Magnetic Refrigeration Module Based on Spark Plasma Sintering, Its Fabrication Method and Application

Abstract

This invention provides a magnetic refrigeration module based on spark plasma sintering, its preparation method, and its applications. The method involves uniformly mixing magnetic refrigeration working fluid powder with high thermal conductivity material powder, and then rapidly densifying the mixture using spark plasma sintering technology to prepare a high-density, high-thermal-conductivity, and machinable magnetic refrigeration module. This module exhibits a uniform thermally conductive network in its microstructure, with a density close to the theoretical value. In terms of mechanical properties, it is suitable for subtractive manufacturing processes and can be precisely machined into complex shapes. Applying this module to an adiabatic demagnetizing refrigeration system enables rapid achievement of milliKJ-level ultra-low temperatures and sustained stable operation over extended periods, with a significantly shortened thermal relaxation time. This invention solves the problems of long preparation cycles, low density, and long thermal relaxation times associated with conventional magnetic refrigeration modules, achieving efficient, low-cost, customizable, and machinable large-scale module production, providing a high-performance solution for the cryogenic needs of cutting-edge fields such as quantum computing and deep space exploration.

Description

Technical Field

[0001] This invention belongs to the field of low-temperature magnetic refrigeration technology, specifically relating to a magnetic refrigeration module based on discharge plasma sintering for use in an adiabatic demagnetizing refrigeration system, its preparation method, and its application. Background Technology

[0002] Adiabatic demagnetization refrigeration (ADR) is an ultra-low temperature refrigeration method based on the magnetocaloric effect (MCE). Its basic principle is as follows: Under adiabatic conditions, an external magnetic field is applied to the refrigerant, magnetizing it and causing it to heat up. This heat is then dissipated through heat exchange. Subsequently, under adiabatic conditions, the refrigerant is demagnetized, and the refrigerant absorbs heat due to the increase in magnetic entropy, thus achieving refrigeration. ADR technology can stably reach sub-Kelvin temperatures (below 1 K), and even milliKelvin (mK) temperatures. Compared with dilution refrigeration and other techniques, it has advantages such as high thermodynamic efficiency, compact system structure, and adaptability to zero-gravity environments. Therefore, it has become a mainstream solution in space exploration (such as satellite payload cooling), quantum technology platforms, and basic scientific research. Furthermore, ADR does not rely on scarce helium resources, significantly reducing operating costs and showing broad application prospects.

[0003] Currently, adiabatic demagnetizing refrigeration technology commonly uses traditional hydrated paramagnetic salts as magnetic refrigerants, such as FeNH4(SO4)2·12H2O (ferric ammonium sulfate, FAA) and KCr(SO4)2·12H2O (potassium chromium sulfate, CPA). While these refrigerants exhibit good magnetocaloric effects within a certain temperature range, they possess inherent drawbacks such as those described below:

[0004] The crystal growth process is complex: the growth of hydrated paramagnetic salt single crystals requires a slow solution method or gel method, the preparation cycle can take several weeks or even months, the efficiency is low, and the crystals are prone to defects.

[0005] Chemically unstable: Because they contain water of crystallization, these salts are prone to deliquescence or weathering in the air, which can lead to the failure of the working fluid. Therefore, they require strict sealed packaging, which increases the complexity and cost of the system.

[0006] Low magnetic ion density: The non-magnetic part of hydrates (such as water molecules) accounts for a large proportion, resulting in a small number of magnetic ions per unit volume and a low magnetic entropy density, which limits the cooling capacity.

[0007] Poor thermal conductivity: The poor thermal conductivity inside the crystal leads to low heat exchange efficiency during magnetization / demagnetization, prolonging the cooling cycle time and affecting overall performance.

