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CN-122010078-A - Potassium europium phosphate extremely-low-temperature magnetic refrigeration material and preparation method and application thereof

CN122010078ACN 122010078 ACN122010078 ACN 122010078ACN-122010078-A

Abstract

The invention belongs to the technical field of magnetic refrigeration materials, and particularly discloses a potassium phosphate europium-doped low-temperature magnetic refrigeration material and a preparation method and application thereof. The material KEuPO 4 belongs to an orthorhombic system, the space group is Pnma, and the material polycrystal block can be prepared by adopting a step solid phase reaction method under the atmosphere of hydrogen-argon mixed gas. The magnetic phase transition temperature of the material is 1.0-1.2K, and the maximum isothermal magnetic entropy change values of the material are respectively 32.8-33.4J/kg.K and 49.7-52.1J/kg.K under the magnetic field change of 0-2T and 0-5T along with the reversible giant magnetocaloric effect, and the material is better than the commercial extremely-low temperature magnetic refrigeration material Gd 3 Ga 5 O 12 . The europium-based phosphate KEuPO 4 material provided by the invention has the advantages of simple preparation process, good material stability, obvious magnetocaloric effect and the like, and has a good application prospect in the field of ultralow-temperature magnetic refrigeration.

Inventors

  • ZHANG YIKUN
  • GONG XIAOLI
  • CHEN WANG
  • ZHANG ZHENQIAN
  • LI LINGWEI

Assignees

  • 杭州电子科技大学

Dates

Publication Date
20260512
Application Date
20260202

Claims (8)

  1. 1. The preparation method of the potassium europium phosphate ultralow-temperature magnetic refrigeration material is characterized by comprising the following steps of: (1) Obtaining a europium source, K 2 CO 3 and NH 4 H 2 PO 4 as raw materials, wherein the europium source is Eu 2 O 3 or Eu (No 3 ) 3 ; (2) Weighing raw materials according to the mol ratio of Eu to K to P of 1:1:1.1 to 1:1.2, fully grinding, uniformly mixing, and presintering for 3-5 hours at 500-570 ℃; (3) Fully grinding the presintered powder, tabletting, performing secondary sintering at 950-1050 ℃ for 7-10 hours, and cooling to room temperature along with a furnace after the secondary sintering is finished to obtain a precursor; (4) Crushing the precursor obtained in the step (3), adding K 2 CO 3 with the dosage of 1-1.25 times that of K 2 CO 3 in the step (2), fully grinding again, uniformly mixing, tabletting, sintering at 1200-1320 ℃ for 12-18 hours, and cooling to room temperature along with a furnace to obtain a KEuPO 4 polycrystalline block, wherein the KEuPO 4 polycrystalline block is used as a potassium europium phosphate ultra-low temperature magnetic refrigeration material and consists of a single phase, belongs to an orthorhombic system, and has a space group of Pnma, a= 7.3590 (2) a, b= 5.5690 (6) a, c= 9.6300 (4) a, and alpha=beta=gamma=90 o .
  2. 2. The process according to claim 1, wherein in the steps (3) and (4), the pressure applied during tabletting is 500 to 800 MPa and the dwell time is 3 to 8 minutes.
  3. 3. The method according to claim 1, wherein the pre-firing in step (2), the sintering in step (3) and the sintering in step (4) are performed in a flowing mixed atmosphere containing hydrogen and argon.
  4. 4. The method according to claim 1, wherein the temperature rise rates of the pre-firing in step (2), the sintering in step (3) and the sintering in step (4) are 3 to 5 ℃.
  5. 5. A method according to claim 3, wherein the hydrogen gas in the mixed atmosphere has a volume fraction of 5-10%.
  6. 6. The method of claim 1, wherein the Eu 2 O 3 、Eu(No 3 ) 3 、NH 4 H 2 PO 4 and K 2 CO 3 are not less than 99.9% pure.
  7. 7. The potassium europium phosphate ultralow temperature magnetic refrigeration material prepared by the preparation method of any one of claims 1-6.
  8. 8. The use of the europium-potassium phosphate ultralow-temperature magnetic refrigeration material according to claim 7, wherein the ultralow-temperature magnetic refrigeration material is subjected to low-temperature magnetic refrigeration at an ambient temperature of 1.0-1.2K ℃ and an external magnetic field of 0-2T and 0-5T, and the isothermal magnetic entropy change of the europium-potassium phosphate ultralow-temperature magnetic refrigeration material reaches 32.8-33.4J/kg.K and 49.7-52.1J/kg.K.

