Application of a hexagonal crystal material Sr6GdSc(BO3)6 in the field of ultra-low temperature magnetic refrigeration
By using the hexagonal crystal material Sr6GdSc(BO3)6 as the magnetic refrigeration material, the problems of poor thermal conductivity and high cost of traditional materials at extremely low temperatures are solved, achieving efficient and stable ultra-low temperature refrigeration effect, which is suitable for ultra-low temperature magnetic refrigeration technology.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTHERN UNIVERSITY OF SCIENCE AND TECHNOLOGY
- Filing Date
- 2026-02-13
- Publication Date
- 2026-05-26
AI Technical Summary
Existing cryogenic refrigeration technologies rely on rare gases and complex machinery. Furthermore, traditional magnetic materials have poor thermal conductivity at extremely low temperatures and are prone to losing their water of crystallization, resulting in low refrigeration efficiency and high costs. This limits the choice of materials and makes it difficult to meet the needs of high-end technology applications.
The hexagonal crystal system material Sr6GdSc(BO3)6 is used as the magnetic refrigeration material. By introducing Gd3+ as a magnetic cation and small molecule ligands Sr2+, Sc2+, and BO33-, the distance between magnetic ions is small, reducing the interaction. The material does not contain water of crystallization and has significant magnetocaloric effect and stability, making it suitable for ultra-low temperature magnetic refrigeration.
It achieves efficient cooling at extremely low temperatures, has good material stability, is simple to prepare, is cost-effective, is suitable for industrial production, exhibits significant magnetic entropy change, and is applicable to the field of ultra-low temperature magnetic refrigeration.
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Figure CN122083535A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of magnetic refrigeration technology, specifically relating to the application of a hexagonal crystal material Sr6GdSc(BO3)6 in the field of ultra-low temperature magnetic refrigeration. Background Technology
[0002] In the development of modern science and technology, extremely low temperature environments have become a fundamental requirement in many cutting-edge scientific fields. Especially in the development of high-end technologies such as condensed matter physics, quantum information science, and space science, effective cryogenic refrigeration technology is crucial for the normal operation of experiments and equipment. However, achieving and maintaining such environments still faces multiple technical challenges.
[0003] Currently, cryogenic (below 1K) refrigeration technologies mainly rely on dilution refrigeration (DR) and adiabatic demagnetization refrigeration (ADR). While DR technology can achieve extremely low temperatures and provide continuous cooling, its dependence on the rare gas helium-3, as well as the complex gas paths and gravity involved, limits its application in special environments such as space exploration. In contrast, ADR technology, with its advantages of high efficiency, no need for complex mechanical support, and no dependence on scarce resources, is considered an alternative technology with significant application potential. ADR technology modulates the temperature of magnetic materials by changing the magnetic field environment. Based on the magnetocaloric effect, that is, under conditions without heat exchange, cooling is achieved by controlling the entropy of the material by changing the magnetic field strength. This process is highly dependent on the performance of the magnetic material used, especially its magnetocaloric effect at low magnetic fields and low temperatures. Although ADR technology has obvious advantages, its practical application efficiency and effectiveness largely depend on the magnetocaloric properties of the magnetic material. Ideal magnetic materials should exhibit efficient magnetic entropy changes at temperatures as low as millikelvin to ensure maximum cooling effect with minimal energy input. However, currently available magnetic materials often fail to meet the requirements for efficient cooling in extremely low-temperature environments, and the variety of materials available is limited, especially in the millikelvin temperature range. Paramagnetic salts widely used in extremely low-temperature regions, such as ferric ammonium sulfate (FeNH4(SO4)2˙12H2O) and potassium chromium sulfate (CrK(SO4)2˙12H2O), contain large amounts of water of crystallization. This poses a potential problem when these paramagnetic salts are used in high-vacuum environments, as they may lose this water of crystallization and consequently lose their adiabatic and demagnetizing cooling capabilities.
