A novel rare earth magnetic refrigeration material and a preparation method thereof

Abstract

The application belongs to the technical field of magnetic refrigeration materials, and particularly relates to a novel rare earth magnetic refrigeration material and a preparation method thereof. 12 The novel rare earth magnetic refrigeration material is composed of metal oxide phases and has a chemical general formula of R3CrGa3FeO, wherein R is a rare earth element, and R is one or two of Ho, Tb, Dy and Gd. The preparation method of the novel rare earth magnetic refrigeration material comprises the following steps: (1) R oxide, Cr oxide, Ga oxide and Fe oxide are mixed by ball milling and then dried, pre-sintering is carried out, and the pre-sintered material is obtained by crushing and sieving; and (2) the pre-sintered material is pressed into a shape after secondary ball milling and then sintered. The novel rare earth magnetic refrigeration material with stable and good magnetic refrigeration effect is obtained by adopting R oxide, Cr oxide, Ga oxide and Fe oxide through a simple solid-phase reaction.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetic refrigeration materials, and particularly relates to a novel rare earth magnetic refrigeration material and a preparation method thereof. BACKGROUND

[0002] In modern society, refrigeration technology has become an indispensable part, involving various aspects such as daily life, industrial and agricultural production, scientific research, and science and technology defense. The commonly used refrigeration technology is the traditional vapor compression refrigeration, which uses the process of compression and relaxation of refrigerant in the compressor to absorb and release heat, so as to realize the purpose of refrigeration by transferring heat from a low-temperature environment to a high-temperature environment. However, this refrigeration technology has problems such as high energy consumption and environmental unfriendliness, and a large amount of heat and noise are generated during the operation of the compressor, and harmful refrigerants are discharged into the atmosphere.

[0003] As a new type of refrigeration technology based on the magnetic heat effect of magnetic materials, magnetic refrigeration technology has received extensive attention and attention in recent years. The magnetic heat effect is an intrinsic property of magnetic materials, which is usually defined as the physical phenomenon of heat release or absorption of magnetic materials when the magnetic field is enhanced or weakened. By changing the external magnetic field, the magnetic moment of the magnetic material changes from order to disorder, thereby causing the heat absorption and release of the magnet, and realizing the refrigeration cycle.

[0004] Compared with the traditional refrigeration technology, the magnetic refrigeration technology has obvious advantages. First, the magnetic refrigeration technology is a green and environmentally friendly refrigeration method, which does not involve any harmful substances in the refrigeration process and has no negative impact on the environment. Second, the magnetic refrigeration technology has the characteristics of energy saving and high efficiency, which can greatly reduce energy consumption and save resources. Finally, the magnetic refrigeration technology is stable and reliable in operation, and has a long-lasting refrigeration effect, which greatly reduces the maintenance cost and maintenance frequency of the equipment. The development and application of magnetic refrigeration technology are closely related to the performance of magnetic refrigeration materials. At present, high-performance magnetic refrigeration materials mainly include Gd-Si-Ge, Gd-Al-Co and other material systems, but these materials are generally high in cost, poor in stability, limited in refrigeration temperature range and complex in process, which limits their commercial application to a certain extent. Therefore, the in-depth study of the magnetic heat effect, especially the exploration of new magnetic refrigeration materials, is still the focus and hotspot in the current scientific research field. SUMMARY

[0005] The purpose of the present application is to provide a novel rare earth magnetic refrigeration material, which has a stable and good magnetic refrigeration effect.

[0006] The novel rare earth magnetic refrigeration material in the technical scheme of the present application is composed of a metal oxide phase, and the chemical general formula is R3CrGa3FeO 12 , wherein R is a rare earth element.

[0007] The metal oxide is low in price, corrosion resistant, and easy to produce a huge magnetic entropy change at a very low temperature due to a large atomic spacing, and is the best magnetic refrigeration material in a temperature range below 20K.

[0008] Further, R is one or two of Ho, Tb, Dy and Gd.

[0009] Further, the new rare earth magnetic refrigeration material has a maximum magnetic entropy change of 8-10JK -1 mol -1 .

[0010] The application further provides a preparation method of the new rare earth magnetic refrigeration material, comprising the following steps:

[0011] (1) mixing R oxide, Cr oxide, Ga oxide and Fe oxide, drying, pre-sintering, crushing and sieving to obtain pre-sintered material;

[0012] (2) secondary ball milling, molding and sintering.

