Silicate single crystal magnetocaloric material for heat insulation, demagnetization and refrigeration as well as preparation method and application thereof

Abstract

The invention provides a silicate single crystal magnetocaloric material for heat insulation, demagnetization and refrigeration as well as a preparation method and application of the silicate single crystal magnetocaloric material. Specifically, the invention provides a silicate single crystal magnetocaloric material for heat insulation, demagnetization and refrigeration, and the silicate single crystal magnetocaloric material has the following chemical formula: Na < 4 + x > Gd < 4 > Si < 4 > O < 16 > F < x >, wherein 0.2 < = x < = 0.8. The invention also provides a method for preparing the single crystal magnetocaloric material. The invention further provides application of the single crystal magnetocaloric material in deep space exploration equipment, a quantum computing low-temperature system or a dilution refrigeration coupling device. The single crystal magnetocaloric material disclosed by the invention has large available magnetic entropy and high refrigeration efficiency in a mikkov temperature zone so as to meet the refrigeration requirement of a large load; the device has high mechanical and chemical stability, and can adapt to space high-vacuum environment and complex working conditions such as spaceflight and mobile platforms.

Description

Technical Field

[0001] The present invention belongs to the field of materials, and specifically relates to a silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration, a preparation method thereof, and an application thereof. Background Art

[0002] Adiabatic Demagnetization Refrigeration (ADR) is a solid-state refrigeration technology that utilizes the magnetocaloric effect to achieve extremely low temperatures. With its high cooling efficiency, highly integrated structure, and no risk of refrigerant leakage, ADR has become a mainstream technology in the field of extremely low-temperature refrigeration.

[0003] ADR technology holds particularly promising applications in deep space exploration and satellite technology. For example, the Astro-E2 satellite, jointly developed by the Japan Aerospace Exploration Agency (JAXA) and NASA, the European Space Agency's (ESA) Herschel Space Observatory, and JAXA's X-ray Astronomy Satellite (XRISM) all utilize ADR as a key cooling solution. Furthermore, this technology can be combined with dilution refrigerators to provide an efficient, stable, low-vibration, ultra-low-temperature environment for quantum computing, further expanding its application scenarios.

[0004] The core of ADR technology lies in the refrigerant—the magnetocaloric material. During a typical refrigeration cycle, the magnetocaloric material first comes into contact with an external heat source while a magnetic field is applied. This reduces the material's spin freedom and magnetic entropy, allowing it to release heat to the outside world. Subsequently, the magnetocaloric material is isolated from the heat sink and the magnetic field is removed. This increases the spin freedom, magnetic entropy, and the material's temperature, allowing heat to be transferred from the refrigeration load to the magnetocaloric material, achieving a cooling effect.

[0005] However, the ADR refrigerants commonly used at present are mostly paramagnetic salts, such as hydrated salts Mn(NH4)2(SO4)2·6H2O (MAS), NH4Fe(SO4)2·12H2O (FAA), KCr(SO4)2·12H2O (CPA), Mg3Ce2(NO3) 12 24H2O (CMN) and rare earth gallium garnet RE3Ga5O 12 (RE = Gd, Dy or Yb, etc.) single crystal or powder crystal. These materials have many limitations: the internal magnetic coupling of hydrated salts is weak, usually only used in the millikelvin temperature range, the operating temperature range is narrow, and the available magnetic entropy change is low, for example, the magnetic entropy change of MAS is 70 mJ K -1 cm -3 , FAA is 53 mJ K -1 cm -3, CPA and CMN were 42 and 16 mJ K, respectively. -1 cm -3 In addition, hydrated paramagnetic salts have slow thermal diffusion at extremely low temperatures, poor crystal mechanical stability, and are prone to dehydration and decomposition, requiring strict humidity and vacuum conditions for use. In contrast, rare earth gallium garnets have higher stability, good low-temperature thermal conductivity, and higher magnetic entropy change (such as Yb3Ga5O 12 The magnetic entropy change is 124 mJ K -1 cm -3 ), but its internal magnetic coupling is large and the available magnetic entropy change is limited, such as Gd3Ga5O 12 A short-range magnetic phase transition occurs at around 800 mK, which limits the refrigeration operating window, usually greater than 300 mK, making it difficult to apply in the milliKelvin temperature range.

