Wide-temperature-range large magnetic entropy lanthanum-iron-silicon-based room-temperature magnetic refrigeration material and preparation method thereof

Abstract

The application discloses a preparation method of a wide-temperature-range large-magnetic-entropy lanthanum-iron-silicon-based room-temperature magnetic refrigeration material, which uses La, Fe, Co and Si powders as raw materials, and prepares the wide-temperature-range large-magnetic-entropy lanthanum-iron-silicon-based room-temperature magnetic refrigeration material through high-energy ball milling of the raw materials under a protective atmosphere, and then through pressing and annealing heat treatment. The high-energy ball milling-annealing method for preparing the lanthanum-iron-silicon-based room-temperature magnetic refrigeration material has the advantages that the obtained lanthanum-iron-silicon-based room-temperature magnetic refrigeration material has a Curie temperature in a room-temperature range, a wide working temperature range and excellent magnetic heat performance, can provide a new idea for preparation of high-performance lanthanum-iron-silicon-based room-temperature magnetic refrigeration material, and has the advantages of simple preparation process, low cost, low requirement on reaction equipment and suitability for popularization and application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetic refrigeration materials, and particularly relates to a wide-temperature-range large-magnetic-entropy lanthanum-iron-silicon-based room-temperature magnetic refrigeration material and a preparation method thereof. BACKGROUND

[0002] Traditional vapor compression refrigeration is the most mature refrigeration technology at present, and has been widely applied to refrigeration equipment such as refrigerators and air conditioners. However, this technology must use fluorine-containing refrigerants which are harmful to the atmosphere. Therefore, it is urgent to explore new refrigeration technologies which are environmentally friendly and energy efficient.

[0003] Magnetic refrigeration is a new type of refrigeration technology which uses magnetic materials with a magneto-caloric effect as refrigeration working medium. It has the advantages of green environmental protection, high energy efficiency and stability, and is a technology which has the potential to replace traditional compressor refrigeration. Gd is a second-order phase transition material which has been widely concerned due to its large magnetic entropy at low field, room-temperature Curie point and wide working temperature range. However, it is difficult to realize commercial application due to its high price and easy oxidation. It is necessary to find materials in other material systems which have equivalent magnetic thermal properties to Gd, such as MnFe(P 1-x As x ), Gd5(Si x Ge 1-x )4, Heusler alloy and La(Fe,Si) 13 alloy, etc. Among them, the La(Fe,Si) 13 alloy system is considered to be the most promising material to replace Gd and be applied to room-temperature magnetic refrigeration technology due to its excellent magneto-caloric effect and non-toxic and environmentally friendly and low-cost constituent elements. However, its ferromagnetic-paramagnetic phase transition can be completed in a very narrow temperature range, which limits its further application. Therefore, it is of great significance to find a preparation method which can make the La(Fe,Si) 13 alloy have a wide magnetic refrigeration working temperature range, high magnetic entropy change and low driving magnetic field.

[0004] Due to the complexity of the NaZn 13 structure of the functional phase La(Fe,Si) 13 phase and the many factors affecting the peritectic reaction during phase formation, the conventional preparation method (such as arc melting and vacuum induction melting) needs to be high-temperature annealed for up to one month to obtain more functional phases. The high-energy ball milling method can greatly shorten the annealing time, reduce energy consumption and ensure the uniformity and stability of the composition and performance of the obtained product after annealing. However, high ball-to-material ratio and high rotation speed in the conventional method can easily cause the material to form cold welding, and cannot truly broaden the La(Fe,Si) 13The purpose of the alloy working temperature zone. Therefore, it has important research and application significance to further explore the preparation method of the lanthanum-iron-silicon-based room-temperature refrigeration material which has the advantages of simple preparation process, low requirement for production equipment, batch preparation and wide magnetic refrigeration working temperature zone. SUMMARY

