A rare earth molybdate low-temperature magnetic refrigeration material and its preparation method and application

Abstract

The present invention belongs to the technical field of rare earth functional materials, and relates to a rare earth molybdate low-temperature magnetic refrigeration material and its preparation method and application. The chemical formula of the rare earth molybdate low-temperature magnetic refrigeration material is RE6MoO 12 The material has a cubic crystal structure and belongs to the #imgabs0# space group. The preparation method is as follows: dissolving a rare earth metal salt and ammonium molybdate to form a solution, adding a complexing agent to the solution for complexation to form a sol, drying the sol to form a gel, heating the gel to 580-680°C for annealing to form a precursor product, pressing the precursor product into a sheet and then heating it to 950-1050°C for sintering to obtain the RE6MoO provided by the present invention. 12 The material exhibits more excellent magnetic refrigeration performance in the low temperature zone, and the preparation method of the material has simple steps, short cycle and low preparation cost.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth functional materials, and relates to a molybdate rare earth low-temperature magnetic refrigeration material and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] In recent years, cryogenic refrigeration technology has played an important strategic role in high-tech fields including cryogenic physics, deep space exploration, and national defense security. At present, liquid helium refrigeration is a more commonly used cryogenic refrigeration method. However, this method not only has low refrigeration efficiency, but also uses scarce helium resources. Therefore, it is urgent to find new alternative refrigeration technologies.

[0004] Magnetic refrigeration technology is a "green" refrigeration technology that realizes refrigeration based on the magnetocaloric effect of materials. Compared with traditional gas compression refrigeration, it has the advantages of high efficiency (actual efficiency can reach 60-70% of the Carnot cycle efficiency), no pollution, simple structure and low noise, so it has become one of the most promising new refrigeration methods in the future. The working principle of magnetic refrigeration is to use an external magnetic field to make the magnetic moment of the magnetic working medium change in an orderly or disordered manner, causing the magnet to absorb and release heat, thereby achieving the purpose of refrigeration.

[0005] In recent decades, rare earth alloys and rare earth manganese oxides have shown certain low-temperature magnetic refrigeration performance. However, most of these materials have problems such as complex preparation process, low magnetic refrigeration capacity, long production cycle or high preparation cost, which limits their application in reality to a certain extent. Therefore, it is of great research significance and value to explore more excellent magnetic refrigeration materials in the low temperature range. Summary of the invention

[0006] In order to solve the deficiencies of the prior art, the present invention aims to provide a rare earth molybdate low-temperature magnetic refrigeration material and a preparation method and application thereof. 12 The material exhibits more excellent magnetic refrigeration performance in the low temperature zone, and the preparation method of the material has simple steps, short cycle and low preparation cost.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] In the first aspect, a rare earth molybdate low-temperature magnetic refrigeration material, whose chemical formula is RE6MoO 12 , the material has a cubic crystal structure and belongs to Space group, where RE is a rare earth element, including Tb, Dy, Ho or Er.

[0009] The low-temperature magnetic refrigeration material provided by the present invention has a larger low-temperature magnetic entropy change and a large relative magnetic refrigeration capacity. Under a magnetic field change of 0 to 2 T, the isothermal magnetic entropy change is 3.1 to 9.8 J / kgK, and the relative magnetic refrigeration capacity is 39.8 to 88.5 J / kg; under a magnetic field change of 0 to 5 T, the isothermal magnetic entropy change is 9.7 to 18.6 J / kgK, and the relative magnetic refrigeration capacity is 184.3 to 334.8 J / kg; under a magnetic field change of 0 to 7 T, the isothermal magnetic entropy change is 12.8 to 21.2 J / kgK, and the relative magnetic refrigeration capacity is 308.3 to 506.2 J / kg.