[0013] The secondary ball milling and sintering after pre-sintering can better control the particle size distribution and phase purity of the magnetic refrigeration material, reduce the impurity content of the pre-sintered material powder, and form a relatively narrow particle size and regular grain morphology.

[0014] Further, the R oxide is one or two of Gd2O3, Tb4O7, Dy2O3 and Ho2O3, the Cr oxide is Cr2O3, the Ga oxide is Ga2O3, and the Fe oxide is Fe2O3.

[0015] Further, the pre-sintering temperature in step (1) is 800-1200℃, and the holding time is 1-10h.

[0016] Further, the heating rate during pre-sintering is 1-10℃ / min.

[0017] Further, the pre-sintering temperature in step (1) is 860-940℃, and the holding time is 1-8h.

[0018] Preferably, the crushing is performed by grinding after being scattered by a cell wall breaker.

[0019] Further, the mesh size of the sieve in step (1) is 80-120 mesh.

[0020] Further, the ball milling speed in steps (1) and (2) is 200-500rpm / min, and the ball milling time is 6-15h.

[0021] Further, the solid material is added with water as the ball milling medium, and the water is 1.5-5.0 times of the mass of the solid material.

[0022] Further, the ball milling ratio is 1:3-6.

[0023] Further, the drying temperature in step (1) is 80-150℃, and the time is 6-20h.

[0024] Further, the pressure for the press forming in step (2) is 10-50MPa, and the time is 10-60min.

[0025] Further, the sintering temperature in step (2) is 1000-1500℃, and the time is 1-10h.

[0026] Further, the heating rate during sintering is 1-10℃ / min.

[0027] Further, the sintering temperature in step (2) is 1240-1350℃, and the time is 1-8h.

[0028] Further, the pre-sintering and sintering are both carried out in air atmosphere.

[0029] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0030] (1) The R oxide, Cr oxide, Ga oxide and Fe oxide are used to obtain the novel rare earth magnetic refrigeration material (R3CrGa3FeO 12 ) with stable and good magnetic refrigeration effect through simple solid phase reaction;

[0031] (2) The metal oxide (R3CrGa3FeO 12 ) as the magnetic refrigeration material is low in price, corrosion-resistant, and has large atomic spacing and large magnetic entropy change at extremely low temperature, and is the best magnetic refrigeration material in the temperature range below 20K;

[0032] (3) The secondary ball milling and sintering after pre-sintering can better control the particle size distribution and phase purity of the magnetic refrigeration material, reduce the impurity content of the pre-sintering material powder, and form relatively narrow particle dispersion and regular grain morphology;

[0033] (4) The novel rare earth magnetic refrigeration material has a large magnetic entropy change value of 9.12J K - 1 mol -1 at 12K and ΔH=5T, and has great application potential in magnetic refrigerants;

[0034] (5) The preparation method of the novel rare earth magnetic refrigeration material is simple in process, concise in steps and easy to operate, which not only improves the production efficiency, but also reduces the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 X-ray diffraction patterns of the new rare earth magnetic refrigeration materials obtained in Example 1 and Example 2;

[0036] Figure 2 ZFC magnetization (χ, main figure) and inverse magnetization (χ -1 , inset) plots of the new rare earth magnetic refrigeration materials obtained in Example 1 and Example 2 under a 200 Oe magnetic field;

[0037] Figure 3 Isothermal magnetization (M-H) curves of the new rare earth magnetic refrigeration materials obtained in Example 1 and Example 2 at different temperatures: (a) Example 1, (b) Example 2;

[0038] Figure 4 -ΔS m -T curves of the new rare earth magnetic refrigeration material obtained in Example 1 under different magnetic field changes: (a) Example 1, (b) Example 2;

[0039] Figure 5 ΔS m vs. temperature curves of the new rare earth magnetic refrigeration materials obtained in Example 1 and Example 2 in a 2T magnetic field. DETAILED DESCRIPTION

[0040] The technical solutions of the present application will be further described and illustrated by specific examples and drawings. It should be understood that the specific examples described herein are only used to help understand the present application and are not used to limit the present application. The drawings used herein are only used to better illustrate the disclosed content and do not limit the scope of protection. If not specifically stated, the raw materials used in the examples of the present application are commonly used raw materials in the art, and the methods used in the examples are conventional methods in the art.

