Extremely-low-temperature magnetic refrigeration material with two-dimensional triangular lattice and preparation method and application of extremely-low-temperature magnetic refrigeration material

Abstract

The invention provides an extremely-low-temperature magnetic refrigeration material of a two-dimensional triangular lattice as well as a preparation method and application of the extremely-low-temperature magnetic refrigeration material. The chemical formula of the extremely-low-temperature magnetic refrigeration material is NdCd3P3, the extremely-low-temperature magnetic refrigeration material belongs to a hexagonal system, and the space group is P63 / mmc. The two-dimensional triangular lattice extremely-low-temperature magnetic refrigeration material NdCd3P3 provided by the invention has a good magnetocaloric effect, can reach an extremely low temperature of 180 mK in the adiabatic demagnetization process, has good heat-conducting property as semimetal, can effectively absorb and release heat under the regulation and control of a magnetic field, overcomes the defects of a traditional paramagnetic salt working medium, and has a good application prospect. And extremely low temperature is simply and efficiently realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic refrigeration. Specifically, the present invention relates to an extremely low-temperature magnetic refrigeration material with a two-dimensional triangular lattice, a preparation method thereof, and an application thereof. Background Art

[0002] The extremely low-temperature technology refers to the refrigeration technology for achieving a temperature range below 1 K, which is of great significance for new discoveries in physics, such as superconductivity and superfluidity. In terms of frontier applications, the extremely low-temperature technology is also an essential supporting condition for deep space exploration and quantum technology research and development. However, currently, common extremely low-temperature refrigeration technologies rely heavily on helium resources, and China's helium resources rely heavily on imports and lack key He3 production capacity, which has become a bottleneck problem for the development of related technologies and industries. Currently, the adiabatic demagnetization refrigeration technology has become the key technology for achieving refrigeration in this temperature range.

[0003] The adiabatic demagnetization refrigeration technology mainly relies on the magnetocaloric effect to achieve refrigeration. It usually uses traditional paramagnetic salt working fluids (mostly hydrates). When the temperature is high, a magnetic field is increased to make the spins of the magnetic material arranged orderly, and the magnetic entropy decreases. At this time, the material is demagnetized under adiabatic conditions, the magnetic entropy increases, and the heat of the load is absorbed to achieve the cooling effect. This technology does not have the problem of relying on the gravity environment, does not rely on helium resources, and is widely used in fields such as quantum computing and deep space exploration due to its advantages of high refrigeration efficiency, low vibration, and high reliability.

[0004] However, the growth process of traditional hydrate paramagnetic salts is complex, their chemical properties are extremely unstable, the density of magnetic ions is low, and at extremely low temperatures, only phonon heat conduction can be relied on, and the heat transfer efficiency is low, and there are many difficulties in the actual use process. In recent years, China has vigorously developed extremely low-temperature adiabatic demagnetization refrigeration materials. Among them, the patent application CN117342598A discloses an extremely low-temperature magnetic refrigeration material, a preparation method thereof, and an application thereof, and specifically discloses using EuCO3 as an extremely low-temperature refrigeration material, but the refrigeration temperature range of this material is near 1 K and cannot reach a lower refrigeration temperature.

[0005] Therefore, the development of new adiabatic demagnetization refrigeration materials will help to break through the technical bottleneck and realize the localization, application, and popularization of extremely low-temperature refrigeration technology. Summary of the Invention

[0006] Aiming at the above problems, the purpose of the present invention is to provide an extremely low-temperature magnetic refrigeration material with a two-dimensional triangular lattice, a preparation method thereof, and an application thereof, which has a good magnetocaloric effect, can reach an extremely low temperature of 180 mK during the adiabatic demagnetization process, has good thermal conductivity, and can effectively absorb and release heat under magnetic field regulation.

[0007] The above object of the present invention is achieved by providing the following technical solutions:

[0008] In a first aspect, the present invention provides a cryogenic magnetic refrigeration material with a two-dimensional triangular lattice, having a chemical formula of NdCd3P3, belonging to the hexagonal crystal system, and having a space group of P63 / mmc.

[0009] For the cryogenic magnetic refrigeration material provided by the present invention, the lattice constants of the cryogenic magnetic refrigeration material are a = b = 4.26 Å and c = 20.91 Å; where a, b, and c represent the lengths of the basis vectors of the unit cell, that is, the side lengths of the unit cell along the three crystal axis directions, a refers to the side length along the x-axis direction, b refers to the side length along the y-axis direction, and c refers to the side length along the z-axis direction.

