 15 min.

[0016] Furthermore, the purity of LuCl3·6H2O, NaF, and Na2CO3 is analytical grade or higher.

[0017] Furthermore, the purity of LuCl3·6H2O, NaF, and Na2CO3 is all >99.99%.

[0018] Furthermore, the heating rate is controlled at 10℃ / min, so that the temperature is raised sequentially from the first temperature to the second temperature, the third temperature, and the fourth temperature.

[0019] Furthermore, the heat preservation process of the mixture is carried out in a large-cavity press.

[0020] Furthermore, the mixture is placed in a high-temperature and high-pressure synthesis assembly block; the high-temperature and high-pressure synthesis assembly block includes pyrophyllite as a pressure transmission medium, a graphite tube as a heating furnace, and a thermocouple for temperature control.

[0021] Furthermore, the thermocouple is an S-type thermocouple.

[0022] This invention combines backgrounds from rare earth mineralogy, crystal chemistry, rare earth element geochemistry, crystallography and mineralogy, crystal optics, optical mineralogy, and crystal materials science. Specifically, it utilizes the principle of the slow formation of lutetium fluoride ore under redox conditions within the Earth to simulate the formation process of lutetium fluoride ore single crystals under high temperature and high pressure. The main chemical reaction equations involved in this invention are as follows:

[0023] LuCl3·6H2O+NaF+Na2CO3→Lu(CO3)F+3NaCl+6H2O

[0024] Under high temperature and high pressure conditions, the selected initial raw material solid, lutetium(III) chloride hexahydrate [molecular formula: LuCl3·6H2O], provides the lutetium element essential for the synthesis of lutetium bastite (lutetium) single crystals. The initial raw material solid, sodium fluoride [molecular formula: NaF], provides the fluorine element essential for the synthesis of lutetium bastite (lutetium) single crystals. The initial raw material solid, anhydrous sodium carbonate [molecular formula: Na2CO3], provides the carbonate ion essential for the synthesis of lutetium bastite (lutetium) single crystals.

[0025] By employing the temperature and pressure conditions and the corresponding stepped heating method of this invention, the dehydration of LuCl3·6H2O and the decomposition of Na2CO3 can be promoted. This not only creates a fluid environment within the sample chamber but also promotes the reaction, thereby promoting the growth of single-crystal samples.

[0026] The present invention discloses the following technical effects:

[0027] Compared to natural lutetium bastnaesite, which contains other impurities, existing reports indicate that the purity of natural lutetium bastnaesite is difficult to reach 70%. The lutetium bastnaesite single crystals grown in this invention are pure and chemically stable, solving the current technical challenge of difficult single crystal growth. Furthermore, the method of this invention has advantages such as simple operation and easy control of conditions. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram illustrating one scenario of high-temperature and high-pressure sample synthesis and assembly according to the present invention;

[0030] Figure 2 This is a micrograph of a single crystal sample of heavy rare earth fluorocarbon cerium ore (lutetium) synthesized in Example 1;

[0031] Figure 3 Raman spectra of the heavy rare earth bastnaesite (lutetium) single crystal sample synthesized in Example 1;

[0032] Figure 4 The image shows the synchrotron radiation single-crystal diffraction pattern of the heavy rare earth fluorocarbon cerium (lutetium) single crystal sample synthesized in Example 1. Detailed Implementation

[0033] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0034] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0035] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0036] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0037] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0038] This invention relates to a high-temperature, high-pressure synthesis method for lutetium carbonate ore, comprising the following steps:

[0039] Step 1: Use LuCl3·6H2O, NaF, and Na2CO3 powders as starting materials, and grind and mix them thoroughly in an agate mortar at a stoichiometric molar ratio of 1:1:1.

[0040] Step 2: Use a tablet press to compress the mixture powder into a shape, and then fill the compressed sample into a platinum sample tube and seal both ends with a welding gun.