[0004] Furthermore, the development and application of magnetic materials must consider cost-effectiveness and environmental impact. Traditional paramagnetic salt magnetic refrigeration materials suffer from decreased thermal conductivity at extremely low temperatures due to the presence of water of crystallization. To improve the thermal conductivity of these materials at extremely low temperatures, gold wires are needed to connect the paramagnetic salts in series during the fabrication process, which significantly increases the cost and complexity of the material. Finding suitable materials requires not only meeting physical performance requirements but also considering both economic and environmental considerations. Researchers are currently dedicated to developing novel, cost-effective magnetic materials with high magnetic entropy changes to adapt to applications in extremely low temperature environments.
[0005] Future research directions for cryogenic refrigeration technology include developing new magnetic materials that need to maintain efficient magnetocaloric properties under extremely low temperatures and magnetic fields. Research also needs to focus on the chemical and structural stability of these materials, which is crucial for ensuring the reliability and efficiency of refrigeration equipment. Furthermore, researchers are exploring ways to reduce production costs by improving existing materials or inventing new synthesis techniques, while ensuring environmental sustainability remains unaffected.
[0006] With the increasing demand for extremely low-temperature conditions, the research and application of these materials will continue to expand, indicating the core position and broad application prospects of magnetic refrigeration technology in future technologies. Researchers are working hard to overcome the shortcomings of existing materials and to find new materials that can operate at low temperatures and low magnetic fields to meet the increasingly demanding requirements of scientific and technological applications. Summary of the Invention
[0007] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes the application of a hexagonal crystal material, Sr6GdSc(BO3)6, in the field of ultra-low temperature magnetic refrigeration. This magnetic refrigeration material exhibits significant magnetocaloric effects and superior low-temperature performance, providing new possibilities for ultra-low temperature magnetic refrigeration technology.
[0008] To address the aforementioned technical problems, this invention provides an application of the hexagonal crystal material Sr6GdSc(BO3)6 in the field of ultra-low temperature magnetic refrigeration.
[0009] Specifically, this invention uses the hexagonal crystal system material Sr6GdSc(BO3)6 as a magnetic refrigeration material. Compared with traditional commercial magnetic refrigeration materials, Sr6GdSc(BO3)6 introduces Gd... 3+ It is a magnetic cation, and has a relatively small molecular weight (Sr). 2+ ,Sc 2 + BO3 3- As a ligand, it exhibits a large magnetocaloric effect at extremely low temperatures. The main reason for this is that the adjacent magnetic cation Gd... 3+The distance between them reaches 7.8 Å, and the magnetic cation Gd 3+ With its large spin and extremely small magnetic anisotropy, the relatively small mass of the ligands ensures the distance between magnetic cations, minimizing the interaction between magnetic ions and thus maintaining the magnetic entropy at the lowest possible temperature. This structural characteristic makes Sr6GdSc(BO3)6 suitable for use in ultra-low temperature magnetic refrigeration. Furthermore, Sr6GdSc(BO3)6 is completely free of water of crystallization, making it more stable and providing better refrigeration performance compared to traditional commercial magnetic refrigeration materials such as ferric ammonium sulfate (FeNH4(SO4)2·12H2O) and potassium chromium sulfate (CrK(SO4)2·12H2O).
[0010] In some embodiments of the present invention, the hexagonal crystal material Sr6GdSc(BO3)6 does not undergo a phase transition at temperatures above 100 mK.
[0011] In some embodiments of the present invention, the hexagonal crystal material Sr6GdSc(BO3)6 satisfies at least one of the following conditions: ① Under a temperature of 1K and a magnetic field variation of 0-3T, the maximum magnetic entropy of the hexagonal crystal material Sr6GdSc(BO3)6 is not less than 59.49 mJ·cm⁻¹. -3 ·K -1 Or 13.61 J·kg -1 ·K -1 ; ② Under a temperature of 1K and a magnetic field variation of 0-2T, the maximum magnetic entropy change of the hexagonal crystal material Sr6GdSc(BO3)6 is not less than 53.95 mJ·cm⁻¹. -3 ·K -1 Or 12.34 J·kg -1 ·K -1 ; ③ Under a temperature of 1K and a magnetic field variation of 0-1T, the maximum magnetic entropy change of the hexagonal crystal material Sr6GdSc(BO3)6 is not less than 39.36 mJ·cm⁻¹. -3 ·K -1 Or 9.01 J·kg -1 ·K -1 .
