Gadolinium-based molybdate magnetic refrigeration material, preparation method and application thereof

Abstract

The application belongs to the field of magnetic refrigeration materials, and particularly discloses a gadolinium-based molybdate magnetic refrigeration material, a preparation method and application thereof. The gadolinium-based molybdate magnetic refrigeration material comprises GdXMoO4, wherein X is F, Cl, Br or I; the magnetic phase transition temperature of the gadolinium-based molybdate magnetic refrigeration material is less than 2K, and the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is greater than or equal to 12J·kg ‑1 ·K ‑1 The gadolinium-based molybdate magnetic refrigeration material has an extremely low magnetic phase transition temperature and a high magnetic heat effect under a low magnetic field, and is a magnetic refrigeration material with excellent performance in an extremely low temperature range, and has a wide application prospect in the field of extremely low temperature magnetic refrigeration.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of magnetic refrigeration materials, and particularly relates to a gadolinium-based molybdate magnetic refrigeration material and a preparation method and application thereof. BACKGROUND

[0002] The ultra-low temperature refrigeration technology is a major national demand and one of key support technologies in cutting-edge science. The low temperature refrigeration technology brings about such magical discoveries as superconductivity and superfluidity, and drives scientists to explore unknown things at lower temperatures. The ultra-low temperature refrigeration technology is usually used in aerospace and space exploration, condensed matter physics, quantum computers and the like. The increasing demand of the scientific field for the refrigeration technology also promotes new changes in the refrigeration technology. The traditional ultra-low temperature refrigeration methods include 3 He adsorption refrigeration and 3 He- 4 He dilution refrigeration technology. The dilution refrigeration can generally obtain lower temperature, but it needs to separately place 3 He、 4 He in different cabins and relies on gravity when running. When applied in the field of aerospace, it is limited. The adsorption refrigeration and the dilution refrigeration both rely on the scarce resource 3 He. 3 He is mainly produced by the by-product of tritium radioactive decay from nuclear reactors or nuclear weapon stockpiles, and the reserves on the earth are very scarce, so it is necessary to find a new refrigeration technology that does not rely on 3 He resource.

[0003] The solid-state phase change material will rapidly generate a thermal response (isothermal entropy change and adiabatic temperature change) under the driving of external fields such as magnetic field, electric field, uniaxial pressure and net water pressure (pressure), i.e. solid-state phase change thermal effect. The effect can absorb and release heat from the surrounding environment, and the heat absorption process can produce refrigeration effect. This kind of material has little impact on the environment, so the solid-state phase change thermal effect provides a theoretical basis for the research and development of a new generation of green refrigeration technology. The magnetic refrigeration technology is a new solid-state refrigeration technology based on the magnetic heat effect (MCE) of magnetic materials, i.e. the physical phenomenon that the magnetic material shows heat release when the magnetic field is enhanced and shows heat absorption when the magnetic field is weakened, and the essence is the change of magnetic moment order (i.e. magnetic entropy change). The adiabatic demagnetization refrigeration (ADR) technology does not rely on 3 He resource, is energy-saving and efficient, and is a more feasible alternative.

[0004] High-performance magnetic heat materials play a key role in magnetic refrigeration technology, and particularly, refrigerants with large magnetic heat effects (MCE) under low applied magnetic field (≤20000kOe) are very desirable because they can simplify the design by using permanent magnets and greatly reduce the cost of magnetic refrigerators, so materials with large magnetic heat effects under low magnetic field have more application prospects. However, in the field of magnetic refrigeration materials, the existing methods not only cannot obtain magnetic refrigeration materials with large magnetic heat effects under low applied magnetic field (especially ≤50kOe), but also usually have defects such as environmental pollution, difficulty in large-scale production, large energy consumption, long preparation period, easy deterioration, and the like, which cannot meet the needs of practical applications.

[0005] Therefore, it is necessary to develop extremely low-temperature magnetic refrigeration materials with large magnetic entropy under lower magnetic field, and simple preparation process, short cycle and suitable for industrial production. SUMMARY

[0006] In view of the defects of the magnetic refrigeration materials in the prior art, such as low magnetic heat effect under low applied magnetic field, and preparation process causing environmental pollution, difficulty in large-scale production, large energy consumption, long preparation period, easy deterioration, and the like, the present application provides a gadolinium-based molybdate magnetic refrigeration material and a preparation method and application thereof.

[0007] To achieve the above-mentioned purpose, the specific technical solutions include the following:

[0008] In a first aspect, the present application provides a gadolinium-based molybdate magnetic refrigeration material, comprising GdXMoO4, X is F, Cl, Br or I; the magnetic phase transition temperature of the gadolinium-based molybdate magnetic refrigeration material is <2K, and the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is ≥12J·kg -1 ·K -1 .

[0009] The gadolinium-based molybdate magnetic refrigeration material of the present application has a magnetic phase transition temperature in an extremely low temperature range and a high magnetic heat effect under a low magnetic field, and is an extremely low-temperature magnetic refrigeration material with excellent performance.