[0041] Step 3: Assemble the platinum sample tube into the high-temperature and high-pressure synthesis assembly block;

[0042] Step 4: The high-temperature and high-pressure assembled block is placed in a six-sided top press for high-temperature and high-pressure reaction. The high-temperature and high-pressure reaction process is as follows:

[0043] Under normal pressure, the pressure is increased to the preset maximum pressure (1.6-2.0 GPa) at a pressurization rate of 0.2 GPa / 15 min, and then the temperature is increased in stages: the temperature is increased to 200℃, 400℃, 600℃ and the maximum temperature (800-950℃) at a heating rate of 10℃ / min, and then held at 200℃, 400℃ and 600℃ for 60 min respectively, and reacted at the maximum temperature for 50-80 h.

[0044] Step 5: Remove the reacted sample and use a diamond cutter to open the platinum sample tube to obtain lutetium fluorocarbonate single crystals.

[0045] The lutetium fluoride single crystal obtained in step 5 is a single phase without any impurity phases.

[0046] The lutetium fluoride (CFC) single crystals prepared by this invention have a hexagonal crystal system with space group P63 / m and cell parameters [not specified]. The crystals are granular, with an average size of 50-80 μm and a maximum size of 100 μm.

[0047] In step 3, the operation of assembling the platinum sample tube onto the high-temperature and high-pressure synthesis assembly block is as follows:

[0048] Drill a hole in the center of the pyrophyllite block on a lathe, then insert a graphite heating tube into the hole, then insert an alumina insulating tube into the graphite heating tube, then insert a platinum sample tube into the middle of the alumina insulating tube, and finally seal the top and bottom ends of the graphite heating tube with pyrophyllite plugs.

[0049] The high-temperature, high-pressure assembly contains thermocouples. During high-temperature, high-pressure operation, the temperature within the sample chamber is calibrated using S-type thermocouples. The S-type thermocouple is a platinum-rhodium 10-platinum thermocouple, a precious metal thermocouple. Its positive electrode (SP) has a nominal chemical composition of platinum-rhodium alloy, containing 10% rhodium and 90% platinum, while the negative electrode (SN) is pure platinum. The maximum long-term operating temperature of this thermocouple is 1300℃, and its maximum short-term operating temperature is 1600℃. Among thermocouples, the S-type thermocouple boasts the highest accuracy, best stability, wide temperature range, and long service life. It exhibits excellent physical and chemical properties, good thermoelectric potential stability, and good oxidation resistance at high temperatures, making it suitable for oxidizing and inert atmospheres. By symmetrically placing each set of S-type thermocouples in the middle of the outer wall of the sample chamber (the outer wall of the alumina insulating tube), the temperature within the sample chamber is calibrated.

[0050] In the high-temperature and high-pressure assembly block of the present invention, pyrophyllite is used as the pressure transmission medium, graphite tube is used as the heating furnace, and thermocouple is used as the temperature control device.

[0051] The dimensions of the high-temperature, high-pressure assembly block can be determined based on the dimensions of the sample housed in the platinum sample tube. Figure 1 This is a schematic diagram illustrating one scenario of high-temperature and high-pressure sample synthesis and assembly according to the present invention.

[0052] The advantages of the high-temperature and high-pressure assembly block of this invention are: ① Thermocouple temperature control is used. The heating system adjusts the heating power through the temperature feedback from the thermocouple, thereby changing the temperature. This method can realize real-time temperature monitoring and is suitable for experiments with high temperature measurement accuracy requirements; ② Pyrophyllite, as a pressure transmission medium, has excellent pressure transmission, machinability, heat resistance, heat insulation and insulation properties; ③ Graphite tubes, as heating furnaces, have high temperature uniformity.

[0053] The present invention will be further described in detail below with reference to the embodiments.

[0054] In this embodiment of the invention: the purity of LuCl3·6H2O powder is >99.99%, the purity of NaF powder is >99.99%, and the purity of Na2CO3 powder is >99.99%.

