A method for preparing a metastable phase manganese-based quadruple perovskite strongly correlated oxide

Abstract

A method for preparing metastable manganese-based tetraple perovskite oxide materials belongs to the fields of functional materials and magnetoresistive materials. Utilizing the lattice matching relationship between alkali metal halide and alkaline earth metal halide fluxes and the metastable manganese-based tetraple perovskite oxide material, the forward Gibbs free energy of the synthesis reaction is reduced. After melting, the flux can act as a solvent to dissolve the oxide raw material. During the cooling process, the metastable manganese-based tetraple perovskite oxide nucleates and grows on the flux crystal surface in a heterogeneous manner. This invention achieves wide-range control of the magnetic properties of the metastable manganese-based tetraple perovskite oxide by regulating the proportion of Cu-site elements; doping with Mn-site elements also changes the valence state of Mn ions, thereby regulating the electrical transport properties of the metastable tetraple perovskite oxide. This significantly reduces the synthesis pressure of the material and enables the large-scale preparation of metastable manganese-based tetraple perovskite oxide to meet the needs of magnetoelectronic devices and spintronic devices.

Description

Technical Field

[0001] This invention belongs to the fields of oxide semiconductors, functional materials, and magnetoresistive materials. Specifically, it relates to a technical method for preparing thermodynamically metastable manganese-based tetrad perovskite oxide powder under high oxygen pressure conditions by using metal halides as fluxes to reduce the forward Gibbs free energy of the synthesis reaction. Compared with traditional high-pressure synthesis methods, this method can significantly reduce the synthesis pressure of the material and achieve large-scale preparation of metastable manganese-based tetrad perovskite oxide to meet the fabrication requirements of magnetoelectronic devices and spintronic devices. Background Technology

[0002] Among many oxide semiconductors, metastable manganese-based tetrad perovskite ACu is a prime example. 3-x B x Mn 4-y C y O 12 (0≤x≤1, 0≤y≤2) simultaneously exhibits ferromagnetism and half-metallicity. [1-3] The a atom is primarily composed of rare earth and alkaline earth elements. Compared to traditional A'B'O3 perovskites, metastable manganese-based tetrad perovskites contain Cu at the A' site. 2+ And Cu 2+ The ratio of A'-site cations to other A'-site cations is 3:1. Due to the small radius of the A'-site cations, the metastable manganese-based tetrad perovskite structure is severely distorted, exhibiting a severe tilt of the MnO6 octahedron. The electrotransport properties of the metastable manganese-based tetrad perovskite can be controlled by adjusting the type and valence state of the A-site element. When the A-site element is in the valence state of 2, such as CaCu3Mn4O 12 [4] Within the temperature range of 50-400K, the resistance decreases with increasing temperature, exhibiting insulator properties; when the element at the A-site is in the trivalent state, the increase in the valence state at the A-site increases the resistance of one Mn atom. 4+ Ions transform into Mn 3+ Ions, thereby initiating Mn 3+ -Mn 4+ Charge transport mechanisms enable materials to transition from insulators to metallics, such as LaCu3Mn4O. 12 [5] Within the temperature range of 50-400K, the resistivity increases with increasing temperature, exhibiting metallic properties. Metastable manganese-based tetrad perovskite oxides are ferromagnetic at low temperatures. From La to Lu, as the size of rare earth ions decreases, the Mn-O bond length in the MnO6 octahedron gradually decreases, the overlap between Mn and O atomic orbitals increases, and the ferromagnetic transition temperature gradually increases. [3] Furthermore, metastable manganese-based tetrad perovskites possess unique magnetoresistance properties; due to their special half-metallic ferromagnetism, their magnetoresistance increases rapidly under the influence of an external magnetic field. For example, CaCu3Mn4O 12For example, this ferromagnetic oxide (T C (355K) exhibits good magnetoresistive response, reaching up to 40% at 20K. [4] Furthermore, its low-field response does not exhibit the strong temperature-dependent decay characteristics found in other perovskite-based systems. In practical applications, this characteristic helps improve temperature stability around room temperature, making it valuable for applications in magnetoelectronic devices, spintronic devices, and other fields.

[0003] Currently, the synthesis of metastable manganese-based tetraperovskites relies on high-pressure synthesis methods. [6,7] First, an active precursor was prepared using a wet chemical method: the raw materials were mixed in stoichiometric proportions and dissolved in citric acid; after the solution was slowly evaporated and decomposed, the precursor was mixed and ground with KClO4, and then sealed in a gold capsule; finally, the material was synthesized using a cylindrical graphite heater and a high-pressure press at 1000℃ and 2-6 GPa. Existing methods for synthesizing metastable manganese-based tetrad perovskite materials require high pressure at GPa levels, necessitate the preparation of active precursors using wet chemical methods, and involve cumbersome synthesis processes with yields as low as 10 mg, which cannot meet the requirements for device fabrication and material characterization.

[0004] In summary, there is currently a lack of an effective method in this field to achieve large-scale synthesis of metastable manganese-based tetrad perovskite materials under relatively low reaction pressure, which cannot meet the potential application needs of magnetoelectronic devices.

[0005] [1]Sánchez-Benítez J,Alonso JA,Falcón H,et al.Preparation underhighpressures and neutron diffraction study of new ferromagneticRCu3Mn4O 12 (R=Pr,Sm,Eu,Gd,Dy,Ho,Tm,Yb)perovskites[J].Journal of Physics:Condensed Matter,2005,17(40):S3063.

[0006] [2]Takata K, Yamada I, Azuma M, et al. Magnetoresistance and electronic structure of the half-metallic ferrimagnet BiCu3Mn4O 12 [J].Physical Review B,2007,76(2):024429.

[0007] [3]Sanchez-Benitez J,Alonso J A,Martínez-Lope M J,et al.Enhancementof the Curie Temperature along the perovskite seriesRCu3Mn4O 12 driven bychemical pressure of R 3+ cations(R=RareEarths)[J].Inorganic chemistry,2010,49(12):5679-5685.

