Double-perovskite rare earth oxide material and preparation method and application thereof

Abstract

The invention relates to the technical field of magnetic materials, and particularly discloses a double-perovskite rare earth oxide material and a preparation method and application thereof, the molecular formula of the double-perovskite rare earth oxide material is RE2FeCrO6, RE is selected from one of Gd, Tb, Dy and Er; the double perovskite rare earth oxide material has antiferromagnetic-paramagnetic secondary phase change at the temperature of 4.3 to 21.4 K; the double-perovskite rare earth oxide material has a standard double-perovskite compound structure, belongs to a Pbnm (62) space group, has antiferromagnetic-paramagnetic secondary phase change at 4.3-21.4 K, has weak hysteresis and excellent magnetocaloric performance, shows huge potential in application of low-temperature magnetic refrigeration, and meanwhile, has good application prospects. The method for preparing the double-perovskite rare earth oxide material adopts a traditional solid phase method, is simple to operate and stable in material performance, and can be used for industrial batch production.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth magnetic functional materials and the technical field of magnetic refrigeration, and in particular to a double perovskite rare earth oxide material and a preparation method thereof. Background Art

[0002] Low-temperature magnetic refrigeration technology plays an important role in application fields such as space technology and medical systems. Magnetocaloric effect (MCE) is an inherent property of all magnetic materials and is closely related to magnetic transition. MCE-based magnetic refrigeration technology has become a promising solid-state refrigeration technology due to its high efficiency and environmental friendliness.

[0003] Perovskite rare earth oxides exhibit a unique colossal magnetoresistance effect due to the inherent strong carrier-spin coupling, accompanied by a giant magnetic entropy change. In addition, perovskite rare earth oxides have the advantages of high chemical stability, high resistivity, easy manufacturing, low cost, light specific gravity, and non-toxicity, making them a promising magnetic refrigeration medium. Therefore, domestic and foreign scholars have conducted extensive research on the preparation and magnetocaloric effect of perovskite rare earth oxides.

[0004] In recent years, people have also paid great attention to MCE materials with low transition temperature. 2 TMTM'O 6 (RE is a rare earth ion, TM and TM' are two different 3d transition metals) Double perovskite oxides have a stable structure, flexible composition, and a considerable MCE due to the large rare earth magnetic moment. However, there is still a large gap between the performance of magnetic refrigeration materials and the requirements of practical applications. At present, magnetic refrigeration technology has not been widely used, but compared with traditional gas compression refrigeration, magnetic refrigeration has the advantages of simple structure, no pollution, high entropy density, small size, high efficiency and low noise. It is a new refrigeration method with great potential in the future. One of the key factors that determines whether this technology can go out of the laboratory is to find high-performance magnetic refrigeration materials. At present, magnetic refrigeration materials are mainly some high-purity rare earth or rare earth metal intermetallic compound materials, which have the disadvantages of high raw material prices and complex preparation processes. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies in the prior art and thereby provide a double perovskite rare earth oxide material and a preparation method and application thereof. The double perovskite rare earth oxide material has a standard double perovskite compound structure, belongs to the Pbnm (62) space group, has an antiferromagnetic-paramagnetic secondary phase transition at 4.3-21.4K, and has weak hysteresis and excellent magnetocaloric properties, showing great potential in the application of low-temperature magnetic refrigeration. At the same time, the method for preparing the double perovskite rare earth oxide material adopts a traditional solid-phase method, is simple to operate, has stable material properties, and can be used for industrial mass production.

[0006] In order to achieve the above-mentioned object, in the first aspect, the present invention provides a double perovskite rare earth oxide material, wherein the molecular formula of the double perovskite rare earth oxide material is RE 2 FeCrO 6 , wherein RE is selected from one of Gd, Tb, Dy and Er;

[0007] The double perovskite rare earth oxide material has an antiferromagnetic-paramagnetic secondary phase transition at 4.3-21.4K.

[0008] Preferably, the double perovskite rare earth oxide material has a double perovskite compound structure and belongs to the Pbnm (62) space group.