[0055] Example 1

[0056] (1) LuCl3·6H2O, NaF and Na2CO3 powders were mixed evenly by grinding in a stoichiometric molar ratio of 1:1:1 as the starting material;

[0057] (2) Use a powder press to press the mixture powder into a cylinder (Φ4.5mm×4.5mm), insert the sample into a platinum tube with a diameter of Φ4.5mm, a height of 4mm and a wall thickness of 0.1mm, and seal both ends with a welding gun;

[0058] (3) Assemble the platinum sample tubes into the high-temperature and high-pressure synthesis assembly block:

[0059] ① Drill a circular through hole with a diameter of 16mm in the center of a pyrophyllite block measuring 32.5mm×32.5mm×32.5mm;

[0060] ② A graphite heating tube with an outer diameter of 16mm and an inner diameter of 14mm is inserted into the circular through hole of the pyrophyllite block;

[0061] ③ Place an alumina insulating tube with an outer diameter of 14 mm and an inner diameter of 4.5 mm inside the graphite heating tube;

[0062] ④ A platinum sample tube is placed in the middle of the alumina insulating tube, and the top and bottom are sealed with pyrophyllite plugs with a diameter of 4.5 mm;

[0063] (4) The high-temperature and high-pressure synthesis assembly block is placed in a six-sided top press for high-temperature and high-pressure reaction (the temperature is controlled by thermocouples during the reaction): Under normal pressure, the pressure is increased to the preset maximum pressure (1.6GPa) at a pressurization rate of 0.2GPa / 15min, and then the temperature is increased in stages: the temperature is increased to 200℃, 400℃, 600℃ and the maximum temperature (800℃) at a heating rate of 10℃ / min, and the temperature is held at 200℃, 400℃ and 600℃ for 60min respectively, and the reaction is carried out at the maximum temperature for 80h.

[0064] (5) After the high temperature and high pressure reaction is completed, the obtained sample is taken out, the platinum sample tube is opened with a diamond cutter, the sample is air-dried naturally, and the lutetium fluorocarbonate single crystal is taken out under a stereomicroscope.

[0065] The lutetium fluoride single crystal prepared in Example 1 has a hexagonal crystal system with space group P63 / m and cell parameters [not specified]. The crystals are granular, with an average size of 50-80 μm and a maximum size of 100 μm.

[0066] Figure 2 This is a micrograph of the heavy rare earth bastnaesite (lutetium) single crystal sample synthesized in Example 1;

[0067] Figure 3 Raman spectra of the heavy rare earth bastnaesite (lutetium) single crystal sample synthesized in Example 1;

[0068] Figure 4 The image shows the synchrotron radiation single-crystal diffraction pattern of the heavy rare earth fluorocarbon cerium (lutetium) single crystal sample synthesized in Example 1.

[0069] Example 2

[0070] (1) LuCl3·6H2O, NaF and Na2CO3 powders were mixed evenly by grinding in a stoichiometric molar ratio of 1:1:1 as the starting material;

[0071] (2) Use a powder press to press the mixture powder into a cylinder (Φ4.5mm×4.5mm), insert the sample into a platinum tube with a diameter of Φ4.5mm, a height of 4mm and a wall thickness of 0.1mm, and seal both ends with a welding gun;

[0072] (3) Assemble the platinum sample tubes into the high-temperature and high-pressure synthesis assembly block:

[0073] ① Drill a circular through hole with a diameter of 16mm in the center of a pyrophyllite block measuring 32.5mm×32.5mm×32.5mm;

[0074] ② A graphite heating tube with an outer diameter of 16mm and an inner diameter of 14mm is inserted into the circular through hole of the pyrophyllite block;

[0075] ③ Place an alumina insulating tube with an outer diameter of 14 mm and an inner diameter of 4.5 mm inside the graphite heating tube;

[0076] ④ A platinum sample tube is placed in the middle of the alumina insulating tube, and the top and bottom are sealed with pyrophyllite plugs with a diameter of 4.5 mm;

[0077] (4) The high-temperature and high-pressure synthesis assembly block is placed in a six-sided top press for high-temperature and high-pressure reaction (the temperature of the reaction process is controlled by thermocouples): Under normal pressure, the pressure is increased to the preset maximum pressure (1.6GPa) at a pressurization rate of 0.2GPa / 15min, and then the temperature is increased in stages: the temperature is increased to 200℃, 400℃, 600℃ and the maximum temperature (850℃) at a heating rate of 10℃ / min, and the temperature is held at 200℃, 400℃ and 600℃ for 60min respectively, and the reaction is carried out at the maximum temperature for 70h.

[0078] (5) After the high temperature and high pressure reaction is completed, the obtained sample is taken out, the platinum sample tube is opened with a diamond cutter, the sample is air-dried naturally, and the lutetium fluorocarbonate single crystal is taken out under a stereomicroscope.

