A seven-membered high-entropy oxide with an equimolar ratio and a preparation process thereof

Abstract

The application belongs to the field of inorganic non-metallic material synthesis, and particularly relates to an equimolar ratio seven-element high-entropy oxide and a preparation process thereof. The preparation process comprises the following steps: seven oxide powders Al2O3, Y2O3, TiO2, ZrO2, NiO, CuO and CeO2 are put into a ball mill tank according to a molar ratio of 1:1:2:2:2:2:2, and anhydrous ethanol and zirconium oxide grinding balls are added, ball milling is carried out in a ball mill, and after the ball milling is completed, the mixture is fully dried, sieved, and a mixed powder is obtained; the mixed powder is subjected to tabletting treatment, and a green body to be fired is obtained; the green body to be fired is placed in an alumina crucible and put into a microwave oven for microwave sintering. The application obtains an equimolar ratio seven-element high-entropy oxide (AlYTiZrNiCuCe)Ox with good solid solution, improves the crystallinity and element uniformity of the seven-element high-entropy oxide, and fully reacts various raw materials, while the process is high in efficiency and low in energy consumption.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of inorganic non-metallic material synthesis, and particularly relates to an equimolar ratio seven-membered high-entropy oxide and a preparation process thereof. BACKGROUND

[0002] As an important branch of new ceramic materials, high-entropy oxides have many advantages such as good thermal stability, high hardness and excellent catalytic performance, and exhibit excellent performance in the fields of catalysis, energy storage and high-temperature protection. At present, the preparation method of high-entropy oxides mainly relies on high-energy consumption heating methods such as muffle furnace, hot-pressing sintering and spark plasma sintering. These traditional preparation methods mainly rely on the mode of heat conduction to realize the preparation of products, which usually requires heating at a high temperature of 1600℃ or above for a long time of not less than 1h. There are still certain limitations in efficiency, energy consumption and product purity, such as high energy consumption, low process efficiency, grain coarsening and element segregation. Microwave sintering technology can take advantage of the penetration ability of microwaves to generate heat by the vibration and friction of atoms in the microwave field, and has the characteristics of high efficiency, energy saving and no thermal gradient. It is mainly applied in binary or ternary systems, and the research on five or more multi-element systems is less. There is no report on equimolar ratio seven-membered high-entropy oxides containing rare earth elements.

[0003] A Chinese invention patent application with the publication number CN116789186A discloses a uniform (ZrTiCoNiNb)O high-entropy oxide powder and a preparation method and application thereof. The (ZrTiCoNiNb)O high-entropy oxide powder is prepared according to the following steps: uniformly ball-milling ZrO2, TiO2, CoO, NiO and Nb2O5 to obtain a raw material mixed powder; loading the raw material mixed powder into a crucible, introducing a temperature field adjusting mechanism, and performing microwave treatment, thereby obtaining a (ZrTiCoNiNb)O high-entropy oxide ceramic powder material. Based on the characteristics of microwave heating, the application introduces a SiC rod to adjust the sample temperature field in the microwave heating and holding structure, so as to obtain a uniform and stable high-entropy oxide ceramic powder by microwave heating. The sintering process is short, fast, environmentally friendly and efficient, and has a good application prospect. However, the XRD detection curve analysis of the patent shows that the prepared powder has strong ZrO2 raw material diffraction peaks, indicating that a large amount of ZrO2 raw material cannot effectively react by the technology, and the purity of the high-entropy oxide target product is low.

