A method for synthesizing a novel dysprosium-containing rare earth fluorocarbonate single crystal

Abstract

The application discloses a synthesis method of a novel dysprosium-containing rare earth fluorocarbonate monocrystal, and belongs to the field of mineral material synthesis of earth science and material science. The synthesis method of the novel dysprosium-containing rare earth fluorocarbonate monocrystal comprises the following steps: mixing DyCl3.6H2O, NaF and NaHCO3 to obtain a mixture, and performing a high-temperature and high-pressure reaction under an oxygen-free condition to obtain the novel dysprosium-containing rare earth fluorocarbonate monocrystal. The application successfully overcomes the technical and theoretical problems of the current difficulty in growing a new type of rare earth fluorocarbonate compound monocrystal and the lack of understanding of related crystal structures. The novel dysprosium-containing rare earth fluorocarbonate compound (Dy8O8F2(CO3)3) monocrystal prepared by the method has the characteristics of a pure substance and good chemical stability.

Description

Technical Field

[0001] The present invention relates to the field of mineral material synthesis in earth science and material science, and in particular to a method for synthesizing a novel rare earth fluorocarbonate single crystal containing dysprosium. Background Art

[0002] Rare Earth Elements (REEs) consist of 17 elements: scandium (Sc), yttrium (Y), and the lanthanide series (lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Their unique electron structures and chemical properties make them valuable in applications such as catalysis, luminescence, magnetism, and new energy. Rare earth fluorocarbonates, as an important class of rare earth minerals and functional materials, have attracted considerable attention due to their unique crystal structure and physicochemical properties (such as optical, electrical, and magnetic properties).

[0003] At present, for common rare earth fluorocarbonates, such as bastnaesite, people have conducted relatively detailed research on their chemical synthesis, crystal structure, thermodynamic properties and solubility. However, there are many rare earth element ores in nature, and there is no research on the existence of bastnaesite. Beyond cordylite and Huanghoite, there is a lack of knowledge about other types of rare earth fluorocarbonate compounds. In particular, there are no reports on the natural occurrence of other types of rare earth fluorocarbonate compounds, nor on their crystal structures and thermodynamic properties. This severely limits our understanding of the enrichment, migration, and mineralization mechanisms of rare earth elements in nature. Therefore, the synthesis of new rare earth fluorocarbonate compounds is of great significance: 1) it further enriches the research field of rare earth chemistry and expands the structure and properties of rare earth compounds; 2) the synthesis of new rare earth fluorocarbonate compounds can be used to study their physical, chemical, and optical properties, thereby gaining a deeper understanding of the structure-property relationships of these compounds and providing a theoretical and experimental basis for further applications; and 3) the synthesis of new rare earth fluorocarbonate compounds can enable the exploration and development of new functional materials, such as luminescent materials, magnetic materials, and optoelectronic materials, with potential application value.

[0004] However, researchers in this field have conducted limited research on the formation mechanisms of new rare earth fluorocarbonate compounds. To date, there are no reports on the growth of single crystals of new rare earth fluorocarbonate compounds and their crystal structure data. Furthermore, there are no detailed descriptions of the synthesis methods of new rare earth fluorocarbonate compounds under high temperature and high pressure conditions, nor are there detailed descriptions of the particle size, morphology, and characterization of the synthesized products. Given the compositional complexity of rare earth fluorocarbonate mineral samples, exploring methods for the artificial synthesis of high-purity single crystals of new rare earth fluorocarbonate compounds is an important prerequisite and foundation for further in-depth research on the crystal structure characteristics of rare earth fluorocarbonate minerals and the formation mechanisms of fluorocarbonate minerals. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for synthesizing a new type of rare earth fluorocarbonate (Dy8O8F2(CO3)3) single crystal containing dysprosium under high temperature and high pressure, so as to solve the current technical and theoretical problems of difficulty in growing single crystals of new types of rare earth fluorocarbonate compounds and lack of understanding of related crystal structures. At the same time, the method has the characteristics of simple experimental operation and easy control of experimental conditions.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide a method for synthesizing a novel rare earth fluorocarbonate single crystal containing dysprosium, comprising the following steps:

[0008] DyCl3·6H2O, NaF and NaHCO3 are mixed to obtain a mixture, and a high-temperature and high-pressure reaction is carried out under oxygen-free conditions to obtain the novel rare earth fluorocarbonate single crystal containing dysprosium.

