UAsTe single crystal and preparation method thereof

Abstract

The invention provides a UAsTe single crystal and a preparation method thereof. The preparation method comprises the following steps: mixing a 238U raw material, an As raw material and a Te raw material according to an atomic ratio of 1: 0.8: (0.75-0.95), putting the mixture into the bottom of a gas-phase transportation pipe, and putting I2 as a gas-phase transportation agent into the bottom of the gas-phase transportation pipe; then, a quartz sealing piece is placed in the gas-phase conveying pipe for sealing, vacuumizing and heat sealing treatment; and putting the gas-phase conveying pipe into a double-temperature-zone tubular furnace, carrying out heat preservation treatment on the gas-phase conveying pipe after heating treatment, observing disappearance of light green in the conveying quartz pipe in the technological process, and finally cooling to room temperature to obtain the UAsTe single crystal. Compared with the prior art in which the stoichiometric ratio of UAsTe is 1: 1: 1, the method has the advantages that the raw material ratio is accurately regulated and controlled, and the double-temperature-zone gas-phase transportation parameters are optimized, so that the generation of toxic by-products such as uranium oxide and arsenic oxide is remarkably inhibited. According to the preparation method disclosed by the invention, the purity of the single crystal is improved by more than 30%, and meanwhile, stable growth of millimeter-scale large-size crystals is realized.

Description

Technical Field

[0001] The present invention relates to the field of crystal growth, and in particular to a UAsTe single crystal and a preparation method thereof. Background Art

[0002] The exploration of novel quantum topological materials remains a core topic in current condensed matter physics research. The discovery of the quantum spin Hall effect in HgTe quantum wells ushered in a new era of quantum research in condensed matter physics. Since then, a series of new quantum materials with unique topological properties have emerged, greatly enriching the scope of condensed matter physics research. These materials include three-dimensional topological insulators, topological semimetals, topological superconductors, and magnetic topological quantum materials.

[0003] Among these topological materials, topological semimetals differ significantly from topological insulators and topological superconductors. Their unique band structure allows band crossing without hybridization, thus preventing the opening of an energy gap. This property enables topological semimetals to exhibit three-dimensional massless Dirac or Weyl fermions with linear dispersion in all three dimensions of momentum space. It is this unique bulk electronic structure that endows topological semimetals with many extraordinary physical properties and provides a broad scope for the realization of a variety of intriguing physical phenomena and potential applications.

[0004] Heavy fermion systems are a typical example of complex, strongly correlated electronic systems, characterized by complex interactions between quasiparticles within them, resulting in a rich array of quantum properties. These properties are not only of great significance in fundamental scientific research but also hold broad application prospects in practical production and everyday life. For example, many heavy fermion materials exhibit superconducting properties, enabling resistance-free electrical conduction under specific conditions, significantly improving power transmission efficiency and effectively saving energy. Furthermore, a key approach to organically combining magnetism with strong correlation is to exploit the competition between the Kondo effect and magnetic ordering. In this mechanism, localized magnetic moments interact with conduction electrons to form many-body entangled states, giving rise to complex physical phenomena. Uranium-based compounds possess a unique dual nature: their 5f electrons can behave both in a localized state and in an itinerant state, making them more interesting to study than the typically localized 4f electrons. In particular, uranium-based compounds often contain multiple 5f electrons, some of which participate in magnetic ordering while others participate in Kondo screening. This complex electronic behavior makes uranium-based compounds ideal platforms for studying topological, magnetic, and strongly correlated physics. Therefore, in-depth research on this type of material will not only help reveal the physical nature of complex strongly correlated electronic systems, but may also provide important theoretical basis and technical support for the development of new functional materials, which has important scientific significance and practical application value.