[0012] Specifically, the hexagonal crystal material Sr6GdSc(BO3)6 does not undergo a phase transition at an extremely low temperature of 100 mK, exhibiting a significant magnetocaloric effect at extremely low temperatures. Furthermore, under a temperature of 1 K and a magnetic field variation of 0–3 T, the hexagonal crystal material Sr6GdSc(BO3)6 can achieve a maximum magnetic entropy change of 59.49 mJ·cm⁻¹. -3 ·K -1 Or 13.61 J·kg-1 ·K -1 Under a temperature of 1 K and a magnetic field variation of 0-2 T, the hexagonal crystal material Sr6GdSc(BO3)6 can achieve a maximum magnetic entropy change of 53.95 mJ·cm⁻¹. -3 ·K -1 Or 12.34 J·kg -1 ·K -1 Under a temperature of 1 K and a magnetic field variation of 0-1 T, the hexagonal crystal material Sr6GdSc(BO3)6 can achieve a maximum magnetic entropy change of 39.36 mJ·cm⁻¹. -3 ·K -1 Or 9.01 J·kg -1 ·K -1 Therefore, the magnetic refrigeration material of the present invention has a significant magnetocaloric effect and superior low-temperature performance.
[0013] In some embodiments of the present invention, the preparation method of the hexagonal crystal system material Sr6GdSc(BO3)6 includes the following steps: (1) Mix Sr-containing compounds, Gd-containing compounds, Sc-containing compounds and B-containing compounds, grind and press them into blocks to obtain initial raw material blocks; (2) After pre-firing the initial raw material block, grind and press it into blocks again to obtain pre-firing blocks; (3) The pre-fired block is sintered to obtain the hexagonal crystal system material Sr6GdSc(BO3)6.
[0014] In some embodiments of the present invention, the Sr-containing compound is selected from at least one of SrCO3, SrO, Sr(OH)2, and SrC2O4.
[0015] In some embodiments of the present invention, the Gd-containing compound is selected from at least one of Gd2O3, Gd2(CO3)3, Gd(NO3)3, Gd(OH)3, and Gd2(C2O4)3.
[0016] In some embodiments of the present invention, the Sc-containing compound is selected from at least one of Sc2O3, Sc2(CO3)3, Sc(NO3)3, Sc(OH)3, and Sc2(C2O4)3.
[0017] In some embodiments of the present invention, the B-containing compound is selected from at least one of H3BO3 and B2O3.
[0018] In some embodiments of the present invention, in step (1), the dosage relationship of the Sr-containing compound, Gd-containing compound, Sc-containing compound, and B-containing compound is 6:1:1:(6-6.6) based on the molar ratio of Sr, Gd, Sc, and B. That is, the dosage relationship of the Sr-containing compound, Gd-containing compound, and Sc-containing compound is the same as the stoichiometric molar ratio of Sr6GdSc(BO3)6, while the dosage of the B-containing compound can be in excess within the range of up to 10%, mainly based on the volatility of the B-containing compound.
[0019] In some embodiments of the present invention, in step (2), the pre-firing temperature is 550-650°C.
[0020] In some embodiments of the present invention, in step (2), the pre-burning time is 5-10 hours.
[0021] In some embodiments of the present invention, in step (3), the sintering temperature is 1050-1150°C.
[0022] In some embodiments of the present invention, the sintering time in step (3) is 24-48 hours.
[0023] In some embodiments of the present invention, in step (3), the sintering adopts a two-stage sintering process, that is, the temperature is first raised to 1050-1150℃ and sintered for 12-24 hours; after cooling to room temperature, it is ground and pressed into blocks, and then the temperature is raised to 1050-1150℃ for the second time and sintered again for 12-24 hours.