[0008] [4]Zeng Z,Greenblatt M,Subramanian M A,et al.Large low-fieldmagnetoresistance in perovskite-type CaCu3Mn4O 12 without doubleexchange[J].Physical review letters,1999,82(15):3164.

[0009] [5]Alonso J A,Sánchez-Ben1tez J,De Andrés A,etal.Enhancedmagnetoresistance in the complex perovskite LaCu3Mn4O 12 [J].Appliedphysics letters,2003,83(13):2623-2625.

[0010] [6]Sánchez-Benítez J,Kayser P,Martínez-Lope M J,et al.High-pressurepreparation and characterization of new metastable oxides:the caseofNdCu3Mn3MO 12 (M=Fe,Cr)[C] / / Journal of Physics:Conference Series.IOPPublishing,2011,325(1):012002.

[0011] [7]Sanchez-Benitez J, Martinez-Lope MJ, Alonso J A. Magnetism, magnetotransport and magnetic structure of ThCu3Mn4O 12 ,prepared at moderate pressures[J].Zeitschrift für Naturforschung B,2008,63(6):655-660. Summary of the Invention

[0012] The purpose of this invention is to provide a method for the large-scale preparation of metastable manganese-based tetrad perovskite oxide material powder and ceramics. The main concept is to utilize the lattice matching relationship between alkali metal halide and alkaline earth metal halide fluxes and metastable manganese-based tetrad perovskite oxide materials to reduce the forward Gibbs free energy of the synthesis reaction. After the flux melts, it can be used as a solvent to dissolve the oxide raw materials. During the cooling process, the metastable manganese-based tetrad perovskite oxide nucleates and grows on the surface of the flux crystal in a non-uniform nucleation manner.

[0013] A method for preparing a metastable phase manganese-based tetrad perovskite oxide material, the method comprising the following steps:

[0014] 1) Design the metastable phase manganese-based tetrad perovskite oxide material composition based on the target electrical transport and magnetoresistance characteristics. According to the selected material composition, weigh the precursors of A-site, Cu, and Mn elements according to the stoichiometric ratio of the target metastable phase manganese-based tetrad perovskite oxide composition, and add excess copper oxide to mix thoroughly. For alkaline earth metal carbonates, the corresponding alkaline earth metal oxides can be obtained by pre-calcination.

[0015] 2) Based on the crystal structure of the target metastable manganese-based tetrad perovskite oxide, select a metal halide flux that has a coherent relationship with its specific crystal face. Weigh the flux according to the proportion of the precursor oxide content and mix the flux and the precursor oxide thoroughly.

[0016] 3) Select the heat treatment temperature according to the flux melting point: First, heat the mixed oxide powder with flux in a high oxygen pressure atmosphere to above the flux melting point, so that the flux melts and the precursor oxide is fully dissolved; then gradually cool down to below the flux melting point and hold for 0.1-48h to allow the flux to gradually solidify. Metastable manganese-based tetrad perovskite oxide precipitates on the surface of the flux crystal in a non-uniform nucleation manner. After holding, slowly cool to room temperature.

[0017] 4) Excess copper oxide and flux are removed by non-oxidizing acid, and other water-soluble impurities are removed by washing, sonication and centrifugation. After drying, pure metastable manganese-based tetrad perovskite oxide powder is obtained. A binder is added to the powder and it is cold-pressed into sheets. Then it is sintered under high oxygen pressure to obtain metastable manganese-based tetrad perovskite oxide ceramic.

[0018] 5) Based on metastable manganese-based tetrad perovskite oxide ceramics, electrodes and other functional layer materials are further introduced to fabricate electronic devices, magnetoelectronic devices, and spintronic devices;

[0019] The particle size and morphology of metastable manganese-based tetrad perovskite oxide powder can be controlled by adjusting the ratio of precursor to flux, oxygen partial pressure, and heat treatment process.

[0020] Further, the chemical composition of the metastable manganese-based tetrad perovskite oxide synthesized in step 1) is ACu. 3- x B x Mn 4-y C y O 12 , 0≤x≤1, 0≤y≤2; where A is a single rare earth element or a combination of multiple rare earth elements, including La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc; a single alkaline earth element or a combination of multiple alkaline earth elements, including Mg, Ca, Sr, Ba; a monovalent ion with a radius close to that of the rare earth element ion, including Li, Na, K, Rb, Cs; a trivalent ion, including Bi, Sb, In; a tetravalent ion, including Ti, Zr, Mn; a single or combination of the above elements. The copper element mentioned in step 1) can be replaced or doped with a divalent or trivalent ion with a radius close to that of the copper ion, including Mn, Fe, Co, Ni, Hg, Ru, Pb; the manganese element mentioned in step 1) can be replaced or doped with a tetravalent ion with a radius close to that of the manganese ion, including Fe, Cr, Ti, Co, Ru, V, Ta, Ge, Sn.

[0021] Further, the precursor in step 1) includes oxides, nitrates, and carbonates of the rare earth, alkaline earth, Cu, and Mn elements; for alkaline earth metal nitrates and carbonates, the corresponding alkaline earth metal oxides can be obtained by pre-calcination decomposition; the pre-calcination temperature should be 1-200°C higher than the decomposition temperature of the corresponding alkaline earth metal nitrates and carbonates; in a preferred embodiment, CaCu3Mn4O is prepared. 12 The raw materials are CaCO3, CuO, and MnO2. The decomposition temperature of CaCO3 is 825℃. The raw material powders are mixed and pre-calcined at 1025℃. In another preferred embodiment, SrCu3Mn4O is prepared. 12The raw materials are SrCO3, CuO, and MnO2. The decomposition temperature of SrCO3 is 1200℃. The raw material powders are mixed and then pre-calcined at 1201℃.