[0009] Preferably, the molar ratio of DyCl3·6H2O, NaF and NaHCO3 is 8:2:22.

[0010] Preferably, the temperature of the high temperature and high pressure reaction is 400-600° C., the pressure is 0.2-1.0 GPa, and the reaction time is 30-100 h.

[0011] More preferably, before the high temperature and high pressure reaction, the steps of gradient pressure increase and gradient temperature increase are further included, specifically: first, the pressure is increased to the pressure required for the reaction at a pressure increase rate of 0.05GPa / 30min, and then the temperature is successively increased to 100°C, 200°C, and 300°C at a temperature increase rate of 10°C / min, and the temperatures are kept at 100°C, 200°C, and 300°C for 30 minutes respectively, and finally the temperature is increased to the temperature required for the reaction at a temperature increase rate of 10°C / min.

[0012] Preferably, the high temperature and high pressure reaction is carried out in a large cavity press.

[0013] More preferably, during the high temperature and high pressure reaction, pyrophyllite is used as the pressure transmission medium, a graphite tube is used as the heating furnace, and a thermocouple is used as the temperature control device.

[0014] More preferably, the thermocouple is a K-type thermocouple.

[0015] The second technical solution of the present invention is to provide a novel rare earth fluorocarbonate single crystal containing dysprosium obtained according to the above-mentioned synthesis method, wherein the chemical formula of the novel rare earth fluorocarbonate single crystal containing dysprosium is Dy8O8F2(CO3)3, the crystal structure is hexagonal, the space group is P63 / m, and the unit cell parameters are

[0016] This invention is based on a multidisciplinary knowledge system including geochemistry, crystallography, and mineralogy. Based on the technical principle of the slow formation of new rare earth fluorocarbonate compounds under high temperature and high pressure conditions, the invention uses a laboratory large-cavity press experimental equipment (a six-sided top large press) to simulate the formation process of single crystals of new rare earth fluorocarbonate compounds containing dysprosium (Dy8O8F2(CO3)3) in a high-temperature and high-pressure environment. The main chemical reaction equation involved in this invention is:

[0017] 8DyCl3·6H2O+22NaHCO3+2NaF=Dy8O8F2(CO3)3+24NaCl+19CO2+59H2O

[0018] The beneficial technical effects of the present invention are as follows:

[0019] In the present invention, the growth process of single crystals of new dysprosium-containing rare earth fluorocarbonate compounds (Dy8O8F2(CO3)3) is carried out in a highly pure laboratory environment. During this period, the sample is placed in a sealed system, which effectively prevents contact with external impurities. The single crystals of the new dysprosium-containing rare earth fluorocarbonate compounds (Dy8O8F2(CO3)3) prepared in this way exhibit the characteristics of a pure substance and have good chemical stability. The present invention successfully overcomes the current technical and theoretical difficulties in growing single crystals of new types of rare earth fluorocarbonate compounds and the lack of understanding of related crystal structures. In addition, the method adopted by the present invention has significant advantages such as simple operating procedures and easy control of experimental conditions, and has good application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1This is a schematic diagram of the crystal structure of the new rare earth fluorocarbonate single crystal containing dysprosium synthesized by the present invention.

[0022] Figure 2 These are micrographs of the novel rare earth fluorocarbonate single crystal containing dysprosium synthesized in Example 1. (a)-(d) represent novel rare earth fluorocarbonate single crystals with different morphologies, respectively.

[0023] Figure 3 This is the Raman spectrum of the new rare earth fluorocarbonate single crystal containing dysprosium synthesized in Example 1.