[0009] In a second aspect, the present invention provides a method for preparing a double perovskite rare earth oxide material, the method comprising: first grinding of rare earth oxide, chromium oxide and iron oxide, first tableting, pre-sintering, first cooling, first cooling, second grinding, second tableting, sintering, second cooling, and second cooling.

[0010] Preferably, the rare earth oxide is selected from Gd 2 O 6 , Tb 2 O 6 、Dy 2 O 6 and Er 2 O 6 One or two or more of the following.

[0011] Preferably, the molar ratio of the rare earth oxide, chromium oxide and iron oxide is 2:1:1, wherein the rare earth oxide is calculated as rare earth atoms, the chromium oxide is calculated as chromium atoms, and the iron oxide is calculated as iron atoms.

[0012] Preferably, the first grinding conditions include: in the presence of grinding media, the time is 1-2 hours.

[0013] Preferably, the first tabletting conditions include: a pressure of 5-10T and a pressure holding time of 3-5min.

[0014] More preferably, the pre-sintering conditions include: a temperature of 800-1200° C., a time of 10-14 h, and a heating rate of 5-10° C. / min.

[0015] Further preferably, the first cooling conditions include: a temperature of 400-700° C. and a cooling rate of 1-3° C. / min.

[0016] More preferably, the first cooling condition includes: a temperature of 20-30°C.

[0017] Preferably, the second grinding conditions include: in the presence of grinding media, the time is 20-40 minutes.

[0018] Preferably, the second tableting conditions include: a pressure of 8-12T and a pressure holding time of 3-5min.

[0019] More preferably, the sintering conditions include: temperature of 1000-1500° C., time of 14-18 h, and heating rate of 5-10° C. / min.

[0020] Further preferably, the second cooling conditions include: a temperature of 400-700° C. and a cooling rate of 1-3° C. / min.

[0021] More preferably, the second cooling condition includes: a temperature of 20-30°C.

[0022] Preferably, the grinding media in the first grinding and the second grinding are alcohol and / or 2-methylpentane.

[0023] In a third aspect, the present invention provides a double perovskite rare earth oxide material prepared according to the method described in the second aspect.

[0024] In a fourth aspect, the present invention provides an application of the double perovskite rare earth oxide material as described in the first aspect or the third aspect in magnetic refrigeration.

[0025] In the above technical scheme, the double perovskite rare earth oxide material of the present invention exhibits an antiferromagnetic (AFM)-paramagnetic (PM) secondary phase transition at 4.3-21.4K, eliminating the hysteresis and thermal hysteresis in the phase transition process, which is beneficial to practical cyclic applications.

[0026] At the same time, materials with first-order magnetic phase transitions are always accompanied by changes in crystal structure or volume jumps, which stimulate huge changes in magnetic entropy in the system. 2 FeCrO 6 、Dy 2 FeCrO 6 and Er 2 FeCrO 6 In the ferromagnetic material, there is also an antiferromagnetic (AFM)-ferromagnetic (FM) first-order phase transition and a Griffith phase (GP) of the FM-PM coexistence state.

[0027] Furthermore, the method for preparing double perovskite rare earth oxide material of the present invention adopts a conventional solid phase method by 2 O 3 Cr 2 O 3 , Fe 2 O 3The finished product is obtained after the raw materials are ground, pressed and sintered. The process is simple, the material performance is stable, it has a large magnetic entropy in the 4.3-21.4K range, and can be used for industrial mass production.

[0028] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 Double perovskite rare earth oxide material RE prepared in Examples 1-4 of the present invention 2 FeCrO 6 XRD pattern of (RE=Gd,Tb,Dy,Er);

[0031] Figure 2 When (a) is H=200Oe, the double perovskite rare earth oxide material Gd prepared in Example 1 2 FeCrO 6 MT (magnetization intensity-temperature) curve; (b) when H = 200Oe, the double perovskite rare earth oxide material Tb prepared in Example 2 2 FeCrO 6 MT curve; (c) when H = 200Oe, the double perovskite rare earth oxide material Dy prepared in Example 3 2 FeCrO 6 MT curve; (d) when H = 200Oe, the double perovskite rare earth oxide material Er prepared in Example 4 2 FeCrO 6 MT curve;