[0006] Given this, the development of new, high-performance ADR refrigerants is particularly necessary. These new refrigerants must meet the following requirements: possess large available magnetic entropy and high refrigeration efficiency in the millikelvin temperature range to meet the cooling needs of large loads; possess high mechanical and chemical stability to adapt to high-vacuum environments in space, as well as complex operating conditions such as aerospace and mobile platforms; and possess low production costs, ease of system integration and miniaturization, and meet the requirements of multi-stage cascade and hybrid refrigeration, laying the foundation for large-scale, engineering-based applications. Summary of the Invention

[0007] Therefore, the purpose of the present invention is to provide a silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration, which has large available magnetic entropy and high refrigeration efficiency in the millikelvin temperature range to meet the refrigeration needs of large loads; it has high mechanical and chemical stability and can adapt to high vacuum environments in space and complex working conditions such as aerospace and mobile platforms.

[0008] Another object of the present invention is to provide a method for preparing the silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration of the present invention, which is simple, has a wide source of raw materials, is low in cost, and is easy to promote in engineering.

[0009] Another object of the present invention is to provide an application of the silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration of the present invention in deep space exploration equipment, quantum computing low temperature systems or dilution refrigeration coupling devices.

[0010] The above-mentioned object of the present invention is achieved through the following technical solutions.

[0011] In a first aspect, the present invention provides a silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration, which has the following chemical formula:

[0012] Na 4+x Gd4Si4O 16 F x;

[0013] Among them, 0.2≤x≤0.8, preferably, 0.4≤x≤0.8, more preferably, 0.6≤x≤0.8.

[0014] In this application, when the value of x is controlled within the range of 0.2 ≤ x ≤ 0.8, a single crystal magnetocaloric material can be obtained. This single crystal magnetocaloric material has a large available magnetic entropy and high cooling efficiency in the millikelvin temperature range, meeting the cooling needs of large loads. When x is outside the range claimed by the present invention, the single crystal magnetocaloric material claimed by the present invention cannot be obtained.

[0015] Preferably, in the silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration according to the present invention, the space group of the single crystal magnetocaloric material is , belongs to the tetragonal crystal system.

[0016] Preferably, in the silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration described in the present invention, Cu target Kα diffraction is used, and its X-ray powder diffraction pattern expressed in 2θ angles has diffraction peaks at 10.7°, 15.1°, 18.0°, 23.6°, 24.0°, 28.2°, 32.1°, 33.1°, 34.2°, 35.7°, 42.0° and 50.2°, and the 2θ angle measurement error is ±0.2°.

[0017] Preferably, in the silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration according to the present invention, the magnetic entropy change of the single crystal magnetocaloric material is greater than or equal to 100 mJ K at a temperature of 2 K and a magnetic field of 2 T. -1 cm -3 .

[0018] Preferably, in the silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration described in the present invention, the magnetic ordering temperature of the single crystal magnetocaloric material is lower than 2 K, more preferably 1 K.

[0019] In a second aspect, the present invention provides a method for preparing the silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration of the present invention, comprising the following steps:

[0020] (1) Sodium carbonate, gadolinium oxide, silicon oxide, and sodium fluoride are mixed in a predetermined molar ratio, and then an inorganic molten salt is added;

[0021] (2) The mixture obtained in step (1) is kept at a high temperature, and then cooled to room temperature by programmed cooling to obtain the silicate single crystal magnetocaloric material.

[0022] In the method of the present invention, the inorganic molten salt does not participate in the reaction, but serves to provide a liquid phase growth environment.

[0023] Preferably, in the method of the present invention, the added mass of the inorganic molten salt is 1.5 to 20 times the total mass of the sodium carbonate, gadolinium oxide, silicon oxide and sodium fluoride.

[0024] Preferably, in the method of the present invention, the inorganic molten salt is selected from at least one of alkali metal or alkaline earth metal chlorides, alkali metal or alkaline earth metal molybdates, and boron oxide.