[0022] Further, the excess CuO ratio in step 1) should be 1%-500% of the metastable manganese-based tetrad perovskite target phase, preferably 5%-200%. Insufficient CuO content in the raw material cannot suppress the formation of the mixed phase, while excessive CuO content is detrimental to its dissolution in the flux. In a preferred example, LaCu3Mn4O is prepared... 12 When the raw material oxide has a La:Cu ratio of 1:4.5 and a CuO excess of 50%, LaCu3Mn4O is finally prepared. 12 Pure phase. (In a general example, EuCu3Mn4O) 12 When the raw material oxide has a Eu:Cu ratio of 1:3.03 and a CuO excess of 1%, EuCu3Mn4O is finally prepared. 12 (and EuMn2O5 mixed phase)

[0023] Further, step 1) involves adjusting the types and ratios of A, Cu, and Mn site elements to regulate the electrical transport properties and magnetic properties of metastable manganese-based tetrad perovskite oxide materials. Changing the types and ratios of A-site and Mn site elements can regulate the electrical transport properties of metastable tetrad perovskite oxides; changing the types and ratios of Cu site elements will affect the magnetic properties of metastable tetrad perovskite oxides.

[0024] Further, the flux mentioned in step 2) includes alkali metal halide fluxes, including LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KCl, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, LiI, NaI, KI, RbI, CsI; alkaline earth metal halide fluxes, including MgF2, CaF2, SrF2, BaF2, MgCl2, CaCl2, SrCl2, BaCl2, MgBr2, CaBr2, SrBr2, BaBr2, MgI2, CaI2, SrI2, BaI2; copper chlorides, including CuCl2, CuCl; and manganese chlorides, including MnCl2, MnCl4, MnCl7. One or more fluxes can be mixed to assist in the growth of the new phase. The proportion of the flux mentioned in step 2) should be 50%-300% of the metastable manganese-based tetrad perovskite target phase. In a preferred embodiment, TbCu3Mn4O is prepared. 12 The added flux is NaF, NaF:TbCu3Mn4O 12 = 1:2; In another preferred embodiment, DyCu3Mn4O is prepared. 12 The added flux is CaCl2, CaCl2: DyCu3Mn4O 12=3:1.

[0025] Further, in step 3), during the heating process, the first step involves heating the oxide powder with added flux to 1-200°C above the flux melting point, allowing the flux to completely melt and fully dissolve the precursor oxide as a solvent; the second step involves cooling the solution to 1-200°C below the flux melting point, allowing the flux to slowly solidify. Because the specific crystal planes of the flux are coherent with the metastable manganese-based tetrad perovskite oxide, the flux can reduce the forward Gibbs free energy of the synthesis reaction, causing the metastable manganese-based tetrad perovskite oxide to precipitate on the crystal surface coherent with the flux through heterogeneous nucleation. The oxygen pressure is 0.2-500 MPa; increasing the oxygen pressure can reduce the forward Gibbs free energy of the synthesis reaction, preferably 1-50 MPa. In a preferred example, SmCu3Mn4O is prepared... 12 The raw materials are Sm₂O₃, CuO, and MnO₂. The flux NaCl has a melting point of 801℃. The process involves first heating to 1001℃ under an oxygen partial pressure of 1 MPa, followed by cooling to 800℃ and holding at that temperature. In another preferred embodiment, GdCu₃Mn₄O₂ is prepared. 12 The raw materials are Gd2O3, CuO, and MnO2. The flux LiCl is selected with a melting point of 605℃. The first step is to heat to 606℃ in an oxygen partial pressure of 100MPa, and the second step is to cool down to 405℃ and hold at that temperature.

[0026] Further, the acidic solution in step 4) includes 1-25% by mass of dilute hydrochloric acid and 1-60% by mass of dilute sulfuric acid; by adjusting the concentration and amount of acid used in conjunction with the CuO content, byproducts can be eliminated to achieve the pure phase preparation of metastable manganese-based tetrad perovskite oxide.

[0027] Compared to the high-pressure synthesis method of this system, the technology provided by this invention significantly reduces the pressure required for material synthesis, simplifies the process flow, and lowers preparation costs. Furthermore, the technology provided by this invention can synthesize thermodynamically metastable phase materials at pressures 2-3 orders of magnitude lower than the press pressure (MPa), and enables large-scale production of this system. It allows for the control of the proportion of A-site elements, influencing the valence state of Mn ions and thus regulating the electrical transport properties of metastable manganese-based tetrad perovskite oxides; by controlling the proportion of Cu-site elements, a wide range of magnetic properties of metastable manganese-based tetrad perovskite oxides can be controlled; doping of Mn-site elements also alters the valence state of Mn ions, thereby regulating the electrical transport characteristics of metastable tetrad perovskite oxides. The prepared materials have application value in magnetoelectronic devices, spintronic devices, and other fields. Attached Figure Description

[0028] Figure 1LaCu3Mn4O prepared using the fluxing method proposed in this invention 12 The X-ray diffraction pattern of the powder shows that the prepared powder is a pure phase powder.

[0029] Figure 2 PrCu3Mn4O prepared using the fluxing method proposed in this invention 12 The X-ray diffraction pattern of the powder shows that the prepared powder is a pure phase powder.

[0030] Figure 3 NdCu3Mn4O prepared using the fluxing method proposed in this invention 12 The X-ray diffraction pattern of the powder shows that the prepared powder is a pure phase powder.

[0031] Figure 4 EuCu3Mn4O prepared by adding 1% excess CuO using the fluxing method proposed in this invention 12 The X-ray diffraction pattern of the powder shows that the prepared powder contains the EuMn2O5 impurity phase.

[0032] Figure 5 CaCu3Mn4O prepared using the fluxing method proposed in this invention 12 The electrical transport characteristic curves of the ceramic show that CaCu3Mn4O exhibits good electrical transport properties within the temperature range of 50-400 K. 12 The electrical resistance of ceramics decreases as the temperature increases, making them insulators.

[0033] Figure 6 LaCu3Mn4O prepared using the fluxing method proposed in this invention 12 The scanning electron microscope image of the powder shows that the particle size is 1-10 μm and the powder is cubic or irregular in shape. Detailed Implementation

[0034] Unless otherwise specified, all raw materials used in this invention are commercially available or prepared according to conventional methods in the art. Unless otherwise defined or stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention.

[0035] Other aspects of the invention will be apparent to those skilled in the art from the disclosure herein.