[0008] In conventional magnetic refrigeration module manufacturing, the working fluid is typically integrated onto the heat bus (usually composed of copper or gold wire arrays) in the form of single crystals or compacts. For example, patent CN115682459A describes a method for directly growing paramagnetic salt crystals onto the heat bus frame, but this process is cumbersome, has a low yield, and poor mechanical stability. Patent CN118031455A uses specially made salt pellets encapsulated within the heat bus frame and relies on a metal casing for sealing, but this also suffers from structural complexity and a long manufacturing cycle. Furthermore, these methods struggle to achieve high densification and uniform thermal conductivity of the working fluid.

[0009] In recent years, novel magnetic refrigeration materials (such as oxide frustrated magnetic materials) have been proposed to replace hydrated paramagnetic salts. For example, patents CN117476303A and CN119811811A employ isostatic pressing or cold pressing techniques to mix powdered working fluids with thermally conductive materials (such as metal powders). However, modules prepared by these conventional pressing methods have low density, loose structure, and numerous micron-sized pores. These pores adsorb exchange gases at low temperatures, disrupting the system vacuum, weakening the heat exchange efficiency between the working fluid and the cold / hot ends, preventing the working fluid from reaching the preset initial temperature, limiting the system's minimum cooling temperature, and resulting in low refrigeration cycle efficiency. Furthermore, cold-pressed modules have poor mechanical strength and are difficult to precision machine, limiting their application in practical systems.

[0010] Spark plasma sintering (SPS) is an advanced powder metallurgy technology that uses pulsed current to generate plasma between powder particles, achieving rapid densification. SPS has been widely used in the preparation of ceramics, metals, and composite materials, but its application in magnetic refrigeration, especially in the molding of cryogenic refrigerants, has not been reported. Traditionally, because magnetic refrigerants are mostly insulating or semiconductor materials (such as oxides), those skilled in the art consider them unsuitable for SPS processes, as pulsed current is difficult to conduct effectively in these materials. However, this invention unexpectedly overcomes this technical prejudice by mixing insulating magnetic refrigerant powder with high thermal conductivity metal powder, utilizing the metal powder to construct the current conduction path. This allows the SPS process to act efficiently on the mixed powder, simultaneously solving the three major technical obstacles faced by magnetic refrigeration modules: low density, poor thermal conductivity, and difficult processing. Summary of the Invention

[0011] The purpose of this invention is to address the problems of long preparation cycles, complex structures, low density, poor thermal conductivity, and insufficient mechanical properties in existing magnetic refrigeration module fabrication methods. To address the shortcomings of traditional hydrated paramagnetic salt working fluids and the porosity and numerous pores in modules caused by cold pressing / isostatic pressing techniques, this invention develops a magnetic refrigeration module based on spark plasma sintering (SPS) and its fabrication method. This method involves uniformly mixing magnetic refrigeration working fluid powder with high thermal conductivity material powder, and then using SPS technology to achieve rapid densification and sintering, forming a high-density, high-thermal-conductivity, and processable magnetic refrigeration module. This module exhibits excellent cooling performance in adiabatic demagnetization refrigeration applications, rapidly reaching milliK (mK) level ultra-low temperatures and maintaining stable operation for extended periods, thereby promoting the large-scale application of adiabatic demagnetization refrigeration technology in fields such as quantum computing and deep space exploration.

[0012] In a first aspect, the present invention provides a method for fabricating a magnetic refrigeration module based on spark plasma sintering, comprising the following steps:

[0013] S1. The magnetic refrigerant powder and the high thermal conductivity material powder are uniformly mixed to form a magnetic-thermal conductive composite material system;

[0014] S2. The composite material system is loaded into a mold and pre-pressed to form a preform;

[0015] S3. The mold is moved into the discharge plasma sintering equipment. Under a protective atmosphere, pressure is applied to the preform in the mold and a pulsed current is passed through for sintering. The sintering parameters include: sintering temperature 500-1000℃, sintering pressure 30-100 MPa, and holding time 10-100 minutes.

[0016] S4. After sintering is complete, cool to room temperature, demold the module, and perform post-processing.