[0010] On the other hand, a method for preparing a rare earth molybdate low-temperature magnetic refrigeration material is provided, wherein a rare earth metal salt and ammonium molybdate are prepared into RE6MoO by a sol-gel method. 12 Material;

[0011] The sol-gel method comprises the following steps: dissolving a rare earth metal salt and ammonium molybdate to form a solution, adding a complexing agent to the solution for complexation to form a sol, drying the sol to form a gel, heating the gel to 580-680° C. for annealing to form a precursor product, pressing the precursor product into a sheet and heating it to 950-1050° C. for sintering to obtain the rare earth metal salt; the rare earth metal salt is a compound containing a rare earth metal element, and the rare earth metal element is Tb, Dy, Ho or Er.

[0012] The present invention firstly adopts annealing at 580-680°C to remove citric acid and various acid radical ions in the dry gel to obtain a metal oxide mixture; then, by tableting, the metal oxide mixture is more closely combined together, atomic diffusion is easier to proceed, the reaction process is accelerated, and the density and strength of the material are improved; then, the mixture is heated to 950-1050°C for sintering, thereby obtaining a cubic crystal structure and belonging to Space group rare earth molybdate low-temperature magnetic refrigeration materials.

[0013] The present invention can obtain high-purity cubic crystal structure and belongs to The space group of molybdate rare earth low-temperature magnetic refrigeration material has a larger low-temperature magnetic entropy change and a large relative magnetic refrigeration capacity.

[0014] In a third aspect, a rare earth molybdate material is used in the preparation of a low-temperature magnetic refrigeration material, wherein the chemical formula of the rare earth molybdate material is RE6MoO 12 , which has a cubic crystal structure and belongs to Space group, where RE is a rare earth element, including Tb, Dy, Ho or Er.

[0015] A fourth aspect is the application of the above-mentioned rare earth molybdate low-temperature magnetic refrigeration material in low-temperature physics research, magnetic refrigeration equipment, deep space exploration or aerospace.

[0016] The beneficial effects of the present invention are:

[0017] The molybdate rare earth low-temperature magnetic refrigeration material provided by the present invention is a paramagnetic material with negligible hysteresis and thermal hysteresis effects. Therefore, as a low-temperature magnetic refrigeration material, it has a higher refrigeration efficiency. This type of material has the characteristics of stable structure and high magnetic density, and exhibits more excellent magnetic refrigeration performance in the low temperature range. Among them, Ho6MoO 12 The maximum relative magnetic refrigeration capacity of the compound reached 506.2 J / kg when ΔH=7T, showing a large low-temperature magnetic refrigeration capacity, and has broad application prospects in the fields of low-temperature physics, deep space exploration, military aerospace, etc.

[0018] The present invention adopts a sol-gel method to prepare a molybdate rare earth low-temperature magnetic refrigeration material. The preparation method has the advantages of simple steps, short cycle, low preparation cost, etc., and is more suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0020] Figure 1 Preparation of samples RE6MoO for Examples 1-4 12 XRD refinement patterns of (RE = Tb, Dy, Ho and Er); a is Tb6MoO 12 , b is Dy6MoO 12 , c is Ho6MoO 12 , d is Er6MoO 12 .

[0021] Figure 2 Preparation of samples RE6MoO for Examples 1-4 12 (RE = Tb, Dy, Ho and Er) ZFC and FC thermomagnetic curves under different magnetic fields; a is Tb6MoO 12 , b is Dy6MoO 12 , c is Ho6MoO 12 , d is Er6MoO 12 .

[0022] Figure 3 Preparation of samples RE6MoO for Examples 1-4 12 (RE = Tb, Dy, Ho and Er) isothermal magnetization curves at different temperatures; a is Tb6MoO 12, b is Dy6MoO 12 , c is Ho6MoO 12 , d is Er6MoO 12 .

[0023] Figure 4 Preparation of samples RE6MoO for Examples 1-4 12 (RE = Tb, Dy, Ho and Er) Curves of magnetic entropy change with temperature under different magnetic field changes; a is Tb6MoO 12 , b is Dy6MoO 12 , c is Ho6MoO 12 , d is Er6MoO 12 . DETAILED DESCRIPTION

[0024] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0026] In view of the fact that the existing known materials with magnetic refrigeration performance have the problem of low magnetic refrigeration capacity, and the process for preparing these materials is complex, the production cycle is long or the preparation cost is high, the present invention proposes a rare earth molybdate low-temperature magnetic refrigeration material and its preparation method and application.