[0024] Figure 4 This is the synchrotron radiation single crystal diffraction pattern of the new rare earth fluorocarbonate single crystal containing dysprosium synthesized in Example 1. DETAILED DESCRIPTION

[0025] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0026] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0027] Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention pertains. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention. It should be noted that any details not described herein are conventional procedures in the art and are not the focus of the present invention.

[0028] The terms “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0029] Dysprosium (Dy), a typical representative of heavy rare earth elements, is commonly found in minerals such as monazite sand, along with other rare earth elements such as erbium (Er) and holmium (Ho). Its abundance in the Earth's crust is 6 ppm, making it one of the more abundant heavy rare earth elements in the Earth's crust, providing a good resource base for its applications. In addition to possessing the common chemical activity of rare earth elements, allowing it to be used as mixed rare earth metals and compounds, dysprosium also possesses excellent optical, electrical, magnetic, and nuclear properties, making it useful in the manufacture of a variety of functional materials and playing an important role in many high-tech fields. For example, dysprosium metal can be used as a magneto-optical storage material with high recording speed and readout sensitivity; its halides are used as metal halide luminescent materials in the manufacture of new lighting sources, dysprosium lamps; and its compounds serve as catalysts in the oil refining and chemical industries. Therefore, developing an efficient and reliable method for synthesizing dysprosium-containing rare earth fluorocarbonate single crystals is of vital importance.

[0030] The present invention provides a method for synthesizing a novel rare earth fluorocarbonate single crystal containing dysprosium, comprising the following steps:

[0031] Step 1: Using analytically pure DyCl3·6H2O powder, NaF powder, and NaHCO3 powder as starting materials, they were thoroughly ground and mixed in an agate mortar in a molar ratio of 8:2:22 to obtain a mixture powder;

[0032] Step 2: Use a tablet press to press the mixed powder into a cylindrical shape, then insert the cylindrical sample into a platinum sample tube and seal both ends with a welding gun;

[0033] Step 3, assembling the platinum sample tube from step 2 into a high-temperature and high-pressure synthesis assembly block;

[0034] Step 4: Place the high-temperature and high-pressure synthesis assembly block assembled with the platinum sample tube in a six-sided top large press for high-temperature and high-pressure reaction. Set the high-temperature and high-pressure reaction temperature to 400-600°C, the pressure to 0.2-1.0 GPa, and the reaction time to 30-100 hours.

[0035] Step 5: Take out the reacted sample, use a diamond cutter to open the platinum sample tube, and select the single crystal of the new dysprosium-containing rare earth fluorocarbonate compound (Dy8O8F2(CO3)3) under a stereo microscope.

[0036] Furthermore, the purity of the analytically pure DyCl3·6H2O powder in step 1 is >99.99%, the purity of the NaF powder is >99.99%, and the purity of the NaHCO3 powder is >99.99%.

[0037] Furthermore, the specific operation of the assembly described in step 3 is: drilling a hole in the center of the phyllite block on a lathe, then first inserting the circular graphite heating tube into the hole, then inserting the alumina insulating tube into the middle of the circular graphite heating tube, then inserting the platinum sample tube into the middle of the alumina insulating tube, and finally sealing the upper and lower ends of the circular graphite heating tube with phyllite plugs.

[0038] Furthermore, a thermocouple is placed in the high-temperature and high-pressure synthesis assembly block described in step 3.

[0039] Furthermore, during the high-temperature and high-pressure reaction, the temperature in the sample chamber is calibrated using a K-type thermocouple. As a temperature sensor, the K-type thermocouple is usually used in conjunction with a display instrument, a recording instrument, and an electronic regulator. The K-type thermocouple can directly measure the surface temperature of liquid vapor and gaseous media and solids in the range of 0°C to 1300°C in various production processes. The nominal chemical composition of the positive electrode (KP) is: Ni:Cr=90:10, and the nominal chemical composition of the negative electrode (KN) is: Ni:Si=97:3. Its operating temperature is -200°C to 1300°C. The K-type thermocouple has the advantages of good linearity, large thermoelectromotive force, high sensitivity, good stability and uniformity, strong anti-oxidation performance, and low price, and is widely used. By placing each set of K-type thermocouples symmetrically in the middle of the outer wall of the sample chamber, the temperature calibration in the sample chamber can be achieved.

