A continuous gradient magnetocaloric material and a method for producing the same

Abstract

The application provides a continuous gradient magnetocaloric material and a preparation method thereof, and comprises the following steps: S1, preparing raw materials according to chemical formulas of material A and material B which are different in composition; S2, preparing material A and material B powders from the raw materials of material A and material B respectively by an induction gas atomization method; S3, gradiently spreading the material A and material B; S4, preparing a cast-state gradient sample from the material A and material B powders by 3D printing; and S5, annealing the cast-state gradient sample to obtain a final continuous gradient magnetocaloric material with uniform organization; wherein material A is selected from magnetocaloric materials, and material B is selected from magnetocaloric materials or non-magnetocaloric materials; when material A and material B are both selected from magnetocaloric materials, material A and material B are selected from the same kind of magnetocaloric materials. The prepared material has the advantages of a wide phase transition temperature range, high refrigeration efficiency and a short preparation period.

Description

Technical Field

[0001] The present invention relates to the field of magnetic refrigeration technology, and in particular to a continuous gradient magnetocaloric material and a preparation method thereof. Background Art

[0002] With the progress of human society and the development of science and technology, refrigeration technology has been widely used in various fields of modern life, such as common refrigerators, air conditioners, as well as aerospace, precision instruments, etc. It can be said that refrigeration technology is an important means to ensure human happiness and social progress. At present, the main refrigeration technology used by humans is mostly gas compression refrigeration technology, which uses gas as a refrigerant, such as Freon. However, these gases are easy to leak and will destroy the ozone layer in the atmosphere, causing ozone holes and causing environmental problems. In addition, gas compression refrigeration technology also has disadvantages such as high energy consumption, low refrigeration efficiency, and toxicity. Therefore, there is an urgent need for a more efficient, green, safe and sustainable refrigeration technology to replace traditional gas compression refrigeration technology. In recent years, magnetic refrigeration technology has attracted much attention due to its high magnetic refrigeration efficiency, compact structure, and no harmful gas production.

[0003] Unlike traditional gas compression refrigeration, magnetic refrigeration uses magnetic materials as the refrigerant. The principle of magnetic refrigeration is based on the magnetocaloric effect of magnetocaloric materials. This change in magnetic entropy causes the material to absorb and release heat, exchanging heat with the surrounding environment and achieving cooling. Therefore, the development and practical application of magnetic refrigeration technology are largely dependent on the properties of magnetocaloric materials. In recent years, researchers have discovered several materials with giant magnetocaloric effects at room temperature, such as Gd-Si-Ge, La-Fe-Si, (Mn,Fe)2(P,Si / Ge) compounds, Mn-based Husler alloys, Mn-Co-Ge, and perovskite oxide alloys. These materials generally exhibit first-order phase transitions, attracting considerable attention for their large magnetic entropy changes at room temperature, their controllable phase transitions, and other excellent physical properties. However, these magnetocaloric materials share a common characteristic: a rapid phase transition spanning a very small temperature range, typically no more than 10K. Consequently, magnetocaloric materials achieve high cooling efficiency only within their phase transition temperature range. However, the operating temperature range of air conditioners on the market is 289-303K (temperature span of about 14K), and the operating temperature range of refrigerators is 253-283K (temperature span of about 30K). Therefore, these magnetocaloric materials cannot meet the demand for refrigeration effects in actual production and life at this stage. In addition, traditional magnetocaloric materials usually require annealing to improve the organization and performance, but this process is very long. For example, bulk NaZn 13The (1:13) type La-Fe-Si compound requires high temperature annealing for 7 days or even two weeks to homogenize the structure, which not only wastes resources but also has a very long preparation cycle, which greatly affects the practical application of magnetocaloric materials.