[0005] The main purpose of the present application is to overcome the shortcomings of the prior art, and provide a preparation method of a wide-temperature-range large-magnetic-entropy lanthanum-iron-silicon-based room-temperature magnetic refrigeration material. The method has simple equipment requirements, low cost, and low technical requirements for operators, and can lay a good foundation for the large-scale preparation and large-scale application of high-performance lanthanum-iron-silicon-based materials.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0007] A preparation method of a wide-temperature-range large-magnetic-entropy lanthanum-iron-silicon-based room-temperature magnetic refrigeration material, which uses La, Fe, Co and Si powders as raw materials, and performs high-energy ball milling on the raw materials under a protective atmosphere, and then performs pressing and annealing heat treatment to prepare the wide-temperature-range large-magnetic-entropy lanthanum-iron-silicon-based room-temperature magnetic refrigeration material.

[0008] In the above scheme, the La 1+z Fe 13-x-y Co x Si y , wherein 0.88≤x≤1.06, 0.8≤y≤1.4, 0≤z≤0.8.

[0009] Preferably, 0.94≤x≤1.02.

[0010] Preferably, 1.0≤y≤1.2.

[0011] Preferably, 0.2≤z≤0.4.

[0012] In the above scheme, the batch preparation method is performed under a protective atmosphere, and specifically includes the following steps:

[0013] 1) Using La powder, Fe powder, Co powder and Si powder as raw materials, and weighing the raw materials according to the stoichiometric ratio of the lanthanum-iron-silicon-based magnetic refrigeration material;

[0014] 2) High-energy ball milling the weighed raw materials to prepare intermetallic compound powder;

[0015] 3) The intermetallic compound powder obtained in step 2) is pressed into a tablet, the pressure is 10-50 MPa, and the pressure holding time is 3-10 min;

[0016] 4) The sample obtained in step 3) is packaged in a quartz tube and subjected to annealing heat treatment and quenching to obtain the lanthanum-iron-silicon-based magnetic refrigeration material.

[0017] In the above scheme, the La powder, Fe powder, Co powder and Si powder are all milled with high purity, and the purity is above 99.5wt.%.

[0018] In the above scheme, the anaerobic condition is a vacuum condition or an inert gas protection condition.

[0019] In the above scheme, the vacuum degree used in the vacuum condition is 1x10 -4 Pa or below; the inert gas can be N2 or Ar gas, etc.

[0020] Further, the purity of the inert gas is above 99.9%.

[0021] In the above scheme, the material of the milling ball used in the high-energy ball milling step is zirconia, tungsten carbide or stainless steel; and the ball-to-material ratio is (20-40):1.

[0022] Preferably, the shaped sample obtained in step 3) is further wrapped with a tantalum foil or a molybdenum foil so as not to directly contact with the quartz tube.

[0023] Preferably, in step 4), a layer of refractory cotton is first laid at the bottom of the quartz tube, which effectively prevents the reaction between La and the quartz tube, thus avoiding the damage of the quartz tube during high-temperature service and affecting the atmosphere condition in the tube.

[0024] In the above scheme, the annealing heat treatment step comprises: first, increasing the temperature from room temperature to 553-593K at a rate of 3-8K / min, then increasing the temperature to 753-793K at a rate of 1-2.5K / min and keeping the temperature for 20-40min, and finally increasing the temperature to 1023-1423K at a rate of 3-8K / min, and the annealing time is 10-20d.

[0025] In the above scheme, the annealed sample is quenched in ice water.

[0026] The lanthanum-iron-silicon-based magnetic refrigeration material prepared according to the above scheme is characterized in that the Curie temperature is in the room temperature range, the maximum magnetic entropy change value under a 2T applied magnetic field is not less than 3.50J·kg -1 ·K -1 , and the full width at half maximum of the entropy change curve is not less than 34.0K.

[0027] Based on the above content, without departing from the basic technical idea of the present application, according to the ordinary technical knowledge and means in the art, the content can also be modified, replaced or changed in various forms.