[0040] The dimensions of the high-temperature and high-pressure synthesis assembly block can be specifically determined based on the dimensions of the sample contained in the platinum sample tube. In the high-temperature and high-pressure synthesis assembly block, pyrophyllite is used as a pressure transmission medium, a circular graphite heating tube is used as a heating furnace, and a K-type thermocouple is used as a temperature control device. The advantages of the high-temperature and high-pressure synthesis assembly block of the present invention are: ① Using a K-type thermocouple to control the temperature, the heating system adjusts the heating power through the temperature feedback from the K-type thermocouple, thereby changing the temperature. This method can achieve real-time monitoring of the temperature and is suitable for experiments that require high temperature measurement accuracy; ② pyrophyllite is used as a pressure transmission medium, which has excellent pressure transmission, machinability, heat resistance, heat preservation and insulation properties; ③ The circular graphite heating tube is used as a heating furnace, and the temperature uniformity is high.

[0041] Furthermore, the heating and pressurizing process of the high temperature and high pressure reaction described in step 4 is: first, the pressure is increased to a preset maximum pressure (0.2-1.0 GPa) at a pressure increase rate of 0.05 GPa / 30 min, and then the temperature is increased in steps, and the steps are as follows: at a heating rate of 10 ° C / min, the temperature is raised to 100 ° C, 200 ° C, 300 ° C and the maximum temperature (400-600 ° C) in sequence, and the temperature is kept at 100 ° C, 200 ° C, and 300 ° C for 30 minutes respectively, and the reaction is carried out at the highest temperature and pressure conditions for 30-100 hours.

[0042] Furthermore, the single crystal of the novel rare earth fluorocarbonate compound (Dy8O8F2(CO3)3) containing dysprosium described in step 5 is a single phase, has no impurity phase, is a hexagonal crystal structure, has a space group of P63 / m, and has a unit cell parameter of The crystals are hexagonal plates, columns, and bipyramids, with a size of 10-20 μm.

[0043] The purity of the analytically pure DyCl3·6H2O powder used in the present invention is greater than 99.99%, the purity of the NaF powder is greater than 99.99%, and the purity of the NaHCO3 powder is greater than 99.99%.

[0044] The raw materials used in the following examples and comparative examples of the present invention are all commercially available products.

[0045] Figure 1 This is a schematic diagram of the crystal structure of the new rare earth fluorocarbonate single crystal containing dysprosium synthesized by the present invention.

[0046] Example 1

[0047] A method for synthesizing a novel rare earth fluorocarbonate single crystal containing dysprosium, comprising the following steps:

[0048] Step 1: Using analytically pure DyCl3·6H2O powder, NaF powder, and NaHCO3 powder as starting materials, they were thoroughly ground and mixed in an agate mortar in a molar ratio of 8:2:22 to obtain a mixture powder;

[0049] Step 2: Use a powder tablet press to press the mixture powder into a cylinder (Φ5mm×5mm), then insert it into a platinum sample tube with a diameter of 5mm, a height of 5mm, and a wall thickness of 0.2mm, and seal both ends with a welding gun;

[0050] Step 3: Drill a circular through hole with a diameter of 12 mm in the center of a 32.5 mm × 32.5 mm × 32.5 mm pyrophyllite block on a lathe; then first insert a circular graphite heating tube with an outer diameter of 12 mm and an inner diameter of 10 mm into the circular through hole of the pyrophyllite block, then insert an alumina insulating tube with an outer diameter of 10 mm and an inner diameter of 5 mm into the middle of the circular graphite heating tube, then insert the platinum sample tube from step 2 into the middle of the alumina insulating tube, and finally seal the upper and lower ends of the circular graphite heating tube with pyrophyllite plugs with a diameter of 5 mm to prepare a high-temperature and high-pressure synthetic assembly block (a K-type thermocouple is placed in the high-temperature and high-pressure synthetic assembly block);