[0025] Preferably, in the method of the present invention, the heat preservation at high temperature in step (2) is carried out under the following conditions: first, heat preservation at 550-800 °C for 24-50 h; and then heat preservation at 800-1500 °C for 50-200 h.

[0026] Preferably, in the method of the present invention, the cooling rate of the programmed cooling in step (2) is 0.5-3°C / h. The present invention does not impose any particular limitation on the cooling rate. If the cooling rate is greater than 3°C / h, the single crystal will grow smaller; if the cooling rate is less than 0.5°C / h, the same result will occur.

[0027] In a third aspect, the present invention provides an adiabatic demagnetization refrigeration device, which includes a hot end, a magnetic field source, a cold end, and the silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration of the present invention, wherein the single crystal magnetocaloric material is processed into thin sheets, blocks, spheres or rods, and the hot end, magnetic field source, cold end and the single crystal magnetocaloric material are connected with oxygen-free high-conductivity copper, and the refrigeration cycle is realized by adjusting the magnetic field strength.

[0028] In a fourth aspect, the present invention provides the use of the silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration of the present invention in deep space exploration equipment, quantum computing low-temperature systems or dilution refrigeration coupling devices.

[0029] The present invention has the following beneficial effects:

[0030] The single-crystal magnetocaloric material of the present invention has excellent refrigeration performance. The material's magnetic ordering temperature is lower than 2 K, the operating temperature range is wide, ranging from 125 mK to 13 K, the magnetic entropy change is large, and the adiabatic demagnetization refrigeration power is high, which is superior to many common refrigeration fluids. At a temperature of 2 K and a magnetic field of 2 T, the magnetic entropy change of the single-crystal magnetocaloric material is greater than or equal to 100 mJ K -1 cm -3 .

[0031] The single crystal magnetocaloric material of the present invention has high stability, good thermal and chemical stability, excellent mechanical properties, simple machining process, can be made into various shapes, meets the needs of compact integrated systems, and has high heat exchange efficiency in continuous refrigeration cycles and adapts to complex working conditions.

[0032] The single crystal magnetocaloric material of the present invention has low cost, is easy to promote, has simple synthesis steps, has a wide source of raw materials and is low in price, is easy to promote through engineering, and has high application value.

[0033] The single crystal magnetocaloric material of the present invention has great engineering potential, is easy to prepare and process, can meet the requirements of multi-stage cascade and mixed refrigeration, and can be applied on a large scale in cutting-edge fields such as deep space exploration and quantum computing. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which:

[0035] Figure 1 The single crystal magnetocaloric material Na prepared in Example 1 of the present invention is shown. 4.8 Gd4Si4O 16 F 0.8 Powder crystal X-ray diffraction experimental diagram;

[0036] Figure 2 The single crystal magnetocaloric material Na prepared in Example 1 of the present invention is shown. 4.8 Gd4Si4O 16 F 0.8 Curve of magnetic susceptibility changing with temperature;

[0037] Figure 3 The single crystal magnetocaloric material Na prepared in Example 1 of the present invention is shown. 4.8 Gd4Si4O 16 F 0.8 The curve of magnetic entropy change with temperature and magnetic field;

[0038] Figure 4 The single crystal magnetocaloric material Na prepared in Example 2 of the present invention is shown. 4.2 Gd4Si4O 16 F 0.2 Powder crystal X-ray diffraction experimental diagram;

[0039] Figure 5 A schematic diagram showing an adiabatic demagnetization refrigeration device according to a specific embodiment of the present invention; wherein: 1 - hot end; 2 - thermal switch; 3 - magnetic field source; 4 - single crystal magnetocaloric material; 5 - cold end;

[0040] Figure 6 The single crystal magnetocaloric material Na of Example 1 of the present invention is shown. 4.8 Gd4Si4O 16 F 0.8 Refrigeration curve and magnetic field change curve of the adiabatic demagnetization refrigeration device;

[0041] Figure 7 The powder crystal X-ray diffraction experimental diagram of the product obtained in Comparative Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below in conjunction with specific embodiments. The examples given are only for illustrating the present invention, not for limiting the scope of the present invention.