[0005] Uranium arsenic telluride (UAsTe) is an important heavy fermion topological material with a stoichiometric ratio of 1:1:1. The compound has a ferromagnetic transition temperature of 66 K and exhibits significant magnetic characteristics. The crystal structure of UAsTe belongs to the tetragonal system with lattice parameters of a=4.151 Å and c=17.273 Å, and the space group is I4 / mmm (139). Its specific heat coefficient is 57 mJ / mol·K 2 , this value indicates that its electronic state has a moderate degree of correlation effect. In UAsTe crystals, the large c / a ratio (c / a≈4.16) and the unique atomic stacking method make it exhibit quasi-two-dimensional crystal structure characteristics. This structural characteristic makes UAsTe crystals easy to cleave along the c-axis, and thin layered dissociation surfaces can be obtained. In addition, its Fermi surface also exhibits quasi-two-dimensional characteristics, which is closely related to the anisotropy of the crystal structure. Under the action of external pressure, the ferromagnetism of UAsTe may undergo a transformation, and a quantum critical point is expected to appear. The appearance of quantum critical points is usually accompanied by a significant enhancement of electron correlation effects and a variety of quantum phase transition behaviors, which provides a rich research space for studying its complex physical properties. Therefore, the development of a method for preparing high-quality UAsTe single crystals has extremely important scientific value and application significance for in-depth study of its unique topological properties, magnetic behavior, and quantum critical phenomena. Summary of the Invention

[0006] The present invention addresses the problems of insufficient purity, limited size, complex process and high cost of UAsTe crystals in the prior art, and provides a UAsTe single crystal and a preparation method thereof.

[0007] The technical method of the present invention is as follows: A method for preparing a UAsTe single crystal, the preparation method comprising: S1. Prepare the product with purity greater than or equal to 99.9%. 238 U raw material, As raw material with a purity greater than or equal to 99.99%, Te raw material with a purity greater than or equal to 99.999%, I2 raw material with a purity greater than or equal to 99.99%, gas phase transport pipe and quartz seal; S2. Under inert atmosphere, 238 The U raw materials are surface polished, cleaned and dried; in the atmospheric environment, the gas phase transport quartz tubes and quartz seals are cleaned and dried; S3, the As raw material, Te raw material, I2 raw material in step S1 and the raw material processed in step S2 238 U raw materials, vapor transport quartz tubes and quartz seals are placed together in a glove box filled with inert gas; S4. In the glove box, 238U raw material, As raw material and Te raw material are mixed in the atomic ratio of 1:0.8:0.75-0.95, and then placed in the bottom of the gas phase transport pipe. I2 is used as the gas phase transport agent at 3-5 mg / cm 3 Weigh and place at the bottom of the gas transport tube; S5. Place a quartz seal in the gas phase transport tube treated in step S4, seal the gas phase transport tube in an inert atmosphere in a glove box, and then remove the glove box; S6, vacuuming and sealing the gas phase transport pipe processed in step S5; S7. Place the gas phase transport tube treated in step S6 into a dual-temperature zone tubular furnace. The reaction end where the raw materials are placed is the reaction end, and the temperature of the reaction end is controlled at 1030±10°C. The quartz seal is the sealing end, and the temperature of the sealing end is controlled at 970±10°C. The gas phase transport tube is subjected to a temperature increase treatment and then a heat preservation treatment. During the process, the disappearance of the light green color in the transmission quartz tube needs to be observed. Finally, the temperature is lowered to room temperature to obtain a UAsTe single crystal.

[0008] Preferably, the 238 The atomic ratio of the U raw material, the As raw material and the Te raw material is 1:0.8:0.9.

[0009] The length of the gas phase transport pipe is 20-40 cm, and the gas phase transport pipe has an inwardly contracted structure 5-15 cm away from the pipe opening, and the inwardly contracted structure fixes the quartz sealing component.

[0010] In the step S2, 238 The U raw material is polished with sandpaper of 1200 mesh or higher, ultrasonically cleaned with anhydrous ethanol, and vacuum dried; the gas phase transport quartz tube and quartz seal are ultrasonically cleaned with anhydrous ethanol, wiped dry or baked.

[0011] The inert atmosphere in steps S2, S3 and S5 is high-purity argon or high-purity nitrogen with a purity greater than or equal to 99.99%.

[0012] In the step S4, the gas phase transport tube requires 0.18-0.25 g of I2 as a gas phase transport agent, and the weighed I2 is placed at the bottom of the gas phase transport tube.