[0051] Step 4: Place the high-temperature and high-pressure synthesis assembly block assembled with the platinum sample tube in a six-sided top large press for high-temperature and high-pressure reaction, specifically: first increase the pressure to 0.2 GPa at a pressure increase rate of 0.05 GPa / 30 min, then increase the temperature to 100°C, 200°C, and 300°C in sequence at a heating rate of 10°C / min, and keep the temperature at 100°C, 200°C, and 300°C for 30 minutes respectively, and finally increase the temperature to 400°C at a heating rate of 10°C / min, and react under these temperature and pressure conditions for 30 hours;

[0052] Step 5: After the high-temperature, high-pressure reaction is completed, the resulting sample is removed and the platinum sample tube is opened using a diamond cutter. After the sample is naturally air-dried, single crystals of the novel dysprosium-containing rare earth fluorocarbonate compound (Dy8O8F2(CO3)3) are selected under a stereomicroscope. Calculations indicate that the yield of the product in this example is over 70%.

[0053] Figure 2 These are micrographs of the novel rare earth fluorocarbonate single crystal containing dysprosium synthesized in Example 1. (a)-(d) represent novel rare earth fluorocarbonate single crystals with different morphologies, respectively.

[0054] Figure 3 This is the Raman spectrum of the new rare earth fluorocarbonate single crystal containing dysprosium synthesized in Example 1.

[0055] Figure 4 This is the synchrotron radiation single crystal diffraction pattern of the new rare earth fluorocarbonate single crystal containing dysprosium synthesized in Example 1.

[0056] Combined with the above data, it can be seen that the single crystal of the novel rare earth fluorocarbonate compound containing dysprosium (Dy8O8F2(CO3)3) synthesized in Example 1 of the present invention is a single phase, without impurity phase, and has a hexagonal crystal structure with a space group of P63 / m and a unit cell parameter of The crystals are in the shape of hexagonal plates, columns, bipyramids, etc., with a size of 10-20 μm.

[0057] Example 2

[0058] A method for synthesizing a novel rare earth fluorocarbonate single crystal containing dysprosium, comprising the following steps:

[0059] Step 1: Using analytically pure DyCl3·6H2O powder, NaF powder, and NaHCO3 powder as starting materials, they were thoroughly ground and mixed in an agate mortar in a molar ratio of 8:2:22 to obtain a mixture powder;

[0060] Step 2: Use a powder tablet press to press the mixture powder into a cylinder (Φ5mm×5mm), then insert it into a platinum sample tube with a diameter of 5mm, a height of 5mm, and a wall thickness of 0.2mm, and seal both ends with a welding gun;

[0061] Step 3: Drill a circular through hole with a diameter of 12 mm in the center of a 32.5 mm × 32.5 mm × 32.5 mm pyrophyllite block on a lathe; then first insert a circular graphite heating tube with an outer diameter of 12 mm and an inner diameter of 10 mm into the circular through hole of the pyrophyllite block, then insert an alumina insulating tube with an outer diameter of 10 mm and an inner diameter of 5 mm into the middle of the circular graphite heating tube, then insert the platinum sample tube from step 2 into the middle of the alumina insulating tube, and finally seal the upper and lower ends of the circular graphite heating tube with pyrophyllite plugs with a diameter of 5 mm to prepare a high-temperature and high-pressure synthetic assembly block (a K-type thermocouple is placed in the high-temperature and high-pressure synthetic assembly block);

[0062] Step 4: Place the high-temperature and high-pressure synthesis assembly block assembled with the platinum sample tube in a six-sided top large press for high-temperature and high-pressure reaction, specifically: first increase the pressure to 0.4 GPa at a pressure increase rate of 0.05 GPa / 30 min, then increase the temperature to 100°C, 200°C, and 300°C in sequence at a heating rate of 10°C / min, and keep the temperature at 100°C, 200°C, and 300°C for 30 minutes respectively, and finally increase the temperature to 450°C at a heating rate of 10°C / min, and react under these temperature and pressure conditions for 50 hours;

[0063] Step 5: After the high-temperature and high-pressure reaction is completed, the obtained sample is taken out, and the platinum sample tube is opened using a diamond cutter. After the sample is naturally air-dried, the single crystal of the new dysprosium-containing rare earth fluorocarbonate compound (Dy8O8F2(CO3)3) is selected under a stereo microscope.