[0004] Therefore, it is necessary for us to develop a continuous gradient magnetocaloric material with a wide phase change temperature range, high cooling efficiency and short preparation cycle to meet actual needs. Summary of the Invention

[0005] The present invention provides a continuous gradient magnetocaloric material and a preparation method thereof. The continuous gradient magnetocaloric material prepared by the method has a wide operating temperature range, good refrigeration performance and a short preparation cycle.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for preparing a continuous gradient magnetocaloric material, comprising:

[0008] Step S1, preparing raw materials according to the chemical formulas of material A and material B with different compositions;

[0009] Step S2: preparing the raw materials of material A and material B into powders of material A and material B respectively by induction atomization;

[0010] Step S3, performing gradient powdering on material A and material B;

[0011] Step S4, preparing the material A and material B powders into a cast gradient sample by 3D printing;

[0012] Step S5, annealing the as-cast gradient sample to obtain a continuous gradient magnetocaloric material with uniform structure;

[0013] Wherein, material A is selected from magnetocaloric material, and material B is selected from magnetocaloric material or non-magnetocaloric material; when material A and material B are both selected from magnetocaloric material, material A and material B are selected from the same magnetocaloric material.

[0014] Optionally, the magnetocaloric material is selected from one of Gd-Si-Ge, La-Fe-Si, (Mn, Fe)2(P, Si / Ge), Mn-based Heusler alloy, Mn-Co-Ge and perovskite oxide; and the non-magnetocaloric material is transition metal Fe.

[0015] Alternatively, the chemical formula of the La-Fe-Si compound is (La 1-x R x )(Fe 13-y-z Mn y Si z), wherein R is a rare earth element, preferably Ce, Pr, or Nd, wherein x ranges from 0 to 0.3, y ranges from 0 to 1, and z ranges from 1 to 2; the phase transition temperature of the prepared continuous gradient magnetocaloric material changes continuously from one end to the other, and the temperature change range is 100 to 400 K. That is, those skilled in the art will appreciate that when preparing the continuous gradient magnetocaloric material, material A is selected from La-Fe-Si, and material B is selected from La-Fe-Si or Fe. Regardless of which material B is selected, the temperature change range claimed in the present invention can be achieved.

[0016] Alternatively, the Mn-based Heusler alloy has the formula Ni 50-m Co m Mn 50-n Ti n , where m and n are in the range of 10-20; the phase transition temperature of the prepared continuous gradient magnetocaloric material changes continuously from one end to the other, and the temperature change range is 100-400 K. That is, those skilled in the art will appreciate that when preparing the continuous gradient magnetocaloric material, material A is selected from a Mn-based Heusler alloy, and material B is selected from a Mn-based Heusler alloy or Fe. Regardless of which material B is selected, the temperature change range claimed in the present invention can be achieved.

[0017] Alternatively, the chemical formula of Gd-Si-Ge is Gd5(Si 1-x Ge x )4, where x ranges from 0 to 1: the phase transition temperature of the prepared continuous gradient magnetocaloric material changes continuously from one end to the other, and the temperature change range is 30 to 280 K. That is, those skilled in the art will appreciate that when preparing the continuous gradient magnetocaloric material, material A is selected from Gd-Si-Ge, and material B is selected from Gd-Si-Ge or Fe. Regardless of which material B is selected, the temperature change range claimed in the present invention can be achieved.

[0018] Alternatively, the chemical formula of (Mn, Fe)2(P, Si / Ge) is (Mn 1-x Fe x )2(P 1-y B y ), wherein B is Si or Ge, and the range of x and y is 0-1; the phase transition temperature of the prepared continuous gradient magnetocaloric material changes continuously from one end to the other, and the temperature change range is 150-350 K. That is, those skilled in the art will appreciate that when preparing the continuous gradient magnetocaloric material, material A is selected from (Mn, Fe)2(P, Si / Ge), and material B is selected from (Mn, Fe)2(P, Si / Ge) or Fe. Regardless of which material B is selected, the temperature change range claimed in the present invention can be achieved.