[0028] The application discloses a batch method of a wide-temperature-range large magnetic entropy lanthanum-iron-silicon-based room-temperature magnetic refrigeration material for the first time, and a lanthanum-iron-silicon-based room-temperature magnetic refrigeration material with uniform composition and stable performance is prepared by a high-energy ball milling-annealing method; first, a step-by-step ball milling method is adopted to effectively prevent problems caused by cold welding in a traditional high-energy ball milling process, the powder yield of the ball milling is greatly improved under the condition that no grinding aid is added, and the powder caking phenomenon caused by cold welding is effectively prevented; further, an annealing process with a gradient temperature rising system is adopted, so that internal stress formed in the ball milling process is fully released, problems such as material deformation or cracking during quenching are effectively prevented, and the main phase is formed; the lanthanum-iron-silicon-based room-temperature refrigeration material has a Curie temperature in the room-temperature range, and can exhibit a wide working temperature range and excellent magnetic heat performance.

[0029] Compared with the prior art, the application has the beneficial effects that:

[0030] 1) The application discloses a preparation method of a wide-temperature-range large magnetic entropy lanthanum-iron-silicon-based room-temperature refrigeration material for the first time, and the lanthanum-iron-silicon-based room-temperature magnetic refrigeration material is prepared by a high-energy ball milling-annealing method; the preparation process is simple, the cost is relatively low, and the requirement for a reaction equipment is not high, so that a good foundation is laid for large-scale preparation and large-scale application of the lanthanum-iron-silicon-based material.

[0031] 2) The lanthanum-iron-silicon-based room-temperature refrigeration material prepared by the application has a Curie temperature in the room-temperature range, a wide working temperature range and excellent magnetic heat performance, and can provide a new idea for preparation of a high-performance lanthanum-iron-silicon-based room-temperature magnetic refrigeration material. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The XRD patterns of the products obtained in the application comparative example 1, the application comparative example 2, the application example 1 and the application example 2 at room temperature are shown in the following table.

[0033] Figure 2 The backscattered electron composition contrast images (hereinafter referred to as BSE images) of the products obtained in the application example 1 and the application example 2 are shown in the following table.

[0034] Figure 3 The magnetic entropy change-temperature curves of the products obtained in the application comparative examples 1-2 and the application examples 1-3 under a 2T applied magnetic field are shown in the following table. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the application, and are not used to limit the application.

[0036] In the following examples, the purity of the La powder is 99.5wt.%, and the purity of the Co powder, the Fe powder and the Si powder is 99.9wt.%.

[0037] X-ray diffraction spectra were collected using a powder X-ray diffractometer, which uses Cu Kα1 characteristic X-rays with a wavelength of 1.5406 A to test the material.

[0038] Microstructure characterization chemical composition analysis was performed using a JEOL JXA-8100 type electron probe microanalysis (EPMA) at 20 kV.

[0039] The magnetization curve (M-H curve) and the thermomagnetic curve (M-T curve) of the sample were measured using a VersaLab vibrating sample magnetometer (VSM) module (a multifunctional VSM manufactured by Quantum Design, USA). The magnetic entropy change ΔS was calculated according to the magnetization curve measured by the VSM.

[0040] Example 1

[0041] A wide-temperature-range large-magnetic-entropy lanthanum-iron-silicon-based room-temperature magnetic refrigeration material, and a preparation method thereof, the preparation method comprising the following steps:

[0042] 1) raw materials were prepared according to the stoichiometric formula of La 1.4 Fe 10.82 Co 0.98 Si 1.2 , and the total weight of the raw material powder was 8 g; the prepared raw materials were loaded into a stainless steel ball mill jar;

[0043] 2) the obtained ball mill jar containing the raw materials was installed on a planetary ball mill, the ball mill jar was made of stainless steel, the ball-to-material ratio was 30:1, and the specific ball milling steps were as follows: in an argon atmosphere, the raw materials were first ball milled at a speed of 500 rpm for 12 h, and every 1.5 h, the ball milling was stopped for 10 min; after the ball milling, the powder was scraped from the jar wall, and then the powder was ball milled at a speed of 200 rpm for 60 min;

