Molten salt assisted oxygen partial pressure self-adjusting intermediate valence transition group oxide preparation method

Abstract

The invention provides a molten salt assisted oxygen partial pressure self-regulation intermediate valence transition group oxide preparation method, and relates to the technical field of functional materials, sensitive resistance materials and devices. According to the preparation method of the molten salt assisted oxygen partial pressure self-regulation intermediate valence transition group oxide, in a closed vacuum environment, molten alkaline earth metal halide serves as a medium, according to dissolution-precipitation balance of oxygen elements in a melt, the oxygen content of a target product in the molten salt and the oxygen partial pressure in the vacuum environment outside the melt are correlated, and the intermediate valence transition group oxide is obtained. And introducing another reaction process of which the oxygen potential is lower than that of the target reaction system into a coarse vacuum environment outside the melt, and accurately and spontaneously adjusting the oxygen partial pressure required by synthesis of the target product multi-dimensional material of the intermediate valence transition group oxides inside and outside the melt, therefore, accurate and high-yield melt internal and external intermediate valence transition group oxide target product multi-dimensional material synthesis is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional materials, sensitive resistance materials and devices, and particularly relates to a method for preparing a molten salt-assisted oxygen partial pressure self-regulating intermediate valence transition group oxide. BACKGROUND

[0002] The intermediate valence transition group oxide has rich phase structures and complex energy band structures, and exhibits metal-insulator phase transition, ultraviolet and visible light band transparency, and high conductivity characteristics in the range of 10 4 -10 6 The intermediate valence transition group oxide has rich phase structures and complex energy band structures, and exhibits metal-insulator phase transition, ultraviolet and visible light band transparency, and high conductivity characteristics in the range of 10 n O 2n-1 , VO2, V n O 2n+1 , and a variety of binary vanadium oxides such as n=2, 3 and 6; and some intermediate valence binary vanadium oxides exhibit metal-insulator phase transition characteristics triggered by characteristic temperatures, accompanied by resistance and optical absorption rate mutations[4-5], which can be applied in sensitive resistance devices, strong light protection and infrared camouflage fields[6]; at the same time, the titanium suboxide magneli phase Ti n O 2n-1 ceramic has conductivity in the range of 10 4 -10 6 The intermediate valence transition group oxide has rich phase structures and complex energy band structures, and exhibits metal-insulator phase transition, ultraviolet and visible light band transparency, and high conductivity characteristics in the range of 10 n O 2n-1 The intermediate valence transition group oxide has rich phase structures and complex energy band structures, and exhibits metal-insulator phase transition, ultraviolet and visible light band transparency, and high conductivity characteristics in the range of 10

[0003] Chinese patent CN118894724A discloses a method for preparing an intermediate-valence vanadium oxide electronic phase change material. This method first involves weighing and mixing a vanadium-containing precursor and a doped metal oxide in the specified molar ratio, then adding a flux, heating to dissolve the material while controlling the oxygen partial pressure, followed by slow cooling and washing with water to obtain the product. Obviously, this method does not provide a precise control method for the oxygen partial pressure, and cannot achieve self-regulation of the oxygen partial pressure. The resulting product has an uneven microstructure and performance distribution, and its quality cannot be improved.

[0004] Chinese patent CN109942022A discloses a one-dimensional metal-doped perovskite niobate piezoelectric material and its preparation method. This method utilizes the similarity of material structures and, under molten salt conditions, prepares a large quantity of one-dimensional metal-doped perovskite niobate piezoelectric materials through a mild evolution of some structures. However, it does not consider the influence of oxygen partial pressure control on the valence state of transition metal elements in the prepared materials. Chinese patent CN116835649A discloses an ultrafine intermediate molybdenum oxide material and its preparation method. This method places ammonium molybdate in a reaction vessel and heats it in a vacuum environment at 400-600℃ for at least 3 hours to obtain the ultrafine intermediate molybdenum oxide material. Similarly, Chinese patent CN112591804A requires high-temperature sintering for preparation, resulting in a longer reaction time and increased costs.

[0005] Currently, the most common method for synthesizing intermediate-valence transition oxide powder materials is the solid-state reaction method, which often relies on high reaction temperatures exceeding 1000℃ and hazardous reducing atmospheres [3,4,10,13] to achieve precise control of the thermodynamic equilibrium oxygen partial pressure. However, deviations in the stoichiometry of the final target product lead to a weakening or loss of the aforementioned physical properties. Besides powder materials, common methods for preparing intermediate-valence transition oxide thin film materials include pulsed laser deposition, molecular beam epitaxy, and magnetron sputtering [11-13]. -6 While achieving the vacuum level of Torr [10-11], it is difficult to prepare low-latitude materials of intermediate valence transition oxides with wafer-sized wafers and precise stoichiometry.

[0006] For example, Chinese patent CN111364006A discloses a method for preparing multivalent metal oxides, which involves introducing a non-inert gas with an electronegativity lower than that of oxygen to compete with oxygen on the growth surface, thereby regulating the chemical potential of oxygen on the oxide growth surface and controlling the valence and phase of metal elements in the oxide. The uneven distribution of the composition of the thin film prepared by magnetron sputtering leads to uneven distribution of the film's properties.

[0007] In summary, existing technologies often rely on hazardous reducing atmospheres to achieve thermodynamic equilibrium and control of oxygen partial pressure. Currently, there is a lack of an effective method for the large-scale preparation of intermediate-valence transition oxide powders and low-dimensional materials that achieves self-regulation of oxygen partial pressure at lower reaction temperatures without the aid of a reducing atmosphere.

[0008] [1]NGAI JH, WALKER FJ, AHN C H. Correlated Oxide Physics and Electronics [J]. Annual Review of Materials Research, 2014, 44(1): 1-17. [2]SANNICOLO T, LAGRANGE M, CABOS A, et al. Metallic Nanowire-BasedTransparent Electrodes for Next Generation Flexible Devices: a Review [J].Small, 2016, 12(44): 6052-6075. [3]NAGASAWA K, BANDO Y, TAKADA T. Growth and Electrical Properties ofV n O 2n-1 (n=3, 4, ..., 8) Single Crystals [J]. Bulletin of the Institute for Chemical Research, Kyoto University, 1972, 49(5): 322-341. [4]KACHI S, KOSUGE K, OKINAKA H. Metal-insulator transition in V n O 2n−1 [J]. Journal of Solid State Chemistry, 1973, 6(2): 258-270. [5]MORIN F J. Oxides Which Show a Metal-to-Insulator Transition at the Neel Temperature [J]. Physical Review Letters, 1959, 3(1): 34-36. [6]BIERMAN D M, LENERT A, KATS M A, et al. Radiative Thermal RunawayDue to Negative-Differential Thermal Emission Across a Solid-Solid PhaseTransition [J]. Physical Review Applied, 2018, 10(2): 021001. [7]SMITH J R, WALSH F C, CLARKE R L. Electrodes based on Magnéliphase titanium oxides: the properties and applications of Ebonex® materials[J]. Journal of Applied Electrochemistry, 1998, 28(10): 1021-1033. [8]KAO W H, PATEL P, HABERICHTER S L. Formation Enhancement of aLead / Acid Battery Positive Plate by Barium Metaplumbate and Ebonex® [J].Journal of The Electrochemical Society, 1997, 144(6): 1907. [9]HAN W-Q, WANG X-L. Carbon-coated Magnéli-phase Ti n O 2n−1 nanobelts asanodes for Li-ion batteries and hybrid electrochemical cells [J]. AppliedPhysics Letters, 2010, 97(24).

[10] NAGAI I, SHIRAKAWA N, IKEDA S-I, et al. Highest conductivity oxide SrMoO3 grown by a floating-zone method under ultralow oxygen partial pressure [J]. Applied Physics Letters, 2005, 87(2).

[11] MIRJOLET M, KATAJA M, HAKALA T K, et al. Optical Plasmon Excitation in Transparent Conducting SrNbO3 and SrVO3 Thin Films [J]. Advanced Optical Materials, 2021, 9(17).

[12] MOYER J A, EATON C, ENGEL‐HERBERT R. Highly Conductive SrVO3 as a Bottom Electrode for Functional Perovskite Oxides [J]. Advanced Materials, 2013, 25(26): 3578-3582.

[13] ZHAO B C, SUN Y P, ZHANG S B, et al. Flux growth and characterization of SrMo 0.93 O3 single crystal [J]. Journal of Crystal Growth, 2006, 290(1): 292-295. Summary of the Invention

[0009] The purpose of this invention is to provide a molten salt-assisted method for preparing intermediate-valence transition oxides with self-regulating oxygen partial pressure. The main concept is as follows: in a coarse vacuum closed environment where oxygen partial pressure is difficult to control accurately, using molten alkaline earth metal halides as a medium, and based on the dissolution-precipitation equilibrium of oxygen on the melt surface, the oxygen content of the target product inside the molten salt is correlated with the oxygen partial pressure in the closed environment outside the melt. Thus, by utilizing different reaction systems within the melt with oxygen potential differences compared to the target product reaction system, the spontaneous regulation of the equilibrium concentration of oxygen partial pressure inside and outside the melt and the large-scale, high-quality synthesis of the intermediate-valence transition oxide target product are achieved. Simultaneously, the synthesis process of the intermediate-valence transition oxide within the melt can also regulate the oxygen partial pressure in the closed environment outside the melt, triggering the nucleation and growth of low-dimensional materials of the intermediate-valence transition oxide outside the melt.

[0010] Compared with previous synthesis methods for corresponding materials, the advantages of the technology provided by this invention are that it eliminates the need for strict control of the oxygen partial pressure within the reaction apparatus. Instead, it introduces molten alkaline earth metal halides as a medium and, based on the oxygen potential diagram of intermediate-valence transition metal oxides, utilizes the oxygen potential differences between different reaction systems to achieve self-regulation of the oxygen partial pressure in a closed environment. This significantly reduces the material synthesis temperature, shortens the reaction time, and allows for flexible control of the stoichiometry of intermediate-valence transition oxides, achieving the goal of large-scale synthesis and preparation of the material system powder and low-dimensional materials. The prepared intermediate-valence transition oxide multidimensional materials have application value in abrupt change thermistors, strong light protection, logic electronic devices, and transparent conductive coatings.