[0032] Figure 3 (a) is the double perovskite rare earth oxide material Gd prepared in Example 1 when ΔH increases from 10kOe to 50kOe. 2 FeCrO 6 -ΔS M -T (magnetic entropy change-temperature) curve; (b) when ΔH increases from 10kOe to 50kOe, the double perovskite rare earth oxide material Tb prepared in Example 2 2 FeCrO 6 -ΔS M -T curve; (c) when ΔH increases from 10kOe to 50kOe, the double perovskite rare earth oxide material Dy prepared in Example 3 2 FeCrO 6 -ΔS M-T curve; (d) when ΔH increases from 10kOe to 50kOe, the double perovskite rare earth oxide material Er prepared in Example 4 2 FeCrO 6 -ΔS M -T curve;

[0033] Figure 4 (a) is the double perovskite rare earth oxide material Gd prepared in Example 1 2 FeCrO 6 dp / dH-H (EPR signal first-order conduction-magnetic field) curve; (b) is the double perovskite rare earth oxide material Tb prepared in Example 2 2 FeCrO 6 dp / dH-H curve; (c) is the double perovskite rare earth oxide material Dy prepared in Example 3 2 FeCrO 6 dp / dH-H curve; (d) is the double perovskite rare earth oxide material Er prepared in Example 4 2 FeCrO 6 dp / dH-H curve; (e) is the double perovskite rare earth oxide material Dy prepared in Example 3 2 FeCrO 6 dp / dH-H curve expansion diagram; (f) is the double perovskite rare earth oxide material Er prepared in Example 4 2 FeCrO 6 dp / dH-H curve expansion diagram;

[0034] Figure 5 (a) is the double perovskite rare earth oxide material Gd prepared in Example 1 2 FeCrO 6 -ΔS M max -ΔH 2 / 3 (Maximum magnetic entropy change --ΔS M max -Δ Field Strength 2 / 3 ) curve; (b) is the double perovskite rare earth oxide material Tb prepared in Example 2 2 FeCrO 6 -ΔS M max -ΔH 2 / 3 Curve; (c) is the double perovskite rare earth oxide material Dy prepared in Example 3 2 FeCrO 6 -ΔS M max -ΔH 2 / 3 Curve; (d) is the double perovskite rare earth oxide material Er prepared in Example 4 2 FeCrO6 -ΔS M max -ΔH 2 / 3 curve;

[0035] Figure 6 (a) is the double perovskite rare earth oxide material Gd prepared in Example 1 2 FeCrO 6 Arrott diagram; (b) is the double perovskite rare earth oxide material Tb prepared in Example 2 2 FeCrO 6 Arrott diagram; (c) is the double perovskite rare earth oxide material Dy prepared in Example 3 2 FeCrO 6 Arrott diagram; (d) is the double perovskite rare earth oxide material Er prepared in Example 4 2 FeCrO 6 Arrott diagram of ; the illustration is the corresponding expanded diagram;

[0036] Figure 7 (a) is the double perovskite rare earth oxide material Gd prepared in Example 1 2 FeCrO 6 -ΔS M / (-ΔS M ) max -θ (magnetic entropy change / maximum magnetic entropy change-scaled temperature) curve; (b) is the double perovskite rare earth oxide material Tb prepared in Example 2 2 FeCrO 6 -ΔS M / (-ΔS M ) max -θ curve; (c) is the double perovskite rare earth oxide material Dy prepared in Example 3 2 FeCrO 6 -ΔS M / (-ΔS M ) max -θ curve; (d) is the double perovskite rare earth oxide material Er prepared in Example 4 2 FeCrO 6 -ΔS M / (-ΔS M ) max -θ curve. DETAILED DESCRIPTION

[0037] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0038] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0039] In a first aspect, the present invention provides a double perovskite rare earth oxide material, wherein the molecular formula of the double perovskite rare earth oxide material is RE 2 FeCrO 6 , wherein RE is selected from one of Gd, Tb, Dy and Er;

[0040] The double perovskite rare earth oxide material has an antiferromagnetic-paramagnetic secondary phase transition at 4.3-21.4K.

[0041] The double perovskite rare earth oxide material of the present invention exhibits an antiferromagnetic (AFM)-paramagnetic (PM) secondary phase transition at 4.3-21.4 K, eliminating the hysteresis and thermal hysteresis during the phase transition, which is beneficial to practical cyclic applications.