[0044] After the ball milling, the powder in the ball mill jar was taken out under the protection of an argon atmosphere, and the powder was pressed into a tablet under the protection of an argon atmosphere, the pressure was 30 MPa, and the time was 5 min;

[0045] 3) a layer of refractory cotton was laid at the bottom of a quartz tube, the tablet sample obtained in step 2) was wrapped with a tantalum foil, and then the tablet sample was placed in the quartz tube, the quartz tube was vacuumized to 1×10 -4 Pa, and the quartz tube was sealed;

[0046] 4) the sealed quartz tube in step 3) was placed in a muffle furnace for annealing heat treatment, and the specific steps included: the temperature was raised to 573 K at a rate of 5 K / min from room temperature, then the temperature was raised to 773 K at a rate of 2 K / min and was kept for 30 min, and finally the temperature was raised to 1323 K at a rate of 5 K / min, the annealing time was 12 d; the final product (La​1.4 Fe 10.82 Co 0.98 Si 1.2 )。

[0047] The phase and microstructure of the product obtained in the example are analyzed as follows:

[0048] The XRD pattern of the product obtained at room temperature is measured by using a Cu target X-ray diffractometer, as shown in the following figure: Figure 1 The main phase is 1:13 phase, and contains a small amount of α-Fe phase and La2O3. The microstructure of the product obtained is analyzed by using EPMA at 20 kV, and the BSE image is shown in the following figure: Figure 2 Combining the EDS and phase analysis results, it can be determined that the compositions of the black, gray and white contrasts are α-Fe phase, 1:13 phase and La2O3 phase, respectively.

[0049] The performance test of the product obtained in the example is as follows:

[0050] The isothermal magnetization curve of the product obtained is measured by using VSM, and the isothermal magnetic entropy change curve of the product obtained is calculated according to the relationship formula of Maxwell equation: As shown in the following figure: Figure 3 The Curie temperature of the product obtained is 300 K, the magnetic entropy change is 4.00 J·kg -1 ·K -1 , and the working temperature range is 34.5 K. According to the calculation formula of relative cooling capacity (RCP), RCP = -ΔS M ·δ FWHM , the relative cooling capacity of the product obtained is 138.0 J·kg -1 .

[0051] Example 2

[0052] A preparation method of a wide-temperature-range large-magnetic-entropy lanthanum-iron-silicon-based room-temperature magnetic refrigeration material, the specific steps are as follows:

[0053] 1) The raw materials are prepared according to the stoichiometric formula of La 1.4 Fe 10.86 Co 0.94 Si 1.2 , the total weight of the raw material powder is 8 g, and the prepared raw materials are loaded into a stainless steel ball mill jar;

[0054] 2) The ball mill jar loaded with the raw materials is installed on a planetary ball mill, the ball material is stainless steel ball, and the ball-to-material ratio is 30:1, and the specific ball milling steps are as follows: in an argon atmosphere, first ball mill at a speed of 500 rpm for 12 h, and stop every 1.5 h for 10 min, then scrape the powder from the jar wall, and then ball mill at a speed of 200 rpm for 60 min;

[0055] After the ball milling, the powder in the ball milling tank was taken out under the protection of argon atmosphere, and the powder was pressed into a tablet under the protection of argon atmosphere, the pressure was 30 MPa, and the time was 5 min;

[0056] 3) A layer of refractory cotton was laid at the bottom of the quartz tube, and the sample after molding in step 2) was wrapped with a tantalum foil and then placed in the quartz tube, which was vacuumized to 1x10 -4 Pa, and the quartz tube was sealed;

[0057] 4) The sealed quartz tube in step 3) was placed in a muffle furnace for annealing heat treatment, and the specific steps included: heating from room temperature to 573 K at a rate of 5 K / min, then heating to 773 K at a rate of 2 K / min and keeping for 30 min, and finally heating to 1323 K at a rate of 5 K / min, and the annealing time was 12 d; quenching in ice water to obtain the final product (La 1.4 Fe 10.86 Co 0.94 Si 1.2 ).

