125 results about "Bismuth ferrite" patented technology

The invention discloses a method for preparing a bismuth ferrite composite catalytic material by using red mud as well as a product and application of the bismuth ferrite composite catalytic material. The method comprises the following steps: mixing chlorine salt and red mud, uniformly stirring, adding a hydrochloric acid solution, uniformly stirring, roasting, recovering flue gas generated in the roasting process, and obtaining roasting residues and roasting dust generated by recovering the flue gas after roasting is finished; and mixing the roasted dust and bismuth nitrate, uniformly stirring, adding the calcined residue, uniformly grinding, adding water, stirring, drying the material, and calcining to obtain the bismuth ferrite composite catalytic material. The preparation process is simple, the red mud is used as a main raw material, and full-amount resource utilization of the red mud can be achieved. The prepared composite catalytic material can be used for efficiently purifying landfill leachate, and COD, ammonia nitrogen, total phosphorus and heavy metal pollution are efficiently removed through a photocatalysis mechanism.

The invention provides an anti-ferroelectric lanthanum ferrite, bismuth ferrite and strontium titanate superlattice film with high energy storage density as well as a preparation method and application thereof. The anti-ferroelectric lanthanum ferrite, bismuth ferrite and strontium titanate superlattice film with high energy storage density comprises a substrate layer, a bottom electrode layer and a plurality of stacked relaxation ferroelectric layers, wherein the bottom electrode layer and the multiple stacked relaxation ferroelectric layers are sequentially arranged on the substrate layer; each relaxor ferroelectric layer sequentially comprises a first functional layer, a second functional layer and a third functional layer from bottom to top; the first functional layer comprises LaFeO3, the second functional layer comprises BiFeO3, and the third functional layer comprises SrTiO3. The anti-ferroelectric lanthanum ferrite, bismuth ferrite and strontium titanate superlattice thin film with the high energy storage density has small electric leakage performance and high polarization value, and more excellent energy storage performance is achieved.

The invention relates to a preparation method of a bismuth ferrite-based composite material. The invention aims to solve the problems of poor conductivity and few active sites of the existing bismuth ferrite electrode material, and provides a preparation method of an efficient electro-catalytic hydrogen evolution catalyst. According to the method, bismuth nitrate, ferric chloride, ethylene glycol, ammonia water, sodium hydroxide, thiourea, ammonium molybdate and cobalt nitrate are used as raw materials, a two-step hydrothermal method is adopted, the bismuth ferrite-based cobalt-doped molybdenum disulfide composite material is prepared, and the preparation method is provided for improving the electro-catalytic hydrogen evolution performance of existing bismuth ferrite.

The invention relates to the technical field of dielectric energy storage device materials, in particular to high-entropy designed bismuth ferrite-based energy storage ceramic as well as a preparation method and application thereof, the chemical composition formula of the material is (0.7-x) Bi < 0.9 > (Sm < 0.5 > Gd < 0.5 >) < 0.1 > FeO < 3-0.3 > (Sr < 0.5 > Ba < 0.5 >) TiO < 3-x > NaNbO < 3-y > MnO < 2 >, the value range of x is 0-0.15, and the value range of y is 0-0.005. The relaxation ferroelectric material is designed by adopting a high-entropy strategy, and various elements occupy the same site of the material to generate lattice distortion, so that the relaxation characteristic of bismuth ferrite-based ceramic is promoted, and a ferroelectric hysteresis loop is optimized. The NaNbO3 anti-ferroelectric material is introduced, the long-range ferroelectric order is destroyed, the local random field is enhanced, and a low Pr value can be obtained. And in addition, the concentration of oxygen vacancies can be reduced by properly adding 0.5% mol of MnO2, so that the leakage current of the material is reduced, the energy storage efficiency is improved, and the material design not only enriches the application field of the high-entropy ceramic, but also provides a new thought for improving the performance of the energy storage ceramic.