[0010] The magnetic phase transition temperature in the present application refers to the temperature at which the material changes from paramagnetic state to antiferromagnetic state.

[0011] The present application can calculate the magnetic entropy change under different magnetic field intensity changes according to the isothermal magnetization curve of the gadolinium-based molybdate magnetic refrigeration material by using the Maxwell relationship, and the maximum magnetic entropy change under the magnetic field intensity change can be obtained. The maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material of the present application is obtained near 1.3K temperature.

[0012] As a preferred embodiment of the present application, X is F or Cl.

[0013] As a preferred embodiment of the present application, the magnetic phase transition temperature of the gadolinium-based molybdate salt magnetic refrigeration material is 0.4 K to 1.8 K, further preferably 1.1-1.4 K, for example specifically can be 0.4 K, 0.6 K, 0.8 K, 1 K, 1.2 K, 1.4 K, 1.6 K, 1.8 K, but not limited to the listed values, other values not listed in the range are also applicable.

[0014] As a preferred embodiment of the present application, the maximum magnetic entropy change of the gadolinium-based molybdate salt magnetic refrigeration material is ≥13 J·kg -1 ·K -1 when the magnetic field changes from 0 to 10 kOe.

[0015] As a further preferred embodiment of the present application, the maximum magnetic entropy change of the gadolinium-based molybdate salt magnetic refrigeration material is 13.5 J·kg -1 ·K -1 to 20 J·kg -1 ·K -1 when the magnetic field changes from 0 to 10 kOe, for example specifically can be 13.5 J·kg -1 ·K -1 , 14.5 J·kg -1 ·K -1 , 15.5 J·kg -1 ·K -1 , 16.5 J·kg -1 ·K -1 , 17.5 J·kg -1 ·K -1 , 18.5 J·kg -1 ·K -1 , 19.5 J·kg -1 ·K -1 , 20 J·kg -1 ·K -1 , but not limited to the listed values, other values not listed in the range are also applicable.

[0016] As a preferred embodiment of the present application, the maximum magnetic entropy change of the gadolinium-based molybdate salt magnetic refrigeration material is ≥30 J·kg -1 ·K -1 when the magnetic field changes from 0 to 20 kOe.

[0017] As a further preferred embodiment of the present application, the maximum magnetic entropy change of the gadolinium-based molybdate salt magnetic refrigeration material is 30 J·kg -1 ·K -1 to 40 J·kg -1 ·K -1 when the magnetic field changes from 0 to 20 kOe, for example specifically can be 30 J·kg-1 · K -1 , 31.5 J·kg -1 · K -1 , 32.5 J·kg -1 · K -1 , 33.5 J·kg -1 · K -1 , 34.5 J·kg -1 · K -1 , 35.5 J·kg -1 · K -1 , 36.5 J·kg -1 · K -1 , 37.5 J·kg -1 · K -1 , 38.5 J·kg -1 · K -1 , 39.5 J·kg -1 · K -1 , 40 J·kg -1 · K -1 , but not limited to the listed values, other unlisted values within the range are also applicable.

[0018] As a preferred embodiment of the present application, the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is ≥ 32 J·kg -1 · K -1 when the magnetic field change is 0-30 kOe; further preferably 35 J·kg -1 · K -1 to 40 J·kg -1 · K -1 , for example, specifically can be 35 J·kg -1 · K -1 , 36 J·kg -1 · K -1 , 37 J·kg -1 · K -1 , 38 J·kg -1 · K -1 , 39 J·kg -1 · K -1 , 40 J·kg -1 · K -1 , but not limited to the listed values, other unlisted values within the range are also applicable.

[0019] As a preferred embodiment of the present application, the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is ≥ 39 J·kg -1 · K -1 when the magnetic field change is 0-40 kOe; further preferably 40 J·kg -1 · K-1 45 J·kg -1 ·K -1 , for example, specifically can be 40 J·kg -1 ·K -1 , 41 J·kg -1 ·K -1 , 42 J·kg -1 ·K -1 , 43 J·kg -1 ·K -1 , 44 J·kg -1 ·K -1 , 45 J·kg -1 ·K -1 , but not limited to the listed values, other unlisted values within this range are also applicable.

[0020] As a preferred embodiment of the present application, the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is 12.5 J·kg -1 ·K -1 to 50 J·kg -1 ·K -1 , further preferably 45 J·kg -1 ·K -1 to 49 J·kg -1 ·K -1 , for example, specifically can be 12.5 J·kg -1 ·K -1 , 15 J·kg -1 ·K -1 , 20 J·kg -1 ·K -1 , 25 J·kg -1 ·K -1 , 30 J·kg -1 ·K -1 , 35 J·kg -1 ·K -1 , 40 J·kg -1 ·K -1 , 45 J·kg -1 ·K -1 , 50 J·kg -1 ·K -1 , but not limited to the listed values, other unlisted values within this range are also applicable.

[0021] As a preferred embodiment of the present application, the gadolinium-based molybdate magnetic refrigeration material includes GdFMoO4, and the maximum magnetic entropy change of the GdFMoO4 is ≥ 14 J·kg -1 ·K -1 under a change in magnetic field of 0-50 kOe.