[0019] Alternatively, the chemical formula of Mn-Co-Ge is (Mn 1-x M x )(Co1-y M′ y )(Ge 1-z X z ), wherein M and M' are transition metal elements, preferably Mn, Fe, Co, or Ni; wherein X is a main group element, preferably Si, Ge, Al, or Ga; wherein x, y, and z range from 0 to 1; and the phase transition temperature of the prepared continuous gradient magnetocaloric material changes continuously from one end to the other, with a temperature range of 150 to 450 K. That is, those skilled in the art will appreciate that when preparing the continuous gradient magnetocaloric material, material A is selected from Mn-Co-Ge, and material B is selected from Mn-Co-Ge or Fe. Regardless of which material B is selected, the temperature range claimed in the present invention can be achieved.

[0020] Optionally, the perovskite oxide has the formula (R 1-x A x )MnO3, wherein R is a rare earth element, preferably La, Ce, Pr, or Nd; wherein A is a divalent metal element, preferably Ca, Ba, or Sr; and wherein x ranges from 0 to 1; the phase transition temperature of the prepared continuous gradient magnetocaloric material changes continuously from one end to the other, within a temperature range of 100 to 350 K. That is, those skilled in the art will appreciate that when preparing the continuous gradient magnetocaloric material, material A is selected from perovskite oxide, and material B is selected from perovskite oxide or Fe. Regardless of which material B is selected, the temperature range claimed in the present invention can be achieved.

[0021] Optionally, in step S1, when configuring the raw materials, when material A and material B contain rare earth elements, Mn or Si, the rare earth elements, Mn or Si are added in an excess amount of 1% to 10% of the atomic ratio on the basis of satisfying the atomic ratio addition amount to compensate for their volatilization and burning loss during the preparation process.

[0022] Optionally, in step S2, the atomization pressure of the induction atomization is 2-10 MPa, and the powder after the induction atomization needs to be sieved to select powder with a particle size range of 5-100 μm.

[0023] Optionally, in step S3, the gradient powder spreading is to spread material A and material B along the diagonal direction of the rectangle without mixing. That is, in the rectangular area within the 3D printer hopper, material A and material B are spread flatly within the rectangular area, along the diagonal of the rectangular area, with material A spread on one side of the diagonal and material B spread on the other side. As those skilled in the art will appreciate, when spreading the powder, material A and material B are not strictly bounded by the diagonal of the rectangular area. Material A and material B may cross the diagonal, but generally the powder is spread along the diagonal direction, and material A and material B do not mix during the spreading process.

[0024] Optionally, in step S3, after the gradient powdering, material A and material B are mixed along the sides of the rectangle, preferably along the short sides of the rectangle.

[0025] Optionally, in step S4, the printing parameters of 3D printing are a layer thickness of 4.5 to 90 μm, a power of 150 to 350 W, a scanning rate of 450 to 1800 mm / s, and a scanning spacing of 10 to 200 μm.

[0026] Optionally, in step S5, the annealing treatment is: annealing under the protection of high-purity protective gas, the annealing temperature is 700-1500° C., the time is 2 hours to 15 days, preferably 2 hours to 36 hours, and cooling is carried out by liquid nitrogen or ice water.

[0027] Furthermore, the present invention also provides the application of continuous gradient magnetocaloric materials in the field of refrigeration.

[0028] The beneficial effects brought about by the technical solution provided by the present invention include at least:

[0029] (1) The present invention broadens the phase change temperature range of the magnetocaloric material by performing a gradient design on the magnetocaloric material, thereby making the cooling efficiency of the material higher;

[0030] (2) Due to the extremely fast cooling rate of 3D printing technology, it can achieve near-nanoscale organizational structures. The fine structure means that the annealing time required to homogenize the organization is shorter, which greatly shortens the material preparation cycle, thus meeting the needs of actual production and life;

[0031] (3) The continuous gradient magnetocaloric material prepared by the present invention will print out gradient components along the gradient direction, and the components correspond to their specific positions in the material, thereby realizing high-throughput preparation of magnetocaloric materials.