[0036] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0037] Example 1: The raw material powders used in this experiment were La₂O₃, CuO, MnO₂, and KCl. First, the stoichiometric ratio of oxide powders (La:Cu:Mn = 1:4.5:4) and excess CuO were weighed. The raw material powders were poured into an agate mortar and mixed. Then, KCl flux was added in a ratio of La₂O₃:KCl = 1:2, and grinding continued until homogeneous. The mixed powder was placed in a quartz tube, the tube opening was plugged with quartz wool, and the tube was placed in a high-pressure furnace, which was filled with oxygen to 7 MPa. The temperature was first raised to 900℃ to melt KCl and dissolve the raw material powder, then lowered to 700℃ and held for 24 hours, and finally slowly cooled to room temperature. The agglomerated powder was removed and re-ground. Excess CuO and flux KCl were washed away with dilute hydrochloric acid, rinsed with deionized water, sonicated, centrifuged, and dried to obtain pure phase LaCu₃Mn₄O₂. 12 Powder, as shown in the attached image Figure 1 As shown, within the temperature measurement range of 50-473K, LaCu3Mn4O 12 It exhibits metallic properties and undergoes a ferromagnetic transition near 361 K. A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain LaCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0038] Example 2: The raw material powders used in this experiment were CaCO3, CuO, MnO2, and KF. First, the stoichiometric ratio of oxide or carbonate powders (Ca:Cu:Mn = 1:4:4) and excess CuO were weighed out. The raw material powders were poured into an agate mortar and mixed evenly, then placed into a quartz tube and placed in a resistance furnace. The mixture was pre-calcined at 1025℃ for 12 hours to decompose CaCO3 into CaO. Then, KF flux was added in a CaO:KF ratio of 1:1 and ground until homogeneous. The mixed powder was placed into a quartz tube, the tube opening was plugged with quartz wool, and the tube was placed in a high-pressure furnace, which was filled with oxygen to 7 MPa. The temperature was first raised to 900℃ to melt KF and dissolve the raw material powder, then lowered to 800℃ and held for 24 hours, finally slowly cooled to room temperature. The agglomerated powder was removed and re-ground in an agate mortar. Excess CuO and KF were washed away with hydrochloric acid, followed by rinsing with deionized water, sonication, centrifugation, and drying to obtain pure phase CaCu3Mn4O. 12 Powder, CaCu3Mn4O, within a temperature measurement range of 50-473K. 12 It exhibits semiconductor properties. A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain CaCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0039] Example 3: The raw material powders used in this experiment were Pr6O 11 CuO, MnO2, KCl. First, weigh out the stoichiometric ratio of oxide powder (Pr:Cu:Mn = 1:4:4) and excess CuO. Pour the raw material powder into an agate mortar and mix. Then, add Pr6O... 11 Add KCl flux at a ratio of 1:2 and continue grinding until homogeneous. Place the mixed powder into a quartz tube, plug the opening with quartz wool, and place it in a high-pressure furnace, filling it with oxygen to 7 MPa. First, raise the temperature to 900℃ to melt the KCl and dissolve the raw powder, then lower the temperature to 700℃ and hold for 24 hours, finally slowly cooling to room temperature. Remove the agglomerated powder and re-grind it. Use a 1:5 mixture of 35% concentrated hydrochloric acid and water to wash away excess CuO and KCl. Rinse with deionized water, sonicate, centrifuge, and dry to obtain pure phase PrCu3Mn4O. 12 Powder, as shown in the attached image Figure 2 As shown, scanning electron microscopy revealed that the powder particle size ranged from 1 to 10 μm. A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain PrCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0040] Example 4: Weigh the corresponding oxides Nd₂O₃, CuO, and MnO₂ according to the elemental ratio Nd:Cu:Mn = 1:4.5:4. Pour the oxide powder into an agate mortar and grind thoroughly until homogeneous. Then, weigh the flux LiCl according to the ratio Nd₂O₃:LiCl = 1:2 and add it to the agate mortar, continuing to mix until homogeneous. Place the mixed powder into a quartz tube, plug it with quartz wool, and place it in a high-pressure furnace. Open the gas cylinder to make the oxygen partial pressure in the high-pressure furnace reach 8 MPa. First, raise the temperature to 805℃ to melt LiCl and dissolve the raw material powder, then lower the temperature to 600℃ and hold for 24 hours, finally slowly cooling to room temperature. Mix 35% concentrated hydrochloric acid and water at a ratio of 1:5, add the powder, and centrifuge to wash away excess CuO and flux KCl from the product. Repeatedly wash and centrifuge with deionized water and alcohol, and finally dry to obtain NdCu₃Mn₄O₂. 12 Pure phase, as attached Figure 3 As shown. A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain NdCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0041] Example 5: The raw materials selected were Sm₂O₃, CuO, and MnO₂ oxide powders. The oxide powders and excess CuO were weighed according to an elemental ratio of Sm:Cu:Mn = 1:4:4, and the flux NaCl was weighed according to a ratio of Sm₂O₃:NaCl = 1:2. The oxide powders and flux were poured into an agate mortar, mixed, and ground until homogeneous. The mixture was placed in a quartz tube, and the opening was plugged with quartz wool. The quartz tube was placed in a high-pressure furnace, and oxygen was introduced to 1 MPa. The temperature was first raised to 1001℃ and held for 2 hours, then slowly lowered to 800℃ and held for 24 hours, and finally slowly cooled to room temperature. After acid washing with dilute hydrochloric acid, the powder was repeatedly rinsed with deionized water and alcohol, and dried to obtain pure phase SmCu₃Mn₄O₂. 12 Powder. A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800℃ for 24 h to obtain SmCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0042] Example 6: The raw materials used in this experiment were high-purity Eu₂O₃, CuO, and MnO₂ oxide powders. Eu₂O₃, CuO, and MnO₂ were weighed according to the elemental ratio Eu:Cu:Mn = 1:4.5:4 and mixed evenly in an agate mortar. Flux KF was weighed according to the ratio Eu₂O₃:KF = 1:3 and added to the agate mortar, grinding together with the mixed powders. After thorough mixing, the mixture was placed in a quartz tube and then placed in a high-pressure furnace. The oxygen cylinder was slowly opened, and oxygen was introduced until the partial pressure reached 4 MPa. The temperature was first raised to 900℃ to melt the flux, then slowly lowered to 700℃ and held for 24 hours. After the high-pressure furnace cooled to room temperature, the block was removed and ground into powder using an agate mortar. Prepare dilute hydrochloric acid by mixing 35% concentrated hydrochloric acid and deionized water in a ratio of 2:1. Wash the powder with the dilute hydrochloric acid and centrifuge repeatedly. Then rinse the powder 3-4 times with deionized water and alcohol. After drying, EuCu3Mn4O is obtained. 