[0022] As a preferred embodiment of the present application, the gadolinium-based molybdate magnetic refrigeration material comprises GdClMoO4, and the maximum magnetic entropy change of the GdClMoO4 is ≥17 J·kg -1 ·K -1 .

[0023] As a preferred embodiment of the present application, the gadolinium-based molybdate magnetic refrigeration material comprises GdFMoO4, and the unit cell information of the GdFMoO4 is as follows: α = γ = 90°, β = 106°, belonging to a monoclinic system, and the space group is P21 / c.

[0024] As a preferred embodiment of the present application, the gadolinium-based molybdate magnetic refrigeration material comprises GdClMoO4, and the unit cell information of the GdClMoO4 is as follows: α = γ = 90°, β = 112°, belonging to a monoclinic system, and the space group is C2 / m.

[0025] In a second aspect, the present application provides a preparation method of the gadolinium-based molybdate magnetic refrigeration material, comprising the following steps:

[0026] S1, mixing Gd2O3, GdX3, MoO3 and a solvent, and sequentially performing ball milling and drying to obtain a mixture;

[0027] S2, sequentially performing first tabletting and first sintering on the mixture to obtain a precursor;

[0028] S3, sequentially performing grinding, second tabletting and second sintering on the precursor to obtain the gadolinium-based molybdate magnetic refrigeration material.

[0029] In the method of the present application, the raw materials are mixed by ball milling first, so that the raw materials are mixed more uniformly, and then tabletting is performed to increase the contact area between the reaction raw materials and reduce the volatilization of the raw materials; first sintering is then performed to form a precursor; grinding and tabletting are continuously performed to increase the uniformity and contact area between the substances again, and the activity of the solid-phase reaction is improved, which is conducive to improving the purity of the product.

[0030] As a preferred embodiment of the present application, in step S1, the GdX3 comprises GdF3.

[0031] As a preferred embodiment of the present application, in step S1, the molar ratio of Gd2O3, GdX3 and MoO3 is Gd2O3:GdX3:MoO3 = 1:(0.9-1.1):(2-4).

[0032] As a preferred embodiment of the present application, in step S1, the ball milling time is 5-8 h.

[0033] As a preferred embodiment of the present application, in step S1, the solvent comprises ethanol.

[0034] As a preferred embodiment of the present application, in step S1, the mass ratio of the total mass of Gd2O3, GdX3, MoO3 to the mass of the solvent is 1:(1-4).

[0035] As a preferred embodiment of the present application, in step S2, the temperature of the first sintering is 600-700℃, for example, specifically can be 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0036] As a preferred embodiment of the present application, in step S2, the time of the first sintering is 4-8h, for example, specifically can be 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0037] As a preferred embodiment of the present application, in step S3, the temperature of the second sintering is 800-1000℃, for example, specifically can be 800℃, 825℃, 850℃, 875℃, 900℃, 925℃, 950℃, 975℃, 1000℃, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0038] As a preferred embodiment of the present application, in step S3, the time of the second sintering is 3-9h, for example, specifically can be 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0039] In a third aspect, the present application provides another method for preparing the gadolinium-based molybdate magnetic refrigeration material, comprising the following steps:

[0040] S1, GdX3·nH2O is first sintered to obtain GdOX, wherein n in GdX3·nH2O represents that GdX3 contains n molecules of crystal water, and n is 1 to 6;

[0041] S2, the GdOX and MoO3 are second sintered under an inert gas atmosphere to obtain the gadolinium-based molybdate magnetic refrigeration material.

[0042] As a preferred embodiment of the present application, in step S1, the GdX3·nH2O comprises GdF3·6H2O.

[0043] As a preferred embodiment of the present application, in step S1, the temperature of the first-time sintering is 400-600℃, for example, specifically can be 400℃, 425℃, 450℃, 475℃, 500℃, 525℃, 550℃, 575℃, 600℃, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0044] As a preferred embodiment of the present application, in step S1, the time of the first-time sintering is 3-6h, for example, specifically can be 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0045] As a preferred embodiment of the present application, in step S2, the temperature of the second-time sintering is 800-1000℃, for example, specifically can be 800℃, 825℃, 850℃, 875℃, 900℃, 925℃, 950℃, 975℃, 1000℃, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0046] As a preferred embodiment of the present application, in step S2, the time of the second-time sintering is 10-20h, for example, specifically can be 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0047] As a preferred embodiment of the present application, in step S2, the second-time sintering is in a sealed environment.

[0048] As a preferred embodiment of the present application, in step S2, the molar ratio of the GdOX and MoO3 is 1:(0.9-1.1).

[0049] As a preferred embodiment of the present application, in step S2, the inert gas atmosphere comprises at least one of nitrogen, helium, argon.

[0050] The present application provides two kinds of solid-phase reaction methods for preparing gadolinium-based molybdate magnetic refrigeration materials, which can efficiently, in a short period and with relatively low energy consumption, prepare gadolinium-based molybdate magnetic refrigeration materials with high magnetic heat effect under low external magnetic field, stable performance and not easy to deteriorate, which are suitable for industrial application.