[0011] The technical solution is as follows:

[0012] A method for preparing intermediate-valence transition oxides with self-regulating oxygen partial pressure using molten salt is disclosed. This method involves using molten alkaline earth metal halides as a medium in a closed vacuum environment. Based on the dissolution-precipitation equilibrium of oxygen in the melt, the oxygen content of the target product inside the molten salt is correlated with the oxygen partial pressure in the vacuum environment outside the melt. Another reaction process with an oxygen potential lower than the target reaction system is introduced into the rough vacuum environment outside the melt. This allows for accurate and spontaneous regulation of the oxygen partial pressure required for the synthesis of multi-dimensional materials of intermediate-valence transition oxides inside and outside the melt, achieving accurate and high-yield synthesis of these materials. Finally, the powder sample is washed with deionized water and dried to obtain intermediate-valence transition oxide powder.

[0013] Optionally, the process of introducing another reaction process with an oxygen potential lower than that of the target reaction system into a rough vacuum environment outside the melt is achieved by using a transition element or compound with an average valence state close to but lower than that of the target product as an oxygen partial pressure control agent.

[0014] Optionally, the use of transition metal elements or compounds with an average valence state close to but lower than that of the target product as oxygen partial pressure control agents is achieved as follows: In a closed environment, molten alkaline earth metal halides can act as a medium to accelerate the establishment of a dissolution-precipitation equilibrium of oxygen on the melt surface, establish the connection between the oxygen content of the target product inside the molten salt and the oxygen partial pressure in the closed environment outside the melt, and complete the spontaneous regulation of the equilibrium oxygen partial pressure inside and outside the melt and the synthesis of the intermediate valence state transition oxide target product powder material by means of the oxidation process of another oxygen partial pressure control agent in the melt.

[0015] While using transition elements or compounds with average valence states close to but lower than the target product as oxygen partial pressure control agents, the synthesis process of intermediate valence state transition oxides in the melt can achieve self-regulation of oxygen partial pressure in the closed environment outside the melt through the migration of oxygen elements in a closed environment. This triggers the nucleation and growth of low-dimensional intermediate valence state transition oxide materials outside the melt on a single crystal substrate with crystallographic alignment.

[0016] The vacuum level of the closed vacuum environment ranges from 0.1 to 10 Pa, which is achieved by using a tube furnace equipped with a mechanical pump, to realize the accurate and large-scale synthesis of transition oxide powders and low-dimensional film materials with complex intermediate valence states.

[0017] Optionally, the intermediate valence state transition oxide material system includes binary or multi-component transition oxides, wherein the transition metal elements include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ta, W, Re, Os, and Ir; the oxide forms formed by the transition metal elements and oxygen elements include TiO, Ti2O3, and Ti... n O 2n-1 The integer n can take values ​​of 3 ≤ n ≤ 9;

[0018] VO, V2O3, V n O 2n-1 The range of integer n in the middle is 3≤n≤9, VO2, V n O 2n+1 The integer n can take the values ​​3 and 6;

[0019] Ae 1-x Re x VO3, where x takes values ​​in the range 0 ≤ x ≤ 1, NbO2, Nb 3n+1 O 8n-2 In the context, the integer n takes values ​​of 25 and 28, and MoO2 and Mo n O 3n-1 The integer n in the middle ranges from 4, 8, 9, 17, and 18, WO2, W n O 3n-1 The integer n in the middle ranges from 3, 5, and 10;

[0020] SrTMO3, where TM represents V, Mo and Nb, ReFe2O4, ReBaFe2O5, Fe3O4, and Mn3O4;

[0021] Wherein: Re represents rare earth elements, including La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, or a single rare earth element or a combination of multiple rare earth elements;

[0022] Ae represents alkaline earth metal elements, including Mg, Ca, Sr, and Ba, or a single alkaline earth metal element or a combination of multiple alkaline earth metal elements.

[0023] Optionally, the raw material for the molten alkaline earth metal halide is an alkaline earth metal halide molten salt. The composition and proportion are determined based on the oxygen potential diagram of the intermediate valence transition oxide reaction system. The synthesis temperature of the target product is determined, and the type and proportion of molten salt with a melting point lower than or equal to the synthesis temperature are selected as fluxes. At the same time, the molten salt is required to dissolve the intermediate valence transition oxide precursor powder at high temperature and not to react with the precursor powder, so that the precursor powder is uniformly dispersed in the melt, thereby accelerating the reaction rate. The molten salt acts as an oxygen exchange medium, and by means of the dissolution-precipitation balance of oxygen on the melt surface, it establishes the connection between the inside and outside of the melt and between different melts in the same closed environment. By means of the redox characteristics of the low oxygen potential reaction system at the synthesis temperature relative to the reaction process of the target product, the self-regulation of the equilibrium oxygen partial pressure in the closed environment is achieved, thereby controlling the oxygen content in the intermediate valence transition oxide target product in the melt.

[0024] Optionally, the alkaline earth metal halide molten salt composition includes LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KCl, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, LiI, NaI, KI, RbI, and CsI. A single molten salt can be used to assist the growth of the new phase, or a mixture of multiple molten salts can be used to assist the growth of the new phase.

[0025] Optionally, in the method for preparing intermediate-valence transition oxide materials with spontaneous oxygen partial pressure regulation assisted by molten salt, the type and proportion of oxygen partial pressure control agent are determined based on the oxygen potential diagram. Transition metal oxides or elemental metals with oxygen potential lower than that of the target product reaction system at the target synthesis temperature can be selected as oxygen partial pressure control agents. With the help of the molten salt medium, the chemical equilibrium between the target product reaction system and the oxygen partial pressure control agent is constructed through the dissolution-precipitation equilibrium of oxygen elements on the surface of different melts inside and outside the melt, thereby achieving self-regulation of oxygen partial pressure in a closed environment. This provides an environment atmosphere within the thermodynamic equilibrium oxygen partial pressure range for intermediate-valence transition oxides inside or outside the melt, triggering the nucleation and growth of the target product on the surface of a single-crystal substrate with crystallographic alignment inside and outside the molten salt melt, accurately controlling the intermediate valence state of the transition elements and realizing the large-scale, multi-dimensional morphological material preparation.

[0026] Optionally, a method for preparing intermediate-valence transition oxides with spontaneous oxygen pressure regulation assisted by molten salt enables the growth of low-latitude intermediate-valence transition oxide materials with a film thickness ranging from 10 nm to 100 μm on the surface of a single-crystal substrate. The single-crystal substrates include lanthanum aluminate, strontium titanate, titanium dioxide, aluminum oxide, yttrium iron garnet, yttrium-doped zirconium oxide, germanium dioxide, magnesium oxide, mica, quartz, doped silicon wafers, and single-crystal silicon substrates with the aforementioned single-crystal substrate materials deposited on their surface as a buffer layer. Alternatively, a sacrificial layer with similar lattice parameters is grown on the surface of the single-crystal substrate, and then the sacrificial layer is removed by heating or dissolution to obtain a self-supporting intermediate-valence transition oxide film. The sacrificial layer includes alkali metal halides and strontium aluminum oxide. The preparation methods for the intermediate-valence transition oxide precursor film include magnetron sputtering, pulsed laser deposition, thermal evaporation, chemical vapor deposition, and sol-gel spin coating.

[0027] Optionally, the metal element in the intermediate valence transition oxide can be partially replaced by one or more other transition metal elements, including Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ta, W, Re, Os, and Ir, and the molar ratio x of the metal element being replaced ranges from 0 to x ≤ 0.5. While obtaining the doped intermediate valence transition oxide polycrystalline powder material, the grain size of the material can be flexibly controlled by controlling the cooling rate. At the same time, by designing a specific patterned metal structure on the surface of the single crystal substrate, an intermediate valence transition oxide material with a specific structure or pattern can be obtained outside the melt. The specific structure includes equally spaced strip or lattice gratings, curved surfaces with a radius of curvature ranging from 10 μm to 10 cm, and equally spaced concentric ring gratings.

[0028] Optionally, the molten salt-assisted oxygen partial pressure self-regulating method for preparing intermediate valence state transition oxides can accurately control the valence state of transition elements and achieve large-scale, multi-dimensional morphological material preparation, while simultaneously preparing V₂O₃ and V₂O₃. n O 2n-1 VO2 exhibits metal-insulator phase transition properties and is applied in abruptly changing thermistors, neuronal logic storage and computation, and strong light protection; TiO, Ti2O3, and Ti... n O 2n-1 Binary titanium oxides possess high resistance to acid and alkali corrosion and high conductivity, making them suitable for applications in fuel cells and electrocatalytic degradation of organic pollutants. The prepared SrTMO3 exhibits high conductivity and transparency in the ultraviolet or visible light bands, making it applicable to transparent electromagnetic shielding and transparent conductive coating applications.

[0029] Optionally, the performance parameters of the intermediate valence transition oxide precursor powder include magnetization M and magnetic susceptibility χ, and the performance parameters of the intermediate valence transition oxide powder include the metal-insulator phase transition temperature T. MIT The latent heat of phase transformation ΔH is determined, and a binder is added to the obtained powder. The powder is then cold-pressed at 10-30 MPa for 10-30 minutes to obtain a cylindrical ceramic preform with a diameter of 6-25 mm and a height of 2-5 mm. This preform is then placed in a sealed environment under vacuum of 0.1-10 Pa and annealed at 600-1000℃ for 12-24 hours to obtain a ceramic material of this composition. The performance parameters of this ceramic material include the metal-insulator phase transition temperature T. MIT The degree of change in resistivity ρ before and after the phase transition Insulator / ρ Metal Room temperature conductivity σ 300K Transmittance T in the 380-750 nm visible light band, temperature coefficient of resistance TCR, and thermistor constant B.

[0030] The technical principle of this invention is as follows: Based on the oxygen potential diagram of intermediate valence transition metal oxides, different reaction systems with different oxygen potentials are introduced into a closed environment; simultaneously, using molten alkaline earth metal halides as a medium, and by leveraging the dissolution-precipitation equilibrium of oxygen on the melt surface, an oxygen partial pressure balance is established between different reaction systems inside and outside the molten salt; ultimately, the equilibrium oxygen partial pressure of the target product reaction system is self-regulated within a closed environment, achieving the goal of large-scale, high-quality synthesis of multidimensional intermediate valence transition metal oxide materials.