[0042] At the same time, materials with first-order magnetic phase transitions are always accompanied by changes in crystal structure or volume jumps, which stimulate huge changes in magnetic entropy in the system. 2 FeCrO 6 、Dy 2 FeCrO 6 and Er 2 FeCrO 6 In the ferromagnetic material, there is also an antiferromagnetic (AFM)-ferromagnetic (FM) first-order phase transition and a Griffith phase (GP) of the FM-PM coexistence state.

[0043] In a preferred embodiment of the present invention, the double perovskite rare earth oxide material has a double perovskite compound structure and belongs to the Pbnm (62) space group.

[0044] In a second aspect, the present invention provides a method for preparing a double perovskite rare earth oxide material, the method comprising: first grinding of rare earth oxide, chromium oxide and iron oxide, first tableting, pre-sintering, first cooling, first cooling, second grinding, second tableting, sintering, second cooling, and second cooling.

[0045] The method for preparing double perovskite rare earth oxide material of the present invention adopts the traditional solid phase method by 2 O 3 Cr 2 O 3 , Fe 2 O3 The finished product is obtained after the raw materials are ground, pressed and sintered. The process is simple, the material performance is stable, it has a large magnetic entropy in the 4.3-21.4K range, and can be used for industrial mass production.

[0046] In a preferred embodiment of the present invention, in order to ensure that the prepared double perovskite rare earth oxide material has good magnetocaloric properties, the rare earth oxide is selected from Gd 2 O 6 , Tb 2 O 6 、Dy 2 O 6 and Er 2 O 6 One or two or more of the following.

[0047] In a preferred embodiment of the present invention, in order to obtain the desired double perovskite oxide material, the molar ratio of the rare earth oxide, chromium oxide and iron oxide is 2:1:1, wherein the rare earth oxide is calculated as rare earth atoms, the chromium oxide is calculated as chromium atoms, and the iron oxide is calculated as iron atoms.

[0048] In a preferred embodiment of the present invention, in order to obtain fine and uniform powder, the first grinding conditions include: in the presence of grinding media, the time is 1-2 hours.

[0049] In a preferred embodiment of the present invention, in order to ensure that the powders are in close contact and react sufficiently during pre-sintering for tableting, the first tableting conditions include: a pressure of 5-10T and a holding time of 3-5min.

[0050] In a preferred embodiment of the present invention, a pre-sintering treatment is performed to remove a portion of structural defects, and the pre-sintering conditions include: a temperature of 800-1200° C., a time of 10-14 h, and a heating rate of 5-10° C. / min.

[0051] In a preferred embodiment of the present invention, the first cooling conditions include: a temperature of 400-700° C. and a cooling rate of 1-3° C. / min.

[0052] In a preferred embodiment of the present invention, the first cooling condition includes: a temperature of 20-30°C.

[0053] In a preferred embodiment of the present invention, in order to obtain fine and uniform powder, the second grinding condition includes: in the presence of grinding media, the time is 20-40 minutes.

[0054] In a preferred embodiment of the present invention, in order to ensure that the powders are in close contact and react during sintering to fully perform tableting, the second tableting conditions include: a pressure of 8-12T and a holding time of 3-5min.

[0055] In a preferred embodiment of the present invention, in order to obtain double perovskite rare earth oxides with high crystallinity, the sintering conditions include: temperature of 1000-1500° C., time of 14-18 h, and heating rate of 5-10° C. / min.

[0056] In a preferred embodiment of the present invention, the second cooling conditions include: a temperature of 400-700° C. and a cooling rate of 1-3° C. / min.

[0057] In a preferred embodiment of the present invention, the second cooling condition includes: a temperature of 20-30° C. In a preferred embodiment of the present invention, in order to obtain fine and uniform powder, the grinding medium in the first grinding and the second grinding is alcohol and / or 2-methylpentane, and the amount of grinding medium added is sufficient to cover the sample.

[0058] In a third aspect, the present invention provides a double perovskite rare earth oxide material prepared according to the method described in the second aspect.