[0064] Example 3

[0065] A method for synthesizing a novel rare earth fluorocarbonate single crystal containing dysprosium, comprising the following steps:

[0066] Step 1: Using analytically pure DyCl3·6H2O powder, NaF powder, and NaHCO3 powder as starting materials, they were thoroughly ground and mixed in an agate mortar in a molar ratio of 8:2:22 to obtain a mixture powder;

[0067] Step 2: Use a powder tablet press to press the mixture powder into a cylinder (Φ5mm×5mm), then insert it into a platinum sample tube with a diameter of 5mm, a height of 5mm, and a wall thickness of 0.2mm, and seal both ends with a welding gun;

[0068] Step 3: Drill a circular through hole with a diameter of 12 mm in the center of a 32.5 mm × 32.5 mm × 32.5 mm pyrophyllite block on a lathe; then first insert a circular graphite heating tube with an outer diameter of 12 mm and an inner diameter of 10 mm into the circular through hole of the pyrophyllite block, then insert an alumina insulating tube with an outer diameter of 10 mm and an inner diameter of 5 mm into the middle of the circular graphite heating tube, then insert the platinum sample tube from step 2 into the middle of the alumina insulating tube, and finally seal the upper and lower ends of the circular graphite heating tube with pyrophyllite plugs with a diameter of 5 mm to prepare a high-temperature and high-pressure synthetic assembly block (a K-type thermocouple is placed in the high-temperature and high-pressure synthetic assembly block);

[0069] Step 4: Place the high-temperature and high-pressure synthesis assembly block assembled with the platinum sample tube in a six-sided top large press for high-temperature and high-pressure reaction. Specifically, first increase the pressure to 0.6 GPa at a pressure increase rate of 0.05 GPa / 30 min, then increase the temperature to 100°C, 200°C, and 300°C in sequence at a heating rate of 10°C / min, and keep the temperature at 100°C, 200°C, and 300°C for 30 minutes respectively. Finally, increase the temperature to 500°C at a heating rate of 10°C / min, and react under these temperature and pressure conditions for 70 hours.

[0070] Step 5: After the high-temperature and high-pressure reaction is completed, the obtained sample is taken out, and the platinum sample tube is opened using a diamond cutter. After the sample is naturally air-dried, the single crystal of the new dysprosium-containing rare earth fluorocarbonate compound (Dy8O8F2(CO3)3) is selected under a stereo microscope.

[0071] Example 4

[0072] A method for synthesizing a novel rare earth fluorocarbonate single crystal containing dysprosium, comprising the following steps:

[0073] Step 1: Using analytically pure DyCl3·6H2O powder, NaF powder, and NaHCO3 powder as starting materials, they were thoroughly ground and mixed in an agate mortar in a molar ratio of 8:2:22 to obtain a mixture powder;

[0074] Step 2: Use a powder tablet press to press the mixture powder into a cylinder (Φ5mm×5mm), then insert it into a platinum sample tube with a diameter of 5mm, a height of 5mm, and a wall thickness of 0.2mm, and seal both ends with a welding gun;

[0075] Step 3: Drill a circular through hole with a diameter of 12 mm in the center of a 32.5 mm × 32.5 mm × 32.5 mm pyrophyllite block on a lathe; then first insert a circular graphite heating tube with an outer diameter of 12 mm and an inner diameter of 10 mm into the circular through hole of the pyrophyllite block, then insert an alumina insulating tube with an outer diameter of 10 mm and an inner diameter of 5 mm into the middle of the circular graphite heating tube, then insert the platinum sample tube from step 2 into the middle of the alumina insulating tube, and finally seal the upper and lower ends of the circular graphite heating tube with pyrophyllite plugs with a diameter of 5 mm to prepare a high-temperature and high-pressure synthetic assembly block (a K-type thermocouple is placed in the high-temperature and high-pressure synthetic assembly block);