[0027] A typical embodiment of the present invention provides a rare earth molybdate low-temperature magnetic refrigeration material, whose chemical formula is RE6MoO 12 , the material has a cubic crystal structure and belongs to Space group, where RE is a rare earth element, including Tb, Dy, Ho or Er.

[0028] Another embodiment of the present invention provides a method for preparing rare earth molybdate low-temperature magnetic refrigeration material, wherein rare earth metal salt and ammonium molybdate are prepared into RE6MoO by a sol-gel method. 12 Material;

[0029] The sol-gel method comprises the following steps: dissolving a rare earth metal salt and ammonium molybdate to form a solution, adding a complexing agent to the solution for complexation to form a sol, drying the sol to form a gel, heating the gel to 580-680° C. for annealing to form a precursor product, pressing the precursor product into a sheet and heating it to 950-1050° C. for sintering to obtain the rare earth metal salt; the rare earth metal salt is a compound containing a rare earth metal element, and the rare earth metal element is Tb, Dy, Ho or Er.

[0030] The rare earth metal salt described in the present invention may be nitrate, sulfate, chloride, etc.

[0031] In some embodiments, the complexing agent is citric acid. Specifically, the ratio of the molar amount of citric acid added to the molar amount of total metal ions is 1.4-2.4:1.

[0032] In some embodiments, the temperature during the complexing process is 85-95°C.

[0033] In some embodiments, the sol is dried at a temperature of 110 to 130° C. and for a drying time of 11 to 13 hours.

[0034] In some embodiments, the annealing time is 4 to 6 hours.

[0035] In some embodiments, the tableting is performed by cold pressing of powder.

[0036] In some embodiments, the sintering time is 3 to 6 hours.

[0037] A third embodiment of the present invention provides an application of a rare earth molybdate material in the preparation of a low-temperature magnetic refrigeration material, wherein the chemical formula of the rare earth molybdate material is RE6MoO 12 , which has a cubic crystal structure and belongs to Space group, where RE is a rare earth element, including Tb, Dy, Ho or Er.

[0038] In some embodiments, the rare earth molybdate material is prepared by a sol-gel method by combining a rare earth metal salt and ammonium molybdate;

[0039] The sol-gel method comprises the following steps: dissolving a rare earth metal salt and ammonium molybdate to form a solution, adding a complexing agent to the solution for complexation to form a sol, drying the sol to form a gel, heating the gel to 580-680° C. for annealing to form a precursor product, pressing the precursor product into a sheet and heating it to 950-1050° C. for sintering to obtain the product.

[0040] In some embodiments, the complexing agent is citric acid. Specifically, the ratio of the molar amount of citric acid added to the molar amount of total metal ions is 1.4-2.4:1.

[0041] Specifically, the temperature during the complexing process is 85-95°C.

[0042] Specifically, the sol is dried at a temperature of 110 to 130° C. and for a drying time of 11 to 13 hours.

[0043] Specifically, the annealing time is 4 to 6 hours.

[0044] Specifically, the tableting is powder cold pressing.

[0045] Specifically, the sintering time is 3 to 6 hours.

[0046] A fourth embodiment of the present invention provides an application of the above-mentioned rare earth molybdate low-temperature magnetic refrigeration material in low-temperature physics research, magnetic refrigeration equipment, deep space exploration or aerospace.

[0047] Specifically, the magnetic refrigeration device may be a magnetic induction refrigeration refrigerator.

[0048] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in combination with specific embodiments and comparative examples.

[0049] Embodiment 1:

[0050] A Tb6MoO 12 The preparation method of low-temperature magnetic refrigeration material comprises the following steps:

[0051] Step 1: Mix terbium nitrate and ammonium molybdate 3+ :Mo 6+ After weighing the ions in a molar ratio of 6:1, add them one by one into deionized water under constant stirring until they dissolve to form a uniform transparent solution.