[0024] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages: (1) The hexagonal magnetic refrigeration material with the chemical formula Sr6GdSc(BO3)6 of this invention is a material with a large magnetocaloric effect at extremely low temperatures. By introducing Gd 3+ It is a magnetic cation with large spin and extremely small magnetic anisotropy; and with a relatively small molecular weight, Sr 2+ ,Sc 2+ BO3 3- As a ligand, it ensures the distance between magnetic cations to minimize the interaction between magnetic ions, thereby maintaining the magnetic entropy at the lowest possible temperature, making it suitable for ultra-low temperature magnetic refrigeration.
[0025] (2) The hexagonal crystal material Sr6GdSc(BO3)6 of the present invention does not undergo a phase transition at an extremely low temperature of 100 mK in the specific heat test, and the magnetic refrigeration material has a large magnetocaloric effect near the temperature of 1 K. The maximum magnetic entropy change under magnetic field changes of 0-1T, 0-2T, and 0-3T are 39.36 mJ·cm⁻¹, respectively. -3 · K-1 Or 9.01 J·kg -1 ·K -1 53.95 mJ·cm -3 ·K -1 Or 12.34 J·kg -1 ·K -1 and 59.49 mJ·cm -3 ·K -1 Or 13.61 J·kg -1 ·K -1 Therefore, the hexagonal crystal system material Sr6GdSc(BO3)6 has significant magnetocaloric effects and excellent low-temperature performance, and has great application prospects in the field of ultra-low temperature magnetic refrigeration technology.
[0026] (3) The hexagonal crystal system material Sr6GdSc(BO3)6 of the present invention does not contain water of crystallization in its crystal structure, has a stable crystal structure, and has a simple preparation process, does not require complex equipment, has a short reaction cycle, and is suitable for large-scale industrial production. Attached Figure Description
[0027] Figure 1 The X-ray diffraction pattern of the magnetic refrigeration material prepared in Example 1 of this invention; Figure 2 The magnetic susceptibility and reciprocal curve of the magnetic refrigeration material prepared in Example 1 of the present invention under zero-field cooling (ZFC) in a magnetic field of 0.1T; Figure 3 The magnetic susceptibility and reciprocal curve of the magnetic refrigeration material prepared in Example 1 of the present invention under field cooling (FC) in a 0.1T magnetic field; Figure 4 The isothermal magnetization curves of the magnetic refrigeration material prepared in Example 1 of the present invention under magnetic field variations of 0-9T and 2-20K are shown. Figure 5 The curves showing the relationship between the magnetic specific heat and temperature of the magnetic refrigeration material prepared in Example 1 of the present invention under different magnetic fields; Figure 6 The curves showing the relationship between magnetic entropy and temperature of the magnetic refrigeration material prepared in Example 1 of the present invention under different magnetic fields; Figure 7 This is a graph showing the magnetic entropy change of the magnetic refrigeration material prepared in Example 1 of the present invention. Detailed Implementation
[0028] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.
[0029] Example 1 A method for preparing a magnetic refrigeration material includes the following steps: (1) Weigh the dried raw materials SrCO3 (99.99%), Gd2O3 (99.99%), Sc2O3 (99.99%) and H3BO3 (99.99%) accurately according to the stoichiometric molar ratio of 12:1:1:12, and grind and mix them thoroughly; use a tablet press to compress the raw materials into blocks to obtain the initial raw material blocks; (2) The initial raw material block obtained in step (1) is placed in a muffle furnace, heated uniformly to 600°C, pre-fired for 5 hours, and then cooled naturally to room temperature; then it is ground and pressed into blocks again to obtain pre-fired blocks; (3) The pre-sintered block obtained in step (2) is sintered, wherein: the sintering adopts a two-stage sintering process, that is, the temperature is raised to 1100℃ for the first time and sintered for 18 hours; after cooling to room temperature, after grinding and pressing, the temperature is raised to 1100℃ for the second time and sintered for another 18 hours to obtain a pure-phase ultra-low temperature magnetic refrigeration material with the chemical formula Sr6GdSc(BO3)6.