[0017] According to the preparation method provided by the present invention, the magnetic refrigerant is preferably one or more materials in a frustrated magnetic material system, such as spin ice materials, pyrochlore oxides, anti-perovskite structure materials, and intermetallic compounds with frustrated lattice structures such as triangular lattices and Kagome lattices. Preferably, the magnetic refrigerant can be Ba6Yb2Ti4O 17 One or more of Gd3BWO9, Ce2Sn2O7, Na2BaCo(PO4)2 and KBaYb(BO3)2.

[0018] In some specific embodiments of the present invention, the magnetic refrigerant is a two-dimensional triangular lattice material Ba6Yb2Ti4O. 17 Or Gd3BWO9.

[0019] According to the preparation method provided by the present invention, the high thermal conductivity material is a metal powder, preferably silver powder, copper powder or gold powder.

[0020] According to the preparation method provided by the present invention, in order to balance thermal conductivity and magnetocaloric properties, the mass ratio of the magnetic refrigerant powder to the high thermal conductivity material powder in step S1 can be 1:0.5 to 1:5, preferably 1:1 to 1:3.

[0021] Preferably, the pre-compression in step S2 forms a preform with a relative density of 30%-60%. In this invention, relative density = actual density / theoretical density × 100%.

[0022] If the pre-compression degree is too low, it can easily lead to powder displacement; if it is too high, it can easily form initial pores, both of which may affect the subsequent SPS densification effect. Preferably, auxiliary vibration is applied during filling in step S2 to reduce powder bridging and ensure uniform powder filling in the mold.

[0023] According to the preparation method provided by the present invention, the heating rate of the discharge plasma sintering in step S3 is 50-150°C / min.

[0024] In an exemplary embodiment of the present invention, the preparation method may include the following steps:

[0025] 1. Raw material preparation: Grind the magnetic refrigerant into a uniform powder and mix it with a high thermal conductivity material powder in a specific ratio. The magnetic refrigerant is preferably a frustrated magnetic material, such as the two-dimensional triangular lattice material Ba6Yb2Ti4O. 17 However, this is not the only applicable working fluid; other working fluids suitable for cryogenic refrigeration (such as Gd-based compounds or other oxides) may also be used. Silver powder is preferred as the high thermal conductivity material, but it is not limited to this; other high thermal conductivity metals (such as copper, gold) or composite materials may also be used. The mixing ratio can be adjusted according to the characteristics of the working fluid and the thermally conductive material, for example, a mass ratio between 1:0.5 and 1:2, with 1:1 being the most preferred.

[0026] 2. Mold Filling: The mixed powder is filled into a high-strength graphite mold (the mold size can be designed according to requirements, such as 12.7 mm or 14 mm in diameter). The mold is vibrated to ensure dense powder filling and reduce initial porosity. Then, upper and lower graphite punches are inserted and initially pressed on a press to form a preform.

[0027] 3. Spark Plasma Sintering: Transfer the compressed mold to the spark plasma sintering equipment and evacuate to 10°C. -2The pressure is below 1 MPa, and then an inert protective gas (such as argon or nitrogen) is introduced as a protective atmosphere. Subsequently, a pressure of 30-100 MPa is applied to the mold and maintained at a constant pressure, while the temperature is increased to the set sintering temperature (e.g., 800°C) at a rate of 50-150°C / min using a pulsed current, and held for 10-100 minutes. During this process, the pulsed current excites plasma between the powder particles, activating the particle surface, promoting diffusion and interfacial bonding, and achieving rapid densification. The sintering temperature, pressure, and holding time can be optimized according to the characteristics of the working fluid and thermally conductive material.

[0028] 4. Cooling and Post-processing: After sintering, the mold is naturally cooled to room temperature (below 100°C) under constant pressure. After depressurization, the magnetic cooling module is removed. Use a lathe or other tools to remove the graphite paper residue adhering to the surface. If necessary, perform precision subtractive processing (such as cutting and milling) to meet specific geometric shape and surface morphology requirements.