[0051] In a fourth aspect, the present application provides an application of the gadolinium-based molybdate magnetic refrigeration material in preparing a magnetic refrigeration device.

[0052] The gadolinium-based molybdate magnetic refrigeration material has high magnetic heat effect in an extremely low temperature range and under a low applied magnetic field, and is very suitable for preparing devices in the technical field of magnetic refrigeration, including condensed matter physics, dark matter search, quantum information science and space exploration.

[0053] Compared with the prior art, the present application has the following beneficial effects:

[0054] (1) The gadolinium-based molybdate magnetic refrigeration material has an extremely low magnetic phase transition temperature, and has high magnetic heat effect under a low magnetic field, in particular, the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is greater than or equal to 12 J·kg -1 ·K -1 ·K under a magnetic field change of 0-50 kOe, and is an extremely low temperature magnetic refrigeration material with superior performance.

[0055] (2) The preparation method of the gadolinium-based molybdate magnetic refrigeration material is a solid phase reaction method, and has the advantages of simple preparation process, short preparation period, low energy consumption, suitability for large-scale industrial production, and no use of substances such as acid or alkali which seriously pollute the environment during the preparation process, and the green environmental protection advantage is remarkable. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 It is a crystal structure diagram of the gadolinium-based molybdate magnetic refrigeration material GdFMoO4 of the present application.

[0057] Figure 2 It is a comparison diagram of the X-ray diffraction spectrum of GdFMoO4 prepared by the present application examples 1-4 and the theoretical spectrum.

[0058] Figure 3 It is a comparison diagram of the X-ray diffraction spectrum of the material prepared by the present application examples 1 and comparative examples 1-2 and the theoretical spectrum of GdFMoO4.

[0059] Figure 4 It is a field cooling (FC) thermomagnetic curve of GdFMoO4 prepared by the present application example 1 under a magnetic field of 500 Oe.

[0060] Figure 5 It is an isothermal magnetization curve of GdFMoO4 prepared by the present application example 1 under a magnetic field change of 0-50 kOe at 0.4 K-1.8 K.

[0061] Figure 6 It is a relationship between magnetic entropy change and temperature of GdFMoO4 prepared by the present application example 5 under different magnetic field changes.

[0062] Figure 7 It is a crystal structure diagram of the gadolinium-based molybdate magnetic refrigeration material GdClMoO4 of the present application.

[0063] Figure 8 X-ray diffraction pattern of GdClMoO4 prepared in Example 5-8 of the present application compared with the theoretical pattern.

[0064] Figure 9 X-ray diffraction pattern of the material prepared in Example 5 and Comparative Examples 3-4 of the present application compared with the theoretical pattern of GdClMoO4.

[0065] Figure 10 Field cooling (FC) thermomagnetic curve of GdClMoO4 prepared in Example 5 of the present application under a magnetic field of 500 Oe.

[0066] Figure 11 Isothermal magnetization curve of GdClMoO4 prepared in Example 5 of the present application under a magnetic field change of 0-50 kOe at 0.4-1.8 K.

[0067] Figure 12 Magnetic entropy change versus temperature of GdClMoO4 prepared in Example 5 of the present application under different magnetic field changes. DETAILED DESCRIPTION

[0068] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below through specific examples. The test methods used in the examples and / or comparative examples are all conventional methods unless otherwise specified; and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0069] Example 1

[0070] A preparation method of a gadolinium-based molybdate magnetic refrigeration material, comprising the following steps:

[0071] S1, mixture preparation: Gd2O3, GdF3 and MoO3 are mixed according to a molar ratio of 1:1:3, then an appropriate amount of anhydrous ethanol is added, followed by ball milling for 6 h and drying to obtain a mixture;

[0072] S2, pre-sintering: the mixture obtained in step S1 is first pressed into a tablet, placed in a tube furnace, and sintered at 600℃ under an argon atmosphere for 6 h to obtain a precursor;

[0073] S3, the precursor obtained in step S2 is ground and secondly pressed into a tablet, placed in a tube furnace, and sintered at 850℃ under an argon atmosphere for 6 h to obtain a GdFMoO4 magnetic refrigeration material.

[0074] Example 2

[0075] A preparation method of a gadolinium-based molybdate magnetic refrigeration material, comprising the following steps:

[0076] S1, mixture preparation: Gd2O3, GdF3 and MoO3 are mixed, and then a proper amount of absolute ethanol is added, followed by ball milling for 6h and drying to obtain a mixture;

[0077] S2, pre-sintering: the mixture obtained in step S1 is subjected to first tabletting, and then placed in a tube furnace for first sintering at 600℃ under argon atmosphere for 6h to obtain a precursor;

[0078] S3, the precursor obtained in step S2 is ground and subjected to second tabletting, and then placed in a tube furnace for second sintering at 800℃ under argon atmosphere for 9h to obtain a GdFMoO4 magnetic refrigeration material.