[0043] Example 1

[0044] This embodiment provides a single crystal magnetocaloric material Na 4.8 Gd4Si4O 16 F 0.8 The preparation method comprises the following steps:

[0045] (1) Sodium carbonate, gadolinium oxide, silicon oxide, sodium fluoride, and boron oxide were placed in a planetary mill at a molar ratio of 2:2:4:0.8:30 and mixed for 1 h to obtain a uniformly mixed mixture; wherein the mass of boron oxide added to the mixture was 1.7 times the total mass of sodium carbonate, gadolinium oxide, silicon oxide, and sodium fluoride.

[0046] (2) The mixture was placed in a muffle furnace and kept at 700 °C for 24 h, then heated to 1100 °C and kept at this temperature for 200 h; the reaction system was then slowly cooled to room temperature at a cooling rate of 2 °C / h to obtain a product with the chemical formula Na 4.8 Gd4Si4O 16 F 0.8 of single crystal materials.

[0047] Characterization methods

[0048] The single crystal magnetocaloric material Na prepared in Example 1 4.8 Gd4Si4O 16 F 0.8 The structure was analyzed by X-ray single crystal diffractometer and the crystal homogeneity was confirmed by powder X-ray diffraction. Figure 1 shown. Figure 1 The obtained single crystal magnetocaloric material Na 4.8 Gd4Si4O 16 F 0.8 It is a tetragonal crystal system with a space group of , the unit cell parameters are a = b = 11.72 Å, c = 5.42 Å, α = β = γ = 90°.

[0049] Figure 1 Using Cu target Kα diffraction, the single crystal magnetocaloric material Na 4.8 Gd4Si4O 16 F 0.8The X-ray powder diffraction pattern expressed in 2θ angles has diffraction peaks at 10.7°, 15.1°, 18.0°, 23.6°, 24.0°, 28.2°, 32.1°, 33.1°, 34.2°, 35.7°, 42.0° and 50.2°, and the 2θ angle measurement error is ±0.2°. Specifically, 10.7° corresponds to Figure 1 Mark "1" in the figure, 15.1° corresponds to Figure 1 Mark "2" in the figure, 18.0° corresponds to Figure 1 Mark "3" in the figure, 23.6° corresponds to Figure 1 The mark "4" in the figure corresponds to 24.0°. Figure 1 Mark "5" in the figure, 28.2° corresponds to Figure 1 The mark "6" in the figure corresponds to 32.1°. Figure 1 Mark "7" in the figure, 33.1° corresponds to Figure 1 The mark "8" in the figure corresponds to 34.2°. Figure 1 Mark "9" in the figure, 35.7° corresponds to Figure 1 The mark "10" in the figure corresponds to 42.0°. Figure 1 The mark "11" in the figure, 50.2° corresponds to Figure 1 Mark "12" in the.

[0050] Low temperature thermal and magnetic performance testing

[0051] Figure 2 The single crystal magnetocaloric material Na of this embodiment is shown 4.8 Gd4Si4O 16 F 0.8 The curve of magnetic susceptibility changing with temperature shows that no magnetic phase transition occurs at a temperature of 2 K, proving that its magnetic ordering temperature is lower than 2 K.

[0052] Figure 3 The single crystal magnetocaloric material Na of this embodiment is shown 4.8 Gd4Si4O 16 F 0.8 The magnetic entropy change curve with temperature and magnetic field, when the external magnetic field B = 7 T, the magnetic entropy change is 294 mJ K -1 cm -3 ; When B = 5 T, the magnetic entropy change is 262 mJ K -1 cm -3 ; When B = 2 T, the magnetic entropy change is 131 mJ K -1 cm -3 ; It shows that the single crystal magnetocaloric material Na 4.8 Gd4Si4O 16 F 0.8There is a large magnetic entropy change at low temperature. In addition, the single crystal magnetocaloric material Na of the present invention 4.8 Gd4Si4O 16 F 0.8 At a temperature of 13 K, there is still a significant magnetic entropy change, proving that it can be used at this temperature.

[0053] Example 2

[0054] This embodiment provides a single crystal magnetocaloric material Na 4.2 Gd4Si4O 16 F 0.2 The preparation method comprises the following steps:

[0055] (1) Sodium carbonate, gadolinium oxide, silicon oxide, sodium fluoride, and sodium molybdate were placed in a planetary mill at a molar ratio of 2:2:4:0.2:20 and mixed for 1 h to obtain a uniformly mixed mixture; wherein the mass of sodium molybdate added to the mixture was 3.5 times the total mass of sodium carbonate, gadolinium oxide, silicon oxide, and sodium fluoride.