12 Pure phase. A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain EuCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0043] Example 7: The raw materials used in this experiment were Gd₂O₃, CuO, and MnO₂ oxide powders. The powders were weighed using an electronic balance according to the elemental ratio of Gd:Cu:Mn = 1:4:4. The weighed oxide powders were then poured into an agate mortar and ground evenly. Flux LiCl was weighed according to the ratio of Gd₂O₃:LiCl = 1:2 and poured into the agate mortar for further mixing. The mixed powders were placed in a quartz tube in a high-pressure furnace. An oxygen cylinder was opened, and oxygen was slowly introduced until the partial pressure reached 100 MPa. The furnace was first heated to 606℃ for 1 hour, then lowered to 405℃ and held for 24 hours, and finally slowly cooled to room temperature. After acid washing with dilute hydrochloric acid, the powders were rinsed with deionized water, centrifuged 3-4 times, and then washed with alcohol. Finally, the powders were dried to obtain GdCu₃Mn₄O₂. 12 Pure phase. A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain GdCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0044] Example 8: Weigh the corresponding oxides Tb4O7, CuO, and MnO2 according to the elemental ratio Tb:Cu:Mn = 1:4:4. After weighing, pour them into an agate mortar and mix. Weigh the flux NaF according to the ratio Tb4O7:NaF = 1:2, pour it into the agate mortar, and continue grinding until the powder color is uniform. Place the powder into a quartz tube, plug the tube opening with quartz wool, and put it into a high-pressure furnace. Inflate with oxygen to 7MPa, heat to 1000℃ to completely melt NaF and dissolve the oxide powder, cool to 900℃ and hold for 24 hours, then slowly cool to room temperature. Place the agglomerated powder into an agate mortar and grind it. After acid washing with dilute hydrochloric acid, wash with deionized water and alcohol, centrifuge, and dry in an oven to obtain TbCu3Mn4O 12 Pure phase. A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain TbCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0045] Example 9: The raw materials used in this experiment were high-purity Dy2O3, CuO, MnO2, and CaCl2 powders. First, the stoichiometric ratio of oxide powders and excess CuO was weighed according to the elemental ratio of Dy:Cu:Mn = 1:4.5:4. The flux CaCl2 was weighed according to the ratio of Dy2O3:CaCl2 = 1:6. The oxide raw materials and flux were poured into an agate mortar and mixed evenly. The mixture was then poured into a quartz tube and the opening was sealed with quartz wool. The quartz tube was placed in a high-pressure furnace, the oxygen cylinder valve was opened, and oxygen was slowly introduced to 6 MPa before the valve was closed. The temperature was first raised to 900℃ until the flux was completely melted, and then held at that temperature for a period of time before being lowered to 700℃ and held for 24 hours. Finally, the temperature was cooled to room temperature. The agglomerated powder was removed and re-ground. After acid washing, the powder was repeatedly rinsed with deionized water and alcohol, centrifuged 3-4 times, and then dried in a drying oven to obtain pure phase DyCu3Mn4O. 12 A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain DyCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0046] Example 10: The raw materials used in the experiment mainly consisted of Ho₂O₃, CuO, and MnO₂ oxide powders. First, using an electronic balance, the stoichiometric ratio of the oxide powders and excess CuO was weighed according to the elemental ratio Ho:Cu:Mn = 1:4:4. This was then poured into an agate mortar and ground. Next, flux was weighed according to the ratio Ho₂O₃:CaCl₂:KCl = 1:1:1 and added to the agate mortar, grinding it together with the mixed powders until homogeneous. The mixture was then placed in a quartz tube and placed in a high-pressure furnace. Oxygen was introduced to 7 MPa, and the furnace was first heated to 850°C and held for 1 hour, then cooled to 700°C and held for 24 hours. After the high-pressure furnace cooled to room temperature, the agglomerated powder was removed and re-ground in the mortar. Concentrated hydrochloric acid was diluted with deionized water at a ratio of 1:5. The powder was then washed with the diluted hydrochloric acid to remove excess CuO and fluxes CaCl2 and KCl. After acid washing, the powder was washed 3-4 times with deionized water and alcohol. After drying, HoCu3Mn4O was obtained. 12 Pure phase. HoCu3Mn4O was obtained by adding a binder to the powder, cold pressing it into sheets, and sintering it at 7 MPa and 800℃ for 24 h. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0047] Example 11: Weigh the corresponding oxide powders Er₂O₃, CuO, and MnO₂ according to the elemental ratio Er:Cu:Mn = 1:4:4, and mix them evenly in an agate mortar. Then, weigh the flux according to the ratio Er₂O₃:NaCl:KF = 1:1:1, and add it to the agate mortar to grind together with the mixed powder. Place the mixed powder in a quartz tube and put it into a high-pressure furnace. Open the oxygen cylinder valve and slowly fill the high-pressure furnace with oxygen until the pressure reaches 7 MPa, then close the valve. Heat the high-pressure furnace to 900℃. After the flux has completely melted and dissolved the oxide powder, cool it down to 700℃ and keep it at that temperature for 24 hours. After cooling to room temperature, take out the agglomerated powder and grind it in an agate mortar. Wash the powder with dilute hydrochloric acid to remove excess CuO and fluxes NaCl and KF. Wash the acid-washed powder 3-4 times with deionized water and alcohol. After drying, obtain the pure phase ErCu₃Mn₄O₂. 12 A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain ErCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0048] Example 12: The raw materials used in this experiment were Tm2O3, CuO, MnO2, and NaBr. First, using an electronic balance, the stoichiometric ratio of oxide powder (Tm:Cu:Mn = 1:4:4) and excess CuO were weighed and ground in an agate mortar until homogeneous. Then, flux NaBr (Tm2O3:NaBr = 1:2) was weighed and mixed with the raw materials in the agate mortar. The raw materials were placed in a quartz tube, and the tube opening was sealed with quartz wool. The quartz tube was placed in a high-pressure furnace. Oxygen was introduced to 5 MPa, and the temperature was first raised to 850℃, then lowered to 700℃ and held for 24 hours. The agglomerated powder was ground in the agate mortar and diluted with 35% concentrated hydrochloric acid and deionized water at a ratio of 1:5. The powder was centrifuged in dilute hydrochloric acid, then washed 3-4 times with deionized water and alcohol, and dried in an oven to obtain TmCu3Mn4O3. 12 Pure phase. A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain TmCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0049] Example 13: The main raw materials used in the experiment were high-purity Yb₂O₃, CuO, MnO₂, and CuCl₂. The corresponding oxides Yb₂O₃, CuO, and MnO₂ were weighed according to the elemental ratio Yb:Cu:Mn = 1:4:4. The flux CuCl₂ was weighed according to the ratio Yb₂O₃:CuCl₂ = 1:2. All powders were poured into an agate mortar and ground evenly, then placed into a quartz tube. The quartz tube was placed in a high-pressure furnace, and oxygen was introduced to 5 MPa. The temperature was first raised to 700℃ and held until CuCl₂ melted and the raw material powder was completely dissolved. Then, the temperature was lowered to 600℃ and held for 24 hours. After cooling to room temperature, the agglomerated powder was removed, re-ground, washed with dilute hydrochloric acid, centrifuged, and then washed with deionized water and alcohol. Finally, it was dried to obtain YbCu₃Mn₄O₂. 