[0079] Example 3

[0080] A preparation method of a gadolinium-based molybdate magnetic refrigeration material, comprising the following steps:

[0081] S1, mixture preparation: Gd2O3, GdF3 and MoO3 are mixed, and then a proper amount of absolute ethanol is added, followed by ball milling for 6h and drying to obtain a mixture;

[0082] S2, pre-sintering: the mixture obtained in step S1 is subjected to first tabletting, and then placed in a tube furnace for first sintering at 600℃ under argon atmosphere for 6h to obtain a precursor;

[0083] S3, the precursor obtained in step S2 is ground and subjected to second tabletting, and then placed in a tube furnace for second sintering at 900℃ under argon atmosphere for 6h to obtain a GdFMoO4 magnetic refrigeration material.

[0084] Example 4

[0085] A preparation method of a gadolinium-based molybdate magnetic refrigeration material, comprising the following steps:

[0086] S1, mixture preparation: Gd2O3, GdF3 and MoO3 are mixed, and then a proper amount of absolute ethanol is added, followed by ball milling for 6h and drying to obtain a mixture;

[0087] S2, pre-sintering: the mixture obtained in step S1 is subjected to first tabletting, and then placed in a tube furnace for first sintering at 700℃ under argon atmosphere for 6h to obtain a precursor;

[0088] S3, the precursor obtained in step S2 is ground and subjected to second tabletting, and then placed in a tube furnace for second sintering at 1000℃ under argon atmosphere for 3h to obtain a GdFMoO4 magnetic refrigeration material.

[0089] Example 5

[0090] A preparation method of gadolinium-based molybdate magnetic refrigeration material, comprising the following steps:

[0091] S1, precursor preparation: 5g of GdCl3·6H2O is placed in a muffle furnace, and a first sintering is carried out at 500 DEG C and the temperature is kept for 4h, to obtain GdOCl;

[0092] S2, mixture preparation: after GdOCl and MoO3 are uniformly mixed according to a molar ratio of 1:1, the mixture is loaded into an alumina crucible, nitrogen is filled and sealed in a quartz tube, and the quartz tube is placed in a muffle furnace, a second sintering is carried out at 900 DEG C and the temperature is kept for 14h, to obtain a GdClMoO4 magnetic refrigeration material.

[0093] Example 6

[0094] A preparation method of gadolinium-based molybdate magnetic refrigeration material, comprising the following steps:

[0095] S1, precursor preparation: 5g of GdCl3·6H2O is placed in a muffle furnace, and a first sintering is carried out at 500 DEG C and the temperature is kept for 4h, to obtain GdOCl;

[0096] S2, mixture preparation: after GdOCl and MoO3 are uniformly mixed according to a molar ratio of 1:1, the mixture is loaded into an alumina crucible, nitrogen is filled and sealed in a quartz tube, and the quartz tube is placed in a muffle furnace, a second sintering is carried out at 800 DEG C and the temperature is kept for 20h, to obtain a GdClMoO4 magnetic refrigeration material.

[0097] Example 7

[0098] A preparation method of gadolinium-based molybdate magnetic refrigeration material, comprising the following steps:

[0099] S1, precursor preparation: 5g of GdCl3·6H2O is placed in a muffle furnace, and a first sintering is carried out at 500 DEG C and the temperature is kept for 4h, to obtain GdOCl;

[0100] S2, mixture preparation: after GdOCl and MoO3 are uniformly mixed according to a molar ratio of 1:1, the mixture is loaded into an alumina crucible, nitrogen is filled and sealed in a quartz tube, and the quartz tube is placed in a muffle furnace, a second sintering is carried out at 850 DEG C and the temperature is kept for 18h, to obtain a GdClMoO4 magnetic refrigeration material.

[0101] Example 8

[0102] A preparation method of gadolinium-based molybdate magnetic refrigeration material, comprising the following steps:

[0103] S1, precursor preparation: 5g of GdCl3·6H2O is placed in a muffle furnace, and a first sintering is carried out at 500 DEG C and the temperature is kept for 4h, to obtain GdOCl;

[0104] S2, mixture preparation: GdOCl and MoO3 were mixed uniformly according to a molar ratio of 1:1, and then were loaded into an alumina crucible, filled with nitrogen and sealed in a quartz tube, and placed in a muffle furnace for second sintering at 1000°C for 10h to obtain GdClMoO4 magnetic refrigeration material.

[0105] Comparative Example 1

[0106] The preparation method of the magnetic refrigeration material of the present comparative example is the same as that of Example 1, except that the first sintering temperature in step S2 is 400°C, and the second sintering temperature in step S3 is 500°C.

[0107] Comparative Example 2

[0108] The preparation method of the magnetic refrigeration material of the present comparative example is the same as that of Example 1, except that the first sintering temperature in step S2 is 900°C, and the second sintering temperature in step S3 is 1200°C.

[0109] Comparative Example 3

[0110] The preparation method of the magnetic refrigeration material of the present comparative example is the same as that of Example 5, except that the first sintering temperature in step S1 is 500°C, and the second sintering temperature in step S2 is 600°C.