[0079] Example 3

[0080] (1) LuCl3·6H2O, NaF and Na2CO3 powders were mixed evenly by grinding in a stoichiometric molar ratio of 1:1:1 as the starting material;

[0081] (2) Use a powder press to press the mixture powder into a cylinder (Φ4.5mm×4.5mm), insert the sample into a platinum tube with a diameter of Φ4.5mm, a height of 4mm and a wall thickness of 0.1mm, and seal both ends with a welding gun;

[0082] (3) Assemble the platinum sample tubes into the high-temperature and high-pressure synthesis assembly block:

[0083] ① Drill a circular through hole with a diameter of 16mm in the center of a pyrophyllite block measuring 32.5mm×32.5mm×32.5mm;

[0084] ② A graphite heating tube with an outer diameter of 16mm and an inner diameter of 14mm is inserted into the circular through hole of the pyrophyllite block;

[0085] ③ Place an alumina insulating tube with an outer diameter of 14 mm and an inner diameter of 4.5 mm inside the graphite heating tube;

[0086] ④ A platinum sample tube is placed in the middle of the alumina insulating tube, and the top and bottom are sealed with pyrophyllite plugs with a diameter of 4.5 mm;

[0087] (4) The high-temperature and high-pressure synthesis assembly block is placed in a six-sided top press for high-temperature and high-pressure reaction (the temperature of the reaction process is controlled by thermocouples): Under normal pressure, the pressure is increased to the preset maximum pressure (1.6GPa) at a pressurization rate of 0.2GPa / 15min, and then the temperature is increased in stages: the temperature is increased to 200℃, 400℃, 600℃ and the maximum temperature (900℃) at a heating rate of 10℃ / min, and the temperature is held at 200℃, 400℃ and 600℃ for 60min respectively, and the reaction is carried out at the maximum temperature for 60h.

[0088] (5) After the high temperature and high pressure reaction is completed, the obtained sample is taken out, the platinum sample tube is opened with a diamond cutter, the sample is air-dried naturally, and the lutetium fluorocarbonate single crystal is taken out under a stereomicroscope.

[0089] Example 4

[0090] (1) LuCl3·6H2O, NaF and Na2CO3 powders were mixed evenly by grinding in a stoichiometric molar ratio of 1:1:1 as the starting material;

[0091] (2) Use a powder press to press the mixture powder into a cylinder (Φ4.5mm×4.5mm), insert the sample into a platinum tube with a diameter of Φ4.5mm, a height of 4mm and a wall thickness of 0.1mm, and seal both ends with a welding gun;

[0092] (3) Assemble the platinum sample tubes into the high-temperature and high-pressure synthesis assembly block:

[0093] ① Drill a circular through hole with a diameter of 16mm in the center of a pyrophyllite block measuring 32.5mm×32.5mm×32.5mm;

[0094] ② A graphite heating tube with an outer diameter of 16mm and an inner diameter of 14mm is inserted into the circular through hole of the pyrophyllite block;

[0095] ③ Place an alumina insulating tube with an outer diameter of 14 mm and an inner diameter of 4.5 mm inside the graphite heating tube;

[0096] ④ A platinum sample tube is placed in the middle of the alumina insulating tube, and the top and bottom are sealed with pyrophyllite plugs with a diameter of 4.5 mm;

[0097] (4) The high-temperature and high-pressure synthesis assembly block is placed in a six-sided top press for high-temperature and high-pressure reaction (the temperature of the reaction process is controlled by thermocouples): Under normal pressure, the pressure is increased to the preset maximum pressure (1.8GPa) at a pressurization rate of 0.2GPa / 15min, and then the temperature is increased in stages: the temperature is increased to 200℃, 400℃, 600℃ and the maximum temperature (900℃) at a heating rate of 10℃ / min, and the temperature is held at 200℃, 400℃ and 600℃ for 60min respectively, and the reaction is carried out at the maximum temperature for 60h.

[0098] (5) After the high temperature and high pressure reaction is completed, the obtained sample is taken out, the platinum sample tube is opened with a diamond cutter, the sample is air-dried naturally, and the lutetium fluorocarbonate single crystal is taken out under a stereomicroscope.