[0032] (4) The present invention uses a 3D printing preparation method, which can be made into any shape according to actual needs. It is environmentally friendly and has good feasibility and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 La obtained in Example 1 of the present invention 0.7 Ce 0.3 Fe 11.65 Si 1.35Morphology of spheres and Fe spherical powders, where (a) is La 0.7 Ce 0.3 Fe 11.65 Si 1.35 ball, (b) is Fe ball;

[0035] Figure 2 Schematic diagram of the method of 3D printing continuous gradient magnetocaloric material in Example 1 of the present invention, where the white ball represents La 0.7 Ce 0.3 Fe 11.65 Si 1.35 Ball, black ball represents Fe ball, (a) is the schematic diagram of gradient powder laying, (b) is the schematic diagram of powder mixing, and (c) is the actual picture of 3D printing;

[0036] Figure 3 The distance La in the backscattering mode of the scanning electron microscope obtained in Example 1 of the present invention is 0.7 Ce 0.3 Fe 11.65 Si 1.35 The tissue morphology of samples taken at different distances from the end, where (a) is 45 mm, (b) is 35 mm, (c) is 25 mm, (d) is 15 mm, and (e) is 5 mm.

[0037] Figure 4 The distance La obtained in Example 1 of the present invention 0.7 Ce 0.3 Fe 11.65 Si 1.35 Magnetic entropy change-temperature curves of samples taken at different distances from the end in a magnetic field of 0 to 2 T;

[0038] Figure 5 This is a physical picture of the continuous gradient magnetocaloric material prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Example 1

[0041] In this embodiment, there are two components of magnetocaloric materials, component 1 and component 2, whose molecular formulas are La 0.7 Ce 0.3 Fe 11.65 Si 1.35 and Fe.

[0042] The continuous gradient magnetocaloric material of the above composition and the additive preparation method thereof include the following steps:

[0043] (1) According to the molecular formula La0.7 Ce 0.3 Fe 11.65 Si 1.35 and Fe to prepare raw materials, wherein the raw materials are commercially available metals La, Ce, Fe, and Si with a purity higher than 99.9 wt.%, wherein La, Ce, and Si are added in an excess amount of 5% atomic ratio to compensate for their volatilization and burning loss during the preparation process;

[0044] (2) Vacuum induction atomization is used to put the prepared raw materials into a crucible, the melting furnace is vacuumed and argon is introduced for melting protection and atomization. The atomization pressure is 4 MPa, and La particles with a particle size range of 0 to 150 μm are obtained. 0.7 Ce 0.3 Fe 11.65 Si 1.35 and Fe spherical powder;

[0045] (3) The spherical powder with a particle size of no more than 150 μm obtained in step (2) is passed through a 270-mesh sieve to obtain a spherical powder with a particle size of no more than 53 μm. The powder with a particle size of no more than 15 μm is separated by gravity and microgravity, and only the La particles with a particle size of 15 to 53 μm that meet the printing requirements are left. 0.7 Ce 0.3 Fe 11.65 Si 1.35 and Fe spherical powder.

[0046] The spherical powder obtained in step (3) was measured using a scanning electron microscope. The test results under the secondary electron mode were as follows: Figure 1 As shown, La 0.7 Ce 0.3 Fe 11.65 Si 1.35 The sphericity of Fe powder is intact, and there is basically no planetary powder and hollow powder.

[0047] (4) Press Figure 2 The gradient powder spreading method shown in the figure spreads the powders of component 1 and component 2 in the 3D printer hopper, and then obtains La by continuous 3D printing. 0.7 Ce 0.3 Fe 11.65 Si 1.35 / Fe uniform gradient cast samples were melted by laser powder bed with a power of 150-300W, a layer thickness of 20-40μm, a scanning speed of 450-1800mm / s, and a scanning interval of 45-90μm.

[0048] (5) La obtained in step (4) 0.7 Ce 0.3 Fe 11.65 Si 1.35The as-cast sample with uniform gradient of NaZn / Fe was annealed under inert gas protection at 1000-1500℃ for 12-36h and quenched in liquid nitrogen or ice water to obtain 13 La 0.7 Ce 0.3 Fe 11.65 Si 1.35 / Fe uniform gradient annealing sample.