The invention relates to the technical field of piezoelectric ceramics, in particular to a bismuth ferrite-lead titanate-zinc bismuth titanate ternary system piezoelectric ceramic material as well as preparation and application thereof. The chemical general formula of the bismuth ferrite-lead titanate-zinc bismuth titanate ternary system piezoelectric ceramic material disclosed by the invention is (1-x-y) BiFeO3-x (PbMez) TiO3-yBi (Zn0. 5Ti0. 5) O3, wherein Me is an alkaline earth metal element, x is equal to 0.4-0.8, y is equal to 0.05-0.3, z is equal to 0.05-0.5, and 1-x-y is greater than 0. The piezoelectric ceramic material has large anisotropy (d33 / d31 is between 5 and 60) and relatively high voltage (d33 is greater than 100pC / N), has a wide application prospect in the technical field of high-frequency image sonar transducers, and solves the problems of low piezoelectric coefficient and piezoelectric anisotropy of the existing bismuth ferrite-lead titanate-zinc bismuth titanate ternary system piezoelectric ceramic material.

The invention discloses a bismuth ferrite-based ceramic material with low energy consumption and high energy storage and a low-temperature rapid sintering preparation method of the bismuth ferrite-based ceramic material, a flash sintering technology is applied to 0.55 BiFeO3-0. 4SrTiO3-0.05 NaNbO3 (BFST-0. 05NN) ceramic, on one hand, the component of 0.6 BiFeO3-0. 4SrTiO3 is close to a morphotropic phase boundary (MPB) to provide high polarization, and the introduction of NaNbO3 improves the structure disorder and promotes the relaxation behavior, so that the energy storage efficiency is improved; on the other hand, by optimizing the electric field (100-250 V / cm) and the flash sintering time under the fixed current density (40 mA / mm < 2 >), reactive densification can be achieved at the very low temperature and within the ultra-short time, and compared with traditional solid sintering, the furnace temperature is reduced by nearly 500 DEG C; flash sintering can realize densification of the ceramic, inhibit grain growth of the ceramic, refine a grain structure, inhibit volatilization of volatile elements and inhibit leakage conductance current at the same time, the lead-free bismuth ferrite-based ceramic with high breakdown and high energy storage and excellent ferroelectric, piezoelectric and energy storage performance is obtained, and green development and high energy storage are realized at the same time.

The invention provides a bismuth ferrite-graphite phase carbon nitride photocatalyst and a preparation method and application thereof, and relates to the technical field of photocatalysis, the preparation method comprises the following steps: dissolving a bismuth source and an iron source in a solvent, mixing with a mineralizing agent, and carrying out a hydrothermal synthesis reaction to obtain bismuth ferrite; performing first roasting treatment on the nitrogen-containing organic matter precursor to obtain graphite-phase carbon nitride; and mixing bismuth ferrite and graphite phase carbon nitride, and carrying out grinding treatment and second roasting treatment to obtain the bismuth ferrite-graphite phase carbon nitride photocatalyst. According to the preparation method, bismuth ferrite and graphite-phase carbon nitride which are prepared respectively are compounded, a Z-type heterojunction can be constructed at an interface of the bismuth ferrite and the graphite-phase carbon nitride, an internal electric field is formed, so that photo-induced electrons and holes are efficiently separated, compounding of the photo-induced electrons and the holes is effectively inhibited, and finally the oxidation-reduction capacity of the material is remarkably enhanced; therefore, the photocatalyst shows excellent photocatalytic performance, high selectivity and good cycle stability.

The invention relates to the technical field of environmental governance, and particularly discloses a bismuth ferrite-based photo-Fenton catalyst and application thereof. The bismuth ferrite-based photo-Fenton catalyst comprises a bismuth ferrite matrix or a catalyst, the bismuth ferrite matrix comprises Fe (NO) 9HO and Bi (NO) 5HO in a molar ratio of 1: 1-1: 1.1, the catalyst is one of metal-doped bismuth ferrite, non-metal-doped bismuth ferrite or a bismuth ferrite composite material, and the loading amount of metal in the metal-doped bismuth ferrite is 0.5-5 wt%. Fe (NO) 9HO and Bi (NO) 5HO are adopted as precursors, the stoichiometric ratio of a bismuth ferrite matrix can be regulated and controlled, generation of impurity phases is inhibited, and it is ensured that the matrix has a complete perovskite structure and a good photoresponse characteristic; meanwhile, modification means such as metal doping, non-metal doping or composite carrier loading are adopted.