12 Pure phase. A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain YbCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0050] Example 14: Weigh the corresponding oxides Lu2O3, CuO, and MnO2 powders according to the elemental ratio Lu:Cu:Mn = 1:4:4, and mix them evenly in an agate mortar. Then weigh the flux according to the ratio Lu2O3:NaBr:MgCl2 = 1:1:1, and add it to the agate mortar for further grinding. Place the mixed powder into a quartz tube and put it into a high-pressure furnace. Open the oxygen cylinder valve and slowly fill it with oxygen to 6MPa. First, raise the temperature to 800℃, then lower it to 600℃ and hold it for 24 hours. After cooling to room temperature, remove the agglomerated powder and grind it in an agate mortar. Wash the powder with dilute hydrochloric acid to remove excess CuO and fluxes NaBr and MgCl2. Wash the acid-washed powder 3-4 times with deionized water and alcohol. After drying, obtain pure phase LuCu3Mn4O 12 A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain LuCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0051] Example 15: The raw material powders used in this experiment were La₂O₃, CaCO₃, CuO, and MnO₂. First, the stoichiometric ratio of oxide or carbonate powders and excess CuO were weighed according to the ratio La:Ca:Cu:Mn = 1:2:12:12. The raw material powders were poured into an agate mortar and mixed evenly, then placed in an alumina crucible and placed in a muffle furnace. The mixture was pre-calcined at 900℃ for 8 hours to decompose the calcium carbonate. Then, KCl flux was added according to the ratio La₂O₃:KCl = 1:6, and grinding continued until homogeneous. The mixed powder was placed into a quartz tube, the tube opening was plugged with quartz wool, and the tube was placed in a high-pressure furnace, which was filled with oxygen to 7 MPa. The temperature was first raised to 900℃ to melt the KCl and dissolve the raw material powder, then lowered to 700℃ and held for 24 hours, and finally slowly cooled to room temperature. The agglomerated powder was removed and re-ground. Excess CuO and KCl were washed away with a 1:5 mixture of concentrated hydrochloric acid and water. The mixture was then rinsed with deionized water, sonicated, centrifuged, and dried to obtain pure-phase La. 0.33 Ca 0.67 Cu3Mn4O 12 Powder. A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800℃ for 24 h to obtain La. 0.33 Ca 0.67 Cu3Mn4O 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0052] Example 16: Weigh the corresponding oxides La₂O₃, CuO, and MnO₂ according to the elemental ratio La:Cu:Mn = 1:1:6. Pour the oxide powder into an agate mortar and grind thoroughly until homogeneous. Then, weigh the flux CaBr₂ according to the ratio La₂O₃:CaBr₂ = 1:2 and add it to the agate mortar, continuing to mix until homogeneous. Place the mixed powder into a quartz tube, plug it with quartz wool, and place it in a high-pressure furnace. Open the gas cylinder to achieve an oxygen partial pressure of 8 MPa in the high-pressure furnace. First, raise the temperature to 800℃ to melt CaBr₂ and dissolve the raw material powder, then lower the temperature to 600℃ and hold for 24 hours. Finally, slowly cool to room temperature. Wash the powder 3-4 times with deionized water and alcohol, and dry it in an oven to obtain LaCuMn₆O. 12 The pure phase undergoes a ferromagnetic transformation near 190 K. A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain LaCuMn6O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0053] Example 17: The raw materials used in this experiment were high-purity Sm₂O₃, CuO, Fe₂O₃, MnO₂, and LiCl powders. First, the stoichiometric ratio of oxide powders and excess CuO was weighed according to the elemental ratio Sm:Cu:Fe:Mn = 1:4:1:3. The flux LiCl was weighed according to the ratio Sm₂O₃:LiCl = 1:2. The oxide raw materials and flux were poured into an agate mortar and mixed evenly. The mixture was then poured into a quartz tube and the opening was sealed with quartz wool. The quartz tube was placed in a high-pressure furnace, the oxygen cylinder valve was opened, and oxygen was slowly introduced to 8 MPa before the valve was closed. The temperature was first raised to 700℃ until the flux was completely melted, and then held at that temperature for a period of time before being lowered to 500℃ and held for 24 hours. Finally, the temperature was cooled to room temperature. The agglomerated powder was removed and re-ground. After acid washing, the powder was repeatedly rinsed with deionized water and alcohol, centrifuged 3-4 times, and then dried in a drying oven to obtain pure phase SmCu₃Mn₃FeO. 12 A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain SmCu3Mn3FeO. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0054] Example 18: The main raw materials used in the experiment were high-purity Y₂O₃, CuO, MnO₂, KCl, and NaCl. The corresponding oxides Y₂O₃, CuO, and MnO₂ were weighed according to the elemental ratio Y:Cu:Mn = 1:4.5:4. The fluxes KCl and NaCl were weighed according to the ratio Y₂O₃:KCl:NaCl = 1:1:1. All powders were poured into an agate mortar and ground evenly, then placed into a quartz tube. The quartz tube was placed in a high-pressure furnace, and oxygen was introduced to 6 MPa. The temperature was first raised to 900℃ and held until the flux melted and the raw material powder was completely dissolved. Then, the temperature was lowered to 700℃ and held for 24 hours. After cooling to room temperature, the agglomerated powder was removed, re-ground, washed with dilute hydrochloric acid, centrifuged, and then washed with deionized water and alcohol. Finally, it was dried to obtain YCu₃Mn₄O₂. 12 Pure phase. A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain YCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0055] Example 19: Weigh out the corresponding oxide or carbonate powders SrCO3, CuO, and MnO2 according to the elemental ratio Sr:Cu:Mn = 1:4:4, pour them into an agate mortar and mix evenly. Place the mortar in a resistance furnace and pre-calcine at 1201℃ for 12 hours to decompose SrCO3 into SrO. Then, weigh out the flux KI according to the ratio SrO:KI = 1:4, pour it into the agate mortar and grind it together with the mixed powder. Put the mixed powder into a high-pressure furnace through a quartz tube, open the oxygen cylinder valve, and slowly fill the high-pressure furnace with oxygen until the pressure reaches 7MPa. Close the valve. Heat the high-pressure furnace to 800℃. After the KI has completely melted and dissolved the oxide powder, cool it down to 600℃ and hold it at that temperature for 24 hours. After cooling to room temperature, take out the agglomerated powder and grind it in the agate mortar. The powder was washed with dilute hydrochloric acid to remove excess CuO and KI. The acid-washed powder was then washed 3-4 times with deionized water and alcohol. After drying, pure phase SrCu3Mn4O was obtained. 12 A binder was added to the powder, which was then cold-pressed into sheets and sintered at 7 MPa and 800 °C for 24 h to obtain SrCu3Mn4O. 12 Ceramics, by further introducing electrodes into ceramics, can be used to fabricate magnetoelectronic devices.