[0029] Secondly, the present invention provides a magnetic refrigeration module, which is prepared by the method provided by the present invention, wherein a high thermal conductivity material in the magnetic refrigeration module forms a continuous network and encapsulates the magnetic refrigeration working fluid.

[0030] According to the magnetic refrigeration module provided by the present invention, the density of the magnetic refrigeration module is more than 90% of the theoretical density. Preferably, the magnetic refrigeration module allows for precision machining through a subtractive manufacturing process.

[0031] According to the magnetic refrigeration module provided by the present invention, a continuous network of highly thermally conductive materials is formed in the magnetic refrigeration module, which encapsulates the magnetic refrigeration working fluid therein.

[0032] The magnetic refrigeration module prepared by the method of the first aspect of the present invention has the following characteristics:

[0033] High density: The module density is close to the theoretical density, which is about twice that of cold pressing technology. There are no obvious micron-level pores inside, and the particle interface is tightly bonded as observed by scanning electron microscopy (SEM).

[0034] High thermal conductivity: High thermal conductivity materials (such as silver powder) form a continuous network in the module, encapsulating the magnetic refrigerant and significantly improving heat transfer efficiency.

[0035] Excellent mechanical properties: The module has high mechanical strength, which can be verified by compression testing, and is adapted to subtractive manufacturing processes to achieve high-precision machining.

[0036] Excellent cooling performance: In the adiabatic demagnetizing cooling test, the module can achieve an extremely low temperature of about 20 mK and maintain it below 100 mK for several hours, with a significantly shortened thermal relaxation time.

[0037] Thirdly, the present invention also provides the application of the magnetic refrigeration module for adiabatic demagnetization refrigeration in the sub-Kelvin temperature range.

[0038] According to the application provided by the present invention, compared with the cold-pressed module without SPS sintering, the magnetic refrigeration module prepared by the method of the present invention reaches the minimum temperature in a time that is more than 75% shorter after demagnetization than the cold-pressed module, and the maintenance time below 100 mK is extended by more than 25%.

[0039] This invention uses spark plasma sintering technology to prepare a magnetic refrigeration module, which has the following significant advantages:

[0040] High preparation efficiency: The SPS process enables rapid sintering, and the entire cycle can be shortened to less than 1 hour, overcoming the problem of long preparation cycles in traditional single crystal growth or cold pressing technologies, and is suitable for large-scale production.

[0041] High density and high cooling capacity: SPS eliminates the micron-level pores in cold pressing technology through plasma activation and high pressure, increasing the module density by more than 1 times, thereby increasing the cooling capacity per unit volume and improving refrigeration efficiency.

[0042] Excellent thermal conductivity: The high thermal conductivity material forms a uniform network, which significantly improves the thermal conduction performance of the module, improves the thermal cycling efficiency, and allows the module to reach the minimum temperature faster after demagnetization (the measured time is reduced by more than 75%).

[0043] Good machinability: The module has high mechanical strength and can be machined into high-precision shapes through conventional subtractive manufacturing (such as turning, milling, and cutting) to meet the design requirements of various magnetic refrigeration systems.

[0044] Flexible material selection: A wide range of magnetic refrigerants and high thermal conductivity materials can be selected, and the ratio can be optimized according to different application scenarios (such as specific temperature ranges or magnetic field conditions) to achieve customized design and balance performance and cost.

[0045] Good chemical stability: The use of stable working fluids such as oxides avoids the deliquescence problem of hydrated paramagnetic salts, eliminates the need for complex sealing, and improves the reliability and lifespan of the module.