[0052] Step 2: Add citric acid, terbium nitrate and ammonium molybdate to the above uniform solution in a molar ratio of 1:2 to citric acid, heat to 90°C, and rapidly stir to form a sol.

[0053] Step 3: Place the above sol in an oven and dry at 120° C. for 12 hours to obtain a gel, and anneal the gel at 580° C. for 6 hours to form a precursor pre-product.

[0054] Step 4: Place the precursor pre-product into a mold with an inner diameter of 2 cm, press it at 20T for 4 minutes, and after the tablet is formed, place it in a corundum crucible, heat it to 1000℃, sinter it for 3h in an air atmosphere, and cool it to room temperature to obtain the finished product. XRD characterization results show that the finished product has a cubic crystal structure with a space group of Its room temperature XRD Rietveld refinement pattern is shown below: Figure 1 As shown in a.

[0055] The Tb6MoO prepared in this example 12 The ZFC and FC thermomagnetic curves of low-temperature magnetic refrigeration materials under different magnetic fields are as follows Figure 2 As shown in a, as the test temperature decreases, the ZFC and FC curves undergo a process from paramagnetic phase transition to antiferromagnetic phase transition, that is, a peak value appears, and its Neel temperature T N It is 3.3K.

[0056] The Tb6MoO prepared in this example 12 The isothermal magnetization curves of low-temperature magnetic refrigeration materials at different temperatures are as follows: Figure 3 As shown in a, at low temperature and low field, the magnetization intensity increases rapidly with the increase of magnetic field, and approaches saturation at high field; at high temperature, the magnetization intensity increases linearly. The inset is the hysteresis loop at 2K, which obviously has no hysteresis, indicating that it has high magnetic refrigeration cycle efficiency in practical applications.

[0057] The Tb6MoO prepared in this example 12 The curves of magnetic entropy change with temperature under different magnetic field changes of low-temperature magnetic refrigeration materials are as follows Figure 4 As shown in a, under the magnetic field change of 0~2T, the isothermal magnetic entropy changes to 3.1J / kgK, under the magnetic field change of 0~5T, the isothermal magnetic entropy changes to 9.7J / kgK; under the magnetic field change of 0~7T, the isothermal magnetic entropy changes to 12.8J / kgK. According to the formula (-ΔS M max is the maximum magnetic entropy change value corresponding to a certain magnetic field change, δT FWHM The relative magnetic refrigeration capacity (RCP) of the finished product can be calculated by the half-width of the curve of magnetic entropy change with temperature. Under the magnetic field change of 0-2T, the RCP is 39.8J / kg; under the magnetic field change of 0-5T, the RCP is 203.7J / kg; under the magnetic field change of 0-7T, the RCP is 308.3J / kg.

[0058] Embodiment 2:

[0059] A Dy6MoO 12 The preparation method of low-temperature magnetic refrigeration material comprises the following steps:

[0060] Step 1: Dysprosium nitrate and ammonium molybdate are mixed in a 3+ :Mo 6+ After weighing the ions in a molar ratio of 6:1, add them one by one into deionized water under constant stirring until they dissolve to form a uniform transparent solution.

[0061] Step 2: Add the total amount of citric acid, dysprosium nitrate and ammonium molybdate to the above uniform solution in a molar ratio of 1:2 to citric acid, heat to 90°C, and rapidly stir to form a sol.

[0062] Step 3: Place the above sol in an oven and dry at 120° C. for 12 hours to obtain a gel, and anneal the gel at 580° C. for 6 hours to form a precursor pre-product.

[0063] Step 4: Place the precursor pre-product into a mold with an inner diameter of 2 cm, press it at 20T for 4 minutes, and after the tablet is formed, place it in a corundum crucible, heat it to 1000℃, sinter it for 3h in an air atmosphere, and cool it to room temperature to obtain the finished product. XRD characterization results show that the finished product has a cubic crystal structure with a space group of Its room temperature XRD Rietveld refinement pattern is shown below: Figure 1 As shown in b.