[0058] The phase and microstructure analysis of the product obtained in this example are as follows:

[0059] The room temperature XRD pattern of the product obtained was determined by using a Cu target X-ray diffractometer, as shown in Figure 1 , the main phase was 1:13 phase, and a small amount of α-Fe phase and La2O3 was contained. The microstructure of the product obtained was characterized by EPMA at 20 kV, and the BSE image is shown in Figure 2 , combined with the EDS and phase analysis results, it can be determined that the compositions of the black, gray and white three contrasts are α-Fe phase, 1:13 phase and La2O3 phase respectively.

[0060] The performance test of the product obtained in this example is as follows:

[0061] The isothermal magnetization curve of the sample was measured by using VSM, and the isothermal magnetic entropy change curve of the sample was calculated according to the relationship formula of Maxwell equation , as shown in Figure 3 , the Curie temperature of the product obtained was 298 K, the magnetic entropy change was 3.63 J·kg -1 ·K -1 , and the working temperature range was 35.9 K. According to the calculation formula of relative refrigeration capacity (RCP), RCP=-ΔS M ·δ FWHM , the relative refrigeration capacity of the product obtained was 130.3 J·kg -1 .

[0062] Example 3

[0063] A wide-temperature-range large magnetic entropy lanthanum-iron-silicon-based room-temperature magnetic refrigeration material, and a preparation method thereof, the method comprising the following steps:

[0064] 1) according to the stoichiometric formula of La 1.2 Fe 10.82 Co 0.98 Si 1.2 , raw materials are configured under the protection of an argon atmosphere, the total weight of the raw material powder is 20 g, and the configured raw materials are loaded into a stainless steel ball mill tank;

[0065] 2) the obtained ball mill tank loaded with the raw materials is installed on a planetary ball mill, the ball mill tank is made of stainless steel, the ball-to-material ratio is 30:1, and the specific ball milling steps are as follows: in an argon atmosphere, the raw materials are first ball milled at a speed of 500 rpm for 12 h, wherein the raw materials are stopped every 1.5 h for 10 min, after the ball milling is completed, the powder is scraped from the tank wall, and then the powder is ball milled at a speed of 200 rpm for 60 min;

[0066] After the ball milling is completed, the powder in the ball mill tank is taken out under the protection of an argon atmosphere, and the powder is pressed into a tablet under the protection of an argon atmosphere, the pressure is 30 MPa, and the time is 5 min;

[0067] 3) a layer of fire-resistant cotton is laid at the bottom of a quartz tube, the sample after the shaping in step 2) is wrapped with a tantalum foil and then placed in the quartz tube, the quartz tube is vacuumized to 1x10 -4 Pa, and the quartz tube is sealed;

[0068] 4) the sealed quartz tube in step 3) is placed in a muffle furnace for annealing heat treatment, and the specific steps include: the temperature is raised to 573 K at a rate of 5 K / min from room temperature, then the temperature is raised to 773 K at a rate of 2 K / min and is kept for 30 min, finally the temperature is raised to 1323 K at a rate of 5 K / min, the annealing time is 12 d, and the sample is quenched in ice water to obtain a final product (La 1.2 Fe 10.82 Co 0.98 Si 1.2 ).

[0069] The performance of the product obtained in the example is tested as follows:

[0070] The isothermal magnetization curve of the sample is measured by using VSM, and the isothermal magnetic entropy change curve of the sample is calculated according to the relationship formula of Maxwell equation , as shown in Figure 3 , the Curie temperature of the obtained product is 302 K, the magnetic entropy change is 3.68 J·kg -1 ·K -1 , and the working temperature range is 35.5 K. According to the calculation formula of relative refrigeration capacity (RCP), RCP=-ΔS M ·δ FWHM , the relative refrigeration capacity of the obtained product is 130.6 J·kg-1 .