[0013] In the step S6, the vacuum treatment step includes: using a mechanical pump and a molecular pump to vacuum the room to less than or equal to 1×10 -3 Pa.

[0014] In the step S6, the sealing is performed by water welding. In the steps S5 and S6, the sealing and fusing time are within 1 hour.

[0015] In the step S7, the temperature program is set to a heating time of 9-11 hours, the reaction end is raised to 1030±10°C, the sealing end is raised to 970±10°C, and the constant temperature time is 150-170 hours. The reaction endpoint is determined by observing the color change in the tube. After the insulation stage is completed, the temperature is naturally cooled to room temperature.

[0016] The present invention also provides a UAsTe single crystal, which is obtained by the preparation method according to any one of claims 1 to 9.

[0017] The beneficial effects of the present invention are: 1. Compared to the existing technology, which uses a stoichiometric ratio of 1:1:1 for UAsTe, this invention significantly suppresses the formation of toxic byproducts such as uranium oxide and arsenic oxide by precisely controlling the raw material ratio (preferably U:As:Te = 1:0.8:0.9) and optimizing dual-temperature zone vapor transport parameters. This preparation method improves single crystal purity by over 30% and enables the stable growth of large, millimeter-sized crystals.

[0018] 2. Compared with the thin strip crystals (about 1 mm in diameter) prepared by traditional methods, the single crystals obtained by the present invention have the following advantages: (1) the crystal size is increased by 3-5 times; (2) the structural uniformity is improved by 40%; (3) the surface defect density is reduced by 60%; (4) it provides a more ideal sample platform for subsequent physical property research.

[0019] 3. In the prior art, the introduction of raw material impurities is one of the important reasons for the poor quality of single crystals. This invention establishes a strict raw material screening system: nuclear grade 238 U (≥99.9%); high-purity As (≥99.99%); ultra-pure Te (≥99.999%); through full vacuum sealing treatment, to ensure zero pollution of raw materials.

[0020] 4. The present invention uses ≥1200 mesh polishing to remove surface impurities, inert gas protection throughout the reaction process, and anhydrous ethanol ultrasonic deep cleaning to reduce the impurity content of the product to ppm level.

[0021] 5. The present invention eliminates the complex precursor preparation process, shortens the preparation cycle to 8 days, reduces energy consumption by 25%, and significantly improves operational safety, solving the industry pain points of high cost and high risk of traditional processes.

[0022] 6. In the existing technology, unreasonable settings of growth temperature and time can easily lead to poor single crystal quality or even growth failure. The present invention innovatively adopts dual-zone gradient control: reaction zone: 1030±10℃; growth zone: 970±10℃; combined with precise constant temperature for 150-170 hours, the crystal growth success rate is increased from 60% to more than 95%.

[0023] 7. This invention successfully solves the four major technical bottlenecks in the field of UAsTe single crystal preparation: insufficient purity (impurity control), size limitation (growth regulation), complex process (process optimization), and high cost (efficiency improvement). BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the atomic structure and single crystal sample diagram of UAsTe in Example 1; wherein, Figure 1 (a) is the atomic structure diagram of UAsTe in Example 1, Figure 1 (b) is the first sample image of UAsTe single crystal; Figure 1 (c) is the second sample image of UAsTe single crystal; Figure 2 This is the EDS composition spectrum of a typical UAsTe single crystal grown in Example 1; Figure 3 is the X-ray diffraction pattern of a typical UAsTe single crystal grown in Example 1; Figure 4 The resistivity curve of a typical UAsTe single crystal grown in Example 1; Figure 5 Specific heat curve of a typical UAsTe single crystal grown in Example 1; Figure 6 This is a pressure curve diagram of a typical UAsTe single crystal grown in Example 1; Figure 7 This is the ARPES spectrum of a typical UAsTe single crystal grown in Example 1; wherein, Figure 7 (a) Brillouin zone diagram of UAsTe; Figure 7 (b) UAsTe single crystal test results KZ picture; Figure 7 (c) UAsTe single crystal test results ΓMX A diagram of the topological structure of the Fermi surface on a plane; Figure 7 (d) is obtained from UAsTe single crystal test ZAR A diagram of the topological structure of the Fermi surface in a plane. DETAILED DESCRIPTION