The application discloses a magnetoelectric heterojunction film and a preparation method thereof. The magnetoelectric heterojunction film comprises a strontium titanate base layer, a strontium ruthenate electrode layer, a bismuth ferrite ferroelectric material layer and a SmCo-based ferromagnetic material layer which are stacked in sequence. The magnetoelectric heterojunction film has the multi-ferroelectric layer room-temperature magnetoelectric coupling effect and the excellent magnetic performance of the ferromagnetic layer, and the magnetoelectric coupling effect of the heterojunction film can be enhanced through the strong exchange bias effect at the interface.

The invention discloses pure-phase bismuth ferrite-strontium titanate ceramic as well as a preparation method and application thereof, and belongs to the field of lead-free ferroelectric ceramic. Comprising the following steps: filling pure-phase BFO-STO precursor powder prepared by a hydrothermal method into a graphite mold, controlling the heating rate to a sintering temperature, and sintering under the conditions of external pressure and heat preservation, so as to finally prepare the BFO-STO ceramic. The BFO-STO ceramic is prepared through SPS sintering, volatilization of Bi < 3 + > and generation of impure phases are effectively inhibited, ferroelectric, dielectric and magnetic properties of the BFO ceramic are effectively improved, and possibility is provided for practical application of the BFO-STO ceramic in the fields of functional sensors, magnetic memories, piezoelectric generators, high-temperature inductors and the like.

The application discloses a kind of bismuth ferrite-barium titanate textured piezoelectric ceramics and preparation method thereof, belong to ceramic preparation technical field, the preparation method includes: with (001) crystal direction BaTiO3 flaky microcrystal as template, with (1-x) BiFeO3-xBaTiO3 ceramic matrix powder is mixed, through casting process, matrix powder is grown along the template crystal direction, during, by controlling the amount of BaTiO3 flaky microcrystal, so that the volume ratio of it and ceramic matrix powder does not exceed 0.06, the thickness of casting film is 30~50 μm, and high-temperature sintering and high-temperature quenching mode with temperature up to 970 ℃~1040 ℃ is used, finally form textured BF-BT ceramic, the formed ceramic has good piezoelectric property and texture degree, and the above method process is simple, without adding additional material.

This invention relates to the field of wastewater treatment technology, specifically to a metal-doped bismuth ferrite-based perovskite composite material, its preparation method, and its applications. The molecular formula of the metal-doped bismuth ferrite-based perovskite composite material is Bi. 1‑x A x Fe 1‑y B y O3; 0 ≤ x < 1, 0

The invention discloses a heat treatment method of high-polarization-intensity bismuth ferrite-lead titanate-barium zirconate titanate based ferroelectric ceramic, which comprises the following steps: arranging an electrode on the surface of a bismuth ferrite-lead titanate-barium zirconate titanate based ferroelectric ceramic sintered body, and then putting the sintered body into a rapid annealing furnace; the preparation method comprises the following steps: heating to 550-650 DEG C from room temperature at a heating rate of 5-80 DEG C / s, carrying out heat preservation for 45-75 seconds, carrying out first rapid annealing, and cooling to room temperature at a cooling rate of 250-350 DEG C / s, thereby obtaining the bismuth ferrite-lead titanate-barium zirconate titanate based ferroelectric ceramic. The heat treatment method provided by the invention can rearrange defects in the ceramic, increase domain conversion switches, improve the performance of the ceramic, and improve the performance of the ceramic. Furthermore, the ferroelectric piezoelectric property of the polarized BF-PT-BZT ceramic is greatly improved, and meanwhile, the polarized BF-PT-BZT ceramic has high Curie temperature.

Disclosed herein is a battery (e.g., a Li-ion battery) comprising: an anode comprising bismuth ferrite and a binder; a cathode; and an electrolyte comprising a lithium compound and a fluoroethylene carbonate (FEC) additive. Batteries with a bismuth ferrite anode having a carboxymethyl cellulose (CMC) binder and a lithium-containing electrolyte with FEC additive, show a capacity of up to 750 mAh / g at 100 mA / g and high capacity retention, with over 400 mAh / g at 500 mA / g after 1,000 cycles.