[0099] Example 5

[0100] (1) LuCl3·6H2O, NaF and Na2CO3 powders were mixed evenly by grinding in a stoichiometric molar ratio of 1:1:1 as the starting material;

[0101] (2) Use a powder press to press the mixture powder into a cylinder (Φ4.5mm×4.5mm), insert the sample into a platinum tube with a diameter of Φ4.5mm, a height of 4mm and a wall thickness of 0.1mm, and seal both ends with a welding gun;

[0102] (3) Assemble the platinum sample tubes into the high-temperature and high-pressure synthesis assembly block:

[0103] ① Drill a circular through hole with a diameter of 16mm in the center of a pyrophyllite block measuring 32.5mm×32.5mm×32.5mm;

[0104] ② A graphite heating tube with an outer diameter of 16mm and an inner diameter of 14mm is inserted into the circular through hole of the pyrophyllite block;

[0105] ③ Place an alumina insulating tube with an outer diameter of 14 mm and an inner diameter of 4.5 mm inside the graphite heating tube;

[0106] ④ A platinum sample tube is placed in the middle of the alumina insulating tube, and the top and bottom are sealed with pyrophyllite plugs with a diameter of 4.5 mm;

[0107] (4) The high-temperature and high-pressure synthesis assembly block is placed in a six-sided top press for high-temperature and high-pressure reaction (the temperature is controlled by thermocouples during the reaction): Under normal pressure, the pressure is increased to the preset maximum pressure (2.0GPa) at a pressurization rate of 0.2GPa / 15min, and then the temperature is increased in stages: the temperature is increased to 200℃, 400℃, 600℃ and the maximum temperature (950℃) at a heating rate of 10℃ / min, and the temperature is held at 200℃, 400℃ and 600℃ for 60min respectively, and the reaction is carried out at the maximum temperature for 50h.

[0108] (5) After the high temperature and high pressure reaction is completed, the obtained sample is taken out, the platinum sample tube is opened with a diamond cutter, the sample is air-dried naturally, and the lutetium fluorocarbonate single crystal is taken out under a stereomicroscope.

[0109] Comparative Example 1

[0110] The only difference from Example 1 is that the staged heating method is not used. The high-temperature and high-pressure reaction process in step (4) is as follows:

[0111] The reaction was carried out at 800℃ and 1.6 GPa for 80 h.

[0112] The results showed that the powder sample in the platinum sample tube solidified into a block and did not form a single crystal sample. Furthermore, the block sample was not lutetium fluorocarbonate. It was impossible to synthesize a single crystal sample of lutetium fluorocarbonate without using a staged heating method.

[0113] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for synthesizing lutetium fluorocarbonate single crystals, characterized in that, Includes the following steps: LuCl3·6H2O, NaF and Na2CO3 were mixed in a molar ratio of 1:1:

1. Under pressure, the mixture was kept at a first temperature, a second temperature and a third temperature for 60 min, and then kept at a fourth temperature for 50-80 h to obtain the lutetium carbonate single crystal. The first temperature is 200-300℃, the second temperature is 400-450℃, the third temperature is 600-650℃, and the fourth temperature is 800-950℃; The pressure value of the pressure condition is 1.6-2.0 GPa.

2. The method for synthesizing lutetium fluorocarbonate single crystals according to claim 1, characterized in that, At normal pressure, the pressure is increased to the preset pressure value at a pressurization rate of 0.2 GPa / 15min.

3. The method for synthesizing lutetium fluorocarbonate single crystals according to claim 1, characterized in that, The purity of LuCl3·6H2O, NaF and Na2CO3 is all >99.99%.

4. The method for synthesizing lutetium fluorocarbonate single crystals according to claim 1, characterized in that, The heating rate is controlled at 10℃ / min, so that the temperature is raised sequentially from the first temperature to the second temperature, the third temperature, and the fourth temperature.

5. The method for synthesizing lutetium fluorocarbonate single crystals according to claim 1, characterized in that, The heat preservation process of the mixture is carried out in a large-cavity press.

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

7. The method for synthesizing lutetium fluorocarbonate single crystals according to claim 6, characterized in that, The thermocouple is an S-type thermocouple.

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