[0025] The following is a clear and complete description of the technical solution of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0026] The present invention provides a method for preparing a UAsTe single crystal, the preparation method comprising: S1. Prepare the product with purity greater than or equal to 99.9%. 238U raw material, As raw material with a purity greater than or equal to 99.99%, Te raw material with a purity greater than or equal to 99.999%, I2 raw material with a purity greater than or equal to 99.99%, gas phase transport pipe and quartz seal.

[0027] In the present invention, the gas-phase transport tube is 20-40 cm long and has a constricted structure 5-15 cm from the tube opening, which secures a quartz seal. Preferably, the gas-phase transport tube is made of quartz, is 30 cm long, and has a constricted structure 10 cm from the opening to secure the quartz seal. The quartz seal can be a quartz plug.

[0028] The present invention establishes a strict raw material screening system: nuclear grade 238 U (≥99.9%); high-purity As (≥99.99%); ultra-pure Te (≥99.999%); through full vacuum sealing treatment, to ensure zero pollution of raw materials.

[0029] S2. Under inert atmosphere, 238 The U raw material is surface polished, cleaned and dried; in an atmospheric environment, the vapor transport quartz tube and quartz seal are cleaned and dried.

[0030] In the present invention, the inert atmosphere is high-purity argon or nitrogen with a purity of 99.99% or higher. High-purity argon or nitrogen with a purity of 99.99% or higher is used to maintain the inert atmosphere throughout the entire process. The inert atmosphere effectively isolates oxygen and moisture, prevents oxidation of the raw materials, and avoids the introduction of additional impurities.

[0031] In the present invention, 238 The raw material U is polished with sandpaper of 1200 grit or greater, ultrasonically cleaned with anhydrous ethanol, and vacuum dried. Here, polishing is performed with sandpaper of 1200 grit or greater to remove surface impurities. For example, 1300 grit, 1500 grit, or 1800 grit sandpaper can be used. The cleaning time is 5-15 minutes. Preferably, the cleaning time is 5-10 minutes.

[0032] In the present invention, the vapor transport quartz tube and the quartz seal are ultrasonically cleaned with anhydrous ethanol and then wiped or baked. The cleaning time is 5-15 minutes. Preferably, the cleaning time is 5-10 minutes.

[0033] Specifically, 238 The processing process of U raw materials is as follows: 238 Wrap the U in aluminum foil and remove it. Use ≥1200 grit sandpaper and anhydrous ethanol to fine-grind the surface. Ultrasonic clean it again with anhydrous ethanol (5-10 minutes) and strictly dry it. For quality control, operate the entire process under an inert atmosphere to ensure that no impurities are introduced.

[0034] Specifically, the processing process of the gas phase transport quartz tube and quartz seal is as follows: the inner and outer walls of the gas phase transport tube and the quartz plug are ultrasonically cleaned with anhydrous ethanol for 5-10 minutes, then taken out and wiped dry, and placed in a glove box together with the manual baffle valve.

[0035] The present invention adopts ≥1200 mesh polishing to remove surface impurities, inert gas protection throughout the reaction process and anhydrous ethanol ultrasonic deep cleaning, so that the impurity content of the product is reduced to ppm level.

[0036] S3, the As raw material, Te raw material, I2 raw material in step S1 and the raw material processed in step S2 238 The U raw material, vapor transport quartz tube and quartz seal are placed together in a glove box filled with inert gas.

[0037] In one embodiment, the inert atmosphere is high-purity argon or nitrogen with a purity greater than or equal to 99.99%. High-purity argon or nitrogen with a purity greater than or equal to 99.99% is used to maintain an inert atmosphere throughout the entire process. The inert atmosphere effectively isolates oxygen and moisture, prevents oxidation of the raw materials, and avoids the introduction of additional impurities.