[0030] Example 2 A method for preparing a magnetic refrigeration material includes the following steps: (1) Weigh the dried raw materials SrCO3 (99.99%), Gd2O3 (99.99%), Sc2O3 (99.99%) and H3BO3 (99.99%) accurately according to the stoichiometric molar ratio of 12:1:1:12.6, and grind and mix them thoroughly; use a tablet press to compress the raw materials into blocks to obtain the initial raw material blocks; (2) The initial raw material block obtained in step (1) is placed in a muffle furnace, heated uniformly to 600°C, pre-fired for 5 hours, and then cooled naturally to room temperature; then it is ground and pressed into blocks again to obtain pre-fired blocks; (3) The pre-sintered block obtained in step (2) is sintered, wherein: the sintering adopts a two-stage sintering process, that is, the temperature is raised to 1100℃ for the first time and sintered for 18 hours; after cooling to room temperature, after grinding and pressing, the temperature is raised to 1100℃ for the second time and sintered for another 18 hours to obtain a pure-phase ultra-low temperature magnetic refrigeration material with the chemical formula Sr6GdSc(BO3)6.
[0031] Example 3 A method for preparing a magnetic refrigeration material includes the following steps: (1) Weigh the dried raw materials SrCO3 (99.99%), Gd2O3 (99.99%), Sc2O3 (99.99%) and B2O3 (99.99%) accurately according to the stoichiometric molar ratio of 12:1:1:6, and grind and mix them thoroughly; use a tablet press to compress the raw materials into blocks to obtain the initial raw material blocks; (2) The initial raw material block obtained in step (1) is placed in a muffle furnace, heated uniformly to 600°C, pre-fired for 5 hours, and then cooled naturally to room temperature; then it is ground and pressed into blocks again to obtain pre-fired blocks; (3) The pre-sintered block obtained in step (2) is sintered, wherein: the sintering adopts a two-stage sintering process, that is, the temperature is raised to 1100℃ for the first time and sintered for 18 hours; after cooling to room temperature, after grinding and pressing, the temperature is raised to 1100℃ for the second time and sintered for another 18 hours to obtain a pure-phase ultra-low temperature magnetic refrigeration material with the chemical formula Sr6GdSc(BO3)6.
[0032] Example 4 A method for preparing a magnetic refrigeration material includes the following steps: (1) Weigh the dried raw materials SrO (99.99%), Gd2O3 (99.99%), Sc2O3 (99.99%) and H3BO3 (99.99%) accurately according to the stoichiometric molar ratio of 12:1:1:12, and grind and mix them thoroughly; use a tablet press to compress the raw materials into blocks to obtain the initial raw material blocks; (2) The initial raw material block obtained in step (1) is placed in a muffle furnace, heated uniformly to 600°C, pre-fired for 5 hours, and then cooled naturally to room temperature; then it is ground and pressed into blocks again to obtain pre-fired blocks; (3) The pre-sintered block obtained in step (2) is sintered, wherein: the sintering adopts a two-stage sintering process, that is, the temperature is raised to 1100℃ for the first time and sintered for 18 hours; after cooling to room temperature, after grinding and pressing, the temperature is raised to 1100℃ for the second time and sintered for another 18 hours to obtain a pure-phase ultra-low temperature magnetic refrigeration material with the chemical formula Sr6GdSc(BO3)6.
[0033] Example 5 A method for preparing a magnetic refrigeration material includes the following steps: (1) Weigh the dried raw materials SrO (99.99%), Gd2O3 (99.99%), Sc2O3 (99.99%) and B2O3 (99.99%) accurately according to the stoichiometric molar ratio of 12:1:1:6, and grind and mix them thoroughly; use a tablet press to compress the raw materials into blocks to obtain the initial raw material blocks; (2) The initial raw material block obtained in step (1) is placed in a muffle furnace, heated uniformly to 600°C, pre-fired for 5 hours, and then cooled naturally to room temperature; then it is ground and pressed into blocks again to obtain pre-fired blocks; (3) The pre-sintered block obtained in step (2) is sintered, wherein: the sintering adopts a two-stage sintering process, that is, the temperature is raised to 1100℃ for the first time and sintered for 18 hours; after cooling to room temperature, after grinding and pressing, the temperature is raised to 1100℃ for the second time and sintered for another 18 hours to obtain a pure-phase ultra-low temperature magnetic refrigeration material with the chemical formula Sr6GdSc(BO3)6.