The application provides a BiFeO3-graphitic carbon nitride photocatalyst and a preparation method and application thereof, relates to the field of photocatalysis technology, and the preparation method comprises the following steps: dissolving a bismuth source and an iron source in a solvent, mixing with a mineralizer, and performing a hydrothermal synthesis reaction to obtain BiFeO3; performing first calcination treatment on a nitrogen-containing organic precursor to obtain graphitic carbon nitride; and performing grinding treatment and second calcination treatment on the mixture of BiFeO3 and graphitic carbon nitride to obtain the BiFeO3-graphitic carbon nitride photocatalyst. The preparation method can construct a Z-type heterojunction at the interface of the separately prepared BiFeO3 and graphitic carbon nitride, form an internal electric field, efficiently separate photo-generated electrons and holes, effectively inhibit the recombination of the photo-generated electrons and holes, finally significantly enhance the redox capacity of the material, and make the material exhibit excellent photocatalytic performance, high selectivity and good cycle stability.

The present invention provides a strontium titanate-based oxide superlattice thin film memristor and a preparation method thereof. The preparation method comprises the following steps: using a niobium-doped strontium titanate single crystal substrate as a bottom electrode; alternately depositing strontium titanate layers and another type of oxide film layer on the surface of the niobium-doped strontium titanate single crystal substrate to prepare a strontium titanate-based oxide superlattice thin film as a storage dielectric layer, wherein the other type of oxide film layer is selected from one of yttrium-doped zirconium oxide, lanthanum cobalt oxide, or bismuth ferrite; and further depositing a metal film as a top electrode on the surface of the substrate coated with the storage dielectric layer obtained in step S2, to obtain a memristor comprising bottom electrode||STO-based oxide superlattice thin film storage dielectric layer||top electrode. The strontium titanate-based oxide superlattice thin film memristor prepared by this preparation method can form a single crystal or a superlattice thin film with high crystal integrity, and the memristor has a low operating voltage and high configuration stability.

The invention discloses a texture preparation method for high-performance lead-free piezoelectric ceramics of bismuth ferrite-barium titanate. The general formula of the ceramic composition is as follows, where the molar fraction ratio of BiFeO3 and BaTiO3 is 2:1, x, y, t, and m all represent molar fractions, and 0 < x ≤ 0.05, 0 < y ≤ 0.05, 0 < t ≤ 0.05, 0 < m ≤ 0.05. In the sintering stage of the invention, a temperature gradient field is constructed to make the ceramic grains grow texture-directionally, and a textured piezoelectric ceramic with a piezoelectric constant d 33 reaching above 1000 pC / N at 350 °C and a T dr reaching above 350 °C is obtained. The preparation process of the invention is simple, and the prepared ceramic has excellent high-temperature performance and can be applied to the field of high-temperature piezoelectricity.

The application discloses a method for preparing a high self-polarization piezoelectric performance bismuth ferrite-based film through multi-element isometric solid solution. The method comprises the following steps: configuring sols of more than three different cations which are solid-solved at B positions of bismuth ferrite, then dropping the sols on a substrate, uniformly coating the sols, solidifying, drying, pyrolyzing and annealing, repeating the dropping, uniformly coating, solidifying, drying, pyrolyzing and annealing processes, and obtaining a bismuth ferrite-based ferroelectric polycrystal film with a required thickness. The sol-gel method is adopted to prepare the multi-element isometric solid solution ferroelectric film, so that accurate component control can be realized, the growth of the material on a large-area substrate is suitable, the equipment and synthesis steps are simple, the material is saved, the cost is low, industrialized production is easy to realize, and the prepared ferroelectric polycrystal film has excellent self-polarization characteristics and a high piezoelectric coefficient, so that the ferroelectric polycrystal film has a wide application prospect in the field of electronic material technology.

The application discloses a low-loss high-Curie-point bismuth ferrite-barium titanate lead-free piezoelectric ceramic material and a preparation method thereof. 1.02 FeO3-(0.25-x)BaTiO3-xCaZrO3+y%GeO2+z%MnO2; wherein x, y and z represent molar fractions, 0.005<=x<=0.020, 0.3<=y<=1, 0.5<=z<=1.5. The application introduces the third component CaZrO3, and adds GeO2 and MnO2, controls the crystal phase composition and the conductive carrier concentration, improves the microstructure, reduces the loss and improves the temperature stability, so that the Curie temperature, the depolarization temperature and the piezoelectricity are obviously improved. The lead-free piezoelectric ceramic material provided by the application has a simple synthesis process, and is expected to be applied to the preparation of high-temperature piezoelectric sensor devices.