[0056] (2) The mixture was placed in a muffle furnace and kept at 550 °C for 24 h, then heated to 800 °C and kept at that temperature for 200 h; the reaction system was then slowly cooled to room temperature at a cooling rate of 2 °C / h to obtain a product with the chemical formula Na 4.2 Gd4Si4O 16 F 0.2 of single crystal materials.

[0057] Characterization methods

[0058] The single crystal magnetocaloric material Na prepared in Example 2 4.2 Gd4Si4O 16 F 0.2 The structure was analyzed by X-ray single crystal diffractometer and the crystal homogeneity was confirmed by powder X-ray diffraction. Figure 4 shown. Figure 4 The obtained single crystal magnetocaloric material Na 4.2 Gd4Si4O 16 F 0.2 It is a tetragonal crystal system with a space group of , the unit cell parameters are a = b = 11.71 Å, c = 5.41 Å, α = β = γ = 90°.

[0059] Figure 4 Using Cu target Kα diffraction, the single crystal magnetocaloric material Na 4.2 Gd4Si4O 16 F 0.2The X-ray powder diffraction pattern expressed in 2θ angles has diffraction peaks at 10.7°, 15.1°, 18.0°, 23.6°, 24.0°, 28.2°, 32.1°, 33.1°, 34.2°, 35.7°, 42.0° and 50.2°, and the 2θ angle measurement error is ±0.2°. 10.7° corresponds to Figure 4 Mark "1" in the figure, 15.1° corresponds to Figure 4 Mark "2" in the figure, 18.0° corresponds to Figure 4 Mark "3" in the figure, 23.6° corresponds to Figure 4 The mark "4" in the figure corresponds to 24.0°. Figure 4 Mark "5" in the figure, 28.2° corresponds to Figure 4 The mark "6" in the figure corresponds to 32.1°. Figure 4 Mark "7" in the figure, 33.1° corresponds to Figure 4 The mark "8" in the figure corresponds to 34.2°. Figure 4 Mark "9" in the figure, 35.7° corresponds to Figure 4 The mark "10" in the figure corresponds to 42.0°. Figure 4 The mark "11" in the figure, 50.2° corresponds to Figure 4 Mark "12" in the.

[0060] Example 3

[0061] The single crystal magnetocaloric material Na prepared in Example 1 4.8 Gd4Si4O 16 F 0.8 Used in adiabatic demagnetization refrigeration devices, such as Figure 5 The adiabatic demagnetization refrigeration device of this embodiment is based on a constant hot end (2 K). The hot end 1 is kept constant at 2 K. The thermal switch 2 is an air-gap type thermal switch. The magnetic field source 3 is a superconducting magnet. The single crystal magnetocaloric material 4 is fabricated into a thin sheet and serves as the core component of the low-temperature refrigeration device. The cold end 5 serves as the load end. All components are connected with oxygen-free, highly conductive copper. The refrigeration cycle is achieved by adjusting the magnetic field strength.

[0062] The device of this embodiment can control the occurrence of magnetocaloric effect by adjusting the magnetic field strength, so that the system can operate at extremely low temperatures.

[0063] Performance test of the device

[0064] The device of this embodiment operates under a constant hot end temperature of 2 K. Specifically, the magnetic field is set to 5 T, 4 T, or 2 T. After the magnetocaloric material and the hot end temperature are balanced, the thermal switch is turned off and the magnetic field is slowly adjusted to zero. The cold end temperature then decreases.

[0065] Figure 6 The single crystal magnetocaloric material Na of Example 1 of the present invention is shown.4.8 Gd4Si4O 16 F 0.8 Cooling curve and magnetic field change curve. Figure 6 It shows that when the demagnetization field is 5 T, the system can work at 125 mK and maintain it for tens of minutes. When the demagnetization field is 4 T, the system can work at around 400 mK and maintain it for several hours. When the demagnetization field is 2 T, the system can work at around 800 mK and maintain it for several hours. This shows that the single crystal magnetocaloric material Na 4.8 Gd4Si4O 16 F 0.8 It has excellent low-temperature magnetic refrigeration capabilities.