[0004] In the seven-membered system, rare earth ions (such as Y 3+ / Ce 4+) radius difference, high temperature diffusion rate mismatch caused by composition segregation and difficult to achieve effective solid solution of elements. Ultra-dense dislocations stabilized in highentropy oxide ceramics (Nature Communications, 2022, 13:2871) studies show that high-entropy oxides synthesized by traditional methods have ultra-dense dislocation structures, but the element distribution uniformity is insufficient. The Chinese invention patent application with publication number CN118290129A discloses a kind of high-entropy oxide ceramic and its preparation method, Al2O3 powder, ZrO2 powder, NiO powder, TiO2 powder, CuO powder, Y2O3 powder and CeO2 powder with a molar ratio of 0.4:0.1:0.1:0.1:0.1:0.1:0.1~0.4 are ball milled and mixed to obtain a mixed powder;The mixed powder is dried, ground and sieved, and then molded under 30~70MPa to obtain a blank;The blank is subjected to microwave sintering at 1150~1350℃ to obtain a high-entropy oxide ceramic. The high-entropy oxide ceramic prepared by the invention has high hardness and density, as well as good fracture toughness. However, the XRD detection results of the sample prepared by the invention show that the seven metal atoms are not solid-solubilized at the same sublattice position, and the sample prepared by the technology does not exist Seven high-entropy oxide phase composition, not seven high-entropy oxide, but a mixture of Y3Al2(AlO4)3, (Y,Ce)(Nb,Ti)2O6 and Al4Ni 15 Ta three compounds;In addition, the molar content of Al2O3 without wave absorption capacity must be 36% or more, while the molar content of NiO and TiO2 with wave absorption capacity is only about 9%, which greatly weakens the wave absorption capacity of the mixed raw materials, reduces the thermal conductivity effect of the wave absorption material composition on the whole mixed raw materials, significantly increases the microwave input power, and further increases the energy consumption. SUMMARY

[0005] To overcome the shortcomings of the existing method, the present application provides a kind of equal molar ratio seven high-entropy oxide and its preparation process, obtains solid solution good equal molar ratio seven high-entropy oxide (AlYTiZrNiCuCe) Ox, fills the research blank of equal molar ratio seven high-entropy oxide, improves the crystallinity and element uniformity of seven high-entropy oxide, various raw materials are completely reacted, and the problems of low process efficiency and high energy consumption in the prior art preparation method are overcome.

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

[0007] A preparation process of an equal molar ratio seven high-entropy oxide, comprising the following steps:

[0008] S1, seven oxide powders Al2O3, Y2O3, TiO2, ZrO2, NiO, CuO, CeO2 are put into a ball mill jar according to a molar ratio of 1:1:2:2:2:2:2, and anhydrous ethanol and zirconium oxide grinding balls are added, ball milling is carried out in a ball mill, after ball milling, it is dried, sieved, and a mixed powder is obtained;

[0009] S2, the mixed powder in step S1 is subjected to tabletting treatment, and a green body to be fired is obtained;

[0010] S3, the green body to be fired in step S2 is placed in an alumina crucible and subjected to microwave sintering in a microwave oven.

[0011] Preferably, the particle size of Al2O3 is 0.5-10 μm, the particle size of Y2O3 is 3-10 μm, the particle size of TiO2 is 1-10 μm, the particle size of ZrO2 is 1-10 μm, the particle size of NiO is 1-10 μm, the particle size of CuO is 3-10 μm, and the particle size of CeO2 is 1-10 μm.

[0012] Preferably, the total weight ratio of anhydrous ethanol to seven oxide powders is 2-10:1.

[0013] Preferably, the ball-to-material ratio in the ball mill jar is 2-10:1.

[0014] Preferably, the rotation speed of the ball mill is 300-500 r / min, and the ball milling time is 6-12 h.

[0015] Preferably, the tabletting pressure is 10-20 MPa, and the pressure holding time is 0.5-5 min.

[0016] Preferably, the microwave sintering is carried out at a temperature rising rate of 3-7 ℃ / min to 1200-1350 ℃, and the holding time is 45-75 min.

[0017] Preferably, the alumina crucible is subjected to drying treatment before use, and an alumina gasket is placed in the bottom of the alumina crucible in advance.

[0018] An equimolar ratio seven-membered high-entropy oxide prepared by the above preparation process, the equimolar ratio seven-membered high-entropy oxide is (AlYTiZrNiCuCe)Ox, x is in the range of 1.8-2.2.

[0019] The positive beneficial effects of the present application are:

[0020] The prior art has not prepared equimolar ratio seven-element high-entropy oxides. Chinese patent application for invention with publication number CN118290129A discloses a high-entropy oxide ceramic and a preparation method thereof, but the high-entropy oxide does not belong to a seven-element high-entropy oxide because the XRD results of phase detection show that the prepared sample does not contain any seven-element high-entropy oxide phase, but is composed of Y3Al2(AlO4)3, (Y, Ce)(Nb, Ti)2O6 and Al4Ni 15 Ta three compounds of the composition of the mixture, it is explained that the patent technology can not meet the preparation requirements of seven-element high-entropy oxide; in addition, the technology requires that the molar content of Al2O3 without wave-absorbing ability must be 36% or more, which reduces the proportion of NiO and TiO2 with wave-absorbing ability, greatly weakening the wave-absorbing ability of the mixed raw materials, which undoubtedly will reduce the heat conduction effect of the wave-absorbing material composition on the whole mixed raw materials, significantly increase the microwave input power, and further increase the energy consumption. In addition, Chinese patent application for invention with publication number CN116789186A discloses a uniform (ZrTiCoNiNb)O high-entropy oxide powder, a preparation method and application thereof, which presents a five-element high-entropy oxide, and the XRD detection spectrum disclosed by the patent shows that the prepared powder has strong diffraction peaks of ZrO2 raw material, indicating that a large amount of ZrO2 raw material cannot effectively react through the technology, the purity of the high-entropy oxide target product is low, and it is shown that the patent technology still has obvious deficiencies in the preparation of high-entropy oxides. The present application first prepares equimolar ratio seven-element high-entropy oxide (AlYTiZrNiCuCe)Ox powder, fills the research blank of equimolar ratio seven-element high-entropy oxide, and achieves the following positive and beneficial effects:

[0021] 1. Compared with traditional preparation methods such as muffle sintering, hot-press sintering and the like, the high-entropy oxide ceramic needs to be synthesized at a temperature of 1600 DEG C or even higher, and the heating time is usually not less than 1 h, the microwave heating technology of the present application can significantly reduce the sintering temperature and shorten the sintering time by utilizing the heat generated by atomic vibration friction in the microwave field, has the characteristics of fast heating rate and uniform thermal field distribution, greatly saves time cost, saves energy, realizes low carbon emission, and can realize the preparation of seven-element high-entropy oxide by pressureless sintering at 1200-1350 DEG C for 45-75 min, the seven-element high-entropy oxide prepared by the present application is cubic crystal, belongs to No. 225 Fm-3m space group, and the anisotropy of the Young's modulus, shear modulus and hardness and other indexes of the cubic crystal system is small, which can effectively improve the hardness and wear resistance of the material; and the lower sintering temperature helps to realize grain refinement and avoid grain coarsening caused by high temperature, compared with the traditional preparation at 1600 DEG C, the seven-element high-entropy oxide powder prepared by the present application has more uniform particle size distribution, the powder particle size is about 10 microns, and there is no obvious particle sintering phenomenon, the prepared powder has uniform element distribution, no obvious segregation, and higher phase purity. In addition, the present application only uses about 8% molar content of Al2O3 powder, and the molar content of NiO and TiO2 with strong wave absorption capacity is about 17%, which greatly increases the conversion ability of microwave energy to heat energy of the wave absorption raw material, thereby improving the heating speed and heat conduction capacity, so as to reduce the microwave input power, and the process efficiency is high and the energy consumption is low.

[0022] 2. In traditional heating, small-size ions often diffuse preferentially, leading to local composition segregation, the present application innovatively utilizes the unique heating effect of the microwave field, under the action of the microwave field, a high-activity environment is formed in the material, this efficient energy transfer mode injects strong power into the solid solution process of large-size cerium ions, significantly reduces the energy barrier of the diffusion and migration of large-size cerium ions and other large-size ions, greatly activates the synchronous migration and cooperative diffusion of cerium ions and other different size ions in the material, effectively drives the large-size cerium ions to overcome the space resistance, greatly improves the uniformity and efficiency of solid solution, and inhibits the generation of impurity phases, solving the problem of difficult solid solution of rare earth elements.

[0023] The rapid overall heating characteristics of microwaves can greatly shorten the residence time of the material in the high-temperature zone, and significantly inhibit the formation and growth opportunities of thermodynamic metastable impurity phases (such as cerium-rich second phases), which fundamentally solves the problem of impurity phase interference commonly seen in rare earth doped materials, and provides a powerful means for efficient and uniform solid solution of large-size rare earth ions in functional materials (such as solid electrolytes, fluorescent powders, and catalytic materials), which has important industrial value for improving the electrochemical performance, optical performance and stability of the material, and opens up a new way for the development of rare earth functional materials.

[0024] In addition, in the high-entropy ceramic phase described in the application, no raw material phase is detected, which indicates that all raw materials in the application participate in the reaction completely, and the reaction is complete, and a seven-element random seven-element solid solution occupies the same sub-lattice position, that is, a seven-element high-entropy oxide ceramic, and the purity of the prepared seven-element high-entropy oxide ceramic is higher.