[0010] Figure 1 is a schematic diagram of the crystal structure of the cryogenic magnetic refrigeration material NdCd3P3 provided by the present invention. Specifically, Figure 1 in (a) shows the positions of atoms in NdCd3P3 in the lattice, where the green atoms represent the magnetic ions Nd 3+ , the blue represents Cd 2+ ions, and the red represents P 3- ions; Figure 1 in (b) shows the triangular lattice structure formed by the magnetic ions Nd 3+ in the two-dimensional plane, and the distance between the Nd 3+ magnetic ions is 4.26 Å.

[0011] For the cryogenic magnetic refrigeration material provided by the present invention, the cryogenic magnetic refrigeration material has two Curie-Weiss behaviors.

[0012] For the cryogenic magnetic refrigeration material provided by the present invention, the cryogenic magnetic refrigeration material has a first Curie-Weiss behavior in the temperature range of 2.2 - 3.7 K and a second Curie-Weiss behavior in the temperature range of 200 - 300 K.

[0013] For the cryogenic magnetic refrigeration material provided by the present invention, the Curie-Weiss temperature of the cryogenic magnetic refrigeration material in the temperature range of 2.2 - 3.7 K is -0.493 K, and the effective magnetic moment in the temperature range of 200 - 300 K is 3.62 μ B .

[0014] For the cryogenic magnetic refrigeration material provided by the present invention, the magnetization intensity of the cryogenic magnetic refrigeration material increases with the increase of the external magnetic field intensity; at a temperature of 1.8 - 15 K, the magnetization of the cryogenic magnetic refrigeration material does not reach saturation at a magnetic field intensity of 7 T.

[0015] For the cryogenic magnetic refrigeration material provided by the present invention, at a temperature of 2.4 K, the maximum magnetic entropy change -ΔS of the cryogenic magnetic refrigeration material under a magnetic field change of 0 - 7 TM ≤ 3.63 J / (kg·K).

[0016] According to the cryogenic magnetic refrigeration material provided by the present invention, wherein, at an ambient temperature of 1.8 K, demagnetization is carried out from an 8 T magnetic field, and when the magnetic field drops to zero, the temperature of the cryogenic magnetic refrigeration material is 180 mK.

[0017] In a second aspect, the present invention provides a preparation method of the cryogenic magnetic refrigeration material described in the first aspect of the present invention, which includes the following steps:

[0018] (1) Mix Cd and P according to the stoichiometric ratio, and then sinter at 200 - 500 °C for 25 - 45 h under anaerobic conditions to obtain a pre - reactant CdP;

[0019] (2) Mix the pre - reactant CdP and Nd according to the stoichiometric ratio, and then sinter for the first time at 500 - 900 °C for 25 - 45 h under anaerobic conditions, and then sinter for the second time at 500 - 900 °C for 25 - 45 h under anaerobic conditions to obtain the cryogenic magnetic refrigeration material.

[0020] According to the preparation method provided by the present invention, wherein, in step (1), sinter at 220 - 280 °C for 30 - 35 h under anaerobic conditions.

[0021] According to the preparation method provided by the present invention, wherein, in step (2), sinter for the first time at 650 - 750 °C for 30 - 35 h under anaerobic conditions.

[0022] According to the preparation method provided by the present invention, wherein, in step (2), sinter for the second time at 650 - 750 °C for 30 - 35 h under anaerobic conditions.

[0023] According to the preparation method provided by the present invention, wherein, in step (1) and / or (2), the anaerobic conditions are selected from one of vacuum sealing, nitrogen atmosphere and inert atmosphere.

[0024] According to the preparation method provided by the present invention, wherein, the preparation method further includes: in step (1) and / or (2), fully grinding the material to be sintered or the sintered material.

[0025] In a third aspect, the present invention provides an application of the cryogenic magnetic refrigeration material described in the first aspect of the present invention or the cryogenic magnetic refrigeration material prepared by the preparation method described in the second aspect of the present invention as an adiabatic demagnetization refrigeration working medium.

[0026] The present invention has at least the following beneficial effects:

[0027] The extremely low temperature magnetic refrigeration material NdCd3P3 with a two-dimensional triangular lattice provided by the present invention has a good magnetocaloric effect, can reach an extremely low temperature of 180 mK during the adiabatic demagnetization process, and at the same time, as a half-metal, it has good thermal conductivity and can effectively absorb and release heat under magnetic field regulation, overcoming the defects of traditional paramagnetic salt working fluids and simply and efficiently achieving extremely low temperature.