[0041] Example 1

[0042] The preparation method of the new rare earth magnetic refrigeration material in this example comprises the following steps:

[0043] (1) According to the element molar ratio of Gd3CrGa3FeO 12 , Gd2O3, Cr2O3, Ga2O3 and Fe2O3 are placed in a ball mill, and 1.5 times the mass of the above components of deionized water is added, ball milling at a speed of 300 rpm / min and a ball-to-material ratio of 1:4 for 6h, drying at 100℃ for 10h, then heating to 880℃ at a rate of 5℃ / min, pre-burning in air atmosphere for 3h, cooling with the furnace, using a cell crusher to break up and then grinding, and sieving with a 100 mesh sieve to obtain the pre-burned material;

[0044] (2) adding 1.5 times the mass of the pre-sintered material of deionized water, twice ball milling the pre-sintered material at 300 rpm / min and a ball-to-material ratio of 1:4 for 8 h, pressing for 15 min under a pressure of 20 MPa, heating at a rate of 5°C / min to 1250°C, sintering in an air atmosphere for 2 h, and cooling to room temperature in the furnace.

[0045] Example 2

[0046] The preparation method of the novel rare earth magnetic refrigeration material of the present example comprises the following steps:

[0047] (1) according to the element molar ratio of Gd3CrGa3FeO 12 , Gd2O3, Cr2O3, Ga2O3 and Fe2O3 are placed in a ball mill, and 2.0 times the mass of the above components of deionized water is added, ball milling at a speed of 280 rpm / min and a ball-to-material ratio of 1:5 for 6 h, drying at 100°C for 12 h, heating at a rate of 6°C / min to 920°C, pre-sintering in an air atmosphere for 3 h, cooling in the furnace, dispersing with a cell wall crusher and then grinding, and sieving with a 120-mesh sieve to obtain pre-sintered material;

[0048] (2) adding 1.5 times the mass of the pre-sintered material of deionized water, twice ball milling the pre-sintered material at 300 rpm / min and a ball-to-material ratio of 1:5 for 8 h, pressing for 20 min under a pressure of 25 MPa, heating at a rate of 6°C / min to 1350°C, sintering in an air atmosphere for 2 h, and cooling to room temperature in the furnace.

[0049] Example 3

[0050] The preparation method of the novel rare earth magnetic refrigeration material of the present example comprises the following steps:

[0051] (1) according to the element molar ratio of Gd3CrGa3FeO 12 , Gd2O3, Cr2O3, Ga2O3 and Fe2O3 are placed in a ball mill, and 2.0 times the mass of the above components of deionized water is added, ball milling at a speed of 280 rpm / min and a ball-to-material ratio of 1:5 for 6 h, drying at 100°C for 12 h, heating at a rate of 6°C / min to 920°C, pre-sintering in an air atmosphere for 3 h, cooling in the furnace, dispersing with a cell wall crusher and then grinding, and sieving with a 120-mesh sieve to obtain pre-sintered material;

[0052] (2) adding 1.5 times the mass of the pre-sintered material of deionized water, twice ball milling the pre-sintered material at 300 rpm / min and a ball-to-material ratio of 1:5 for 8 h, pressing for 20 min under a pressure of 25 MPa, heating at a rate of 6°C / min to 1350°C, sintering in an air atmosphere for 2 h, and cooling to room temperature in the furnace.

[0053] Example 4

[0054] The preparation method of the novel rare earth magnetic refrigeration material of the present embodiment comprises placing Gd203, Cr203, Ga203 and Fe203 in a ball mill according to the element molar ratio of Gd3CrGa3FeO 12 , adding deionized water with a mass 1.5 times that of the above components, ball milling at a speed of 300 rpm / min and a ball-to-material ratio of 1:4 for 6 h, baking at 100°C for 10 h, then increasing the temperature to 880°C at a rate of 6°C / min, pre-baking in an air atmosphere for 5 h, cooling in the furnace, using a cell crusher to break up and then grinding, and sieving using a 100-mesh sieve.

[0055] Example 5

[0056] The preparation method of the novel rare earth magnetic refrigeration material of the present embodiment comprises placing Gd203, Cr203, Ga203 and Fe203 in a ball mill according to the element molar ratio of Gd3CrGa3FeO 12 , adding deionized water with a mass 1.5 times that of the above components, ball milling at a speed of 300 rpm / min and a ball-to-material ratio of 1:4 for 6 h, baking at 100°C for 10 h, then increasing the temperature to 880°C at a rate of 6°C / min, pre-baking in an air atmosphere for 5 h, cooling in the furnace, using a cell crusher to break up and then grinding, and sieving using a 100-mesh sieve.