Description

Potassium europium phosphate extremely-low-temperature magnetic refrigeration material and preparation method and application thereof Technical Field The invention relates to the technical field of rare earth magnetic functional materials, in particular to a potassium phosphate europium extremely-low-temperature magnetic refrigeration material and a preparation method and application thereof. Background The high-performance extremely low temperature refrigeration technology has wide application prospect and plays an irreplaceable role in the scientific fields of quantum computation, space detection, high-energy physics, low-temperature superconduction, nuclear technology and the like. The fields generally require cold source equipment to have the requirements of small vibration, low noise, high stability, long working period and the like. The magnetic refrigeration technology is a novel solid refrigeration mode for realizing refrigeration by utilizing the material magnetocaloric effect, and compared with the traditional gas compression/expansion refrigeration technology, the magnetic refrigeration has the advantages of compact structure, less moving parts, long service life, difficult leakage, no dependence on gravity, potential high efficiency and the like, and can completely meet the requirements. The magnetocaloric effect is a physical phenomenon of heat absorption/release accompanied by the change of magnetic moment order of a material system due to the change of an external magnetic field. The magnitude of the material magnetocaloric effect is critical to determine the refrigerating capacity and efficiency of the material. The current research on very low temperature magnetic refrigeration materials mainly focuses on hydrate paramagnetic salts such as FeNH 4(SO4)2·12H2 O (ferric ammonium sulfate, FAA), mn (NH 4)2(SO4)2·6H2 O (manganese ammonium sulfate, MAS), KCr (SO 4)2·12H2 O (chromium potassium sulfate, CPA) and rare earth gallium garnet Gd 3Ga5O12 (GGG) single crystals or powder to be used commercially, but the magnetic refrigeration materials have the defects of relatively small magnetic entropy change value under low magnetic field change generally, certain limitation in the use process, such as slow thermal diffusion of the hydrate paramagnetic salt, easy dehydration of water molecules, poor crystal stability, relatively complex preparation process and the like. The prior art such as "A New Type of Divalent Europium Compound MEuPO, (M = K, Rb, Cs), its Synthesis, Crystal Structure, and Properties" discloses a preparation method of potassium europium phosphate, which comprises the steps of preparing EuPO 4 precursor by the reaction of Eu (NO 3)3 or Eu 2O3) and phosphate, and using alkali metal potassium as a reducing agent, and the total preparation period takes days, the reaction is slow, the mass production is difficult, and the method is not suitable for magnetic refrigeration materials, because the magnetic refrigeration materials can play a role in refrigeration with higher yield, and can be applied to magnetic refrigeration. Disclosure of Invention Aiming at the problems and the defects, the invention provides a potassium europium phosphate ultralow-temperature magnetic refrigeration material and a preparation method thereof. The material has a chemical formula of KEuPO 4 polycrystal blocks, has the advantages of simple preparation process, good material stability, obvious magnetocaloric effect and the like, and can be applied to ultralow-temperature magnetic refrigeration. The invention aims to solve the problems of small magnetic entropy change, complex preparation process, long preparation period and poor stability of the existing extremely-low-temperature magnetic refrigeration material. The invention provides a potassium europium phosphate ultralow temperature magnetic refrigeration material, which has a molecular formula of KEuPO 4, is composed of single phases, belongs to an orthorhombic system, has a space group of Pnma, has lattice constants of a= 7.3590 (2) a, b= 5.5690 (6) a, c= 9.6300 (4) a, and alpha=beta=gamma=90 o, can be obtained by adopting a stepwise solid phase reaction method in a hydrogen-argon mixed gas atmosphere, and simultaneously discloses application of the potassium europium phosphate in ultralow temperature magnetic refrigeration, wherein the magnetic phase transition temperature of the potassium europium phosphate is 1.0-1.2K, and the isothermal magnetic entropy change maximum values are 32.8-33.4J/kg.K and 49.7-52.1J/kg.K under the conditions of an external magnetic field of 0-2T and 0-5T. Specifically, the invention provides a preparation method of a potassium europium phosphate ultralow-temperature magnetic refrigeration material, which comprises the following steps: (1) Obtaining a europium source, K 2CO3 and NH 4H2PO4 as raw materials, wherein the europium source is Eu 2O3 or Eu (No 3)3; (2) Weighing raw materials according to the mol ratio of Eu to K to P