[0031] The above technical solution has at least the following advantages compared with the existing technology:

[0032] The above-mentioned solution proposes a method for preparing intermediate valence transition metal oxides with self-regulating oxygen partial pressure assisted by molten salt. This method can solve the technical problems existing in the prior art, including: difficulty in mass-producing intermediate valence transition metal oxide powder materials with precise stoichiometry, difficulty in synthesizing intermediate valence transition metal oxide thin film materials with precise stoichiometry, and the requirement that the preparation process of intermediate valence transition metal oxide materials must be completed in a reducing atmosphere above 1000°C.

[0033] The products prepared by subsequent processing of intermediate-valence transition oxide powders of the present invention include abrupt change thermistor devices, battery electrodes, electrocatalytic electrodes, flat panel display film coatings, terahertz modulation devices, and transparent conductive electrodes. The intermediate-valence titanium oxide products prepared have the properties of acid and alkali radiation resistance, electrochemical window stability, and high conductivity of 1500 S / cm. Their stability in strong acid and alkali media is superior to that of the prior art.

[0034] The intermediate valence vanadium oxide abrupt change thermistor prepared in this invention exhibits a wide temperature detection range of 50-400 K and a performance of 10 3 -10 5 The resistance change rate of Ω is significantly higher than that of existing technologies, exhibiting superior performance in both temperature detection range and resistance change rate. The transparent conductive electrode prepared using SrTMO3 (TM = V, Nb, Mo) thin film material possesses high transmittance in the ultraviolet to visible light range while maintaining a conductivity of 10 Ω. 4 -10 6 Within its range, its conductivity is superior to that of existing technologies.

[0035] In summary, compared with the traditional casting-rolling method, the present invention introduces a self-regulating mechanism of molten alkali metal halides and oxygen partial pressure, which enables the batch synthesis of multidimensional materials of intermediate valence transition metal oxides with precise stoichiometric ratios without relying on dangerous high-temperature reducing atmospheres. The prepared multidimensional materials of intermediate valence transition metal oxides can be applied to abrupt change thermistor devices, battery electrodes, electrocatalytic electrodes, flat panel display film coatings, terahertz modulation devices, and transparent conductive electrodes. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1This is a schematic diagram of the apparatus structure for the method of preparing intermediate valence state transition oxides with molten salt-assisted oxygen partial pressure self-regulation according to the present invention;

[0038] Figure 2 This is an X-ray diffraction pattern of V2O3 powder material prepared by the molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxide preparation method of Example 1 of the present invention;

[0039] Figure 3 This is the X-ray diffraction pattern of V3O5 powder material prepared by the molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxide preparation method of Example 2 of the present invention;

[0040] Figure 4 This is a graph showing the relationship between the resistivity of V3O5 powder material prepared by the molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxide preparation method of Example 2 of the present invention and temperature.

[0041] Figure 5 This is an X-ray diffraction pattern of the V2O3 / Al2O3(0001) thin film material prepared by the molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxide preparation method of Example 1 of the present invention;

[0042] Figure 6 This is a graph showing the relationship between the resistance of the V3O5 / Al2O3(0001) thin film material prepared by the molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxide preparation method of Embodiment 2 of the present invention and the temperature. Detailed Implementation

[0043] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0044] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0045] In the embodiments of the present invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that when the distinction is not emphasized, their intended meanings are consistent.

[0046] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0047] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0048] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, such as... Figure 1 As shown, the method for preparing intermediate-valence transition oxides with molten salt-assisted oxygen partial pressure self-regulation is carried out in a closed vacuum environment using molten alkaline earth metal halides as a medium. Based on the dissolution-precipitation equilibrium of oxygen in the melt, the oxygen content of the target product inside the molten salt is correlated with the oxygen partial pressure in the vacuum environment outside the melt. Another reaction process with an oxygen potential lower than that of the target reaction system is introduced into the rough vacuum environment outside the melt. This allows for accurate and spontaneous regulation of the oxygen partial pressure required for the synthesis of multi-dimensional materials of intermediate-valence transition oxide target products inside and outside the melt, thereby achieving accurate and high-yield synthesis of multi-dimensional materials of intermediate-valence transition oxide target products inside and outside the melt. Finally, the powder sample is washed with deionized water and dried to obtain intermediate-valence transition oxide powder.

[0049] Specifically, the process of introducing an oxygen potential lower than that of the target reaction system into a rough vacuum environment outside the melt is achieved by using a transition element or compound with an average valence state close to but lower than that of the target product as an oxygen partial pressure control agent.

[0050] Specifically, the use of transition metal elements or compounds with an average valence state close to but lower than that of the target product as oxygen partial pressure control agents is achieved as follows: In a closed environment, molten alkaline earth metal halides can act as a medium to accelerate the establishment of a dissolution-precipitation equilibrium of oxygen on the melt surface, establish a connection between the oxygen content of the target product inside the molten salt and the oxygen partial pressure in the closed environment outside the melt, and complete the spontaneous regulation of the equilibrium oxygen partial pressure inside and outside the melt and the synthesis of the intermediate valence state transition oxide target product powder material by means of the oxidation process of another oxygen partial pressure control agent in the melt.

[0051] While using transition elements or compounds with average valence states close to but lower than the target product as oxygen partial pressure control agents, the synthesis process of intermediate valence state transition oxides in the melt can achieve self-regulation of oxygen partial pressure in the closed environment outside the melt through the migration of oxygen elements in a closed environment. This triggers the nucleation and growth of low-dimensional intermediate valence state transition oxide materials outside the melt on a single crystal substrate with crystallographic alignment.

[0052] The vacuum level of the closed vacuum environment ranges from 0.1 to 10 Pa, which is achieved by using a tube furnace equipped with a mechanical pump, to realize the accurate and large-scale synthesis of transition oxide powders and low-dimensional film materials with complex intermediate valence states.

[0053] Specifically, the material system of intermediate valence state transition oxides includes binary or multi-component transition oxides, wherein the transition metal elements include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ta, W, Re, Os, and Ir; the oxide forms formed by the transition metal elements and oxygen include TiO, Ti2O3, and Ti... n O 2n-1 The integer n can take values ​​of 3 ≤ n ≤ 9;

[0054] VO, V2O3, V n O 2n-1 The range of integer n in the middle is 3≤n≤9, VO2, V n O 2n+1 The integer n can take the values ​​3 and 6;

[0055] Ae 1-x Re x VO3, where x takes values ​​in the range 0 ≤ x ≤ 1, NbO2, Nb 3n+1 O 8n-2 In the context, the integer n takes values ​​of 25 and 28, and MoO2 and Mo n O 3n-1 The integer n in the range includes 4, 8, 9, 17, and 18, WO2, W n O 3n-1 The integer n in the middle ranges from 3, 5, and 10;

[0056] SrTMO3, where TM represents V, Mo and Nb, ReFe2O4, ReBaFe2O5, Fe3O4, and Mn3O4;

[0057] Wherein: Re represents rare earth elements, including La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, or a single rare earth element or a combination of multiple rare earth elements;

[0058] Ae represents alkaline earth metal elements, including Mg, Ca, Sr, and Ba, or a single alkaline earth metal element or a combination of multiple alkaline earth metal elements.

[0059] Specifically, the raw material for molten alkaline earth metal halides is molten alkaline earth metal halide salt. The composition and proportion are determined based on the oxygen potential diagram of the intermediate-valence transition oxide reaction system. The synthesis temperature of the target product is determined, and the type and proportion of molten salt with a melting point lower than or equal to the synthesis temperature are selected as fluxes. At the same time, the molten salt is required to dissolve the intermediate-valence transition oxide precursor powder at high temperature and molten state, and not to react with the precursor powder, so that the precursor powder is uniformly dispersed in the melt, thereby accelerating the reaction rate. The molten salt acts as an oxygen exchange medium, and by means of the dissolution-precipitation balance of oxygen on the melt surface, it establishes the connection between the inside and outside of the melt and between different melts in the same closed environment. By means of the redox characteristics of the low oxygen potential reaction system at the synthesis temperature relative to the reaction process of the target product, the self-regulation of the equilibrium oxygen partial pressure in the closed environment is achieved, thereby controlling the oxygen content in the intermediate-valence transition oxide target product in the melt.

[0060] Specifically, the alkaline earth metal halide molten salt components include LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KCl, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, LiI, NaI, KI, RbI, and CsI. A single molten salt is used to assist the growth of the new phase, or a mixture of multiple molten salts is used to assist the growth of the new phase.

[0061] In particular, in the method for preparing intermediate-valence transition oxide materials with spontaneous oxygen partial pressure regulation assisted by molten salt, the type and proportion of oxygen partial pressure control agent are determined based on the oxygen potential diagram. Transition metal oxides or elemental metals with oxygen potential lower than that of the target product reaction system at the target synthesis temperature can be selected as oxygen partial pressure control agents. With the help of molten salt medium, the chemical equilibrium between the target product reaction system and the oxygen partial pressure control agent is constructed through the dissolution-precipitation equilibrium of oxygen element on its surface inside and outside the melt, achieving self-regulation of oxygen partial pressure in a closed environment. This provides an environment atmosphere within the thermodynamic equilibrium oxygen partial pressure range for intermediate-valence transition oxides inside or outside the melt, triggering the nucleation and growth of the target product on the surface of a single-crystal substrate with crystallographic alignment inside and outside the molten salt melt. This accurately controls the intermediate valence state of the transition elements and realizes the large-scale, multi-dimensional morphological material preparation.

[0062] Specifically, a method for preparing intermediate-valence transition oxides with molten salt-assisted oxygen pressure spontaneous regulation enables the growth of low-latitude intermediate-valence transition oxide materials with a film thickness ranging from 10 nm to 100 μm on the surface of a single-crystal substrate. The single-crystal substrates include lanthanum aluminate, strontium titanate, titanium dioxide, aluminum oxide, yttrium iron garnet, yttrium-doped zirconium oxide, germanium dioxide, magnesium oxide, mica, quartz, doped silicon single crystals, and single-crystal silicon substrates with the aforementioned single-crystal substrate materials deposited on their surface as a buffer layer. Alternatively, a sacrificial layer with similar lattice parameters can be grown on the surface of the single-crystal substrate, and then the sacrificial layer can be removed by heating or dissolution to obtain a self-supporting intermediate-valence transition oxide film. The sacrificial layer includes alkali metal halides and strontium aluminum oxide. The preparation methods for the intermediate-valence transition oxide precursor film include magnetron sputtering, pulsed laser deposition, thermal evaporation, chemical vapor deposition, and sol-gel spin coating.