[0071] Reducing the amount of rare earth elements can further reduce the cost, i.e. reducing z = 0.4 in Example 1 to z = 0.2 and using the process of the present application to prepare in bulk, the resulting product still has a room temperature region and has a relative cooling capacity comparable to that prepared in small amount, indicating that the present application can be used to prepare in bulk.

[0072] Comparative Example 1

[0073] A preparation method of a lanthanum-iron-silicon-based room temperature magnetic refrigeration material, the specific steps are as follows:

[0074] 1) According to La 1.4 Fe 10.82 Co 0.98 Si 1.2 The stoichiometric formula is configured under the protection of argon atmosphere, and the total weight of the raw material powder is 8g; the prepared raw material is loaded into a stainless steel ball mill jar;

[0075] 2) The obtained ball mill jar containing raw materials is installed on a planetary ball mill, and the ball milling speed is set to 500rpm for 13h; the ball milling speed is stainless steel ball, and the ball to material ratio is 30:1;

[0076] After ball milling, the powder in the ball mill jar is taken out under the protection of argon atmosphere, and the powder is pressed into a tablet under the protection of argon atmosphere, the pressure is 30MPa, and the time is 5min;

[0077] 3) A layer of refractory cotton is laid at the bottom of the quartz tube, and the sample formed in step 2) is wrapped with tantalum foil and placed in the quartz tube, vacuumed to 1×10 -4 Pa, and the quartz tube is sealed;

[0078] 4) The sealed quartz tube of step 3) is placed in a muffle furnace for annealing heat treatment, the specific steps include: heating from room temperature to 573K at a rate of 5K / min, then heating to 773K at a rate of 2K / min and keeping for 30min, finally heating to 1323K at a rate of 5K / min, and the annealing time is 12d; quenching in ice water, obtaining the final product (La 1.4 Fe 10.82 Co 0.98 Si 1.2 ).

[0079] The obtained product is subjected to phase analysis, as shown in Figure 1 , the obtained product contains a large amount of impurities including La2O3 phase and unreacted α-Fe phase in addition to 1:13 phase.

[0080] The isothermal magnetization curve of the sample is measured by VSM, and the relationship formula of Maxwell equation is The isothermal magnetic entropy change curve of the sample was calculated, as shown in Figure 3 The Curie temperature of the obtained product was 296K, the magnetic entropy change was 2.80J·kg -1 ·K -1 , and the working temperature range was 24.0K. The relative cooling power (RCP) of the obtained product was calculated by the formula RCP = -ΔS M ·δ FWHM , and the relative cooling power was 67.2J·kg -1 .

[0081] Comparative Example 2

[0082] A preparation method of a lanthanum-iron-silicon-based room-temperature magnetic refrigeration material, the specific steps are as follows:

[0083] 1) The raw materials were prepared according to the stoichiometric formula of La 1.4 Fe 10.82 Co 0.98 Si 1.2 , and the total weight of the raw material powder was 8g; the prepared raw materials were loaded into a stainless steel ball mill jar;

[0084] 2) The obtained ball mill jar containing raw materials was installed on a planetary ball mill, the ball material was stainless steel ball, and the ball-to-material ratio was 30:1, and the specific ball milling steps were as follows: in argon, first ball milling at a speed of 500rpm for 12h, stopping every 1.5h for 10min, after ball milling, the powder was scraped from the jar wall, and then ball milling at 200rpm for 60min;

[0085] After ball milling, the powder in the ball mill jar was taken out under argon atmosphere, and the powder was pressed into a tablet under argon atmosphere, the pressure was 30MPa, and the time was 5min;

[0086] 3) A layer of refractory cotton was laid at the bottom of the quartz tube, the sample after forming in step 2) was wrapped with tantalum foil and placed in the quartz tube, vacuumed to 1×10 -4 Pa, and the quartz tube was sealed;

[0087] 4) The sealed quartz tube of step 3) was placed in a muffle furnace for annealing heat treatment, the specific steps included: heating from room temperature to 1323K at a rate of 5K / min, and the annealing time was 12d; quenching in ice water, and the final product (La 1.4 Fe 10.82 Co 0.98 Si 1.2 ) was obtained.