[0049] The La obtained in step (5) above 0.7 Ce 0.3 Fe 11.65 Si 1.35 The following tests were performed on the Fe uniform gradient annealed samples:

[0050] (1) Use scanning electron microscopy to measure the tissues of different parts of the uniform gradient annealed sample obtained in step (5). The test results in backscattering mode are as follows. Figure 3 Shown is the distance La 0.7 Ce 0.3 Fe 11.65 Si 1.35 Scanning electron microscope photos of samples taken at 5mm, 15mm, 25mm, 35mm, and 45mm from the end show the distance from La 0.7 Ce 0.3 Fe 11.65 Si 1.35 The farther away from the end, the more α-Fe phase (black) increases and becomes coarser, while the 1:13 phase (gray) decreases and becomes finer, indicating that it has a continuous gradient change organization.

[0051] (2) The isothermal magnetization curve (MH curve) of the product of this embodiment was measured on a magnetic measurement system (Versalab Free measurement system designed by Quantum Design, USA), and then according to Maxwell's relationship: The magnetic entropy change ΔS can be calculated from the isothermal magnetization curve. Figure 3 Shows the distance La in the product of this embodiment 0.7 Ce 0.3 Fe 11.65 Si 1.35 The dependence of ΔS on temperature at 5mm, 15mm and 25mm ends under 2T magnetic field change. 0.7 Ce 0.3 Fe 11.65 Si 1.35 The maximum magnetic entropy change of the samples with 5mm, 15mm and 25mm diameters appears near the phase transition temperature of 200K, 195K and 190K. Under the 2T magnetic field, the maximum magnetic entropy change of the samples is 9.84Jkg -1 K-1 (5mm), 11.11Jkg -1 K -1 (15mm), 8.06Jkg -1 K -1 (25mm), indicating that the sample of this example can indeed obtain a wide phase transition temperature and has high magnetocaloric performance. Currently, the permanent magnet NdFeB can obtain a magnetic field of 2T, so the magnetic entropy change of the material under a 2T magnetic field change has attracted much attention. It can be seen that under a 2T magnetic field change, the maximum magnetic entropy change of the product of this example is 9.84Jkg -1 K -1 (5mm), 11.11J kg -1 K -1 (15mm), 8.06Jkg -1 K -1 (25mm), which is significantly higher than the magnetic entropy change of the traditional room temperature magnetic refrigeration material Gd (under a 2T magnetic field, the magnetic entropy change is 5.0Jkg -1 K -1 ), indicating that the product of this embodiment can be used as a better room temperature functional material.

[0052] Example 2

[0053] In this embodiment, there are two components of magnetocaloric materials, component 1 and component 2, whose molecular formulas are LaFe 11 Si2 and LaFe 12 Si1.

[0054] The continuous gradient magnetocaloric material of the above composition and the additive preparation method thereof include the following steps:

[0055] (1) According to the molecular formula LaFe 11 Si2 and LaFe 12 Si1 prepares raw materials, which are commercially available metals La, Fe, and Si with a purity higher than 99.9wt.%, wherein La and Si are added in excess at an atomic ratio of 5% to compensate for their volatilization and burning losses during the preparation process;

[0056] (2) Using vacuum induction atomization, the prepared raw materials are placed in a crucible, the melting furnace is evacuated and argon is introduced for melting protection and atomization, the atomization pressure is 4 MPa, and LaFe particles with a particle size range of 0 to 150 μm are obtained. 11 Si2 and LaFe 12 Si1 spherical powder;

[0057] (3) The spherical powder with a particle size of no more than 150 μm obtained in step (2) is passed through a 270-mesh sieve to obtain a spherical powder with a particle size of no more than 53 μm. The powder with a particle size of no more than 15 μm is separated by gravity and microgravity, and only the LaFe particles with a particle size of 15 to 53 μm that meet the printing requirements are left. 11 Si2 and LaFe 12 Si1 spherical powder.