[0063] Specifically, the metal element in the intermediate valence transition oxide can be partially replaced by one or more other transition metal elements, including Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ta, W, Re, Os, and Ir, and the molar ratio x of the metal element being replaced ranges from 0 to x ≤ 0.5. While obtaining doped intermediate valence transition oxide polycrystalline powder materials, the grain size of the material can be flexibly controlled by controlling the cooling rate. At the same time, by designing a specific patterned metal structure on the surface of a single crystal substrate, intermediate valence transition oxide materials with a specific structure or pattern can be obtained outside the melt. The specific structure includes equally spaced strip or lattice gratings, curved surfaces with a radius of curvature ranging from 10 μm to 10 cm, and equally spaced concentric ring gratings.

[0064] In particular, the molten salt-assisted oxygen partial pressure self-regulating method for preparing intermediate valence state transition oxides can accurately control the valence state of transition elements and achieve large-scale, multi-dimensional morphological material preparation. Simultaneously, the prepared V₂O₃ and V₂O₃... n O 2n-1 VO2 exhibits metal-insulator phase transition properties and is applied in abruptly changing thermistors, neuronal logic storage and computation, and strong light protection; TiO, Ti2O3, and Ti... n O 2n-1 Binary titanium oxides possess high resistance to acid and alkali corrosion and high conductivity, making them suitable for applications in fuel cells and electrocatalytic degradation of organic pollutants. The prepared SrTMO3 exhibits high conductivity and transparency in the ultraviolet or visible light bands, making it applicable to transparent electromagnetic shielding and transparent conductive coating applications.

[0065] Example 1

[0066] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0067] Weigh out V and VO2 according to the elemental molar ratio V:VO2 = 1:3, and grind them thoroughly in an agate mortar. Based on the thermodynamic equilibrium phase diagram of V2O3, select 800℃ as the reaction temperature. KCl with a melting point of 770℃ is then selected as the flux. Weigh out KCl with a molar ratio of VO2:KCl = 1:10, add the thoroughly mixed VO2 and metallic V powder, and grind thoroughly again. Press the mixture into blocks with a diameter of 10mm using a press, and then place them in an alumina crucible. Furthermore, based on the equilibrium oxygen partial pressure of intermediate-valence transition oxides at 800℃, metallic V powder with an equilibrium oxygen partial pressure lower than that of V2O3 is selected as the oxygen partial pressure control agent. Simultaneously, weigh out metallic V powder according to a mass ratio of 5:1 between the target product V2O3 and the oxygen partial pressure control agent metallic V powder. KCl with a molar ratio of V:KCl = 1:10 was weighed out. The oxygen partial pressure control agent was mixed with KCl and ground evenly. The mixture was then cold-pressed into blocks with a diameter of 10 mm and placed in another alumina crucible. The two alumina crucibles and a 2-inch Al₂O₃(0001) single-crystal substrate with metallic V deposited on its surface were placed in a quartz furnace tube equipped with a mechanical pump and a well-sealed stainless steel flange with an inner diameter of 100 mm. Air was extracted from the quartz furnace tube using the mechanical pump to create a rough vacuum environment with a vacuum level ranging from 0.1 to 1 Pa. The mixture was then sintered at 900 °C for 30 min, followed by a holding time at 800 °C for 24 h. Finally, the powder sample was rinsed with deionized water and dried to obtain pure-phase V₂O₃ powder and V₂O₃ / Al₂O₃(0001) wafers. The X-ray diffraction pattern of the prepared V₂O₃ powder material is shown below. Figure 2 As shown.

[0068] A binder was added to the obtained powder, and the cold pressing process was completed by holding the pressure at 25-30 MPa for 20-30 minutes; a cylindrical ceramic green body with a diameter of 6-25 mm and a height of 2-5 mm was obtained; the green body was placed in a closed environment with a vacuum range of 0.1-1 Pa and annealed at 800℃ for 24 hours to obtain the ceramic material of this composition. The X-ray diffraction of the prepared V2O3 / Al2O3(0001) thin film material is as follows. Figure 5 As shown, the prepared ceramic and thin film materials undergo a low-temperature insulating phase to high-temperature metallic phase transition near the phase transition characteristic temperature of 170K, triggering a resistivity abrupt change of 10. 4 It can be used to prepare low-temperature transient thermistors.

[0069] Example 2

[0070] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0071] Weigh V and VO2 according to the elemental molar ratio V:VO2 = 1:5, and grind them thoroughly in an agate mortar. Based on the thermodynamic equilibrium phase diagram of V3O5, 800℃ is selected as the reaction temperature. KCl, with a melting point of 770℃, is then used as the flux. Weigh KCl at a molar ratio of VO2:KCl = 1:10, add the thoroughly mixed VO2 and metallic V powder, and grind thoroughly again. Press the mixture into 10mm diameter blocks and place them in an alumina crucible. Then, based on the equilibrium oxygen partial pressure of V3O5 at 800℃, V2O3 powder, with an equilibrium oxygen partial pressure lower than that of V3O5, is selected as the oxygen partial pressure control agent. V2O3 powder is weighed at a mass ratio of 5:2 to the target product V3O5. KCl with a molar ratio of V:KCl = 1:10 was weighed, and the oxygen partial pressure control agent was mixed and ground evenly with KCl. The mixture was then cold-pressed into blocks with a diameter of 10 mm and placed in another alumina crucible. The two alumina crucibles and a 2-inch Al2O3(0001) single-crystal substrate with metallic V deposited on its surface were placed in a quartz furnace tube equipped with a mechanical pump and a well-sealed stainless steel flange with an inner diameter of 100 mm. Air was extracted from the quartz furnace tube using the mechanical pump to create a rough vacuum environment with a vacuum level ranging from 0.1 to 1 Pa. The mixture was then sintered at 900 °C for 30 min, followed by a holding time at 800 °C for 24 h. Finally, the powder sample was rinsed with deionized water and dried to obtain pure-phase V3O5 powder and V3O5 / Al2O3(0001) wafers. The X-ray diffraction pattern of the prepared V3O5 powder material is shown below. Figure 3 As shown in the figure. The resistivity of the prepared V3O5 powder material changes with temperature as follows. Figure 4 As shown.

[0072] A binder was added to the obtained powder, and the cold pressing process was completed by holding the pressure at 20-30 MPa for 15-30 minutes; a cylindrical ceramic green body with a diameter of 6-25 mm and a height of 2-5 mm was obtained; the green body was placed in a closed environment with a vacuum range of 0.1-1 Pa and annealed at 750℃ for 24 hours to obtain the ceramic material of this composition. The resistance of the prepared V3O5 / Al2O3(0001) thin film material as a function of temperature is shown in the figure below. Figure 6 As shown, a low-temperature insulating phase transforms into a high-temperature metallic phase near the phase transition characteristic temperature of 420K, triggering a 10-fold change in resistivity, which can be used to prepare abrupt change thermistors.

[0073] Example 3

[0074] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0075] Weigh out V and VO2 according to the elemental molar ratio V:VO2=1:11, and grind them thoroughly in an agate mortar until uniform. Based on V6O... 11 Based on the thermodynamic equilibrium phase diagram, 600℃ was selected as the reaction temperature. Therefore, a NaCl and KCl eutectic molten salt with a melting point of 550℃ and a mass ratio of 44:56 was determined as the flux. NaCl and LiCl with a molar ratio of VO2:NaCl:LiCl = 1:0.3:0.7 were weighed out, and a uniformly mixed VO2 and metallic V powder were added. The mixture was then thoroughly ground again and cold-pressed into blocks with a diameter of 10mm, which were then placed in an alumina crucible. Further processing was then performed based on V6O... 11 The equilibrium oxygen partial pressure at 600℃ is selected such that its equilibrium oxygen partial pressure is lower than V6O. 11 V5O9 powder was used as an oxygen partial pressure control agent, according to the target product V6O 11 The precursors of oxygen partial pressure control agent V5O9, VO2 powder and metallic V powder, were weighed in a mass ratio of 1:0.04:0.96. Simultaneously, NaCl and LiCl were weighed in a molar ratio of V:NaCl:LiCl = 1:0.3:0.7. The oxygen partial pressure control agent precursor was mixed with the NaCl and LiCl eutectic molten salt and ground evenly. The mixture was then cold-pressed into 10mm diameter blocks and placed in another alumina crucible. The two alumina crucibles and a 2-inch single-crystal silicon substrate with metallic V deposited on its surface were placed in a quartz furnace tube equipped with a mechanical pump and a 100mm inner diameter stainless steel flange with good airtightness. Air was evacuated from the quartz furnace tube using the mechanical pump to create a rough vacuum environment with a vacuum level ranging from 0.1 to 1 Pa. The mixture was then sintered at 650℃ for 30 min, followed by holding at 600℃ for 24 h. Finally, the powder sample was rinsed with deionized water and dried to obtain pure-phase V6O. 11 Powder and V6O 11 / Si thin film materials.

[0076] A binder is added to the obtained powder, and the cold pressing process is completed by holding the pressure at 20-30 MPa for 10-25 minutes; a cylindrical ceramic blank with a diameter of 6-25 mm and a height of 2-5 mm is obtained; the blank is placed in a closed environment with a vacuum range of 1-10 Pa and annealed at 550℃ for 24 hours to obtain a ceramic material of this composition. It undergoes a low-temperature insulating phase to high-temperature metallic phase transformation near the phase transformation characteristic temperature of 250K, and the resistivity change triggered by this transformation is 100 times. It can be used to prepare low-temperature abrupt change thermistors.