[0088] The isothermal magnetization curve of the sample was measured by VSM, and the isothermal magnetic entropy change curve of the sample was calculated according to the relationship formula of Maxwell equation , as shown in Figure 3As shown, the Curie temperature of the obtained product is 301 K, and the magnetic entropy change is 3.50 J·kg -1 ·K -1 , and the working temperature range is 36.3 K. According to the calculation formula of relative refrigeration capacity (RCP), RCP = -ΔS M ·δ FWHM , the relative refrigeration capacity of the obtained product is 127.1 J·kg -1 .

[0089] The above examples are only examples for clearly illustrating the present application, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can also be made by those skilled in the art, and here it is not necessary or impossible to exhaust all the embodiments, and the obvious changes or variations still fall within the protection scope of the present application.

Claims

1. A method for preparing a wide-temperature-range large-magnetic-entropy La-Fe-Si-based room-temperature magnetic refrigeration material, characterized in that, La, Fe, Co, Si powders are used as raw materials, and the raw materials are subjected to high-energy ball milling under a protective atmosphere, followed by pressing and annealing heat treatment; The stoichiometric formula of the lanthanum-iron-silicon-based room-temperature magnetic refrigeration material is La 1+z Fe 13-x-y Co x Si y , wherein 0.88≤x≤1.06, 0.8≤y≤1.4, 0≤z≤0.8; The high-energy ball milling step comprises: firstly, ball milling at a speed of 300-600 rpm for 10-24 h, wherein it is stopped for 5-20 min every 1-2 h; then, the powder is scraped from the tank wall, and finally, ball milling at a speed of 50-250 rpm for 30-90 min.

2. The production method according to claim 1, characterized by, The preparation method is carried out under a protective atmosphere, and specifically comprises the following steps: 1) La powder, Fe powder, Co powder and Si powder are used as raw materials, and the raw materials are weighed according to the stoichiometric ratio of the lanthanum-iron-silicon-based room-temperature magnetic refrigeration material; 2) The weighed raw materials are subjected to high-energy ball milling to prepare intermetallic compound powder; 3) The intermetallic compound powder obtained in step 2) is pressed into a tablet for molding; 4) The sample obtained in step 3) is packaged in a quartz tube, and subjected to annealing heat treatment and quenching to obtain the lanthanum-iron-silicon-based room-temperature magnetic refrigeration material.

3. The preparation method according to claim 2, characterized in that, The protective atmosphere is a vacuum condition or an inert gas protection condition.

4. The preparation method according to claim 2, characterized in that, The high-energy ball milling is carried out under a protective atmosphere, and the ball-to-material ratio used is (20-40):

1.

5. The preparation method according to claim 2, characterized in that, The pressure used in the tablet molding step is 10-50 MPa, and the pressure holding time is 3-10 min.

6. The preparation method according to claim 2, characterized in that, The molded sample obtained in step 3) is further sealed and wrapped with a tantalum foil or a molybdenum foil.

7. The preparation method according to claim 2, characterized in that, The annealing heat treatment step comprises: firstly, increasing the temperature from room temperature to 553-593 K at a rate of 3-8 K / min, then increasing the temperature to 753-793 K at a rate of 1-2.5 K / min and maintaining for 20-40 min, and finally, increasing the temperature to 1023-1423 K at a rate of 3-8 K / min, and the annealing time is 10-20 d.

8. The lanthanum-iron-silicon-based magnetic refrigeration material produced by the production method according to any one of claims 1 to 7, characterized in that The Curie temperature is in the room temperature region, and the maximum magnetic entropy change value is not less than 3.50 J·kg -1 ·K -1 under the external magnetic field of 2T. The full width at half maximum of the entropy change curve is not less than 34.0 K.

Images