[0076] Step 4: Place the high-temperature and high-pressure synthesis assembly block assembled with the platinum sample tube in a six-sided top large press for high-temperature and high-pressure reaction. Specifically, first increase the pressure to 0.8 GPa at a pressure increase rate of 0.05 GPa / 30 min, then increase the temperature to 100°C, 200°C, and 300°C in sequence at a heating rate of 10°C / min, and keep the temperature at 100°C, 200°C, and 300°C for 30 minutes respectively. Finally, increase the temperature to 550°C at a heating rate of 10°C / min, and react under these temperature and pressure conditions for 90 hours.

[0077] Step 5: After the high-temperature and high-pressure reaction is completed, the obtained sample is taken out, and the platinum sample tube is opened using a diamond cutter. After the sample is naturally air-dried, the single crystal of the new dysprosium-containing rare earth fluorocarbonate compound (Dy8O8F2(CO3)3) is selected under a stereo microscope.

[0078] Example 5

[0079] A method for synthesizing a novel rare earth fluorocarbonate single crystal containing dysprosium, comprising the following steps:

[0080] Step 1: Using analytically pure DyCl3·6H2O powder, NaF powder, and NaHCO3 powder as starting materials, they were thoroughly ground and mixed in an agate mortar in a molar ratio of 8:2:22 to obtain a mixture powder;

[0081] Step 2: Use a powder tablet press to press the mixture powder into a cylinder (Φ5mm×5mm), then insert it into a platinum sample tube with a diameter of 5mm, a height of 5mm, and a wall thickness of 0.2mm, and seal both ends with a welding gun;

[0082] Step 3: Drill a circular through hole with a diameter of 12 mm in the center of a 32.5 mm × 32.5 mm × 32.5 mm pyrophyllite block on a lathe; then first insert a circular graphite heating tube with an outer diameter of 12 mm and an inner diameter of 10 mm into the circular through hole of the pyrophyllite block, then insert an alumina insulating tube with an outer diameter of 10 mm and an inner diameter of 5 mm into the middle of the circular graphite heating tube, then insert the platinum sample tube from step 2 into the middle of the alumina insulating tube, and finally seal the upper and lower ends of the circular graphite heating tube with pyrophyllite plugs with a diameter of 5 mm to prepare a high-temperature and high-pressure synthetic assembly block (a K-type thermocouple is placed in the high-temperature and high-pressure synthetic assembly block);

[0083] Step 4: Place the high-temperature and high-pressure synthesis assembly block assembled with the platinum sample tube in a six-sided top large press for high-temperature and high-pressure reaction, specifically: first increase the pressure to 1.0 GPa at a pressure increase rate of 0.05 GPa / 30 min, then increase the temperature to 100°C, 200°C, and 300°C in sequence at a heating rate of 10°C / min, and keep the temperature at 100°C, 200°C, and 300°C for 30 minutes respectively, and finally increase the temperature to 600°C at a heating rate of 10°C / min, and react under these temperature and pressure conditions for 100 hours;

[0084] Step 5: After the high-temperature and high-pressure reaction is completed, the obtained sample is taken out, and the platinum sample tube is opened using a diamond cutter. After the sample is naturally air-dried, the single crystal of the new dysprosium-containing rare earth fluorocarbonate compound (Dy8O8F2(CO3)3) is selected under a stereo microscope.

[0085] Comparative Example 1

[0086] The only difference from Example 1 is that the parameter settings of the high temperature and high pressure reaction are adjusted as follows: first, the pressure is increased to 0.2 GPa at a pressure increase rate of 0.05 GPa / 30 min, and then the temperature is increased to 400°C at a heating rate of 50°C / min, and the reaction is carried out under these temperature and pressure conditions for 30 hours.

[0087] It can be observed that under the reaction conditions of this comparative example, single crystals of the novel rare earth fluorocarbonate compound (Dy8O8F2(CO3)3) cannot be synthesized.