[0111] Comparative Example 4

[0112] The preparation method of the magnetic refrigeration material of the present comparative example is the same as that of Example 5, except that the first sintering temperature in step S1 is 900°C, and the second sintering temperature in step S2 is 1100°C.

[0113] Table 1

[0114]

[0115] Table 2

[0116]

[0117]

[0118] Performance test:

[0119] (1) The GdFMoO4 and GdClMoO4 samples prepared in each example were subjected to X-ray powder diffraction phase analysis by using a D8A A25 type X-ray diffractometer (XRD) of Brucker company.

[0120] (2) The GdFMoO4 and GdClMoO4 samples prepared in Examples 1 and 5 are subjected to magnetic heat performance test and analysis, and the magnetic entropy change (-ΔS M ) can be determined from the magnetization-temperature curve by the Maxwell relation as follows: max The maximum value of the obtained magnetic entropy change is the maximum magnetic entropy change (-ΔS M ), wherein the magnetization-temperature curve is obtained from the isothermal magnetization curve.

[0121] Maxwell relation:

[0122]

[0123] wherein ΔS M (T,H) is the magnetic entropy change, M is the magnetization, T is the temperature, and H is the applied magnetic field.

[0124] Figure 1 is the crystal structure diagram of the gadolinium-based molybdate magnetic refrigeration material GdFMoO4 of the present application, and the results are shown in the attached Figure 2 It can be seen that the samples of Examples 1-4 all have good matching with the standard pattern, indicating that the GdFMoO4 magnetic refrigeration materials are prepared in Examples 1-4. The XRD pattern of the sample in Example 2-4 has a small amount of impurity peaks near 33°, and the XRD pattern of the sample in Example 3 has impurity peaks near 24° and 26°, indicating that there are a small amount of impurity phases in these materials. The XRD pattern of the sample in Example 1 has good matching with the standard pattern, indicating that the sample has high purity and is composed of a single GdFMoO4 phase, belongs to monoclinic system, and has a space group of P21 / c and a cell parameter α = γ = 90°, β = 106°. It is indicated that the sintering temperature and sintering time need to be adjusted during preparation in order to obtain GdFMoO4 with better purity.

[0125] Figure 3XRD patterns of GdFMoO4 prepared by the present application, comparative example 1 and comparative example 2. It can be seen that the sintering temperature of comparative example 1-2 is too low or too high, which leads to the failure to successfully synthesize GdFMoO4 magnetic refrigeration material with high purity. The method of the present application first forms a precursor by first sintering, and then prepares gadolinium molybdate magnetic refrigeration material by second sintering. The two sintering processes for preparing gadolinium molybdate magnetic refrigeration material can effectively improve the reactivity and the purity of gadolinium molybdate magnetic refrigeration material. High-purity samples reduce the interference of impurities. The higher the purity, the more heat released or absorbed by the material during the magnetization and demagnetization process in the magnetic field, which can achieve higher magnetic entropy change and improve the magnetic refrigeration efficiency. The present application can select the first sintering temperature of 600-700℃ and the first sintering time of 4-8h, and the second sintering temperature of 800-1000℃ and the second sintering time of 3-9h for preparing GdFMoO4 magnetic refrigeration material. Under the above sintering conditions, GdFMoO4 magnetic refrigeration material with high purity can be prepared, and the magnetic refrigeration efficiency is improved.

[0126] Figure 2 is a thermal magnetic curve of the GdFMoO4 sample prepared by the present application at a magnetic field of 500 Oe under field cooling (FC). Figure 4 Figure 3 is an isothermal magnetization curve of the GdFMoO4 sample prepared by the present application at 0-50kOe magnetic field change and 0.4-1.8K. Figure 5 Figure 4 is a magnetic entropy change-temperature curve of the GdFMoO4 sample prepared by the present application at different magnetic field changes.

[0127] Figure 5 is a magnetic entropy change-temperature curve of the GdFMoO4 sample prepared by the present application at different magnetic field changes. Figure 6 Figure 6 is a magnetic entropy change-temperature curve of the GdFMoO4 sample prepared by the present application at different magnetic field changes. Figure 6 It can be seen that the maximum magnetic entropy change -ΔS max of the material appears at 1.1K-1.3K. Figure 6 It can be seen that when the magnetic field change is 10, 20 and 50kOe, the maximum magnetic entropy change values are 14.9J·kg -1 ·K -1 , 32.3J·kg -1 ·K -1 and 46.5J·kg -1 ·K -1 , respectively, which has a large magnetic heat effect at a low applied magnetic field (especially ≤50kOe).

[0128] Figure 7 Figure 7 is a crystal structure diagram of the magnetic refrigeration material GdFMoO4 of the present application.Figure 8 For the XRD patterns of Examples 5-8, it can be seen that the samples of Examples 5-8 all have good match with the standard pattern, indicating that GdClMoO4 magnetic refrigeration materials are prepared in Examples 5-8. The XRD pattern of the sample in Example 6 has impurity peaks near 22°, 29° and 32°, the XRD pattern of the sample in Example 7 has an impurity peak near 29°, and the XRD pattern of the sample in Example 8 has impurity peaks near 17° and 32°, indicating that there are less impurity phases in these materials, and the XRD pattern of the sample in Example 5 has good match with the standard pattern, indicating that the sample has high purity and is composed of a single GdClMoO4 phase, belongs to monoclinic system, and has a crystal cell parameter of α = γ = 90°, β = 106°. It is indicated that during preparation, the sintering temperature and sintering time need to be adjusted so as to obtain GdClMoO4 with higher purity.