[0064] The Dy6MoO prepared in this example 12 The ZFC and FC thermomagnetic curves of low-temperature magnetic refrigeration materials under different magnetic fields are as follows Figure 2 As shown in b, as the test temperature decreases, the ZFC and FC curves undergo a process from paramagnetic phase transition to antiferromagnetic phase transition, that is, a peak value appears, and its Neel temperature T N It is 2.1K.

[0065] The Dy6MoO prepared in this example 12 The isothermal magnetization curves of low-temperature magnetic refrigeration materials at different temperatures are as follows: Figure 3 As shown in b, at low temperature and low field, the magnetization intensity increases rapidly with the increase of magnetic field, and approaches saturation at high field; at high temperature, the magnetization intensity increases linearly. The inset is the hysteresis loop at 2K, which obviously has no hysteresis, indicating that it has high magnetic refrigeration cycle efficiency in practical applications.

[0066] The Dy6MoO prepared in this example 12 The curves of magnetic entropy change with temperature under different magnetic field changes of low-temperature magnetic refrigeration materials are as follows Figure 4 As shown in Figure b, under the magnetic field change of 0~2T, the isothermal magnetic entropy changes to 8.2J / kgK, under the magnetic field change of 0~5T, the isothermal magnetic entropy changes to 18.3J / kgK; under the magnetic field change of 0~7T, the isothermal magnetic entropy changes to 20.7J / kgK. According to the formula (-ΔS M max is the maximum magnetic entropy change value corresponding to a certain magnetic field change, δT FWHM The relative magnetic refrigeration capacity (RCP) of the finished product can be calculated by the half-width of the curve of magnetic entropy change with temperature. Under the magnetic field change of 0-2T, the RCP is 73.9J / kg; under the magnetic field change of 0-5T, the RCP is 311.1J / kg; under the magnetic field change of 0-7T, the RCP is 473.9J / kg.

[0067] Embodiment 3:

[0068] A kind of Ho6MoO 12 The preparation method of low-temperature magnetic refrigeration material comprises the following steps:

[0069] Step 1: Mix holmium nitrate and ammonium molybdate in a 3+ :Mo 6+ After weighing the ions in a molar ratio of 6:1, add them one by one into deionized water under constant stirring until they dissolve to form a uniform transparent solution.

[0070] Step 2: Add citric acid, holmium nitrate and ammonium molybdate to the above uniform solution in a molar ratio of 1:2 to citric acid, heat to 90°C, and stir rapidly to form a sol.

[0071] Step 3: Place the above sol in an oven and dry at 120° C. for 12 hours to obtain a gel, and anneal the gel at 580° C. for 6 hours to form a precursor pre-product.

[0072] Step 4: Place the precursor pre-product into a mold with an inner diameter of 2 cm, press it at 20T for 4 minutes, and after the tablet is formed, place it in a corundum crucible, heat it to 1000℃, sinter it for 3h in an air atmosphere, and cool it to room temperature to obtain the finished product. XRD characterization results show that the finished product has a cubic crystal structure with a space group of Its room temperature XRD Rietveld refinement pattern is as follows Figure 1 As shown in c.

[0073] Ho6MoO prepared in this example 12 The ZFC and FC thermomagnetic curves of low-temperature magnetic refrigeration materials under different magnetic fields are as follows Figure 2 As shown in Figure c, as the test temperature decreases, the ZFC and FC curves undergo a process from a paramagnetic phase transition to an antiferromagnetic phase transition. Since its Néel temperature is lower than 2K, its ZFC and FC curves do not show a peak.

[0074] Ho6MoO prepared in this example 12 The isothermal magnetization curves of low-temperature magnetic refrigeration materials at different temperatures are as follows: Figure 3 As shown in Figure c, at low temperature and low field, the magnetization intensity increases rapidly with the increase of magnetic field, and approaches saturation at high field; at high temperature, the magnetization intensity increases linearly. The inset is the hysteresis loop at 2K, which obviously has no hysteresis, indicating that it has high magnetic refrigeration cycle efficiency in practical applications.