[0056] Example 20: The raw materials used in this experiment were high-purity Eu₂O₃, CuO, and MnO₂ oxide powders. Eu₂O₃, CuO, and MnO₂ were weighed according to the elemental ratio Eu:Cu:Mn = 1:3.03:4 and mixed evenly in an agate mortar. Flux KF was weighed according to the ratio Eu₂O₃:KF = 1:3 and added to the agate mortar, grinding together with the mixed powders. After thorough mixing, the mixture was placed in a quartz tube and placed in a high-pressure furnace. The oxygen cylinder was slowly opened, and oxygen was introduced until the partial pressure reached 4 MPa. The temperature was first raised to 900℃ to melt the flux, then slowly lowered to 700℃ and held for 24 hours. After the high-pressure furnace cooled to room temperature, the block was removed and ground into powder using an agate mortar. The powder was washed 3-4 times with deionized water and alcohol, and dried to obtain EuCu₃Mn₄O₂. 12 The mixed phase with EuMn2O5, as shown in the attached figure. Figure 4 As shown, adding excess CuO helps suppress the formation of impurity phases.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the substantive technical content of the present invention. The substantive technical content of the present invention is broadly defined within the scope of the claims. Any technical entity or method completed by others that is completely identical to or an equivalent modification of the claims is considered to be covered within the scope of the claims.