[0046] Wide range of applications: This module is suitable for a variety of cryogenic systems, such as adiabatic demagnetizing refrigerators, providing high-performance and high-reliability refrigeration solutions for fields such as quantum computing, deep space exploration, and physical property measurement. Attached Figure Description

[0047] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein:

[0048] Figure 1The image shows a magnetic refrigeration module fabricated based on spark plasma sintering (SPS) in Embodiment 1 of the present invention, which is formed into concave and frustum structures respectively by cutting.

[0049] Figure 2 The SEM microstructure of the magnetic refrigeration module prepared by cold pressing in Comparative Example 1 (Figures a and b) is compared with that prepared by spark plasma sintering in Example 1 (Figures c and d).

[0050] Figure 3 The cooling curves of the magnetic refrigeration modules prepared by cold pressing (dashed line) in Comparative Example 1 and by spark plasma sintering (solid line) in Example 1 are compared; the inset is a magnified comparison of the temperature near zero magnetic field.

[0051] Figure 4 The image shows the uniaxial compressive load-displacement curve of the magnetic refrigeration module obtained in Example 1. Detailed Implementation

[0052] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0053] Example 1

[0054] This embodiment exemplarily describes the fabrication process of a magnetic refrigeration module, using a two-dimensional triangular lattice frustrated magnetic material Ba6Yb2Ti4O. 17 Take silver powder as an example.

[0055] Step 1: Raw material preparation

[0056] Ba6Yb2Ti4O 17 The bulk material is ground into a uniform powder with a particle size controlled at 10-50 μm. High-purity silver powder (particle size 10-50 μm) is then mixed with Ba6Yb2Ti4O. 17 The powders were mixed at a 1:1 mass ratio, with a total mass of 6 grams. The mixture was then stirred for 2 hours using a ductile iron mixer to ensure uniform distribution.

[0057] Step 2: Mold filling

[0058] A high-strength graphite mold (13.1 mm inner diameter) was selected, and the inner wall of the mold was lined with graphite paper to prevent sticking. The mixed powder was slowly filled into the mold while the mold was vibrated to increase the filling density. The upper and lower graphite punches were inserted, and the mold was initially pressed on a universal testing machine with a pressure of 10 MPa to form a preform with a relative density of approximately 45%.

[0059] Step 3: Spark Plasma Sintering

[0060] Transfer the mold to the SPS equipment and evacuate to 5×10⁻⁶.-2 The pressure was increased to 50 MPa, and then high-purity argon was introduced as a protective atmosphere. SPS parameters: axial pressure of 50 MPa was applied and maintained at a constant pressure; heating was carried out at a heating rate of 100°C / min to the sintering temperature of 800°C; and held at that temperature for 30 minutes. During this period, a pulsed current was passed through the mold and the powder to generate plasma, promoting particle surface activation and densification. After sintering, heating was stopped, and the powder was allowed to cool naturally to room temperature under the maintained pressure.

[0061] Step 4: Post-processing

[0062] Remove the sintered module and use a CNC lathe to remove the residual graphite paper on the surface to obtain a cylindrical magnetic refrigeration module (12.7 mm in diameter and about 6 mm in height).

[0063] Figure 1 This is a photograph of the magnetic refrigeration module obtained in this embodiment. The sample in the photograph was formed into concave and frustum structures by cutting.

[0064] Comparative Example 1

[0065] Preparation of Ba6Yb2Ti4O by cold pressing 17 / Silver Powder Cold Press Module

[0066] Raw materials: Same as in Example 1, high-purity silver powder and Ba6Yb2Ti4O 17 The powders are mixed in a 1:1 mass ratio, with a total mass of 6 grams.

[0067] Molding: The mixed powder is filled into a steel mold (inner diameter 12 mm), and a pressure of 10 MPa is applied on a universal testing machine and held for 300 minutes without sintering.

[0068] Post-processing: After demolding, a cold-pressed module (12 mm in diameter and 11 mm in height) is obtained.