[0075] Ho6MoO prepared in this example 12 The curves of magnetic entropy change with temperature under different magnetic field changes of low-temperature magnetic refrigeration materials are as follows Figure 4As shown in Figure c, under the magnetic field change of 0 to 2T, the isothermal magnetic entropy changes to 9.8J / kgK, under the magnetic field change of 0 to 5T, the isothermal magnetic entropy changes to 18.6J / kgK; under the magnetic field change of 0 to 7T, the isothermal magnetic entropy changes to 21.1J / kgK. According to the formula (-ΔS M max is the maximum magnetic entropy change value corresponding to a certain magnetic field change, δT FWHM The relative magnetic refrigeration capacity (RCP) of the finished product can be calculated by the half-width of the curve of magnetic entropy change with temperature. Under the magnetic field change of 0-2T, the RCP is 88.5J / kg; under the magnetic field change of 0-5T, the RCP is 334.8J / kg; under the magnetic field change of 0-7T, the RCP is 506.2J / kg.

[0076] Embodiment 4:

[0077] A kind of Er6MoO 12 The preparation method of low-temperature magnetic refrigeration material comprises the following steps:

[0078] Step 1: Mix erbium nitrate and ammonium molybdate in a 3+ :Mo 6+ After weighing the ions in a molar ratio of 6:1, add them one by one into deionized water under constant stirring until they dissolve to form a uniform transparent solution.

[0079] Step 2: Add citric acid to the above uniform solution, the total amount of erbium nitrate and ammonium molybdate and the molar ratio of citric acid to 1:2, heat to 90°C, and rapidly stir to form a sol.

[0080] Step 3: Place the above sol in an oven and dry at 120° C. for 12 hours to obtain a gel, and anneal the gel at 580° C. for 6 hours to form a precursor pre-product.

[0081] Step 4: Place the precursor pre-product into a mold with an inner diameter of 2 cm, press it at 20T for 4 minutes, and after the tablet is formed, place it in a corundum crucible, heat it to 1000℃, sinter it for 3h in an air atmosphere, and cool it to room temperature to obtain the finished product. XRD characterization results show that the finished product has a cubic crystal structure with a space group of Its room temperature XRD Rietveld refinement pattern is shown below: Figure 1 As shown in d.

[0082] The Er6MoO prepared in this example 12 The ZFC and FC thermomagnetic curves of low-temperature magnetic refrigeration materials under different magnetic fields are as follows Figure 2 As shown in Figure d, as the test temperature decreases, the ZFC and FC curves undergo a process from a paramagnetic phase transition to an antiferromagnetic phase transition. Since its Néel temperature is lower than 2K, its ZFC and FC curves do not show a peak.

[0083] The Er6MoO prepared in this example 12 The isothermal magnetization curves of low-temperature magnetic refrigeration materials at different temperatures are as follows: Figure 3 As shown in Figure d, at low temperature and low field, the magnetization intensity increases rapidly with the increase of magnetic field, and approaches saturation at high field; at high temperature, the magnetization intensity increases linearly. The inset is the hysteresis loop at 2K, which obviously has no hysteresis, indicating that it has high magnetic refrigeration cycle efficiency in practical applications.

[0084] The Er6MoO prepared in this example 12 The curves of magnetic entropy change with temperature under different magnetic field changes of low-temperature magnetic refrigeration materials are as follows Figure 4 As shown in d, under the magnetic field change of 0~2T, the isothermal magnetic entropy changes to 8.6J / kgK, under the magnetic field change of 0~5T, the isothermal magnetic entropy changes to 18.1J / kgK; under the magnetic field change of 0~7T, the isothermal magnetic entropy changes to 21.2J / kgK. According to the formula (-ΔS M max is the maximum magnetic entropy change value corresponding to a certain magnetic field change, δT FWHM The relative magnetic refrigeration capacity (RCP) of the finished product can be calculated by the half-width of the curve of magnetic entropy change with temperature. Under the magnetic field change of 0-2T, the RCP is 51.5J / kg; under the magnetic field change of 0-5T, the RCP is 235.9J / kg; under the magnetic field change of 0-7T, the RCP is 381.4J / kg.