[0025] 3. The larger the particle size of the raw material, the smaller the specific surface energy, the more difficult the atomic diffusion and solid solution, and the lower the price of the raw material. The material raw material adopted in the application is micron grade, which reduces the price of the raw material, solves the problem of atomic diffusion and solid solution between raw materials with large particle size, reduces the difficulty of preparation of high-entropy oxide ceramics, and promotes the market application of high-entropy oxide ceramics. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 XRD diffraction pattern of the seven-element high-entropy oxide with equal molar ratio in the application example 1-3;

[0027] Figure 2 SEM micro-morphology diagram of the seven-element high-entropy oxide with equal molar ratio in the application example 1 and 3;

[0028] Figure 3 SEM element distribution diagram of the seven-element high-entropy oxide with equal molar ratio in the application example 1;

[0029] Figure 4 SEM element distribution diagram of the seven-element high-entropy oxide with equal molar ratio in the application example 3. DETAILED DESCRIPTION

[0030] The application will be further described below in combination with some specific embodiments.

[0031] Example 1

[0032] A preparation process of an equal-molar-ratio seven-element high-entropy oxide (AlYTiZrNiCuCe)O2, comprising the following steps:

[0033] S1, seven oxide powders Al2O3, Y2O3, TiO2, ZrO2, NiO, CuO and CeO2 with purity not less than 99.9% are put into a ball mill jar according to a molar ratio of 1:1:2:2:2:2:2, wherein the particle size of Al2O3 is 0.5-10 um, the particle size of Y2O3 is 3-10 um, the particle size of TiO2 is 1-10 um, the particle size of ZrO2 is 1-10 um, the particle size of NiO is 1-10 um, the particle size of CuO is 3-10 um, and the particle size of CeO2 is 1-10 um, and anhydrous ethanol and zirconium oxide grinding balls are added, the total weight ratio of anhydrous ethanol and the seven oxide powders is 2:1, the ball-to-material ratio in the ball mill jar is 2:1, the planetary ball mill is ball milled, the rotation speed of the ball mill is 300 r / min, the ball milling time is 12 h, and after the ball milling is completed, the mixed slurry is sufficiently dried at 60 DEG C, and is passed through a 200 mesh screen to obtain a mixed powder with uniform mixing;

[0034] S2, the mixed powder in step S1 is tabletted, the tabletting pressure is 20 MPa, the pressure maintaining time is 1 min, and the diameter of the to-be-sintered green body after the compression molding is 30 mm and the thickness is 4 mm;

[0035] S3, the alumina crucible is dried in a drying box at 80 DEG C for 2 h before use, the alumina gasket prepared in advance with a pressure of 50 MPa or more is placed at the bottom of the alumina crucible, the to-be-sintered green body obtained in step S2 is placed above the alumina gasket in the alumina crucible, and the microwave sintering is carried out in a microwave oven, the temperature is raised to 1300 DEG C at a temperature raising rate of 5 DEG C / min, and the temperature is maintained for 45 min, and after the temperature maintaining is completed, the furnace is naturally cooled, and the product is detected, and the detection results are shown in Figures 1-3 .

[0036] From the sample 1 spectrum of Figure 1 , it can be seen that the prepared sample is mainly a high-entropy oxide phase, a seven-element solid solution with seven elements randomly occupying the same sub-lattice position is obtained, and only a weak diffraction peak of an AlCe intermetallic compound is present, and the diffraction peak intensity is extremely low, which indicates that the content is extremely low, which shows that the atom solid solution is complete and good, and the prepared product is an equimolar seven-element high-entropy oxide. In addition, it can be known from the XRD diffraction spectrum that the seven-element high-entropy oxide obtained in the application inherits the crystal structure of ZrO2, which is a cubic crystal and belongs to the 225th Fm-3m space group.

[0037] The sample prepared in Example 1 is subjected to SEM analysis, as shown in Figure 2 a and its enlarged schematic Figure 2 c, there is no obvious second phase trace, the particle surface is relatively smooth, the powder particle size is relatively uniform, the powder particle size is about 10 um, and there is no obvious particle sintering phenomenon.

[0038] From the sample 1 spectrum of Figure 3It can be seen that all elements are contained in the sample, and each element is uniformly distributed on a micron scale, indicating that each element is well dissolved, indicating the successful preparation of the equimolar ratio seven-element high-entropy oxide phase.