[0057] Example 6

[0058] The difference between the present embodiment and Example 1 is only that step (1) comprises placing Gd203, Cr203, Ga203 and Fe203 in a ball mill according to the element molar ratio of Gd3CrGa3FeO 12 , adding deionized water with a mass 1.5 times that of the above components, ball milling at a speed of 300 rpm / min and a ball-to-material ratio of 1:4 for 6 h, baking at 100°C for 10 h, then increasing the temperature to 880°C at a rate of 6°C / min, pre-baking in an air atmosphere for 5 h, cooling in the furnace, using a cell crusher to break up and then grinding, and sieving using a 100-mesh sieve.

[0059] Example 7

[0060] The difference between the present embodiment and Example 1 is only that step (1) comprises placing Gd203, Cr203, Ga203 and Fe203 in a ball mill according to the element molar ratio of Gd3CrGa3FeO 12Gd2O3, Cr2O3, Ga2O3and Fe2O3were put into a ball mill, 1.5 times the mass of deionized water of the above components was added, and the mixture was ball milled at a speed of 300 rpm / min and a ball-to-material ratio of 1:4 for 6 h. After being baked at 100 °C for 10 h, the temperature was increased to 1050 °C at a rate of 5 °C / min, and the pre-fired material was baked in an air atmosphere for 3 h. The pre-fired material was ground after being broken up using a cell crusher and sieved using a 100-mesh sieve.

[0061] Example 8

[0062] The difference between this example and Example 1 is that in step (2), 1.5 times the mass of deionized water of the pre-fired material was added, the pre-fired material was ball milled for 8 h at a speed of 300 rpm / min and a ball-to-material ratio of 1:4, and the pre-fired material was sintered at 1450 °C in an air atmosphere for 2 h.

[0063] Example 9

[0064] The difference between this example and Example 1 is that in step (2), 1.5 times the mass of deionized water of the pre-fired material was added, the pre-fired material was ball milled for 8 h at a speed of 300 rpm / min and a ball-to-material ratio of 1:4, and the pre-fired material was sintered at 1450 °C in an air atmosphere for 2 h.

[0065] Comparative Example 1

[0066] The preparation method of the novel rare earth magnetic refrigeration material of the present comparative example comprises the following steps:

[0067] (1) Gd2O3, Cr2O3and Ga2O3were put into a ball mill in a molar ratio of 3:4:4, 1.5 times the mass of deionized water of the above components was added, and the mixture was ball milled at a speed of 300 rpm / min and a ball-to-material ratio of 1:4 for 6 h. After being baked at 100 °C for 10 h, the temperature was increased to 880 °C at a rate of 5 °C / min, and the pre-fired material was baked in an air atmosphere for 3 h. The pre-fired material was ground after being broken up using a cell crusher and sieved using a 100-mesh sieve to obtain the pre-fired material; 12 Gd2O3, Cr2O3and Ga2O3were put into a ball mill in a molar ratio of 3:4:4, 1.5 times the mass of deionized water of the above components was added, and the mixture was ball milled at a speed of 300 rpm / min and a ball-to-material ratio of 1:4 for 6 h. After being baked at 100 °C for 10 h, the temperature was increased to 880 °C at a rate of 5 °C / min, and the pre-fired material was baked in an air atmosphere for 3 h. The pre-fired material was ground after being broken up using a cell crusher and sieved using a 100-mesh sieve to obtain the pre-fired material;

[0068] (2) 1.5 times the mass of deionized water of the pre-fired material was added, the pre-fired material was ball milled for 8 h at a speed of 300 rpm / min and a ball-to-material ratio of 1:4, and the pre-fired material was sintered at 1250 °C in an air atmosphere for 2 h.