[0066] The single crystal magnetocaloric material Na of Example 1 of the present invention 4.8 Gd4Si4O 16 F 0.8 When the demagnetization field is 5 T, the lowest operating temperature is 125 mK, and at a temperature of 13 K, there is still a considerable magnetic entropy change of 79 mJ K -1 cm -3 , proving its wide operating temperature range (125 mK~13 K).

[0067] Comparative Example 1

[0068] The preparation method for this comparative example was similar to that of Example 1, except that the raw material ratio was changed. Sodium carbonate, gadolinium oxide, silicon oxide, sodium fluoride, and boron oxide were placed in a planetary mill at a molar ratio of 2:2:4:0.1:1. The final product was a powder, with no single crystals present.

[0069] In order to further characterize the structure of the product, powder X-ray diffraction was performed on the product, and the results were as follows: Figure 7 shown. Figure 7 The X-ray diffraction results of the powdered material do not match the crystal structure of the single crystal magnetocaloric material of the present invention, and cannot be indexed using a single space group. This proves that the product obtained in this comparative example is not a single phase, but a mixture.

[0070] In other words, if the amount of sodium fluoride is too small, single crystal materials cannot be produced. That is, the silicate single crystal magnetocaloric material used for adiabatic demagnetization refrigeration must have the following chemical formula: Na 4+x Gd4Si4O 16 F x ; Among them, 0.2≤x≤0.8.

Claims

1. A silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration, having the following chemical formula: On 4+x Gd4Si4O 16 F x ; in, 0.2≤x≤0.8。 2. The silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration according to claim 1, wherein: The space group of the single crystal magnetocaloric material is , belongs to the tetragonal crystal system.

3. The silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration according to claim 1, wherein: Using Cu target Kα diffraction, its X-ray powder diffraction pattern expressed in 2θ angles has diffraction peaks at 10.7°, 15.1°, 18.0°, 23.6°, 24.0°, 28.2°, 32.1°, 33.1°, 34.2°, 35.7°, 42.0° and 50.2°, and the 2θ angle measurement error is ±0.2°.

4. The silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration according to claim 1, wherein: When the temperature is 2K and the magnetic field is 2 T, the magnetic entropy change of the single crystal magnetocaloric material is greater than or equal to 100 mJ K -1 cm -3 ; Preferably, the magnetic ordering temperature of the single crystal magnetocaloric material is lower than 2 K.

5. A method for preparing the silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration according to any one of claims 1 to 4, comprising the following steps: (1) Sodium carbonate, gadolinium oxide, silicon oxide, and sodium fluoride are mixed in a predetermined molar ratio, and then an inorganic molten salt is added; (2) The mixture obtained in step (1) is kept at a high temperature, and then cooled to room temperature by programmed cooling to obtain the silicate single crystal magnetocaloric material.

6. The method according to claim 5, wherein: The added mass of the inorganic molten salt is 1.5 to 20 times the total mass of the sodium carbonate, gadolinium oxide, silicon oxide and sodium fluoride.

7. The method according to claim 5, wherein: The inorganic molten salt is selected from at least one of chlorides of alkali metals or alkaline earth metals, molybdates of alkali metals or alkaline earth metals, and boron oxide.

8. The method according to claim 5, wherein The heat preservation at high temperature in step (2) is carried out under the following conditions: first, heat preservation at 550-800°C for 24-50 h; then heat preservation at 800-1500°C for 50-200 h; Preferably, the cooling rate of the programmed cooling in step (2) is 0.5-3°C / h.

9. An adiabatic demagnetization refrigeration device, comprising a hot end, a magnetic field source, a cold end, and the silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration according to any one of claims 1 to 4, wherein the single crystal magnetocaloric material is processed into a thin sheet, a block, a sphere or a rod.

10. Use of the silicate single crystal magnetocaloric material for adiabatic demagnetization refrigeration according to any one of claims 1 to 4 in deep space exploration equipment, quantum computing cryogenic systems or dilution refrigeration coupling devices.

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