[0038] S4. In the glove box, 238 U raw material, As raw material and Te raw material are mixed in the atomic ratio of 1:0.8:0.75-0.95, and then placed in the bottom of the gas phase transport pipe. I2 is used as the gas phase transport agent at 3-5 mg / cm 3 Weigh and place it at the bottom of the gas transport tube.

[0039] Preferably, the 238 The atomic ratio of the U raw material, the As raw material and the Te raw material is 1:0.8:0.9.

[0040] In the present invention, the gas phase transport tube requires 0.18-0.25 g of I2 as a gas phase transport agent, and the weighed I2 is placed at the bottom of the gas phase transport tube.

[0041] For example, 238 The U, As, and Te raw materials were precisely controlled to maintain an atomic ratio of 1:0.8:0.9. 0.18-0.25g of iodine was added as a transport medium. After the ingredients were mixed, they were placed into a gas-phase transport tube. All raw materials were weighed and loaded into tubes in a glove box according to the operating specifications.

[0042] S5. Place a quartz seal in the gas phase transport tube treated in step S4, seal the gas phase transport tube in an inert atmosphere in a glove box, and then take the glove box out.

[0043] S6, vacuuming and sealing the gas phase transport pipe processed in step S5.

[0044] In the present invention, the vacuum treatment step includes: using a mechanical pump and a molecular pump to vacuum the air to a value less than or equal to 1×10 -3 Pa.

[0045] In the present invention, the sealing is performed by water welding and the sealing time is within 1 hour.

[0046] Specifically, the vacuum sealing process is carried out in steps. After the initial sealing, the glove box is removed and vacuumed by a mechanical pump + a molecular pump (≤1×10 -3 Pa). Immediately perform water welding sealing. The key to the technology is that all sealing operations must be completed within 1 hour.

[0047] S7. Place the gas phase transport tube treated in step S7 into a dual-temperature zone tubular furnace. The reaction end where the raw materials are placed is the reaction end, and the temperature of the reaction end is controlled at 1030±10°C. The quartz seal is the sealing end, and the temperature of the sealing end is controlled at 970±10°C. The gas phase transport tube is subjected to a temperature increase treatment and then a heat preservation treatment. During the process, the disappearance of the light green color in the transmission quartz tube needs to be observed. Finally, the tube is cooled to room temperature to obtain a UAsTe single crystal.

[0048] In the present invention, the temperature program is set to a heating time of 9-11 hours, the reaction end is raised to 1030±10°C, the sealing end is raised to 970±10°C, and the constant temperature time is 150-170 hours. The reaction endpoint is determined by observing the color change in the tube (the disappearance of the light green color in the transmission quartz tube needs to be observed). After the insulation stage is completed, the temperature is naturally cooled to room temperature.

[0049] In the present invention, 238 A U:As:Te atomic ratio of 1:0.8:0.75-0.95 is crucial for minimizing the formation of toxic and hazardous byproducts. Furthermore, adjusting the raw material ratio effectively suppresses byproduct formation. Vacuum control is crucial for ensuring crystal quality, and the holding time needs to be dynamically adjusted based on the raw material quantity. This process achieves high-quality production of UAsTe single crystals by optimizing the raw material ratio, improving temperature control, and enhancing sealing technology, effectively overcoming the technical challenges of low purity and small size associated with traditional methods.

[0050] In summary, this invention addresses the existing challenges of low purity, poor quality, small size, and complex processes in the preparation of UAsTe single crystals by optimizing the raw material ratio, growth conditions, and process flow. This allows for the stable growth of high-quality, large-scale single crystal samples. This has important applications in fields such as nuclear materials research and quantum device development. The successful preparation of high-quality single crystal samples that meet scientific research needs provides a new material platform for related research.

[0051] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0052] The present invention is described in detail below by way of examples and experimental examples, which are merely illustrative and do not limit the present invention in any way.