[0069] Characterization and Testing

[0070] A sample block was taken from the magnetic refrigeration module prepared in Example 1. The sample surface was coarsely ground with a diamond grinding wheel, and then finely ground with 1500 grit, 3000 grit and 10000 grit sandpaper in sequence to obtain a flat observation surface. The polished sample was ultrasonically cleaned with alcohol and placed in a vacuum drying oven to dry for 2 hours.

[0071] 1. SEM micromorphological characterization

[0072] The magnetic refrigeration module prepared in Example 1 was polished to obtain a flat observation surface. The microstructure of the refrigeration module was observed using a scanning electron microscope (SEM) at an accelerating voltage of 15 kV and a working distance of 5 mm. The silver powder formed a three-dimensional mesh structure with tight interface bonding, no obvious cracks or micron-sized pores. This was compared with the cold-pressed module prepared in Comparative Example 1. Figure 2 As shown, the magnetic refrigeration module prepared in Example 1 has a high degree of densification.

[0073] 2. Density test

[0074] Three samples (numbered 1, 2, and 3) were randomly selected from the magnetic refrigeration module prepared in Example 1. Each sample had a diameter of 12.7 mm and a height of 10 mm. Both ends of the samples were sanded. The density of each sample was obtained by measuring its volume and mass, and the results are shown in Table 1. The average density was 6.7 g / cm³. 3 It is close to the theoretical density (7.317 g / cm³). 3 The density reached 91.7%.

[0075] The density of the module in Comparative Example 1 was measured to be 4.911 g / cm³ using the same method. 3 The density is 67%.

[0076] 3. Characterization of refrigeration performance

[0077] The magnetic refrigeration module (6 g in mass, 3 g in effective working fluid content) prepared in the example was thermally connected to a ruthenium oxide temperature sensor and fixed to an adiabatic demagnetizing refrigeration measuring device using a polymer plastic tube. The device includes a superconducting magnet, a gas thermal switch, and a vacuum chamber.

[0078] First, a 6T magnetic field is applied at a high temperature (20K) to magnetize the refrigeration module, which is then pre-cooled to an initial temperature of 2K. Adiabatic conditions are achieved through a gas thermal switch, and then the magnetic field is slowly reduced to zero at a constant rate (50 Oe / s).

[0079] Temperature sensor recordings show that the cooling temperature of the module in Embodiment 1 of this invention can be reduced to as low as 23.7 mK. The module of this invention uses only 3 grams of effective frustrated magnetic material and maintains a temperature below 100 mK for more than 4 hours under heat leakage conditions on the order of 0.1 microwatts.

[0080] Compared with the cold-pressed module prepared in Comparative Example 1, the SPS module of the present invention reaches the minimum temperature in a time that is reduced by more than 75% (see Comparative Example 1). Figure 3 (see illustration), and the maintenance time below 100 mK was extended by 25% (see illustration). Figure 3 These results demonstrate that the magnetic refrigeration module prepared using SPS technology in this invention has excellent thermal relaxation performance and refrigeration efficiency.

[0081] 4. Mechanical property characterization

[0082] Uniaxial compression testing was performed using a universal testing machine. The specimen was placed in the center of the lower clamp of the testing machine, and the upper clamp applied downward pressure at a constant displacement rate of 0.06 mm / min until the specimen showed obvious fracture. The maximum compressive force was recorded. The compressive strength was calculated based on the specimen's cross-sectional area using the following formula:

[0083] Compressive strength = maximum compressive force / cross-sectional area.

[0084] The test performance results are shown in Table 1 and Figure 4 As shown.

[0085] Table 1

[0086] Sample Maximum compressive force kN compressive strength (MPa) <![CDATA[Density g / cm 3 > 1 20.94 164.01 6.70 2 21.07 164.78 6.83 3 20.76 161.35 6.57

[0087] The load-displacement curves of the three specimens are as follows: Figure 4 As shown, the compression curve indicates that the sample exhibits linear elastic deformation before reaching the maximum load, and no significant plastic deformation occurs after fracture, demonstrating that the module of this invention possesses good rigidity. The mechanical properties of this module meet the requirements of subsequent subtractive machining (such as lathe cutting and milling), and no cracking or chipping occurs during the machining process.