[0059] In a fourth aspect, the present invention provides an application of the double perovskite rare earth oxide material as described in the first aspect or the third aspect in magnetic refrigeration.

[0060] The present invention will be described in detail below through examples. In the following examples, the drugs and pharmaceutical agents are all conventional commercial products.

[0061] Example 1

[0062] (1) Ingredients: High-purity oxide Gd 2 O 3 (99.99%), Cr 2 O 3 (99.9%), Fe 2 O 3 (99.9%) as raw material, according to the sample chemical formula Gd 2 FeCrO 6 Weigh the raw materials at the molar ratio of each element (2:1:1);

[0063] (2) Grinding: Put the above raw materials into a mortar and add alcohol just enough to cover the sample, and grind for 1.5 hours to obtain sample powder;

[0064] (3) Tableting: Pour the sample powder obtained in step (2) into a tableting mold, apply a pressure of 7T, and maintain the pressure for 4 minutes to form a sample slice;

[0065] (4) Pre-sintering: The sample slice in step (3) is placed in a muffle furnace for pre-sintering at a heating rate of 7°C / min, a pre-sintering temperature of 1000°C, and a pre-sintering time of 12 hours. After pre-sintering, the sample slice is cooled to 600°C at a cooling rate of 2°C / min and naturally cooled to room temperature.

[0066] (5) Crushing and grinding: crush the pre-sintered sample slices in an agate mortar, add alcohol that covers the sample, and grind for 30 min to obtain sample powder;

[0067] (6) Tableting: The sample powder crushed and ground in step (5) is placed in the tableting mold again, a pressure of 10 T is applied, and the pressure is maintained for 4 min to form a sample slice;

[0068] (7) Sintering: The sample slice in step (6) was placed in a muffle furnace for sintering at a heating rate of 7°C / min, a sintering temperature of 1300°C, and a sintering time of 16 h. After sintering, the temperature was cooled to 600°C at a cooling rate of 2°C / min and naturally cooled to room temperature to obtain Gd 2 FeCrO 6 Double perovskite rare earth oxide material, denoted as B1.

[0069] Example 2

[0070] The preparation method of Example 1 was followed, except that the Gd 2 O 3 Replace with Tb 2 O 3 Other conditions remain unchanged, and Tb is obtained. 2 FeCrO 6 Double perovskite rare earth oxide material, denoted as B2.

[0071] Example 3

[0072] The preparation method of Example 1 was followed, except that the Gd 2 O 3 Replaced by Dy 2 O 3 Other conditions remain unchanged, Dy 2 FeCrO 6 Double perovskite rare earth oxide material, denoted as B3.

[0073] Example 4

[0074] The preparation method of Example 1 was followed, except that the Gd 2 O 3 Replace with Er 2 O 3 Other conditions remain unchanged, and Er is obtained.2 FeCrO 6 Double perovskite rare earth oxide material, denoted as B4.

[0075] Test Example 1

[0076] The double perovskite rare earth oxide materials of Examples 1-4 were analyzed by X-ray diffractometer (XRD). Figure 1 .

[0077] Depend on Figure 1 It can be seen that the double perovskite rare earth oxide materials of embodiments 1-4 of the present invention all have a standard double perovskite compound structure and belong to the Pbnm (62) space group. As the atomic number of the rare earth ion increases, the radius of the rare earth ion gradually decreases, resulting in a decrease in the lattice constants a, b and c.

[0078] Test Example 2

[0079] The double perovskite rare earth oxide materials of Examples 1-4 were subjected to temperature-dependent magnetic susceptibility (MT) tests and hysteresis loop (MH) tests using a vibrating sample magnetometer (VSM), and magnetic entropy change calculations were performed. The specific test results are shown in Tables 1 and Figure 2-7 shown.

[0080] Table 1

[0081]

[0082] It can be seen from the above data that all four groups of samples have large magnetic entropy changes, among which the double perovskite rare earth oxide material Gb 2 FeCrO 6 The maximum magnetic entropy change is as high as 30.31 J / kg K.