[0034] Performance testing 1. Structural Characterization The magnetic refrigeration material prepared in Example 1 was characterized using XRD. The XRD characterization results were analyzed using the Rietveld refinement method. The XRD test results and refinement fitting results are shown below. Figure 1 As shown, Figure 1 In the diagram: the horizontal axis 2θ (degree) represents the diffraction angle, the vertical axis Intensity represents the diffraction peak intensity, Yobs represents the XRD test data, Ycalc represents the refined fitting result, Yobs-Ycalc represents the difference between the test data and the refined result, and BPK represents the Bragg diffraction peak position. Figure 1 It can be seen that the magnetic refrigeration material prepared in Example 1 is a pure phase material with the chemical formula Sr6GdSc(BO3)6.
[0035] The crystal structure of the magnetic refrigeration material Sr6GdSc(BO3)6 prepared in Example 1 was determined using a Rigaku Miniflex 600 powder X-ray diffractometer. The test angle range was 10-120°, the step size was 0.02°, and the scanning speed was 0.2° / min. Rietveld refinement results showed that the synthesized Sr6GdSc(BO3)6 material belongs to the hexagonal crystal system, space group R-3(148), and the cell parameters are: a=b=12.3496, c=9.2817; α=β=90.00°, γ=120.00°.
[0036] 2. Magnetic Test The magnetic properties of the magnetic refrigeration material prepared in Example 1 were studied using the Quantum Design PPMS DynaCool integrated property measurement system, as detailed below: The zero-field cooling (ZFC) and band-field cooling (FC) magnetic susceptibility curves of the magnetic refrigeration material prepared in Example 1 were tested under a temperature range of 2-300 K and a magnetic field of 0.1 T. The results are as follows: Figure 2 and Figure 3 As shown. The reciprocals of the zero-field cooling (ZFC) and band-field cooling (FC) magnetic susceptibility curves were fitted using the Curie-Weiss law, revealing that the compound is a paramagnetic material within the test temperature range. The fitted Curie constant was C = 7.87 emu·K·mol⁻¹. -1 The effective magnetic moment μ obtained by fitting eff = 7.935μ B , compared with the calculated value of 7.94 μ B Very close, Werther's constant θ CW = -0.03329 K, which indicates that the material has extremely weak antiferromagnetic interaction and that the magnetic entropy can be retained to the extremely low temperature range, making it suitable for use in extremely low temperature magnetic refrigeration.
[0037] The isothermal magnetization curves of the magnetic refrigeration material prepared in Example 1 were tested within a temperature range of 2-20K and a magnetic field range of 0-9T. The results are as follows: Figure 4 As shown. At a fixed temperature, the magnetization of the material gradually increases with the increase of the magnetic field. At a temperature of 2K, the saturation magnetization value of 7μ is reached at a magnetic field of 7T. B It is exactly the same as the theoretical saturation magnetization value.
[0038] 3. Specific heat test The specific heat of the magnetic refrigeration material prepared in Example 1 was studied using the Quantum Design PPMS DynaCool integrated property measurement system and a dilution refrigerator (DR), as detailed below: The specific heat behavior of the magnetic refrigeration material prepared in Example 1 was studied within a temperature range of 0.1-18 K and a magnetic field range of 0-3 T. After deducting the phonon specific heat, the following results were obtained: Figure 5 The magnetic specific heat of the refrigeration material with the chemical formula Sr6GdSc(BO3)6 is shown. Under a fixed magnetic field, within the test temperature range, the magnetic specific heat of this material first increases and then decreases as the temperature decreases. Integrating the magnetic specific heat with respect to temperature yields the following results: Figure 6 The curves showing the relationship between magnetic entropy and temperature under different magnetic fields demonstrate that the magnetic entropy can be well maintained up to the extremely low temperature range, proving that the material can be used for thermal insulation, demagnetization, and refrigeration in the extremely low temperature range.