[0039] Example 2

[0040] A preparation process of an equimolar ratio seven-element high-entropy oxide (AlYTiZrNiCuCe)O2, comprising the following steps:

[0041] S1, seven oxide powders Al2O3, Y2O3, TiO2, ZrO2, NiO, CuO and CeO2 with a purity of not less than 99.9% are placed in a ball mill jar according to a molar ratio of 1:1:2:2:2:2:2, wherein the particle size of Al2O3 is 0.5-10 μm, the particle size of Y2O3 is 3-10 μm, the particle size of TiO2 is 1-10 μm, the particle size of ZrO2 is 1-10 μm, the particle size of NiO is 1-10 μm, the particle size of CuO is 3-10 μm, and the particle size of CeO2 is 1-10 μm, and anhydrous ethanol and zirconium oxide grinding balls are added, the total weight ratio of anhydrous ethanol to the seven oxide powders is 2:1, the ball-to-material ratio in the ball mill jar is 2:1, and the planetary ball mill is ball milled, the rotation speed of the ball mill is 300 r / min, the ball milling time is 12 h, and after the ball milling is completed, the mixed slurry is dried at 60℃, and then sieved through a 200 mesh screen to obtain a mixed powder with uniform mixing;

[0042] S2, the mixed powder of step S1 is tabletted, the tabletting pressure is 20 MPa, the pressure holding time is 1 min, and the diameter of the green body after compression molding is 30 mm and the thickness is 4 mm;

[0043] S3, the alumina crucible is dried in a drying box at 80℃ for 2h before use, the alumina gasket prepared in advance with a pressure of 50 MPa or more is placed at the bottom of the alumina crucible, the green body obtained in step S2 is placed above the alumina gasket in the alumina crucible, and then the microwave sintering is carried out in a microwave oven, the temperature is raised to 1300℃ at a rate of 5℃ / min, and the temperature is maintained for 75 min, and then the furnace is naturally cooled after the temperature maintaining is completed, and the product is detected, and the detection results are shown in Figure 1 .

[0044] From Figure 1The sample 2 spectrum can be known that the prepared sample is mainly the phase of high-entropy oxide, a seven-element random seven-element solid solution occupying the same sub-lattice position is obtained, compared with the XRD of sample 1, the type of second phase changes, the AlCe compound disappears, and only a weak diffraction peak of the Ni-Al-O compound is left, but the diffraction peak intensity of the Ni-Al-O compound is very low, which indicates that the content is very low, which shows that the solid solution of each atom is complete and good, and the prepared product is an equimolar seven-element high-entropy oxide. In addition, the XRD diffraction spectrum analysis can obtain that the seven-element high-entropy oxide inherits the crystal structure of ZrO2, which is cubic crystal and belongs to the Fm-3m space group No. 225.

[0045] Example 3

[0046] An equimolar seven-element high-entropy oxide (AlYTiZrNiCuCe)O2 preparation process, comprising the following steps:

[0047] S1, seven kinds of oxide powders Al2O3, Y2O3, TiO2, ZrO2, NiO, CuO, CeO2 with purity not less than 99.9% are put into a ball mill jar according to the molar ratio 1:1:2:2:2:2:2, wherein the particle size of Al2O3 is 0.5-10 μm, the particle size of Y2O3 is 3-10 μm, the particle size of TiO2 is 1-10 μm, the particle size of ZrO2 is 1-10 μm, the particle size of NiO is 1-10 μm, the particle size of CuO is 3-10 μm, and the particle size of CeO2 is 1-10 μm, and anhydrous ethanol and zirconium oxide grinding balls are added, the total weight ratio of anhydrous ethanol and seven kinds of oxide powders is 2:1, the ball-to-material ratio in the ball mill jar is 2:1, the planetary ball mill is ball milled, the rotation speed of the ball mill is 300 r / min, the ball milling time is 12 h, and after the ball milling is completed, the mixed slurry is fully dried at 60℃, and is passed through a 200 mesh screen to obtain a mixed powder with uniform mixing;

[0048] S2, the mixed powder of step S1 is tabletted, the tabletting pressure is 20 MPa, the pressure holding time is 1 min, and the diameter of the to-be-sintered green body after compression molding is 30 mm and the thickness is 4 mm;

[0049] S3, the alumina crucible is placed in a drying box at 80℃ for 2h before use, the alumina gasket prepared in advance with a pressure of 50 MPa or more is placed at the bottom of the alumina crucible, the to-be-sintered green body obtained in step S2 is placed above the alumina gasket in the alumina crucible, and is placed in a microwave oven for microwave sintering, the temperature is raised to 1350℃ at a temperature raising rate of 5℃ / min, and the temperature is kept for 45 min, and after the temperature keeping is completed, the furnace is naturally cooled down, and the product is detected, and the detection results are shown in Figure 1 、 Figure 2 and Figure 4 .