[0058] (4) Press Figure 2 The gradient powder spreading method shown in the figure spreads the powders of component 1 and component 2 in the 3D printer hopper, and then obtains LaFe by continuous 3D printing. 11 Si2 / LaFe 12 For Si1 uniform gradient cast samples, the power is 150-300W, the layer thickness is 20-40μm, the scanning speed is 450-1800mm / s, and the scanning interval is 45-90μm.

[0059] (5) LaFe obtained in step (4) 11 Si2 / LaFe 12 Si1 uniform gradient cast sample was annealed under inert gas protection at 1000-1500℃ for 12-36h and quenched in liquid nitrogen or ice water to obtain NaZn 13 LaFe 11 Si2 / LaFe 12 Si1 uniform gradient annealing sample. Figure 5 This is a physical picture of the continuous gradient magnetocaloric material prepared in Example 2 of the present invention.

[0060] Example 3:

[0061] In this embodiment, there are two components of magnetocaloric materials, component 1 and component 2, with molecular formulas of Ni 37.5 Co 12.5 Mn 35 Ti 15 and Ni 35.5 Co 14.5 Mn 35 Ti 15 .

[0062] The continuous gradient magnetocaloric material of the above composition and the additive preparation method thereof include the following steps:

[0063] (1) According to the molecular formula Ni 37.5 Cp 12.5 Mn 35 Ti 15 and Ni 35.5 Co 14.5 Mn 35 Ti 15Prepare raw materials, which are commercially available metals Ni, Co, Mn, and Ti with a purity higher than 99.9 wt.%, wherein Mn is added in excess at an atomic ratio of 5% to compensate for its volatilization and burning loss during the preparation process;

[0064] (2) Using vacuum induction atomization, the prepared raw materials are placed in a crucible, the melting furnace is vacuumed and argon is introduced for melting protection and atomization, the atomization pressure is 4MPa, and Ni with a particle size range of 0 to 150μm is obtained 37.5 Co 12.5 Mn 35 Ti 15 and Ni 35.5 Co 14.5 Mn 35 Ti 15 Spherical powder;

[0065] (3) The spherical powder with a particle size of no more than 150 μm obtained in step (2) is passed through a 270-mesh sieve to obtain a spherical powder with a particle size of no more than 53 μm. The powder with a particle size of no more than 15 μm is separated by gravity and microgravity, and only Ni particles with a particle size of 15 to 53 μm that meet the printing requirements are left. 37.5 Co 12.5 Mn 35 Ti 15 and Ni 35.5 Co 14.5 Mn 35 Ti 15 Spherical powder.

[0066] (4) Press Figure 2 The gradient powder spreading method shown in the figure spreads the powders of component 1 and component 2 in the 3D printer hopper, and then obtains Ni by continuous 3D printing. 37.5 Co 12.5 Mn 35 Ti 15 / Ni 35.5 Co 14.5 Mn 35 Ti 15 For uniform gradient cast samples, the power is 150-300 W, the layer thickness is 20-40 μm, the scanning speed is 450-1800 mm / s, and the scanning interval is 45-90 μm.

[0067] (5) Ni obtained in step (4) 37.5 Co 12.5 Mn 35 Ti 15 / Ni 35.5 Co 14.5 Mn 35 Ti 15The uniform gradient cast sample was annealed under inert gas protection at 800-1000℃ for 2-36h and quenched in liquid nitrogen or ice water to obtain Ni with a gradient structure of martensite and austenite. 37.5 Co 12.5 Mn 35 Ti 15 / Ni 35.5 Co 14.5 Mn 35 Ti 15 Uniform gradient annealing samples.