Claims

1. A method for preparing a metastable phase manganese-based tetrad perovskite oxide material, characterized in that, The method can synthesize thermodynamically metastable phase materials under pressures 2-3 orders of magnitude lower than the press, and achieve large-scale preparation of this system. The control of the proportion of A-site elements affects the valence state of Mn ions, thereby controlling the electrical transport properties of metastable manganese-based tetrad perovskite oxides. By controlling the proportion of Cu-site elements, a wide range of magnetic properties of metastable manganese-based tetrad perovskite oxides can be controlled. Doping with Mn-site elements also changes the valence state of Mn ions, thereby controlling the electrical transport characteristics of metastable tetrad perovskite oxides. The method includes the following steps: 1) Design the metastable manganese-based tetrad perovskite oxide material composition based on the target electrical transport and magnetoresistance characteristics. According to the selected material composition, weigh the precursors of A-site, Cu, and Mn elements according to the stoichiometric ratio of the target metastable manganese-based tetrad perovskite oxide composition, and add excess copper oxide for thorough mixing. For alkaline earth metal carbonates, obtain the corresponding alkaline earth metal oxides through pre-calcination. The excess CuO ratio should be 5%-500% of the target metastable manganese-based tetrad perovskite phase. 2) Based on the crystal structure of the target metastable manganese-based tetrad perovskite oxide, select a metal halide flux with a coherent relationship to its specific crystal plane. Weigh the flux according to the proportion of the precursor oxide content, and mix the flux and precursor oxide thoroughly. The proportion of the flux should be 50%-300% of the target metastable manganese-based tetrad perovskite phase. 3) Select the heat treatment temperature according to the flux melting point: First, heat the mixed oxide powder with flux in a high oxygen pressure atmosphere to above the flux melting point, so that the flux melts and the precursor oxide is fully dissolved; then gradually cool down to below the flux melting point and hold for 0.1-48 h to allow the flux to gradually solidify. Metastable manganese-based tetrad perovskite oxide precipitates on the surface of the flux crystal in a non-uniform nucleation manner. After holding, slowly cool to room temperature. In the heating process, the first step involves heating the oxide powder with added flux to 1-200°C above the flux melting point, allowing the flux to completely melt and fully dissolve the precursor oxide as a solvent. The second step involves cooling the solution to 1-200°C below the flux melting point, allowing the flux to slowly solidify. Because the specific crystal planes of the flux are coherent with the metastable manganese-based tetraple perovskite oxide, the flux can reduce the forward Gibbs free energy of the synthesis reaction, causing the metastable manganese-based tetraple perovskite oxide to precipitate on the coherent crystal surface with the flux via heterogeneous nucleation. The oxygen pressure is 0.2-500 MPa; increasing the oxygen pressure reduces the forward Gibbs free energy of the synthesis reaction. 4) Excess copper oxide and flux are removed by non-oxidizing acid, and other water-soluble impurities are removed by washing, sonication and centrifugation. After drying, pure metastable manganese-based tetrad perovskite oxide powder is obtained. A binder is added to the powder and it is cold-pressed into sheets. Then it is sintered under high oxygen pressure to obtain metastable manganese-based tetrad perovskite oxide ceramic. 5) Based on metastable manganese-based tetrad perovskite oxide ceramics, electrodes and other functional layer materials are further introduced to fabricate electronic devices, magnetoelectronic devices, and spintronic devices; The particle size and morphology of metastable manganese-based tetrad perovskite oxide powder can be controlled by adjusting the ratio of precursor to flux, oxygen partial pressure and heat treatment process. The chemical composition of the metastable manganese-based tetrad perovskite oxide synthesized in step 1) is ACu. 3-x B x Mn 4-y C y O 12 0 x 1,0 y 2; where A is a single rare earth element or a combination of multiple rare earth elements, including La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc; a single alkaline earth element or a combination of multiple alkaline earth elements, including Mg, Ca, Sr, Ba; a monovalent ion with a radius close to that of the rare earth element ion, including Li, Na, K, Rb, Cs; a trivalent ion, including Bi, Sb, In; a tetravalent ion, including Ti, Zr, Mn; a single or combination of the above elements; the copper element mentioned in step 1) may or may not be replaced or doped with a divalent or trivalent ion with a radius close to that of the copper ion, including Mn, Fe, Co, Ni, Hg, Ru, Pb; the manganese element mentioned in step 1) may or may not be replaced or doped with a tetravalent ion with a radius close to that of the manganese ion, including Fe, Cr, Ti, Co, Ru, V, Ta, Ge, Sn.

2. The method for preparing a metastable phase manganese-based tetrad perovskite oxide material as described in claim 1, characterized in that, The precursors mentioned in step 1) include oxides, nitrates, and carbonates of the rare earth, alkaline earth, Cu, and Mn elements; for alkaline earth metal nitrates and carbonates, the corresponding alkaline earth metal oxides are obtained by pre-calcination decomposition; the pre-calcination temperature should be 1-200 ℃ higher than the decomposition temperature of the corresponding alkaline earth metal nitrates and carbonates.

3. The method for preparing a metastable phase manganese-based tetrad perovskite oxide material as described in claim 1, characterized in that, When preparing LaCu3Mn4O 12 When the ratio of La to Cu in the raw material oxide is 1:4.5, and CuO is in excess by 50%, LaCu3Mn4O is finally prepared. 12 Pure phase.

4. The method for preparing a metastable phase manganese-based tetrad perovskite oxide material as described in claim 1, characterized in that, Step 1) involves adjusting the types and ratios of A, Cu, and Mn site elements to regulate the electrical transport properties and magnetic properties of metastable manganese-based tetrad perovskite oxide materials; changing the types and ratios of A and Mn site elements regulates the electrical transport properties of metastable tetrad perovskite oxides; changing the types and ratios of Cu site elements affects the magnetic properties of metastable tetrad perovskite oxides.

5. The method for preparing a metastable phase manganese-based tetrad perovskite oxide material as described in claim 1, characterized in that, The flux mentioned in step 2) includes alkali metal halide fluxes, including LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KCl, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, LiI, NaI, KI, RbI, CsI; alkaline earth metal halide fluxes, including MgF2, CaF2, SrF2, BaF2, MgCl2, CaCl2, SrCl2, BaCl2, MgBr2, CaBr2, SrBr2, BaBr2, MgI2, CaI2, SrI2, BaI2; copper chlorides, including CuCl2, CuCl; and manganese chlorides, including MnCl2. One or more fluxes are used in combination to assist in the growth of the new phase.

6. The method for preparing a metastable phase manganese-based tetrad perovskite oxide material as described in claim 1 or 5, characterized in that, When preparing TbCu3Mn4O 12 The added flux is NaF, NaF:TbCu3Mn4O 12 =1:2; when preparing DyCu3Mn4O 12 The added flux is CaCl2, CaCl2: DyCu3Mn4O 12 =3:

1.

7. The method for preparing a metastable phase manganese-based tetrad perovskite oxide material as described in claim 1, characterized in that, Step 3) When preparing SmCu3Mn4O 12 The raw materials are Sm₂O₃, CuO, and MnO₂. The flux NaCl has a melting point of 801 °C. The process involves first heating to 1001 °C under an oxygen partial pressure of 1 MPa, followed by cooling to 800 °C and holding at that temperature. This is used to prepare GdCu₃Mn₄O₂. 12 The raw materials are Gd2O3, CuO, and MnO2. The flux LiCl is selected with a melting point of 605 ℃. The first step is to heat to 606 ℃ in an oxygen partial pressure of 100 MPa, and the second step is to cool down to 405 ℃ and hold at that temperature.

8. The method for preparing a metastable phase manganese-based tetrad perovskite oxide material as described in claim 1, characterized in that, Step 4) The non-oxidizing acid includes dilute hydrochloric acid with a mass fraction of 1-25% and dilute sulfuric acid with a mass fraction of 1-60%. By adjusting the concentration and amount of acid used in conjunction with the CuO content, byproducts are eliminated to achieve the pure phase preparation of metastable manganese-based tetrad perovskite oxide.

Images