[0053] Example 1 This embodiment provides a new method for preparing high-quality UAsTe single crystals, comprising the following steps: S1. Preparation of experimental raw materials and equipment. Use high-purity raw materials: 238 U (99.9%), As (99.99%), Te (99.999%), I2 (99.99%). The gas phase transport tube is made of quartz, 30 cm long, and has a retracted structure 10 cm from the opening to fix the quartz plug.

[0054] S2. Pretreatment of raw materials and equipment. 238 U treatment: polish with 1200 grit sandpaper under inert gas protection 238 The U surface was then ultrasonically cleaned (with anhydrous ethanol for 5 minutes) and dried for later use. Gas phase transport tube and quartz plug treatment: In an atmospheric environment, the inner and outer walls were ultrasonically cleaned with anhydrous ethanol for 5 minutes, dried, and transferred to a glove box.

[0055] S3, inert gas environment operation. 238 U, As, Te, I2) and equipment are placed in a glove box filled with high-purity argon or nitrogen (99.99%) to ensure an oxygen-free and water-free environment.

[0056] S4, ingredients and tubes. According to atomic ratio 238 U:As:Te = 1:0.8:0.9 Weigh the raw materials and place them at the bottom of the gas phase transport tube. Add I2 as a transport agent (3 mg / cm 3 ), quickly insert the quartz plug and seal the tube body with a manual baffle valve to isolate it from the external environment.

[0057] S5. Vacuum treatment and sealing. 238 After the U raw material, As raw material, Te raw material and gas phase transport agent I2 raw material are prepared, they are placed in the gas phase transport tube, which is connected to the mechanical pump-molecular pump system and vacuumed to 0.8×10 -3 Pa. The tube body is then sealed using a water welder to ensure that the quartz plug is completely fused to the tube wall.

[0058] S6. Crystal Growth. Place the sealed gas phase transport tube in a dual-zone tube furnace. Heat the reaction end to 1030°C over 10 hours and hold for 160 hours. Simultaneously heat the sealed end to 970°C. After holding, cool naturally to room temperature.

[0059] S7. Product extraction. The vapor transport tube is broken open, and large-sized UAsTe single crystals grow between the reaction end and the sealed end, with byproducts concentrated at the reaction end.

[0060] Figure 1 (a) and Figure 1 (b) is the atomic structure and single crystal sample of UAsTe prepared in Example 1. The single crystal sample is very bright and flat under a microscope. The size of the typical single crystal prepared in this example is 4×3×1.5mm. 3 , which is consistent with the quasi-two-dimensional tetragonal crystal structure characteristics of UAsTe. Figure 2 This is the EDS composition spectrum of a typical UAsTe single crystal grown in this example. The composition of the UAsTe single crystal perfectly conforms to the stoichiometric ratio of U:As:Te=1:1:1. Figure 3 This is the X-ray diffraction pattern of a typical UAsTe single crystal grown in this example, which only has the diffraction peak of the (001) face cluster. Figure 4 This is the resistivity curve of a typical UAsTe single crystal grown in this example, with a ferromagnetic transition temperature of approximately 66 K. Figure 5 This is a graph showing the specific heat of a typical UAsTe single crystal grown in this example. The ferromagnetic transition temperature is around 66 K. Figure 6 This is a pressure curve of a typical UAsTe single crystal grown in this example, showing the change of ferromagnetic transition temperature under pressure. Figure 7 This is the ARPES spectrum of a typical UAsTe single crystal grown in this example. Its Fermi surface is clearly visible, indicating that the quality of the single crystal is very high.

[0061] Example 2 This embodiment provides a new method for preparing high-quality UAsTe single crystals, comprising the following steps: S1. Preparation of experimental raw materials and equipment. Use high-purity raw materials: 238 U (99.9%), As (99.9997%), Te (99.999%), I2 (99.99%). The gas phase transport tube is made of quartz, 30 cm long, and has a retracted structure 10 cm from the opening to fix the quartz plug.

[0062] S2. Pretreatment of raw materials and equipment. 238 U treatment: polish with 1500 grit sandpaper under inert gas protection 238 The U surface was then ultrasonically cleaned (anhydrous ethanol, 10 minutes), dried and set aside. Gas transport tube and quartz plug treatment: In an atmospheric environment, the inner and outer walls were ultrasonically cleaned with anhydrous ethanol (5 minutes), dried and transferred to a glove box.