[0068] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a continuous gradient magnetocaloric material, characterized in that: include: Step S1, preparing raw materials according to the chemical formulas of material A and material B with different compositions; Step S2: preparing the raw materials of material A and material B into powders of material A and material B respectively by induction atomization; Step S3: Gradient spreading of materials A and B. Gradient spreading of materials A and B is performed along the diagonal direction of the rectangle without mixing. After gradient spreading, materials A and B are mixed along the side direction of the rectangle. Step S4, preparing the material A and material B powders into a cast gradient sample by 3D printing; Step S5: annealing the as-cast gradient sample to obtain a continuous gradient magnetocaloric material with uniform structure; the annealing temperature is 700-1500° C., the time is 2 hours to 15 days, and the material is cooled by liquid nitrogen or ice water; wherein material A is selected from magnetocaloric materials, and material B is selected from magnetocaloric materials or non-magnetocaloric materials; When material A and material B are both selected from magnetocaloric materials, material A and material B are selected from the same magnetocaloric material; The magnetocaloric material is selected from one of Gd-Si-Ge, La-Fe-Si, (Mn, Fe)2(P, Si / Ge), Mn-based Heusler alloy, Mn-Co-Ge and perovskite oxide; the non-magnetocaloric material is transition metal Fe.

2. The method according to claim 1, characterized in that The chemical formula of La-Fe-Si is (La 1-x R x )(Fe 13-y- z Mn y Si z ), where R is a rare earth element, where x ranges from 0 to 0.3, y ranges from 0 to 1, and z ranges from 1 to 2; the phase transition temperature of the prepared continuous gradient magnetocaloric material changes continuously from one end to the other, and the temperature change range is 100~400K.

3. The method according to claim 2, characterized in that The R elements are selected as Ce, Pr, and Nd.

4. The method according to claim 1, wherein The chemical formula of Mn-based Heusler alloy is Ni 50-m Co m Mn 50- n Ti n , where m and n range from 10-20; the phase transition temperature of the prepared continuous gradient magnetocaloric material changes continuously from one end to the other, and the temperature change range is 100~400K.

5. The method according to claim 1, wherein The chemical formula of Gd-Si-Ge is Gd5(Si 1-x Ge x )4, where x ranges from 0 to 1; the phase transition temperature of the prepared continuous gradient magnetocaloric material changes continuously from one end to the other, and the temperature range is 30~280 K.

6. The method according to claim 1, characterized in that The chemical formula of (Mn, Fe)2(P, Si / Ge) is (Mn 1-x Fe x )2(P 1-y B y ), where B is Si or Ge, and the range of x and y is 0-1; the phase transition temperature of the prepared continuous gradient magnetocaloric material changes continuously from one end to the other, and the temperature change range is 150~350 K.

7. The method according to claim 1, characterized in that The chemical formula of Mn-Co-Ge is (Mn 1-x M x )(Co 1-y M′ y )(Ge 1-z X z ), where M and M′ are transition metal elements, X is a main group element, and the range of x, y, and z is 0-1; the phase transition temperature of the prepared continuous gradient magnetocaloric material changes continuously from one end to the other, and the temperature change range is 150~450 K.

8. The method according to claim 7, characterized in that M and M' are Mn, Fe, Co, and Ni elements; X is Si, Ge, Al, and Ga elements.

9. The method according to claim 1, characterized in that The chemical formula of perovskite oxide is (R 1-x A x )MnO3, where R is a rare earth element, A is a divalent metal element, and x ranges from 0 to 1; the phase transition temperature of the prepared continuous gradient magnetocaloric material changes continuously from one end to the other, and the temperature change range is 100~350 K.

10. The method according to claim 9, characterized in that R is selected from La, Ce, Pr, and Nd elements; A is selected from Ca, Ba, and Sr elements.

11. The method according to claim 1, wherein In step S1, when preparing the raw materials, if material A and material B contain rare earth elements, Mn or Si, the rare earth elements, Mn or Si are added in excess at an atomic ratio of 1% to 10%; In step S2, the atomization pressure of the induction atomization is 2-10 MPa, and the powder after the induction atomization is sieved to select powder with a particle size range of 5-100 μm; In step S5, the annealing treatment time is 2 hours to 36 hours.

12. Application of the continuous gradient magnetocaloric material prepared by the method according to any one of claims 1 to 11 in the field of refrigeration.

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