[0028] In addition, the preparation method of NdCd3P3 provided by the present invention is simple, the raw materials are inexpensive, the preparation period is short, and the prepared NdCd3P3 has a compact structure, which is suitable for large-scale industrial production and application. Brief Description of the Drawings

[0029] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings, where:

[0030] Figure 1 is a schematic diagram of the crystal structure of the rare earth metal phosphide NdCd3P3 with a two-dimensional triangular lattice structure of the present invention; among them, the green atoms represent the magnetic ions Nd 3+ , the blue represents Cd 2+ ions, and the red represents P 3- ions;

[0031] Figure 2 is a comparison diagram of the X-ray diffraction pattern of the NdCd3P3 material prepared in Example 1 of the present invention and its standard card;

[0032] Figure 3 is the susceptibility temperature curve and the reciprocal susceptibility curve of the NdCd3P3 material prepared in Example 1 of the present invention;

[0033] Figure 4 is the isothermal magnetization curve of the NdCd3P3 material prepared in Example 1 of the present invention at different temperatures from 1.8 K to 15 K;

[0034] Figure 5 is the curve of the isothermal magnetic entropy change of the NdCd3P3 material prepared in Example 1 of the present invention changing with the magnetic field during the isothermal magnetization process;

[0035] Figure 6 is the temperature change curve of the NdCd3P3 material prepared in Example 1 of the present invention after demagnetization at the initial magnetic fields of 2 T, 4 T, 6 T, and 8 T starting from the initial temperature of 1.8 K under quasi-adiabatic conditions, where the gray dashed line refers to the linear cooling behavior of an ideal paramagnetic salt in an ideal state;

[0036] Figure 7 is the temperature change curve of the NdCd3P3 material prepared in Example 1 of the present invention with time during the magnetic field reduction process and after the magnetic field drops to zero; among them, the inset is an enlarged view of the temperature change of the sample after the magnetic field returns to zero. Detailed implementation manners

[0037] The present invention will be further described in detail below with reference to specific embodiments. The provided embodiments are only for clarifying the present invention and not for limiting the scope of the present invention.

[0038] Example 1

[0039] The two-dimensional triangular lattice material NdCd3P3 is synthesized by a solid-state reaction method

[0040] (1) Using Cd and P as raw materials, after uniformly grinding and mixing them according to the stoichiometric ratio of 1:1, they are vacuum-sealed in a quartz tube to prevent Cd and P from reacting with O2, and then sintered at 250 °C for 30 h. After taking out, it is fully ground to obtain the pre-reaction product CdP (actually a mixture of Cd2P, Cd2P3, Cd, P, etc., but the molar ratio of Cd and P is still 1:1) for the subsequent preparation process;

[0041] (2) Using Nd and the pre-reaction product CdP as raw materials, they are uniformly mixed according to the stoichiometric ratio of 1:3 and fully ground to make the reaction more complete during the sintering process. Subsequently, it is vacuum-sealed in a quartz tube (to prevent each component from reacting with O2 in the air), first sintered at 700 °C for 30 h, taken out and fully ground, and then sintered at 700 °C for the second time for 30 h to obtain a pure-phase powder.

[0042] Figure 2 It is a comparison diagram of the X-ray diffraction pattern of the NdCd3P3 material prepared in Example 1 of the present invention with its standard card. As can be seen from the figure, the NdCd3P3 material is successfully prepared in the present invention.

[0043] Example 2

[0044] The two-dimensional triangular lattice material NdCd3P3 is synthesized according to the method of Example 1, and the difference from Example 1 is as follows:

[0045] In step (1), sinter at 220 °C for 35 h; in step (2), sinter at 650 °C for the first time for 35 h, and then sinter at 650 °C for the second time for 35 h.

[0046] After testing, the X-ray diffraction pattern of the NdCd3P3 material prepared in Example 2 is compared with its standard card Figure 1 consistent.

[0047] Example 3

[0048] The two-dimensional triangular lattice material NdCd3P3 is synthesized according to the method of Example 1, and the difference from Example 1 is as follows:

[0049] In step (1), sinter at 280 °C for 30 h; in step (2), sinter for the first time at 750 °C for 30 h, and then sinter for the second time at 750 °C for 30 h.

[0050] After testing, the X-ray diffraction pattern of the NdCd3P3 material prepared in Example 3 was compared with its standard card Figure 1 and found to be consistent.