[0129] Figure 9 is the X-ray diffraction pattern of GdClMoO4 prepared in Example 5, Comparative Example 3 and Comparative Example 4 of the present application. It can be seen that the sintering temperature of Comparative Examples 3-4 is too low or too high, which results in failure to successfully synthesize GdClMoO4 magnetic refrigeration material with high purity. The method of the present application first converts GdX3·nH2O containing crystal water into GdOX through first sintering, and then sintering GdOX with MoO3 to prepare gadolinium molybdate magnetic refrigeration material, so that the reactivity and the purity of the gadolinium molybdate magnetic refrigeration material can be effectively improved. In the present application, the first sintering temperature can be selected as 400-600°C, the first sintering time can be selected as 3-6h, the second sintering temperature can be selected as 800-1000°C, and the second sintering time can be selected as 10-20h, so that GdClMoO4 magnetic refrigeration material with high purity can be prepared under the above sintering conditions, and the magnetic refrigeration efficiency is improved.

[0130] Figure 1 is the XRD pattern of GdClMoO4 prepared in Example 5 of the present application. Figure 10 Figure 2 is the FC thermomagnetic curve of the GdClMoO4 sample prepared in Example 5 of the present application under a magnetic field of 500 Oe. Figure 11 Figure 3 is the isothermal magnetization curve of the GdClMoO4 sample prepared in Example 5 of the present application at 0.4K-1.8K under a magnetic field change of 0-50kOe. It can be seen from the figure that the magnetization of the material increases rapidly with the increase of the external magnetic field under an external magnetic field of 15kOe, and tends to be saturated when the magnetic field is 50kOe, and the magnetic phase transition temperature is <2K.

[0131] Figure 4 is the magnetic entropy change of the GdClMoO4 sample prepared in Example 5 of the present application under different magnetic field changes, which is calculated according to the isothermal magnetization curve at different temperatures by using Maxwell relationship. Figure 12The relationship between magnetic entropy change and temperature of the GdClMoO4 sample prepared in Embodiment 5 of the present application under different magnetic field changes is shown in Figure 2. Figure 12 It can be seen that the maximum magnetic entropy change -ΔS max of the material appears at 1.1K-1.3K. Figure 12 It can be seen that when the magnetic field change is 10, 20 and 50kOe, the maximum magnetic entropy change values are 17.4J·kg -1 ·K -1 , 34.0J·kg -1 ·K -1 and 48.2J·kg -1 ·K -1 respectively, and the material has a large magnetic heat effect at a low applied magnetic field (especially ≤50kOe), and is an excellent extremely low temperature magnetic refrigeration material.

[0132] In summary, the present application adopts solid phase reaction sintering to obtain two new types of extremely low temperature magnetic refrigeration materials, which have excellent magnetic heat performance at extremely low temperature, and have a broad application prospect in the field of extremely low temperature magnetic refrigeration.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application, and although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method of preparing a gadolinium-based molybdate magnetic refrigeration material, characterized in that, The method comprises the following steps: S1, mixing Gd2O3, GdX3, MoO3 and a solvent, sequentially performing ball milling and drying to obtain a mixture; S2, sequentially performing first tabletting and first sintering on the mixture to obtain a precursor; the temperature of the first sintering is 600-700 DEG C, and the time of the first sintering is 4-8 h; the molar ratio of Gd2O3, GdX3 and MoO3 is Gd2O3: GdX3: MoO3 = 1: (0.9-1.1): (2-4); S3, sequentially performing grinding, second tabletting and second sintering on the precursor to obtain the gadolinium-based molybdate magnetic refrigeration material GdXMoO4, wherein X is F, Cl, Br or I; the temperature of the second sintering is 800-1000 DEG C, and the time of the second sintering is 3-9 h.

2. The method for preparing the gadolinium-based molybdate magnetic refrigeration material as described in claim 1, characterized in that, In step S1, the GdX3 comprises GdF3.

3. A gadolinium-based molybdate magnetic refrigeration material, characterized in that, The gadolinium-based molybdate magnetic refrigeration material is prepared by the method of claim 1 or 2, has a magnetic phase transition temperature < 2 K, and has a maximum magnetic entropy change ≥ 12 J·kg-1·K-1 under a magnetic field change of 0-50 kOe. -1 ·K -1 .

4. The gadolinium-based molybdate magnetic refrigerant material of claim 3, wherein, At least one of the following conditions is met: I. Under the magnetic field change of 0-10kOe, the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is ≥13J·kg -1 ·K -1 ; II. In the magnetic field change of 0-20kOe, the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is ≥30J·kg -1 ·K -1 ; III. In the magnetic field change of 0-30kOe, the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is ≥32J·kg -1 ·K -1 ; IV. In the magnetic field change of 0-40kOe, the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is ≥39J·kg -1 ·K -1 .