[0077] Example 4

[0078] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0079] Ti and TiO2 were weighed according to an elemental molar ratio of Ti:TiO2 = 1:5 and ground thoroughly in an agate mortar. Based on the thermodynamic equilibrium phase diagram of Ti3O5, 800℃ was selected as the reaction temperature. KCl, with a melting point of 770℃, was then chosen as the flux. KCl with a molar ratio of TiO2:KCl = 1:10 was weighed and added to the uniformly mixed TiO2 and metallic Ti powder. The mixture was ground thoroughly again and then cold-pressed into blocks with a diameter of 10mm, which were then placed in an alumina crucible. Furthermore, based on the equilibrium oxygen partial pressure of Ti3O5 at 800℃, Ti2O3 powder, with an equilibrium oxygen partial pressure lower than that of Ti3O5, was selected as the oxygen partial pressure control agent. The reaction was then carried out according to the target product Ti3O5 and the oxygen partial pressure control... The Ti2O3 powder formulation was weighed in a mass ratio of 5:2. Simultaneously, KCl with a molar ratio of Ti:KCl = 1:10 was weighed. The oxygen partial pressure control agent and KCl were mixed and ground evenly, then cold-pressed into blocks with a diameter of 10 mm using a press. These blocks were then placed in another alumina crucible. The two alumina crucibles were placed in a quartz furnace tube equipped with a mechanical pump and a 100 mm inner diameter stainless steel flange with good airtightness. The air inside the quartz furnace tube was evacuated using the mechanical pump to create a rough vacuum environment with a vacuum degree ranging from 0.1 to 1 Pa. The mixture was then sintered at 900℃ for 30 min, followed by holding at 800℃ for 24 h. Finally, the powder sample was rinsed with deionized water and dried to obtain pure phase Ti3O5 powder.

[0080] A binder is added to the obtained powder, and the cold pressing process is completed by holding the pressure in the range of 20-30 MPa for 10-25 minutes; a cylindrical ceramic blank with a diameter range of 6-25 mm and a height range of 2-5 mm is obtained; the blank is placed in a closed environment with a vacuum range of 1-10 Pa and annealed at 700℃ for 12 hours to obtain a ceramic material of this composition. It undergoes a low-temperature insulating phase to high-temperature metallic phase transformation near the phase transformation characteristic temperature of 237K, and the resistivity change triggered by it is 100 times, which can be used to prepare abrupt change thermistors.

[0081] Example 5

[0082] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0083] Weigh out Ti and TiO2 according to the elemental molar ratio Ti:TiO2 = 1:11, and grind them thoroughly in an agate mortar until uniform. Based on Ti6O... 11Based on the thermodynamic equilibrium phase diagram, 600℃ was selected as the reaction temperature. Therefore, a NaCl and LiCl eutectic molten salt with a melting point of 550℃ and a mass ratio of 44:56 was determined as the flux. NaCl and LiCl with a molar ratio of TiO2:NaCl:LiCl = 1:0.3:0.7 were weighed out, and a uniformly mixed TiO2 and metallic Ti powder were added. The mixture was then thoroughly ground again and cold-pressed into blocks with a diameter of 10mm using a press, and then placed in an alumina crucible. Further processing was then performed based on Ti6O... 11 The equilibrium oxygen partial pressure at 600℃ is selected to be lower than that of Ti6O. 11 Ti5O9 powder was used as an oxygen partial pressure control agent, according to the target product Ti6O 11 The precursor TiO2 powder and metallic Ti powder of the oxygen partial pressure control agent Ti5O9 were weighed in a mass ratio of 1:0.04:0.96. Simultaneously, NaCl and LiCl in a molar ratio of Ti:NaCl:LiCl = 1:0.3:0.7 were weighed. The oxygen partial pressure control agent precursor was mixed with the NaCl and LiCl eutectic molten salt and ground evenly. The mixture was then cold-pressed into 10mm diameter blocks and placed in another alumina crucible. These two alumina crucibles were placed in a quartz furnace tube equipped with a mechanical pump and a 100mm inner diameter stainless steel flange with good airtightness. Air was extracted from the quartz furnace tube using the mechanical pump to create a rough vacuum environment with a vacuum level ranging from 0.1 to 1 Pa. The mixture was then sintered at 650℃ for 30 min, followed by holding at 600℃ for 24 h. Finally, the powder sample was rinsed with deionized water and dried to obtain pure phase Ti6O. 11 powder.

[0084] A binder is added to the obtained powder, and the cold pressing process is completed by holding the pressure at 20-30 MPa for 10-20 minutes; a cylindrical ceramic blank with a diameter of 6-25 mm and a height of 2-5 mm is obtained; the blank is placed in a closed environment with a vacuum of 1-10 Pa and annealed at 600℃ for 15 hours to obtain a ceramic material of this composition. It undergoes a low-temperature insulating phase to high-temperature metallic phase transformation near the phase transformation characteristic temperature of 130K, and the resistivity change triggered by this transformation is 40 times. It can be used to prepare low-temperature abrupt change thermistors.

[0085] Example 6

[0086] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0087] Weigh out VO2 and TiO2 according to the elemental molar ratio VO2:TiO2 = 0.95:0.05, and grind them thoroughly in an agate mortar until uniform. Based on V... 0.95 Ti 0.05Based on the thermodynamic equilibrium phase diagram of O2, 600℃ was selected as the reaction temperature. Therefore, a NaCl and LiCl eutectic molten salt with a melting point of 550℃ and a mass ratio of 44:56 was chosen as the flux. NaCl and LiCl in a molar ratio of VO2:NaCl:LiCl = 1:0.3:0.7 were weighed out and added to a uniformly mixed VO2 and TiO2 powder. The mixture was then thoroughly ground again and cold-pressed into 10mm diameter blocks, which were then placed in an alumina crucible. Further processing was then performed based on V... 0.95 Ti 0.05 The equilibrium oxygen partial pressure of O2 at 600℃ is chosen to be lower than V. 0.95 Ti 0.05 O2's V6O 11 Powder is used as an oxygen partial pressure control agent, according to the target product V 0.95 Ti 0.05 O2 and oxygen partial pressure control agent V6O 11 The precursor VO2 powder and metallic V powder were weighed in a mass ratio of 1:0.04:0.96. Simultaneously, NaCl and LiCl were weighed in a molar ratio of V:NaCl:LiCl = 1:0.3:0.7. The oxygen partial pressure control precursor was mixed with the NaCl and LiCl eutectic molten salt and ground evenly. The mixture was then cold-pressed into 10mm diameter blocks and placed in another alumina crucible. Both alumina crucibles were placed in a quartz furnace tube equipped with a mechanical pump and a 100mm inner diameter stainless steel flange with good airtightness. Air was extracted from the quartz furnace tube using the mechanical pump to create a rough vacuum environment with a vacuum level ranging from 0.1 to 1 Pa. The mixture was then sintered at 650℃ for 30 min, followed by holding at 600℃ for 24 h. Finally, the powder sample was rinsed with deionized water and dried to obtain pure phase V. 0.95 Ti 0.05 O2 powder.

[0088] A binder is added to the obtained powder, and the cold pressing process is completed by holding the pressure at 20-30 MPa for 10-15 minutes; a cylindrical ceramic blank with a diameter of 6-25 mm and a height of 2-5 mm is obtained; the blank is placed in a closed environment with a vacuum range of 1-10 Pa and annealed at 550℃ for 24 hours to obtain a ceramic material of this composition. The ceramic material undergoes a low-temperature insulating phase to high-temperature metallic phase transformation near the phase transformation characteristic temperature of 320K, accompanied by a sudden change in infrared absorption rate. The resistivity change triggered by this change is 100 times, which has potential application value in the preparation of abrupt change thermistors and infrared camouflage scenarios.

[0089] Example 7

[0090] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0091] Weigh out VO2 and Cr2O3 according to the elemental molar ratio VO2:Cr2O3 = 0.95:0.025, and grind them thoroughly in an agate mortar until uniform. Based on V... 0.95 Cr 0.05 Based on the thermodynamic equilibrium phase diagram of O2, 600℃ was selected as the reaction temperature. Therefore, a NaCl and LiCl eutectic molten salt with a melting point of 550℃ and a mass ratio of 44:56 was chosen as the flux. NaCl and LiCl with a molar ratio of VO2:NaCl:LiCl = 1:0.3:0.7 were weighed out and added to a uniformly mixed VO2 and Cr2O3 powder. The mixture was then thoroughly ground again and cold-pressed into 10mm diameter blocks, which were then placed in an alumina crucible. Further processing was then performed based on V... 0.95 Cr 0.05 The equilibrium oxygen partial pressure of O2 at 600℃ is chosen to be lower than V. 0.95 Cr 0.05 O2's V6O 11 Powder is used as an oxygen partial pressure control agent, according to the target product V 0.95 Cr 0.05 O2 and oxygen partial pressure control agent V6O 11 The precursor VO2 powder and metallic V powder were weighed in a mass ratio of 1:0.04:0.96. Simultaneously, NaCl and LiCl were weighed in a molar ratio of V:NaCl:LiCl = 1:0.3:0.7. The oxygen partial pressure control precursor was mixed with the NaCl and LiCl eutectic molten salt and ground evenly. The mixture was then cold-pressed into 10mm diameter blocks and placed in another alumina crucible. Both alumina crucibles were placed in a quartz furnace tube equipped with a mechanical pump and a 100mm inner diameter stainless steel flange with good airtightness. Air was extracted from the quartz furnace tube using the mechanical pump to create a rough vacuum environment with a vacuum level ranging from 0.1 to 1 Pa. The mixture was then sintered at 650℃ for 30 min, followed by holding at 600℃ for 24 h. Finally, the powder sample was rinsed with deionized water and dried to obtain pure phase V. 0.95 Cr 0.05 O2 powder.

[0092] A binder is added to the obtained powder, and the cold pressing process is completed by holding the pressure at 20-25 MPa for 10-15 minutes; a cylindrical ceramic blank with a diameter of 6-25 mm and a height of 2-5 mm is obtained; the blank is placed in a closed environment with a vacuum range of 1-10 Pa and annealed at 550℃ for 24 hours to obtain a ceramic material of this composition. The ceramic material undergoes a low-temperature insulating phase to high-temperature metallic phase transformation near the phase transformation characteristic temperature of 360K, accompanied by a sudden change in infrared absorption rate. The resistivity change triggered by this change is 10 times, which has potential application value in the preparation of abrupt change thermistors and infrared camouflage scenarios.