[0051] Magnetic property characterization

[0052] The magnetic properties of the two-dimensional triangular lattice material NdCd3P3 prepared in Example 1 were characterized using a Quantum Design MPMS testing system, and the susceptibility and magnetization data are as Figures 3 - 5 shown.

[0053] Figure 3 are the susceptibility temperature curve and the reciprocal susceptibility curve of the NdCd3P3 material prepared in Example 1. Among them, Figure 3 in (a) are the susceptibility temperature curve and the reciprocal susceptibility curve of the NdCd3P3 material in the range of 1.8 - 25 K, as well as the Curie-Weiss fitting curve in the range of 2.2 - 3.7 K; Figure 3 in (b) are the susceptibility temperature curve and the reciprocal susceptibility curve of the NdCd3P3 material in the range of 1.8 - 300 K, as well as the Curie-Weiss fitting curve in the range of 200 - 300 K.

[0054] Figure 3 The results in show that the NdCd3P3 material satisfies the Curie-Weiss law at low temperatures. In the temperature range of 2.2 - 3.7 K, the Weiss temperature of the magnetic ion Nd 3+ is -0.493 K. After the spin-orbit coupling of the Nd 3+ ions, under the action of the crystal field, the ground state is a doublet, showing an effective spin-1 / 2 and a weak antiferromagnetic interaction in the low-temperature region. As the temperature increases, the crystal field splits the first excited doublet and begins to contribute magnetism, showing a second Curie-Weiss behavior, and the fitted effective magnetic moment is 3.62 μ B , which is the same as the effective magnetic moment of the Nd 3+ free ion.

[0055] The magnetization-field variation data of the NdCd3P3 material prepared in Example 1 was tested. Figure 4 are the isothermal magnetization curves of the NdCd3P3 material at different temperatures in the range of 1.8 - 15 K; Figure 5 is the curve of the isothermal magnetic entropy change versus magnetic field during the isothermal magnetization process of the NdCd3P3 material calculated according to the Maxwell relationship.

[0056] AsFigure 4 As shown, the magnetization of NdCd3P3 increases with the increase of the external magnetic field, and the magnetic moment is not saturated at 7 T. Integrating according to the Maxwell relation, the entropy change in the isothermal magnetization process at different temperatures is obtained, as Figure 5 shown. At a temperature of 2.4 K, the magnetic entropy can be changed by 2.087 J / (mol·K) under a magnetic field of 7 T. This shows that NdCd3P3 can effectively absorb and release heat under magnetic field control to achieve the purpose of refrigeration.

[0057] Since the NdCd3P3 materials prepared in Examples 2 and 3 are consistent with Example 1 in terms of composition and XRD structure, after testing and verification, the NdCd3P3 materials prepared in Examples 2 and 3 also exhibit the same characteristics as Example 1 in terms of magnetic properties.

[0058] Magnetic refrigeration property characterization

[0059] The NdCd3P3 material prepared in Example 1 was ground evenly. Without mixing any heat-conducting medium such as silver powder, etc., only the powder of the above material was applied with a pressure of 7 - 8 MPa for 3 hours to form a cylinder with a diameter of 10 mm, and a thermometer was placed on its surface. Using an adiabatic demagnetization refrigeration measurement device, an adiabatic demagnetization test was carried out in a commercial Quantum Design PPMS test system.

[0060] Under quasi-adiabatic conditions, starting from an initial temperature of 1.8 K, the temperature change curves of the NdCd3P3 material prepared in Example 1 after demagnetization under initial magnetic fields of 2 T, 4 T, 6 T, and 8 T are as Figure 6 shown, where the gray dashed line refers to the linear cooling behavior of an ideal paramagnetic salt in an ideal state. Figure 6 The results show that at an ambient temperature of 1.8 K, when demagnetized from a magnetic field of 8 T, when the magnetic field drops to zero, the temperature reaches 180 mK.

[0061] Figure 7 is the temperature change curve of the NdCd3P3 material prepared in Example 1 with time during the process of decreasing the magnetic field and after the magnetic field drops to zero; where the inset is an enlarged view of the temperature change of this sample after the magnetic field returns to zero. Figure 7 The results show that the temperature of the NdCd3P3 material has dropped to the lowest after the magnetic field drops to zero and remains at the lowest temperature for a long time. This shows that the NdCd3P3 material has good thermal conductivity and cold capacity and is a good cryogenic magnetic refrigeration working medium.