[0085] RE6MoO prepared in Examples 1 to 4 12 The crystal structure parameters are shown in Table 1.

[0086] Table 1 RE6MoO 12 Crystal structure parameters of (RE = Tb, Dy, Ho and Er)

[0087]

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A rare earth molybdate low-temperature magnetic refrigeration material, characterized in that: Its chemical formula is RE6MoO 12 , the material has a cubic crystal structure and belongs to Space group, where RE is a rare earth element, including Tb, Dy, Ho or Er.

2. A method for preparing a rare earth molybdate low-temperature magnetic refrigeration material, characterized in that: RE6MoO was prepared by sol-gel method by combining rare earth metal salts with ammonium molybdate. 12 Material; The sol-gel method comprises the following steps: dissolving a rare earth metal salt and ammonium molybdate to form a solution, adding a complexing agent to the solution for complexation to form a sol, drying the sol to form a gel, heating the gel to 580-680° C. for annealing to form a precursor product, pressing the precursor product into a sheet and heating it to 950-1050° C. for sintering to obtain the rare earth metal salt; the rare earth metal salt is a compound containing a rare earth metal element, and the rare earth metal element is Tb, Dy, Ho or Er.

3. The method for preparing the rare earth molybdate low-temperature magnetic refrigeration material according to claim 2, characterized in that: The complexing agent is citric acid; preferably, the ratio of the molar amount of citric acid added to the molar amount of total metal ions is 1.4 to 2.4:1; Or, the temperature during the complexation process is 85-95°C; Alternatively, the sol is dried at a temperature of 110 to 130° C. and for a drying time of 11 to 13 hours.

4. The method for preparing the rare earth molybdate low-temperature magnetic refrigeration material according to claim 2, characterized in that: The annealing time is 4 to 6 hours; Or, tableting is cold pressing of powder; Alternatively, the sintering time is 3 to 6 hours.

5. Application of a rare earth molybdate material in the preparation of a low-temperature magnetic refrigeration material, wherein the chemical formula of the rare earth molybdate material is RE6MoO 12 , which has a cubic crystal structure and belongs to Space group, where RE is a rare earth element including Tb, Dy, Ho or Er.

6. The use according to claim 5, characterized in that: The rare earth molybdate material is prepared by using a sol-gel method to combine rare earth metal salt and ammonium molybdate; The sol-gel method comprises the following steps: dissolving a rare earth metal salt and ammonium molybdate to form a solution, adding a complexing agent to the solution for complexation to form a sol, drying the sol to form a gel, heating the gel to 580-680° C. for annealing to form a precursor product, pressing the precursor product into a sheet and heating it to 950-1050° C. for sintering to obtain the product.

7. The use according to claim 5, characterized in that: The complexing agent is citric acid; preferably, the ratio of the molar amount of citric acid added to the molar amount of total metal ions is 1.4 to 2.4:1; Or, the temperature during the complexation process is 85-95°C; Alternatively, the sol is dried at a temperature of 110 to 130° C. and for a drying time of 11 to 13 hours.

8. The use according to claim 5, characterized in that: The annealing time is 4 to 6 hours; Or, tableting is cold pressing of powder; Alternatively, the sintering time is 3 to 6 hours.

9. Application of the rare earth molybdate low-temperature magnetic refrigeration material according to claim 1 or the rare earth molybdate low-temperature magnetic refrigeration material obtained by the preparation method according to any one of claims 2 to 4 in low-temperature physics research, magnetic refrigeration equipment, deep space exploration or aerospace.

10. The use according to claim 9, characterized in that: The magnetic refrigeration device is a magnetic induction refrigeration refrigerator.

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