[0093] Example 8

[0094] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0095] Weigh out VO2 and WO3 according to the elemental molar ratio VO2:WO3 = 0.99:0.01, and grind them thoroughly in an agate mortar until uniform. 0.99 W 0.01 Based on the thermodynamic equilibrium phase diagram of O2, 600℃ was selected as the reaction temperature. Therefore, a NaCl and LiCl eutectic molten salt with a melting point of 550℃ and a mass ratio of 44:56 was chosen as the flux. NaCl and LiCl in a molar ratio of VO2:NaCl:LiCl = 1:0.3:0.7 were weighed out and added to a uniformly mixed VO2 and WO3 powder. The mixture was then thoroughly ground again and cold-pressed into 10mm diameter blocks, which were then placed in an alumina crucible. Further processing was then performed based on V... 0.99 W 0.01 The equilibrium oxygen partial pressure of O2 at 600℃ is chosen to be lower than V. 0.99 W 0.01 O2's V6O 11 Powder is used as an oxygen partial pressure control agent, according to the target product V 0.99 W 0.01 O2 and oxygen partial pressure control agent V6O 11 The precursor VO2 powder and metallic V powder were weighed in a mass ratio of 1:0.04:0.96. Simultaneously, NaCl and LiCl were weighed in a molar ratio of V:NaCl:LiCl = 1:0.3:0.7. The oxygen partial pressure control precursor was mixed with the NaCl and LiCl eutectic molten salt and ground evenly. The mixture was then cold-pressed into 10mm diameter blocks and placed in another alumina crucible. Both alumina crucibles were placed in a quartz furnace tube equipped with a mechanical pump and a 100mm inner diameter stainless steel flange with good airtightness. Air was extracted from the quartz furnace tube using the mechanical pump to create a rough vacuum environment with a vacuum level ranging from 0.1 to 1 Pa. The mixture was then sintered at 650℃ for 30 min, followed by holding at 600℃ for 24 h. Finally, the powder sample was rinsed with deionized water and dried to obtain pure phase V. 0.99 W 0.01 O2 powder.

[0096] A binder is added to the obtained powder, and the cold pressing process is completed by holding the pressure at 20-25 MPa for 10-15 minutes; a cylindrical ceramic blank with a diameter of 6-25 mm and a height of 2-5 mm is obtained; the blank is placed in a closed environment with a vacuum range of 1-10 Pa and annealed at 600℃ for 24 hours to obtain a ceramic material of this composition. It undergoes a low-temperature insulating phase to high-temperature metallic phase transformation near the phase transformation characteristic temperature of 300K, accompanied by a sudden change in infrared absorption rate. The resistivity change triggered by this change is 10 times, which has potential application value in the preparation of abrupt change thermistors and infrared camouflage scenarios.

[0097] Example 9

[0098] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0099] Weigh out VO2 and Ta2O5 according to the elemental molar ratio VO2:Ta2O5 = 0.95:0.025, and grind them thoroughly in an agate mortar until uniform. Based on V... 0.95 Ta 0.05 Based on the thermodynamic equilibrium phase diagram of O2, 600℃ was selected as the reaction temperature. Therefore, a NaCl and LiCl eutectic molten salt with a melting point of 550℃ and a molar ratio of 3:7 was chosen as the flux. NaCl and LiCl with a molar ratio of VO2:NaCl:LiCl = 1:0.3:0.7 were weighed out and added to a uniformly mixed VO2 and Ta2O5 powder. The mixture was then thoroughly ground again and cold-pressed into 10mm diameter blocks, which were then placed in an alumina crucible. Further processing was then based on V... 0.95 Ta 0.05 The equilibrium oxygen partial pressure of O2 at 600℃ is chosen to be lower than V. 0.95 Ta 0.05 O2's V6O 11 Powder is used as an oxygen partial pressure control agent, according to the target product V 0.95 Ta 0.05 O2 and oxygen partial pressure control agent V6O 11The precursor VO2 powder and metallic V powder were weighed in a mass ratio of 1:0.04:0.96. Simultaneously, NaCl and LiCl were weighed in a molar ratio of V:NaCl:LiCl = 1:0.3:0.7. The oxygen partial pressure control precursor was mixed with the NaCl and LiCl eutectic molten salt and ground evenly. The mixture was then cold-pressed into 10mm diameter blocks and placed in another alumina crucible. Both alumina crucibles were placed in a quartz furnace tube equipped with a mechanical pump and a 100mm inner diameter stainless steel flange with good airtightness. Air was extracted from the quartz furnace tube using the mechanical pump to create a rough vacuum environment with a vacuum level ranging from 0.1 to 1 Pa. The mixture was then sintered at 650℃ for 30 min, followed by holding at 600℃ for 24 min. Finally, the powder sample was rinsed with deionized water and dried to obtain pure phase V. 0.95 Ta 0.05 O2 powder.

[0100] A binder is added to the obtained powder, and the cold pressing process is completed by holding the pressure at 20-25 MPa for 10-15 minutes; a cylindrical ceramic blank with a diameter of 6-25 mm and a height of 2-5 mm is obtained; the blank is placed in a closed environment with a vacuum range of 1-10 Pa and annealed at 550℃ for 24 hours to obtain a ceramic material of this composition. It undergoes a low-temperature insulating phase to high-temperature metallic phase transformation near the phase transformation characteristic temperature of 310K, accompanied by a sudden change in infrared absorption rate. The resistivity change triggered by this change is 10 times, which has potential application value in the preparation of abrupt change thermistors and infrared camouflage scenarios.

[0101] Example 10

[0102] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0103] Weigh out V, VO2, and Al2O3 according to the elemental molar ratio V:VO2:Al2O3 = 1:3:0.02, and grind them thoroughly in an agate mortar until uniform. (V...) 0.99 Al 0.01 Based on the thermodynamic equilibrium phase diagram of VO2O3, 800℃ was selected as the reaction temperature. Therefore, KCl with a melting point of 770℃ was chosen as the flux. KCl with a molar ratio of VO2:KCl = 1:10 was weighed out and added to a uniformly mixed mixture of VO2, Al2O3, and metallic V powder. The mixture was then thoroughly ground and cold-pressed into 10mm diameter blocks, which were then placed in an alumina crucible. Furthermore, based on the equilibrium oxygen partial pressure of intermediate-valence transition oxides at 800℃, a reaction temperature lower than (V2O3 / Al2O3) was selected. 0.99 Al 0.01 Metallic V powder of 2O3 is used as an oxygen partial pressure control agent, according to the target product (V 0.99Al 0.01 The mass ratio of O2O3 to oxygen partial pressure control agent metal V powder is 5:1. Simultaneously, KCl with a molar ratio of V:KCl = 1:10 is weighed. The oxygen partial pressure control agent and KCl are mixed and ground evenly, then cold-pressed into 10mm diameter blocks and placed in another alumina crucible. These two alumina crucibles are then placed in a quartz furnace tube equipped with a mechanical pump and a 100mm inner diameter stainless steel flange with good airtightness. Air is extracted from the quartz furnace tube using the mechanical pump to create a rough vacuum environment with a vacuum degree ranging from 0.1 to 1 Pa. The sample is then sintered at 900℃ for 30 minutes, followed by holding at 800℃ for 24 hours. Finally, the powder sample is rinsed with deionized water and dried to obtain the pure phase (V2O3). 0.99 Al 0.01 )2O3 powder.

[0104] A binder is added to the obtained powder, and the cold pressing process is completed by holding the pressure at 25-30 MPa for 25-30 minutes; a cylindrical ceramic blank with a diameter of 6-25 mm and a height of 2-5 mm is obtained; the blank is placed in a closed environment with a vacuum range of 0.1-1 Pa and annealed at 800℃ for 24 hours to obtain the ceramic material of this composition. The prepared ceramic undergoes a low-temperature insulating phase to high-temperature metallic phase transformation near the phase transformation characteristic temperature of 170K, which triggers a resistivity abrupt change of 200 times; a low-temperature metallic phase to high-temperature insulating phase transformation occurs near 380K, which triggers a resistivity abrupt change of 5 times.

[0105] Example 11

[0106] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0107] Weigh W and WO3 according to the elemental molar ratio W:WO3 = 1:2, and grind them thoroughly in an agate mortar. Based on the thermodynamic equilibrium phase diagram of WO2, 800 ℃ is selected as the reaction temperature. KCl, with a melting point of 770 ℃, is then selected as the flux. KCl with a molar ratio of WO3:KCl = 1:10 is weighed and added to the uniformly mixed WO3 and W powder. The mixture is ground thoroughly again and then cold-pressed into 10 mm diameter blocks, which are then placed in an alumina crucible. Furthermore, based on the equilibrium oxygen partial pressure of intermediate-valence transition oxides at 800 ℃, W powder with an equilibrium oxygen partial pressure lower than that of WO2 is selected as the oxygen partial pressure control agent. W powder is weighed according to a mass ratio of 5:1 (target product WO2 to oxygen partial pressure control agent W powder), and KCl with a molar ratio of W:KCl = 1:10 is also weighed. The oxygen partial pressure control agent and KCl are mixed and ground thoroughly, and then cold-pressed into 10 mm diameter blocks. The sample was shaped into a 1 mm block and placed in another alumina crucible. The two alumina crucibles and a 2-inch Al2O3(0001) single crystal substrate with W deposited on its surface were placed in a quartz furnace tube with a mechanical pump and a 100 mm inner diameter stainless steel flange. The air inside the quartz furnace tube was evacuated by the mechanical pump to create a rough vacuum environment with a vacuum degree ranging from 0.1 to 1 Pa. The sample was then sintered at 900 °C for 30 min and then held at 800 °C for 24 h. Finally, the powder sample was rinsed with deionized water and dried to obtain pure phase WO2 powder and WO2 / Al2O3(0001) wafers.

[0108] A binder is added to the obtained powder, and the cold pressing process is completed by holding the pressure at 15-25 MPa for 20-30 minutes; a cylindrical ceramic green body with a diameter of 6-25 mm and a height of 2-5 mm is obtained; the green body is placed in a closed environment with a vacuum range of 0.1-1 Pa and annealed at 800℃ for 12 hours to obtain ceramic materials of this composition. The prepared ceramic and thin film materials exhibit metallic phase transport relationships in the temperature range of 3-400 K, and their room temperature conductivity is 1.3 × 10⁻⁶. 4 .