5. The gadolinium-based molybdate magnetic refrigerant material of claim 3, wherein, At least one of the following conditions is met: I. The gadolinium-based molybdate magnetic refrigeration material comprises GdFMoO4, wherein the maximum magnetic entropy change of the GdFMoO4 is ≥ 14 J·kg -1 ·K -1 ; II. The gadolinium-based molybdate magnetic refrigeration material comprises GdClMoO4, wherein the maximum magnetic entropy change of the GdClMoO4 is ≥ 17 J·kg -1 ·K -1 .

6. The gadolinium-based molybdate magnetic refrigerant material of claim 3, wherein, At least one of the following conditions is met: I. The gadolinium-based molybdate magnetic refrigeration material comprises GdFMoO4, and the unit cell information of the GdFMoO4 is as follows: a = 5.298 Å, b = 12.444 Å, c = 6.746 Å, α = γ = 90 DEG, β = 106 DEG, belonging to a monoclinic system, and the space group is P21 / c; II. The gadolinium-based molybdate magnetic refrigeration material comprises GdClMoO4, and the unit cell information of the GdClMoO4 is as follows: a = 10.287 Å, b = 7.307 Å, c = 6.871 Å, α = γ = 90 DEG, β = 112 DEG, belonging to a monoclinic system, and the space group is C2 / m.

7. A method of gadolinium-based molybdate magnetic refrigerant material, characterized by, The method comprises the following steps: S1, first sintering GdX3·nH2O to obtain GdOX, wherein n in GdX3·nH2O represents that GdX3 contains n molecules of crystal water, and n is 1 to 6; the temperature of the first sintering is 400-600 DEG C, and the time of the first sintering is 3-6 h; S2, second sintering the GdOX and MoO3 in an inert gas atmosphere to obtain the gadolinium-based molybdate magnetic refrigeration material GdXMoO4, wherein X is F, Cl, Br or I; the temperature of the second sintering is 800-1000 DEG C, and the time of the second sintering is 10-20 h; the molar ratio of the GdOX and MoO3 is 1: (0.9-1.1).

8. The method of claim 7, wherein the gadolinium-based molydate magnetic refrigerant material is prepared by the steps of: dissolving gadolinium oxide in a solution of molybdenum trioxide; and adding a base to the solution to precipitate the gadolinium-based molydate magnetic refrigerant material. In step S1, the GdX3·nH2O comprises GdF3·6H2O.

9. A gadolinium-based molybdate magnetic refrigeration material, characterized in that, The gadolinium-based molybdate magnetic refrigeration material is prepared by the method of claim 7 or 8; the magnetic phase transition temperature of the gadolinium-based molybdate magnetic refrigeration material is less than 2 K, and the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is greater than or equal to 12 J·kg -1 ·K -1 .

10. The gadolinium-based molybdate magnetic refrigerant material of claim 9, wherein, At least one of the following conditions is met: I. In the magnetic field change of 0-10kOe, the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is ≥13J·kg -1 ·K -1 ; II. In the magnetic field change of 0-20kOe, the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is ≥30J·kg -1 ·K -1 ; III. In the magnetic field change of 0-30kOe, the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is ≥32J·kg -1 ·K -1 ; IV. In the magnetic field change of 0-40kOe, the maximum magnetic entropy change of the gadolinium-based molybdate magnetic refrigeration material is ≥39J·kg -1 ·K -1 .

11. The gadolinium-based molybdate magnetic refrigerant material of claim 9, wherein, At least one of the following conditions is met: I. The gadolinium-based molybdate magnetic refrigeration material comprises GdFMoO4, wherein the maximum magnetic entropy change of the GdFMoO4 is ≥ 14 J·kg -1 ·K -1 ; II. The gadolinium-based molybdate magnetic refrigeration material comprises GdClMoO4, wherein the maximum magnetic entropy change of the GdClMoO4 is ≥ 17 J·kg -1 ·K -1 .

12. The gadolinium-based molybdate magnetic refrigerant material of claim 9, wherein, At least one of the following conditions is met: I. The gadolinium-based molybdate magnetic refrigeration material comprises GdFMoO4, and the unit cell information of the GdFMoO4 is as follows: a = 5.298 Å, b = 12.444 Å, c = 6.746 Å, α = γ = 90 DEG, β = 106 DEG, belonging to a monoclinic system, and the space group is P21 / c; II. The gadolinium-based molybdate magnetic refrigeration material comprises GdClMoO4, and the unit cell information of the GdClMoO4 is as follows: a=10.287 Å, b=7.307 Å, c=6.871 Å, α=γ=90°, β=112°, belonging to a monoclinic system, and the space group is C2 / m.

13. Use of the gadolinium-based molybdate magnetic refrigeration material according to any one of claims 3-6 or 9-12 in the preparation of a magnetic refrigeration device.

Images