[0083] Depend on Figure 4 It can be seen that the double perovskite rare earth oxide material Tb prepared in Examples 2-4 of the present invention 2 FeCrO 6 、Dy 2 FeCrO 6 and Er 2 FeCrO 6 The GP behavior was observed in the double perovskite system, which may lead to the reduction of MCE. The proposed mechanism for the GP behavior is due to the BO 6 or B'O 6 The two-phase competition and the intrinsic dislocation of the octahedron destroy the periodicity of the structure but introduce AFM superexchange coupling and / or magnetic frustration in FM compounds.

[0084] At the same time, by Figure 5 MH curve and -ΔS M max-ΔH 2 / 3 The curves show that the four systems of Examples 1-4 of the present invention experienced an AFM-PM secondary phase transition at 4.3-21.4K.

[0085] further, Figure 6 (b)- Figure 6 The Arrott diagram analysis of (d) shows that the Tb prepared in Examples 2-4 of the present invention 2 FeCrO 6 、Dy 2 FeCrO 6 and Er 2 FeCrO 6 The sample undergoes an AFM-FM first-order phase transition at low temperature and low field. Figure 7 (b)- Figure 7 (d) -ΔS M / (-ΔS M ) max This is also confirmed by the failure of the -θ curve to normalize.

[0086] Moreover, the Gd prepared in Example 1 of the present invention 2 FeCrO 6 It has weak hysteresis and excellent magnetocaloric properties (when ΔH=50kOe, -ΔS M max =30.31 J / kg K, RCP =312.8 J / kg), which shows great potential in the application of low-temperature magnetic refrigeration.

[0087] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0088] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0089] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A double perovskite rare earth oxide material, characterized in that: The molecular formula of the double perovskite rare earth oxide material is RE2FeCrO6, wherein RE is selected from one of Gd, Tb, Dy and Er; The double perovskite rare earth oxide material has an antiferromagnetic-paramagnetic secondary phase transition at 4.3-21.4K.

2. The double perovskite rare earth oxide material according to claim 1, characterized in that: The double perovskite rare earth oxide material has a double perovskite compound structure and belongs to the Pbnm (62) space group.

3. A method for preparing a double perovskite rare earth oxide material, characterized in that: The method comprises: first grinding rare earth oxide, chromium oxide and iron oxide, first tabletting, pre-sintering, first cooling, first cooling, second grinding, second tabletting, sintering, second cooling and second cooling.

4. The method according to claim 3, characterized in that The rare earth oxide is selected from one or two or more of Gd2O6, Tb2O6, Dy2O6 and Er2O6.

5. The method according to claim 3 or 4, characterized in that: The molar ratio of the rare earth oxide, chromium oxide and iron oxide is 2:1:1, wherein the rare earth oxide is calculated as rare earth atoms, the chromium oxide is calculated as chromium atoms, and the iron oxide is calculated as iron atoms.

6. The method according to any one of claims 3 to 5, characterized in that: The first grinding conditions include: in the presence of a grinding medium for a time of 1-2 hours; Preferably, the first tabletting conditions include: a pressure of 5-10T and a holding time of 3-5min; More preferably, the pre-sintering conditions include: temperature of 800-1200°C, time of 10-14h, heating rate of 5-10°C / min; Further preferably, the first cooling conditions include: temperature of 400-700°C, cooling rate of 1-3°C / min; More preferably, the first cooling condition includes: a temperature of 20-30°C.

7. The method according to any one of claims 3 to 6, characterized in that: The second grinding conditions include: in the presence of grinding media, the time is 20-40 minutes; Preferably, the second tableting conditions include: a pressure of 8-12T, and a holding time of 3-5min; More preferably, the sintering conditions include: temperature of 1000-1500°C, time of 14-18h, heating rate of 5-10°C / min; Further preferably, the second cooling conditions include: temperature of 400-700°C, cooling rate of 1-3°C / min; More preferably, the second cooling condition includes: a temperature of 20-30°C.

8. The method according to claim 7, characterized in that The grinding media in the first grinding and the second grinding are alcohol and / or 2-methylpentane.

9. A double perovskite rare earth oxide material prepared according to the method according to any one of claims 3 to 8.

10. Use of the double perovskite rare earth oxide material according to claim 1 or 2 or the double perovskite rare earth oxide material according to claim 9 in magnetic refrigeration.

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