[0063] S3, inert gas environment operation. 238U, As, Te, I2) and equipment are placed in a glove box filled with high-purity argon or nitrogen (99.99%) to ensure an oxygen-free and water-free environment.

[0064] S4, ingredients and tubes. According to atomic ratio 238 U:As:Te = 1:0.8:0.9 Weigh the raw materials and place them at the bottom of the gas phase transport tube. Add I2 as a transport agent (5 mg / cm 3 ), quickly insert the quartz plug and seal the tube body with a manual baffle valve to isolate it from the external environment.

[0065] S5. Vacuum treatment and sealing. 238 After the U raw material, As raw material, Te raw material and gas phase transport agent I2 raw material are prepared, they are placed in the gas phase transport tube, which is connected to the mechanical pump-molecular pump system and vacuumed to 1.0×10 -3 Pa. The tube body is then sealed using a water welder to ensure that the quartz plug is completely fused to the tube wall.

[0066] S6. Crystal Growth. Place the sealed gas phase transport tube in a dual-zone tube furnace. Heat the reaction end to 1030°C over 10 hours and hold for 150 hours. Simultaneously heat the sealed end to 970°C. After holding, cool naturally to room temperature.

[0067] S7. Product extraction. The vapor transport tube is broken open, and large-sized UAsTe single crystals grow between the reaction end and the sealed end, with byproducts concentrated at the reaction end.

[0068] It has been determined that the crystal prepared in this example has only a diffraction peak of the (001) face cluster, and has a ferromagnetic transition point of 66 K in the resistivity and specific heat curves. The crystal is a UAsTe single crystal.

[0069] Example 3 This embodiment provides a new method for preparing high-quality UAsTe single crystals, comprising the following steps: S1. Preparation of experimental raw materials and equipment. Use high-purity raw materials: 238 U (99.92%), As (99.992%), Te (99.999%), I2 (99.99%). The gas phase transport tube is made of quartz, 30 cm long, and has a retracted structure 10 cm from the opening to fix the quartz plug.

[0070] S2. Pretreatment of raw materials and equipment. 238 U treatment: polish with 1300 grit sandpaper under inert gas protection 238 The U surface was then ultrasonically cleaned (with anhydrous ethanol for 8 minutes) and dried for later use. Treatment of the gas phase transport tube and quartz plug: In an atmospheric environment, the inner and outer walls were ultrasonically cleaned with anhydrous ethanol for 5 minutes, dried, and transferred to a glove box.

[0071] S3, inert gas environment operation. 238 U, As, Te, I2) and equipment are placed in a glove box filled with high-purity argon or nitrogen (99.992%) to ensure an oxygen-free and water-free environment.

[0072] S4, ingredients and tubes. According to atomic ratio 238 U:As:Te = 1:0.8:0.9 Weigh the raw materials and place them at the bottom of the gas phase transport tube. Add I2 as a transport agent (4 mg / cm 3 ), quickly insert the quartz plug and seal the tube body with a manual baffle valve to isolate it from the external environment.

[0073] S5. Vacuum treatment and sealing. 238 After the U raw material, As raw material, Te raw material and gas phase transport agent I2 raw material are prepared, they are placed in the gas phase transport tube, which is connected to the mechanical pump-molecular pump system and vacuumed to 0.9×10 -3 Pa. The tube body is then sealed using a water welder to ensure that the quartz plug is completely fused to the tube wall.

[0074] S6. Crystal Growth. Place the sealed gas phase transport tube in a dual-zone tube furnace. Heat the reaction end to 1020°C over 11 hours and hold for 170 hours. Simultaneously heat the sealed end to 970°C. After holding, cool naturally to room temperature.

[0075] S7. Product extraction. The vapor transport tube is broken open, and large-sized UAsTe single crystals grow between the reaction end and the sealed end, with byproducts concentrated at the reaction end.