[0069] According to the X-ray diffraction spectrum (Fig. 1), the diffraction peaks of the prepared material are consistent with the diffraction peaks of the standard spectrum of the Gd5Cr4Ga2O12phase, and the diffraction peaks of the Gd2O3, Cr2O3and Ga2O3phases are not found. Figure 1As shown in the figure, pure Gd3CrGa3FeO was obtained in Examples 1 and 2, respectively. 12 and Ho3CrGa3FeO 12 ;like Figure 2 As shown in the χ-T curve, it can be seen that Gd3CrGa3FeO 12 and Ho3CrGa3FeO 12 At low temperatures, it exhibits a ferromagnetic state. However, as the temperature increases, the magnetization decreases sharply near the Curie temperature, indicating a phase transition from ferromagnetism (FM) to paramagnetism (PM), caused by the χ²-coefficient of magnetization. -1 The -T curve shows that Gd3CrGa3FeO 12 and Ho3CrGa3FeO 12 In the paramagnetic region, the reciprocal of the magnetic susceptibility exhibits a linear relationship with temperature, conforming to the Curie-Weiss law; such as Figure 3 As shown, with the increase of magnetic field strength, Gd3CrGa3FeO 12 and Ho3CrGa3FeO 12 The magnetization gradually increases and approaches saturation at a temperature of 5K and a magnetic field of 5T, which is very close to the theoretical value; for example Figure 4 As shown, Gd3CrGa3FeO 12 and Ho3CrGa3FeO 12 -ΔS m The -T curve peaks near 12K, and the magnetic entropy change gradually increases with increasing ΔH. When the applied magnetic field is 5T, Gd3CrGa3FeO 12 and Ho3CrGa3FeO 12 Maximum magnetic entropy change -ΔS m max They are 9.12JK respectively -1 mol -1 and 8.98JK -1 mol -1 ;like Figure 5 As shown, the Gd3CrGa3FeO obtained in Examples 1 and 2 12 and Ho3CrGa3FeO 12 They exhibit similar magnetic refrigeration effects; Example 4 involved pre-firing at 880℃ without secondary ball milling and sintering, and Example 5 involved sintering at 1250℃ without pre-firing, resulting in Gd3CrGa3FeO. 12The particle size distribution is uneven, the impurity content is also increased, and the magnetic refrigeration effect is poor; the rare earth magnetic refrigeration material obtained in Example 6 is pre-fired at a lower temperature, the rare earth magnetic refrigeration material obtained in Example 7 is pre-fired at a higher temperature, the rare earth magnetic refrigeration material obtained in Example 8 is sintered at a lower temperature, the rare earth magnetic refrigeration material obtained in Example 9 is sintered at a higher temperature, the rare earth magnetic refrigeration material obtained in Examples 6-9 has a RCrO3 impurity peak and the magnetic refrigeration effect is poor; the magnetic entropy change peak value of the magnetic refrigeration material in Comparative Example 1 is reduced and the magnetic refrigeration effect is obviously poor.

[0070] Finally, it should be noted that the specific embodiments described herein are merely illustrative of the spirit of the present application, and are not intended to limit the embodiments of the present application. Those skilled in the art can make various modifications or supplements to the described embodiments or replace them with similar ways. Here, all embodiments do not need to be fully described. Any obvious changes or variations derived from the spirit of the present application still fall within the scope of the present application, and any additional limitations are contrary to the spirit of the present application.

Claims

1. A rare earth magnetic refrigeration material, characterized by, The rare earth magnetic refrigeration material is composed of a metal oxide phase, and has a general chemical formula of R3CrGa3FeO 12 wherein R is one or two of Ho, Tb, Dy, and Gd.

2. The rare earth magnetic refrigeration material of claim 1, wherein, The rare earth magnetic refrigeration material has a maximum magnetic entropy change value of 8-10 J K at 12 K and Delta H=5 T -1 mol -1 .

3. A method of producing a rare earth magnetic refrigeration material as claimed in claim 1, characterized by, The method comprises the following steps: (1) mixing R oxide, Cr oxide, Ga oxide and Fe oxide by ball milling, drying, pre-sintering, crushing and sieving to obtain pre-sintered material; (2) pressing the pre-sintered material into a shape after secondary ball milling, and then sintering.

4. The production method according to claim 3, characterized by, The R oxide is one or two of Gd2O3, Tb4O7, Dy2O3 and Ho2O3, the Cr oxide is Cr2O3, the Ga oxide is Ga2O3, and the Fe oxide is Fe2O3.

5. The preparation method according to claim 3, characterized in that, The pre-sintering temperature in step (1) is 800-1200 DEG C, and the holding time is 1-10 h.

6. The preparation method according to claim 3, characterized in that, The mesh size of the sieve in step (1) is 80-120 mesh.

7. The preparation method according to claim 3, characterized in that, The ball milling speed in steps (1) and (2) is 200-500 rpm / min, and the ball milling time is 6-15 h.

8. The preparation method according to claim 7, characterized in that, Water with a mass of 1.5-5.0 times that of the solid material is added as the ball milling medium.

9. The preparation method according to claim 3, characterized in that, The sintering temperature in step (2) is 1000-1500 DEG C, and the time is 1-10 h.

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