[0039] according to Figure 6 The curves showing the relationship between magnetic entropy and temperature for this material under different magnetic fields can be used to calculate the curves showing the relationship between magnetic entropy change and temperature for this material under different magnetic field variations, such as... Figure 7 As shown. By Figure 7 It can be seen that the material exhibits a large magnetocaloric effect near 1K, with maximum magnetic entropy changes of 39.36 mJ·cm under magnetic field variations of 0-1T, 0-2T, and 0-3T, respectively. -3 ·K -1 Or 9.01 J·kg -1 ·K -1 53.95 mJ·cm -3 ·K -1 Or 12.34 J·kg -1 ·K -1 and 59.49 mJ·cm -3 ·K -1 Or 13.61 J·kg -1 ·K -1 .
[0040] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.
Claims
1. Application of a hexagonal crystal material Sr6GdSc(BO3)6 in the field of ultra-low temperature magnetic refrigeration.
2. The application according to claim 1, characterized in that, The hexagonal crystal material Sr6GdSc(BO3)6 does not undergo a phase transition at temperatures above 100 mK.
3. The application according to claim 1, characterized in that, The hexagonal crystal system material Sr6GdSc(BO3)6 satisfies at least one of the following conditions: ① Under a temperature of 1K and a magnetic field variation of 0-3T, the maximum magnetic entropy of the hexagonal crystal material Sr6GdSc(BO3)6 is not less than 59.49 mJ·cm⁻¹. -3 ·K -1 Or 13.61 J·kg -1 ·K -1 ; ② Under a temperature of 1K and a magnetic field variation of 0-2T, the maximum magnetic entropy change of the hexagonal crystal material Sr6GdSc(BO3)6 is not less than 53.95 mJ·cm⁻¹. -3 ·K -1 Or 12.34 J·kg -1 ·K -1 ; ③ Under a temperature of 1 K and a magnetic field variation of 0-1 T, the maximum magnetic entropy change of the hexagonal crystal material Sr6GdSc(BO3)6 is not less than 39.36 mJ·cm. -3 ·K -1 Or 9.01 J·kg -1 ·K -1 .
4. The application according to any one of claims 1-3, characterized in that, The preparation method of the hexagonal crystal system material Sr6GdSc(BO3)6 includes the following steps: (1) Mix Sr-containing compounds, Gd-containing compounds, Sc-containing compounds and B-containing compounds, grind and press them into blocks to obtain initial raw material blocks; (2) After pre-firing the initial raw material block, grind and press it into blocks again to obtain pre-firing blocks; (3) The pre-fired block is sintered to obtain the hexagonal crystal system material Sr6GdSc(BO3)6.
5. The application according to claim 4, characterized in that, The Sr-containing compound is selected from at least one of SrCO3, SrO, Sr(OH)2, and SrC2O4.
6. The application according to claim 4, characterized in that, The Gd-containing compound is selected from at least one of Gd2O3, Gd2(CO3)3, Gd(NO3)3, Gd(OH)3, and Gd2(C2O4)3.
7. The application according to claim 4, characterized in that, The Sc-containing compound is selected from at least one of Sc2O3, Sc2(CO3)3, Sc(NO3)3, Sc(OH)3, and Sc2(C2O4)3; and / or, the B-containing compound is selected from at least one of H3BO3 and B2O3.
8. The application according to claim 4, characterized in that, In step (1), the ratio of the amounts of the Sr-containing compound, the Gd-containing compound, the Sc-containing compound and the B-containing compound is 6:1:1:(6-6.6) based on the molar ratio of Sr, Gd, Sc and B.
9. The application according to claim 4, characterized in that, In step (2), the pre-firing temperature is 550-650℃; and / or the pre-firing time is 5-10 hours.
10. The application according to claim 4, characterized in that, In step (3), the sintering temperature is 1050-1150℃; and / or the sintering time is 24-48 hours.