[0088] Comparative Example 2

[0089] The only difference from Example 1 is that the reaction time of the high temperature and high pressure reaction is changed from 30 h to 5 h.

[0090] It can be observed that under the reaction conditions of this comparative example, single crystals of the novel rare earth fluorocarbonate compound (Dy8O8F2(CO3)3) cannot be synthesized.

[0091] Comparative Example 3

[0092] The only difference from Example 1 is that the parameter settings of the high temperature and high pressure reaction are adjusted as follows: first, the pressure is increased to 0.2 GPa at a pressure increase rate of 0.05 GPa / 30 min, and then the temperature is successively increased to 100°C, 200°C, and 300°C at a heating rate of 10°C / min, and the temperatures are kept at 100°C, 200°C, and 300°C for 30 minutes, respectively. Finally, the temperature is increased to 800°C at a heating rate of 10°C / min, and the reaction is carried out under these temperature and pressure conditions for 30 hours.

[0093] It can be observed that under the reaction conditions of this comparative example, single crystals of the novel rare earth fluorocarbonate compound (Dy8O8F2(CO3)3) cannot be synthesized.

[0094] Comparative Example 4

[0095] The only difference from Example 1 is that the parameter settings of the high temperature and high pressure reaction are adjusted as follows: first, the pressure is increased to 5.0 GPa at a pressure increase rate of 0.05 GPa / 30 min, and then the temperature is successively increased to 100°C, 200°C, and 300°C at a heating rate of 10°C / min, and the temperatures are kept at 100°C, 200°C, and 300°C for 30 minutes, respectively. Finally, the temperature is increased to 400°C at a heating rate of 10°C / min, and the reaction is carried out under these temperature and pressure conditions for 30 hours.

[0096] It can be observed that under the reaction conditions of this comparative example, single crystals of the novel rare earth fluorocarbonate compound (Dy8O8F2(CO3)3) cannot be synthesized.

[0097] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for synthesizing a novel rare earth fluorocarbonate single crystal containing dysprosium, characterized in that: The following steps are involved: Mixing DyCl3·6H2O, NaF and NaHCO3 to obtain a mixture, and subjecting it to a high-temperature and high-pressure reaction under oxygen-free conditions to obtain the novel rare earth fluorocarbonate single crystal containing dysprosium; The molar ratio of DyCl3·6H2O, NaF and NaHCO3 is 8:2:22; The temperature of the high temperature and high pressure reaction is 400-600 ° C, the pressure is 0.2-1.0 GPa, and the reaction time is 30-100 h; Before the high-temperature and high-pressure reaction, the steps of gradient pressure increase and gradient temperature increase are further included, specifically: first, the pressure is increased to the pressure required for the reaction at a pressure increase rate of 0.05 GPa / 30min, and then the temperature is successively increased to 100°C, 200°C, and 300°C at a temperature increase rate of 10°C / min, and the temperatures are kept at 100°C, 200°C, and 300°C for 30 minutes respectively, and finally the temperature is increased to the temperature required for the reaction at a temperature increase rate of 10°C / min.

2. The synthesis method according to claim 1, wherein The high temperature and high pressure reaction is carried out in a large cavity press.

3. The synthesis method according to claim 2, characterized in that During the high-temperature and high-pressure reaction, pyrophyllite is used as a pressure transmission medium, a graphite tube is used as a heating furnace, and a thermocouple is used as a temperature control device.

4. The synthesis method according to claim 3, characterized in that The thermocouple is a K-type thermocouple.

5. A novel rare earth fluorocarbonate single crystal containing dysprosium obtained by the synthesis method according to any one of claims 1 to 4, characterized in that: The chemical formula of the novel dysprosium-containing rare earth fluorocarbonate single crystal is Dy8O8F2(CO3)3, and it has a hexagonal structure with a space group of P63 / m and unit cell parameters of a = 7.6104(2) Å, c = 15.4557(7) Å, and V = 773.40(5) Å. 3 .

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