[0109] Example 12

[0110] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0111] Weigh Mo and MoO3 according to the elemental molar ratio of Mo:MoO3 = 1:2, and grind them thoroughly in an agate mortar. Based on the thermodynamic equilibrium phase diagram of MoO2, 800℃ is selected as the reaction temperature. KCl with a melting point of 770℃ is then chosen as the flux. Weigh KCl with a molar ratio of MoO3:KCl = 1:10, add the thoroughly mixed MoO3 and metallic Mo powder, and grind thoroughly again. Press the mixture into blocks with a diameter of 10mm, and then place them in an alumina crucible. Based on the equilibrium oxygen partial pressure of intermediate-valence transition oxides at 800℃, metallic Mo powder with an equilibrium oxygen partial pressure lower than that of MoO2 is selected as the oxygen partial pressure control agent. Weigh metallic Mo according to a mass ratio of the target product MoO2 to the oxygen partial pressure control agent metallic Mo powder of 7:1. While preparing the powder, weigh out KCl with a molar ratio of Mo:KCl = 1:10, mix the oxygen partial pressure control agent with KCl and grind it evenly. Press the mixture into blocks with a diameter of 10 mm using a press, and then place them in another alumina crucible. Place the two alumina crucibles and a 2-inch Al2O3(0001) single crystal substrate with metallic Mo deposited on its surface in a quartz furnace tube equipped with a mechanical pump and a stainless steel flange with good airtightness and an inner diameter of 100 mm. Use the mechanical pump to extract the air from the quartz furnace tube to create a rough vacuum sealed environment with a vacuum degree range of 0.1-1 Pa. Then sinter at 900℃ for 30 min, and then hold at 800℃ for 24 h. Finally, rinse the powder sample with deionized water and dry it to obtain pure phase MoO2 powder and MoO2 / Al2O3(0001) wafers.

[0112] A binder was added to the obtained powder, and the cold pressing process was completed by holding the pressure at 20-30 MPa for 20-30 minutes; a cylindrical ceramic green body with a diameter of 6-25 mm and a height of 2-5 mm was obtained; the green body was placed in a closed environment with a vacuum range of 0.1-1 Pa and annealed at 700℃ for 12 hours to obtain ceramic materials of this composition. The prepared ceramic and thin film materials exhibit metallic phase transport relationships in the temperature range of 3-400 K, and their room temperature conductivity is 1.5 × 10⁻⁶. 4 .

[0113] Example 13

[0114] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0115] SrO, Mo, and MoO3 were weighed according to the elemental molar ratio of SrO:Mo:MoO3 = 3:1:2 and ground thoroughly in an agate mortar. Based on the thermodynamic equilibrium phase diagram of SrMoO3, 700℃ was selected as the reaction temperature. Therefore, a NaCl and KCl eutectic molten salt with a melting point of 656℃ and a mass ratio of 44:56 was selected as the flux. NaCl and KCl with a molar ratio of VO2:NaCl:KCl = 1:4.4:5.6 were weighed and added to the uniformly mixed SrO, Mo, and MoO3 powder. The mixture was ground thoroughly again and then cold-pressed into blocks with a diameter of 10mm using a press. These blocks were then placed in an alumina crucible. Furthermore, based on the equilibrium oxygen partial pressure of intermediate-valence transition oxides at 700℃, Zr metal sheets with an equilibrium oxygen partial pressure lower than that of SrMoO3 were selected as the oxygen flux. For the partial pressure control agent, Zr metal sheets were weighed in a 1:1 mass ratio (SrMoO3 target product to Zr metal sheets), along with NaCl and KCl in a molar ratio of Mo:NaCl:KCl = 1:4.4:5.6. The oxygen partial pressure control agent was mixed evenly with the NaCl and KCl eutectic molten salt and then placed in another alumina crucible. The two alumina crucibles were then placed in a quartz furnace tube with a mechanical pump and a 100mm inner diameter stainless steel flange with good airtightness. The air inside the quartz furnace tube was evacuated using the mechanical pump to create a rough vacuum sealed environment with a vacuum degree ranging from 0.1 to 1 Pa. The sample was then sintered at 800℃ for 30 min, followed by holding at 700℃ for 24 min. Finally, the powder sample was rinsed with deionized water and dried to obtain pure phase SrMoO3 powder.

[0116] A binder is added to the obtained powder, and the cold pressing process is completed by holding the pressure at 15-25 MPa for 10-15 minutes; a cylindrical ceramic green body with a diameter of 6-25 mm and a height of 2-5 mm is obtained; the green body is placed in a closed environment with a vacuum of 0.1-1 Pa and annealed at 700℃ for 12 hours to obtain a ceramic material of this composition, which has a room temperature conductivity of 5×10⁻⁶. 6 Furthermore, it is transparent in the ultraviolet and visible light bands, making it valuable for applications in transparent displays, transparent electromagnetic shielding, photovoltaic energy storage, and oxide transistors.

[0117] Example 14

[0118] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0119] SrO, Nb, and Nb2O5 were weighed according to the elemental molar ratio of SrO:Nb:Nb2O5 = 5:1:2, and ground thoroughly in an agate mortar. Based on the thermodynamic equilibrium phase diagram of SrNbO3, 800℃ was selected as the reaction temperature. KCl with a melting point of 770℃ was then chosen as the flux. KCl with a molar ratio of Nb:KCl = 1:1 was weighed and added to the uniformly mixed SrO, Nb, and Nb2O5 powders. The mixture was ground thoroughly again and then cold-pressed into blocks with a diameter of 10mm, which were then placed in an alumina crucible. Furthermore, based on the equilibrium oxygen partial pressure of intermediate-valence transition oxides at 800℃, Zr metal sheets with an equilibrium oxygen partial pressure lower than that of SrNbO3 were selected as the oxygen partial pressure control agent. Zr metal sheets were weighed according to a mass ratio of 1:1 between the target product SrNbO3 and the oxygen partial pressure control agent Zr metal sheets. Simultaneously, Zr metal sheets with a molar ratio of Zr:Nb2O5 were weighed. A 1:1 mixture of KCl and oxygen partial pressure control agent was prepared and homogenized with the KCl molten salt, then placed in another alumina crucible. The two alumina crucibles were then placed in a quartz furnace tube equipped with a mechanical pump and a 100mm inner diameter stainless steel flange with good airtightness. Air was extracted from the quartz furnace tube using the mechanical pump to create a rough vacuum environment with a vacuum level ranging from 0.1 to 1 Pa. The sample was then sintered at 900℃ for 30 minutes, followed by holding at 800℃ for 24 hours. Finally, the powder sample was rinsed with deionized water and dried to obtain pure-phase SrNbO3 powder.

[0120] A binder is added to the obtained powder, and the cold pressing process is completed by holding the pressure at 20-30 MPa for 20-30 minutes; a cylindrical ceramic green body with a diameter ranging from 6-25 mm and a height ranging from 2-5 mm is obtained; the green body is placed in a closed environment with a vacuum range of 0.1-1 Pa and annealed at 750℃ for 12 hours to obtain a ceramic material of this composition, which has a room temperature electrical conductivity of 2.8 × 10⁻⁶. 5 Furthermore, it is transparent in the ultraviolet and visible light bands, making it valuable for applications in transparent displays, transparent electromagnetic shielding, photovoltaic energy storage, and oxide transistors.

[0121] Example 15

[0122] A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, the method being as follows:

[0123] SrO and VO2 were weighed according to an elemental molar ratio of SrO:VO2 = 1:1 and ground thoroughly in an agate mortar. Based on the thermodynamic equilibrium phase diagram of SrVO3, 800 ℃ was selected as the reaction temperature. KCl, with a melting point of 770 ℃, was then used as the flux. KCl with a molar ratio of VO2:KCl = 1:1 was weighed and added to the uniformly mixed SrO and VO2 powders. The mixture was ground thoroughly again and then cold-pressed into blocks with a diameter of 10 mm, which were then placed in an alumina crucible. Furthermore, based on the equilibrium oxygen partial pressure of intermediate-valence transition oxides at 800 ℃, metallic V powder with an equilibrium oxygen partial pressure lower than that of SrVO3 was selected as the oxygen partial pressure control agent. Metallic V powder was weighed according to a mass ratio of the target product SrVO3 to the oxygen partial pressure control agent metallic V powder of 1:1. Simultaneously, KCl with a molar ratio of V:KCl=1:1 was weighed out, and the oxygen partial pressure control agent was mixed evenly with the KCl molten salt. Then, the mixture was placed in another alumina crucible. The two alumina crucibles were placed in a quartz furnace tube with an inner diameter of 100 mm and equipped with a mechanical pump and a stainless steel flange with good airtightness. The air inside the quartz furnace tube was evacuated by the mechanical pump to create a rough vacuum sealed environment with a vacuum degree range of 0.1-1 Pa. The mixture was then sintered at 900℃ for 30 min, and then held at 800℃ for 24 h. Finally, the powder sample was rinsed with deionized water and dried to obtain pure phase SrVO3 powder.

[0124] A binder is added to the obtained powder, and the cold pressing process is completed by holding the pressure at 25-30 MPa for 20-30 minutes; a cylindrical ceramic green body with a diameter ranging from 6-25 mm and a height ranging from 2-5 mm is obtained; the green body is placed in a closed environment with a vacuum range of 0.1-1 Pa and annealed at 800℃ for 12 hours to obtain a ceramic material of this composition, which has a room temperature electrical conductivity of 3.8 × 10⁻⁶. 6 Furthermore, it is transparent in the ultraviolet and visible light bands, making it valuable for applications in transparent displays, transparent electromagnetic shielding, photovoltaic energy storage, and oxide transistors.

[0125] The above-mentioned solution proposes a method for preparing intermediate valence transition metal oxides with self-regulating oxygen partial pressure assisted by molten salt. This method can solve the technical problems existing in the prior art, including: difficulty in mass-producing intermediate valence transition metal oxide powder materials with precise stoichiometry, difficulty in synthesizing intermediate valence transition metal oxide thin film materials with precise stoichiometry, and the requirement that the preparation process of intermediate valence transition metal oxide materials must be completed in a reducing atmosphere above 1000°C.

[0126] The products prepared by subsequent processing of intermediate-valence transition oxide powders of the present invention include abrupt change thermistor devices, battery electrodes, electrocatalytic electrodes, flat panel display film coatings, terahertz modulation devices, and transparent conductive electrodes. The intermediate-valence titanium oxide products prepared have the properties of acid and alkali radiation resistance, electrochemical window stability, and high conductivity of 1500 S / cm. Their stability in strong acid and alkali media is superior to that of the prior art.