[0088] Example 2

[0089] This embodiment prepares the GBWO-silver powder magnetic refrigeration module using a method similar to that of Embodiment 1, as detailed below:

[0090] Working medium: Gd3BWO9 (GBWO, particle size 5-10 μm);

[0091] High thermal conductivity material: silver powder (99.9% purity, particle size 3-5μm);

[0092] Mixing ratio: 1:1, total mass 6g;

[0093] SPS parameters: pressure 40 MPa, heating rate 80℃ / min, sintering temperature 700℃, holding time 20 minutes;

[0094] The performance was characterized and tested in the same manner as in Example 1, and the results are as follows: density 91%, minimum cooling temperature 168 mK, and the duration of holding below 300 mK for more than 3 hours.

[0095] This embodiment demonstrates that the preparation method of the present invention has broad material adaptability, and the composition of the material can be customized according to application requirements.

[0096] It should be noted that the specification and specific embodiments of this invention only exemplarily illustrate the use of Ba6Yb2Ti4O 17 The specific scheme and test results using Gd3BWO9 as the core refrigerant are described. However, the scope of protection of this invention is not limited to the specific form disclosed. Any equivalent substitution, modification, or simple variation of the technical solution based on the spirit of this invention, as well as all equivalent changes made using the content of the claims of this invention, are within the scope of this invention.

Claims

1. A method for the production of a magnetic refrigeration module based on spark plasma sintering, characterized in that, The method comprises the following steps: S1. uniformly mixing magnetic refrigeration working substance powder and high thermal conductivity material powder to form a magneto-thermal-thermal conductivity composite material system; S2. loading the composite material system into a mold and pre-pressing to form a preform; S3. moving the mold into a spark plasma sintering device, applying pressure to the preform in the mold and inputting pulse current for sintering under a protective atmosphere, wherein the sintering parameters include: sintering temperature 500-1000℃, sintering pressure 30-100MPa, and holding time 10-100 minutes; S4. cooling to room temperature after sintering is completed, demolding the module, and performing post-processing, The magnetic refrigeration working substance is a frustrated magnetic material, and the frustrated magnetic material is selected from one or more of spin ice materials, pyrochlore oxides, inverse perovskite structure materials, intermetallic compounds with a frustrated lattice structure of a triangular lattice, and intermetallic compounds with a frustrated lattice structure of a Kagome lattice. The high thermal conductivity material is silver powder, copper powder, or gold powder.

2. The production method according to claim 1, wherein, The mass ratio of the magnetic refrigeration working substance powder to the high thermal conductivity material powder in step S1 is 1:0.5 to 1:

5.

3. The production method according to claim 2, wherein, The mass ratio of the magnetic refrigeration working substance powder to the high thermal conductivity material powder in step S1 is 1:1 to 1:

3.

4. The production method according to claim 1, wherein The preform formed after pre-pressing in step S2 has a relative density of 30%-60%.

5. The production method according to claim 1, wherein The temperature rising rate of the spark plasma sintering in step S3 is 50-150°C / min.

6. A magnetic refrigeration module characterized in that, The magnetic refrigeration module is prepared by the method of any one of claims 1 to 5, wherein the high thermal conductivity material in the magnetic refrigeration module forms a continuous network and wraps the magnetic refrigeration working substance.

7. The magnetic refrigeration module of claim 6, wherein, The density of the magnetic refrigeration module is more than 90% of the theoretical density.

8. The magnetic refrigeration module of claim 6, wherein, The magnetic refrigeration module allows precise machining through subtractive manufacturing processes.

9. Use of the magnetic refrigeration module of any one of claims 6 to 8 for adiabatic demagnetization refrigeration in the sub-Kelvin temperature region.

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