[0050] From Figure 1As shown in the diffraction pattern of Sample 3, the prepared sample mainly consists of a high-entropy oxide phase. A seven-element solid solution was obtained, with seven elements randomly occupying the same sublattice positions. Only weak diffraction peaks of the Ni-Al-O compound were observed, but the relative intensity of the Ni-Al-O diffraction peaks was further reduced compared to Sample 2, indicating that Ni-Al-O was further dissolved and its content was further reduced. This demonstrates that each atom is completely and well dissolved, and the prepared product is an equimolar seven-element high-entropy oxide. Furthermore, XRD diffraction pattern analysis revealed that the obtained seven-element high-entropy oxide inherits the crystal structure of ZrO2, is cubic, and belongs to space group 225 (Fm-3m).

[0051] The samples prepared in Example 3 were analyzed by SEM, such as... Figure 2 b and its enlarged illustration Figure 2 As shown in d, there are no obvious traces of a second phase, the particle surface is relatively smooth, the powder particle size is relatively uniform, the powder particle diameter is about 10μm, and there is no obvious particle sintering phenomenon.

[0052] from Figure 4 It can be seen that the sample contains all elements and the elements are evenly distributed, indicating the successful preparation of the equimolar ratio of the seven-member high-entropy oxide phase.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A process for the preparation of equimolar ratio of seven-membered high entropy oxides, characterized by, The preparation method comprises the following steps: S1, seven kinds of oxide powders Al2O3, Y2O3, TiO2, ZrO2, NiO, CuO, CeO2 are put into a ball mill jar according to the molar ratio of 1:1:2:2:2:2:2, and anhydrous ethanol and zirconium oxide balls are added, and ball milling is carried out in a ball mill, and after ball milling, it is dried, sieved, and mixed powder is obtained; S2, the mixed powder in step S1 is pressed into a tablet, and a green body is obtained; S3, the green body in step S2 is placed in an alumina crucible and put into a microwave oven for microwave sintering.

2. The process for the preparation of equimolar ratio seven-membered high entropy oxide compound as claimed in claim 1 wherein, The Al2O3 particle size is 0.5-10μm, the Y2O3 particle size is 3-10μm, the TiO2 particle size is 1-10μm, the ZrO2 particle size is 1-10μm, the NiO particle size is 1-10μm, the CuO particle size is 3-10μm, and the CeO2 particle size is 1-10μm.

3. The process for the preparation of equimolar ratio seven-membered high entropy oxide compound as claimed in claim 1 wherein, The total weight ratio of anhydrous ethanol to seven kinds of oxide powders is 2-10:

1.

4. The process for the preparation of equimolar ratio seven-membered high entropy oxide compound as claimed in claim 1 wherein, The ball-to-material ratio in the ball mill jar is 2-10:

1.

5. The process for the preparation of equimolar ratio seven-membered high entropy oxides as claimed in claim 1 wherein, The rotation speed of the ball mill is 300-500r / min, and the ball milling time is 6-12h.

6. The process for the preparation of equimolar ratio seven-membered high entropy oxides as claimed in claim 1 wherein, The tabletting pressure is 10-20MPa, and the pressure holding time is 0.5-5min.

7. The process for the preparation of equimolar ratio seven-element high entropy oxide according to claim 1, wherein, The microwave sintering is heated to 1200-1350℃ at a heating rate of 3-7℃ / min, and the holding time is 45-75min.

8. The process for the preparation of equimolar ratio seven-membered high entropy oxides as claimed in any one of claims 1 to 7, wherein the process is characterized by, The alumina crucible is dried before use, and an alumina gasket is placed at the bottom of the alumina crucible in advance.

9. An equimolar ratio seven-membered high-entropy oxide prepared by the preparation process of any one of claims 1-8.

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