[0076] It has been determined that the crystal prepared in this example has only a diffraction peak of the (001) face cluster, and has a ferromagnetic transition point of 66 K in the resistivity and specific heat curves. The crystal is a UAsTe single crystal.

[0077] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a UAsTe single crystal, characterized in that: The preparation method comprises: S1. Prepare the product with purity greater than or equal to 99.9%. 238 U raw material, As raw material with a purity greater than or equal to 99.99%, Te raw material with a purity greater than or equal to 99.999%, I2 raw material with a purity greater than or equal to 99.99%, gas phase transport pipe and quartz seal; S2. Under inert atmosphere, 238 The U raw materials are surface polished, cleaned and dried; in the atmospheric environment, the gas phase transport quartz tubes and quartz seals are cleaned and dried; S3, the As raw material, Te raw material, I2 raw material in step S1 and the raw material processed in step S2 238 U raw materials, vapor transport quartz tubes and quartz seals are placed together in a glove box filled with inert gas; S4. In the glove box, 238 U raw material, As raw material and Te raw material are mixed in the atomic ratio of 1:0.8:0.75-0.95, and then placed in the bottom of the gas phase transport pipe. I2 is used as the gas phase transport agent at 3-5 mg / cm 3 Weigh and place at the bottom of the gas transport tube; S5. Place a quartz seal in the gas phase transport tube treated in step S4, seal the gas phase transport tube in an inert atmosphere in a glove box, and then remove the glove box; S6, vacuuming and sealing the gas phase transport pipe processed in step S5; S7. Place the gas phase transport tube treated in step S6 into a dual-temperature zone tubular furnace. The reaction end where the raw materials are placed is the reaction end, and the temperature of the reaction end is controlled at 1030±10°C. The quartz seal is the sealing end, and the temperature of the sealing end is controlled at 970±10°C. The gas phase transport tube is subjected to a temperature increase treatment and then a heat preservation treatment. During the process, the disappearance of the light green color in the transmission quartz tube needs to be observed. Finally, the temperature is lowered to room temperature to obtain a UAsTe single crystal.

2. The preparation method according to claim 1, characterized in that described 238 The atomic ratio of the U raw material, the As raw material and the Te raw material is 1:0.8:0.

9.

3. The preparation method according to claim 1, characterized in that In the step S2, 238 The U raw material is polished with sandpaper of 1200 mesh or higher, ultrasonically cleaned with anhydrous ethanol, and vacuum dried; the gas phase transport quartz tube and quartz seal are ultrasonically cleaned with anhydrous ethanol, wiped dry or baked.

4. The preparation method according to claim 1, characterized in that The inert atmosphere in steps S2, S3 and S5 is high-purity argon or high-purity nitrogen with a purity greater than or equal to 99.99%.

5. The preparation method according to claim 1, characterized in that The length of the gas phase transport pipe is 20-40 cm, and the gas phase transport pipe has an inwardly contracted structure 5-15 cm away from the pipe opening, and the inwardly contracted structure fixes the quartz sealing component.

6. The preparation method according to claim 1, characterized in that In the step S4, the gas phase transport tube requires 0.18-0.25 g of I2 as a gas phase transport agent, and the weighed I2 is placed at the bottom of the gas phase transport tube.

7. The preparation method according to claim 1, characterized in that In the step S6, the step of vacuuming includes: Use mechanical pump and molecular pump to evacuate to less than or equal to 1×10 -3 Pa.

8. The preparation method according to claim 1, characterized in that In the step S6, the sealing is performed by water welding. In the steps S5 and S6, the sealing and fusing time are within 1 hour.

9. The preparation method according to claim 1, characterized in that In the step S7, the temperature program is set to a heating time of 9-11 hours, the reaction end is raised to 1030±10°C, the sealing end is raised to 970±10°C, and the constant temperature time is 150-170 hours. The reaction endpoint is determined by observing the color change in the tube. After the insulation stage is completed, the temperature is naturally cooled to room temperature.

10. A UAsTe single crystal, characterized in that The UAsTe single crystal is obtained by the preparation method according to any one of claims 1 to 9.

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