[0062] Since the NdCd3P3 materials prepared in Examples 2 and 3 are consistent with those in Example 1 in terms of composition and XRD structure, after testing and verification, the NdCd3P3 materials prepared in Examples 2 and 3 also exhibit the same characteristics as those in Example 1 in terms of magnetic refrigeration performance.

[0063] From the above performance characterization, it can be seen that the NdCd3P3, a two-dimensional triangular lattice cryogenic magnetic refrigeration material provided by the present invention, has a good magnetocaloric effect, can reach an extremely low temperature of 180 mK during adiabatic demagnetization, and at the same time, as a half-metal, it has good thermal conductivity, overcoming the defects of traditional paramagnetic salt working fluids and simply and efficiently achieving extremely low temperatures. In addition, the preparation method of NdCd3P3 provided by the present invention is simple, the raw materials are inexpensive, the preparation cycle is short, and the structure of the prepared NdCd3P3 material is compact, which is suitable for large-scale industrial production and application.

[0064] The above are only several exemplary embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the present invention. Any equivalent or equivalent embodiments obtained by making some changes or modifications using the disclosed technical content by those skilled in the art without departing from the technical solution of the present invention fall within the scope of the present invention.

Claims

1. A cryogenic magnetic refrigeration material with a two-dimensional triangular lattice, having the chemical formula NdCd3P3, belonging to the hexagonal crystal system, and having the space group P63 / mmc.

2. The cryogenic magnetic refrigeration material according to claim 1, wherein, The lattice constants of the cryogenic magnetic refrigeration material are a = b = 4.26 Å and c = 20.91 Å.

3. The cryogenic magnetic refrigeration material according to claim 1 or 2, wherein, The cryogenic magnetic refrigeration material has two Curie-Weiss behaviors. Preferably, the cryogenic magnetic refrigeration material has the first Curie-Weiss behavior in the temperature range of 2.2 - 3.7 K and the second Curie-Weiss behavior in the temperature range of 200 - 300 K. Preferably, the cryogenic magnetic refrigeration material has a Curie-Weiss temperature of -0.493 K in the temperature range of 2.2 - 3.7 K and an effective magnetic moment of 3.62 μ in the temperature range of 200 - 300 K B .

4. The cryogenic magnetic refrigeration material according to any one of claims 1 to 3, wherein The magnetization of the cryogenic magnetic refrigeration material increases with the increase of the external magnetic field strength; at a temperature of 1.8 - 15 K, the magnetization of the cryogenic magnetic refrigeration material does not reach saturation at a magnetic field strength of 7 T.

5. The cryogenic magnetic refrigeration material according to any one of claims 1 to 4, wherein At a temperature of 2.4 K, the maximum magnetic entropy change -ΔS of the cryogenic magnetic refrigeration material under a magnetic field change of 0 - 7 T M ≤ 3.63 J / (kg·K).

6. The cryogenic magnetic refrigeration material according to any one of claims 1 to 5, wherein, At an ambient temperature of 1.8 K, demagnetization is carried out from a magnetic field of 8 T. When the magnetic field drops to zero, the temperature of the cryogenic magnetic refrigeration material is 180 mK.

7. A preparation method of the cryogenic magnetic refrigeration material according to any one of claims 1 to 6, comprising the following steps: (1) Mix Cd and P according to the stoichiometric ratio, and then sinter at 200 - 500 °C for 25 - 45 h under anaerobic conditions to obtain the precursor CdP. (2) Mix the precursor CdP and Nd according to the stoichiometric ratio, and then first sinter at 500 - 900 °C for 25 - 45 h under anaerobic conditions, and then second sinter at 500 - 900 °C for 25 - 45 h under anaerobic conditions to obtain the cryogenic magnetic refrigeration material.

8. The preparation method according to claim 7, wherein, In step (1), sinter at 220 - 280 °C for 30 - 35 h under anaerobic conditions. Preferably, in step (2), first sinter at 650 - 750 °C for 30 - 35 h under anaerobic conditions. Preferably, in step (2), second sinter at 650 - 750 °C for 30 - 35 h under anaerobic conditions. Preferably, in step (1) and / or (2), the anaerobic condition is selected from one of vacuum sealing, nitrogen atmosphere, and inert atmosphere.

9. The preparation method according to claim 7 or 8, wherein The preparation method further includes: in step (1) and / or (2), fully grinding the material to be sintered or the sintered material.

10. Application of the cryogenic magnetic refrigeration material according to any one of claims 1 to 6 or the cryogenic magnetic refrigeration material prepared by the preparation method according to any one of claims 7 to 9 as an adiabatic demagnetization refrigeration working medium.

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