[0127] The intermediate valence vanadium oxide abrupt change thermistor prepared in this invention exhibits a wide temperature detection range of 50-400 K and a performance of 10 3 -10 5 The resistance change rate of Ω is significantly higher than that of existing technologies, exhibiting superior performance in both temperature detection range and resistance change rate. The transparent conductive electrode prepared using SrTMO3 (TM = V, Nb, Mo) thin film material possesses high transmittance in the ultraviolet to visible light range while maintaining a conductivity of 10 Ω. 4 -10 6 Within its range, its conductivity is superior to that of existing technologies.

[0128] In summary, compared with the traditional casting-rolling method, the present invention introduces a self-regulating mechanism of molten alkali metal halides and oxygen partial pressure, which enables the batch synthesis of multidimensional materials of intermediate valence transition metal oxides with precise stoichiometric ratios without relying on dangerous high-temperature reducing atmospheres. The prepared multidimensional materials of intermediate valence transition metal oxides can be applied to abrupt change thermistor devices, battery electrodes, electrocatalytic electrodes, flat panel display film coatings, terahertz modulation devices, and transparent conductive electrodes.

[0129] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0130] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0131] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0132] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides, characterized in that, The method for preparing intermediate-valence transition oxides with molten salt-assisted oxygen partial pressure self-regulation involves using molten alkaline earth metal halides as a medium in a closed vacuum environment. Based on the dissolution-precipitation equilibrium of oxygen in the melt, the oxygen content of the target product inside the molten salt is correlated with the oxygen partial pressure in the vacuum environment outside the melt. Another reaction process with an oxygen potential lower than that of the target reaction system is introduced into the rough vacuum environment outside the melt. This allows for accurate and spontaneous regulation of the oxygen partial pressure required for the synthesis of multi-dimensional materials of intermediate-valence transition oxides inside and outside the melt, achieving accurate and high-yield synthesis of multi-dimensional materials of intermediate-valence transition oxides inside and outside the melt. Finally, the powder sample is washed with deionized water and dried to obtain intermediate-valence transition oxide powder.

2. The method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides according to claim 1, characterized in that, The aforementioned process of introducing an oxygen potential lower than that of the target reaction system into a rough vacuum environment outside the melt is achieved by using a transition element or compound with an average valence state close to but lower than that of the target product as an oxygen partial pressure control agent.

3. The method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides according to claim 2, characterized in that, The method of using transition metal elements or compounds with an average valence state close to but lower than that of the target product as oxygen partial pressure control agents is as follows: In a closed environment, molten alkaline earth metal halides can act as a medium to accelerate the establishment of a dissolution-precipitation equilibrium of oxygen on the melt surface, establish the connection between the oxygen content of the target product inside the molten salt and the oxygen partial pressure in the closed environment outside the melt, and complete the spontaneous regulation of the equilibrium oxygen partial pressure inside and outside the melt and the synthesis of the intermediate valence state transition oxide target product powder material by means of the oxidation process of another oxygen partial pressure control agent in the melt. While using transition elements or compounds with average valence states close to but lower than the target product as oxygen partial pressure control agents, the synthesis process of intermediate valence state transition oxides in the melt can achieve self-regulation of oxygen partial pressure in the closed environment outside the melt through the migration of oxygen elements in a closed environment. This triggers the nucleation and growth of low-dimensional intermediate valence state transition oxide materials outside the melt on a single crystal substrate with crystallographic alignment. The vacuum level of the closed vacuum environment ranges from 0.1 to 10 Pa, which is achieved by using a tube furnace equipped with a mechanical pump, to realize the accurate and large-scale synthesis of transition oxide powders and low-dimensional film materials with complex intermediate valence states.

4. The method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides according to claim 1, characterized in that, Material systems of intermediate-valence transition oxides include binary or multi-component transition oxides, wherein the transition metal elements include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ta, W, Re, Os, and Ir; the oxide forms formed by the transition metal elements and oxygen include TiO, Ti2O3, and Ti... n O 2n-1 The integer n can take values ​​of 3 ≤ n ≤ 9; VO, V2O3, V n O 2n-1 The range of integer n in the middle is 3≤n≤9, VO2, V n O 2n+1 The integer n can take the values ​​3 and 6; Ae 1-x Re x VO3, where x takes values ​​in the range 0 ≤ x ≤ 1, NbO2, Nb 3n+1 O 8n-2 In the context, the integer n takes values ​​of 25 and 28, and MoO2 and Mo n O 3n-1 The integer n in the middle ranges from 4, 8, 9, 17, and 18, WO2, W n O 3n-1 The integer n in the middle ranges from 3, 5, and 10; SrTMO3, where TM represents V, Mo and Nb, ReFe2O4, ReBaFe2O5, Fe3O4, and Mn3O4; Wherein: Re represents rare earth elements, including La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, or a single rare earth element or a combination of multiple rare earth elements; Ae represents alkaline earth metal elements, including Mg, Ca, Sr, and Ba, or a single alkaline earth metal element or a combination of multiple alkaline earth metal elements.

5. The method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides according to claim 1, characterized in that, The raw material for molten alkaline earth metal halides is molten alkaline earth metal halide salt. The composition and proportion are determined based on the oxygen potential diagram of the intermediate-valence transition oxide reaction system. The synthesis temperature of the target product is determined, and the type and proportion of molten salt with a melting point lower than or equal to the synthesis temperature are selected as flux. At the same time, the molten salt is required to dissolve the intermediate-valence transition oxide precursor powder at high temperature and molten state, and not to react with the precursor powder, so that the precursor powder is uniformly dispersed in the melt, thereby accelerating the reaction rate. The molten salt acts as an oxygen exchange medium, and by means of the dissolution-precipitation equilibrium of oxygen on the melt surface, it establishes the connection between the inside and outside of the melt and between different melts in the same closed environment. By means of the redox characteristics of the low oxygen potential reaction system at the synthesis temperature relative to the reaction process of the target product, the self-regulation of the equilibrium oxygen partial pressure in the closed environment is achieved, thereby controlling the oxygen content of the intermediate-valence transition oxide target product in the melt.

6. The method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides according to claim 5, characterized in that, Alkaline earth metal halide molten salt components include LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KCl, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, LiI, NaI, KI, RbI, and CsI. A single molten salt can be used to assist the growth of a new phase, or a mixture of multiple molten salts can be used to assist the growth of a new phase.

7. The method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides according to claim 1, characterized in that, In the method for preparing intermediate-valence transition oxide materials with spontaneous oxygen partial pressure regulation assisted by molten salt, the type and proportion of oxygen partial pressure control agent are determined based on the oxygen potential diagram. Transition metal oxides or elemental metals with oxygen potential lower than that of the target product reaction system at the target synthesis temperature can be selected as oxygen partial pressure control agents. With the help of molten salt medium, the chemical equilibrium between the target product reaction system and the oxygen partial pressure control agent is constructed through the dissolution-precipitation equilibrium of oxygen element on its surface inside and outside the melt, achieving self-regulation of oxygen partial pressure in a closed environment. This provides an environment atmosphere within the thermodynamic equilibrium oxygen partial pressure range for intermediate-valence transition oxides inside or outside the melt, triggering the nucleation and growth of the target product on the surface of a single-crystal substrate with crystallographic alignment inside and outside the molten salt melt. This accurately controls the intermediate valence state of the transition elements and realizes the large-scale, multi-dimensional morphological material preparation.

8. The method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides according to claim 1, characterized in that, A method for preparing intermediate-valence transition oxides with molten salt-assisted oxygen pressure spontaneous regulation enables the growth of low-latitude intermediate-valence transition oxide materials with a film thickness ranging from 10 nm to 100 μm on the surface of a single-crystal substrate. The single-crystal substrates include lanthanum aluminate, strontium titanate, titanium dioxide, aluminum oxide, yttrium iron garnet, yttrium-doped zirconium oxide, germanium dioxide, magnesium oxide, mica, quartz, doped silicon wafers, and single-crystal silicon substrates with the aforementioned single-crystal substrate materials deposited on their surface as a buffer layer. Alternatively, a sacrificial layer with similar lattice parameters can be grown on the surface of the single-crystal substrate, and then the sacrificial layer can be removed by heating or dissolution to obtain a self-supporting thin film of intermediate-valence transition oxides. The sacrificial layer includes alkali metal halides and strontium aluminum oxide. Methods for preparing intermediate-valence transition oxide precursor thin films include: magnetron sputtering, pulsed laser deposition, thermal evaporation, chemical vapor deposition, and sol-gel spin coating.

9. The method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides according to claim 1, characterized in that, In intermediate-valence transition oxides, the metal element can be partially replaced by one or more other transition metal elements, including Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ta, W, Re, Os, and Ir. The molar ratio x of the metal element being replaced ranges from 0 to x ≤ 0.

5. While obtaining doped intermediate-valence transition oxide polycrystalline powder materials, the grain size of the material can be flexibly controlled by controlling the cooling rate. Simultaneously, by designing a specific patterned metal structure on the surface of a single-crystal substrate, intermediate-valence transition oxide materials with a specific structure or pattern can be obtained outside the melt. The specific structure includes equally spaced strip or lattice gratings, curved surfaces with a radius of curvature ranging from 10 μm to 10 cm, and equally spaced concentric ring gratings.

10. The method for preparing molten salt-assisted oxygen partial pressure self-regulating intermediate valence state transition oxides according to claim 4, characterized in that, The molten salt-assisted oxygen partial pressure self-regulating method for preparing intermediate valence state transition oxides can accurately control the valence state of transition elements and achieve large-scale, multi-dimensional morphological material preparation. Simultaneously, it can prepare V₂O₃ and V₂O₃. n O 2n-1 VO2 exhibits metal-insulator phase transition properties and is applied in abruptly changing thermistors, neuronal logic storage and computation, and strong light protection; TiO, Ti2O3, and Ti... n O 2n-1 Binary titanium oxides possess high resistance to acid and alkali corrosion and high conductivity, making them suitable for applications in fuel cells and electrocatalytic degradation of organic pollutants. The prepared SrTMO3 exhibits high conductivity and transparency in the ultraviolet or visible light bands, making it applicable to transparent electromagnetic shielding and transparent conductive coating applications.

Images