The invention discloses a method for preparing a heterogeneous metal catalyst based on waste lithium cobalt oxide modified bismuth ferrite and application, relates to the field of solid waste resource utilization and beneficiation wastewater treatment, and synchronously solves the environmental problems of biomass-waste positive electrode solid waste treatment, beneficiation wastewater treatment and the like. The method comprises the following steps: carrying out mechanical wet grinding on biomass waste and a waste lithium battery positive electrode material, then introducing organic acid with coordination-precipitation dual functions to leach wet-ground slurry, and carrying out solid-liquid separation to directly obtain cobalt-containing leached residues; then heterogeneous metal doping is carried out on the multiferroic Bi2Fe4O9 (BFO) to construct the Co3O4-C / BFO composite catalyst with a stable heterogeneous interface, and the Co3O4-C / BFO composite catalyst is applied to removal of black powder in beneficiation wastewater. According to the method, waste lithium battery recycling, biomass solid waste conversion and functional catalyst modification are deeply fused, the problems that a traditional wet method is long in technological process, low in metal separation efficiency and high in catalyst preparation cost are solved, and an efficient and low-carbon solution is provided for solid waste recycling and industrial wastewater cooperative treatment.

The invention discloses a preparation method of a bismuth ferrite-based homojunction superlattice based on molecular beam epitaxy. The preparation method comprises the following steps: transferring a substrate into an MBE (Molecular Beam Epitaxial) growth chamber, wherein the temperature of the substrate is lower than the evaporation temperature of a Bi source; the Bi source and the Fe source are heated, and the beam size is adjusted; ozone is adopted as an epitaxial growth atmosphere, a Bi source and a Fe source are mixed in a growth chamber, an oxygen-vacancy-free bismuth ferrite epitaxial film is firstly grown in an epitaxial mode to serve as a ferroelectric phase, and after oxygen pressure is reduced, an oxygen-vacancy-containing bismuth ferrite film is grown in an epitaxial mode to serve as a defect ferroelectric phase; the two times of epitaxial growth are alternately and respectively grown to obtain the bismuth ferrite-based homojunction superlattice. The oxygen vacancy content in each layer of bismuth ferrite is regulated and controlled by controlling ozone partial pressure of bismuth ferrite in the epitaxial process, a depolarization field is provided at a homogeneous interface by introducing a bismuth ferrite layer containing oxygen vacancies, and the bismuth ferrite / oxygen vacancy bismuth ferrite homojunction superlattice is prepared; and the surface of the prepared superlattice has clear and parallel atomic steps.

The invention discloses a preparation method of a functionalized palladium quantum dot loaded bismuth ferrite nanorod piezoelectric catalytic hydrogen evolution material, and belongs to the technical field of new energy catalytic materials. According to the invention, a palladium quantum dot loaded bismuth ferrite nanorod (Pd-BFO) cocatalyst is constructed by a simple method of electrostatic spinning and chemical reduction. The material can be used as a mechanical energy and chemical energy conversion platform and is used for efficient piezoelectric catalytic hydrogen evolution reaction. Under ultrasonic irradiation, the strong piezoelectric response of bismuth ferrite can induce ferroelectric polarization, and a built-in polarization field is formed to separate charges. Palladium quantum dots serve as a cocatalyst, transfer and enrichment of polarized charges can be promoted, the charge separation efficiency is improved, meanwhile, water adsorption and hydrogen desorption energy barriers are optimized, and therefore the piezoelectric catalytic hydrogen evolution activity is remarkably improved. The 0.5 wt% Pd-BFO material obtained through optimization can achieve the excellent hydrogen evolution rate of 4253.44 [mu] mol.g <-1 >. H <-1 >, and the performance of the Pd-BFO material is superior to that of most reported piezoelectric catalysts at present.

The invention discloses a preparation method of a lanthanum-doped bismuth ferrite film system material, the film material is Bi < 1-x > LaxFeO3 (wherein x is 0.05-0.30), a sol-gel method is used for synthesizing powder, and then the powder is sintered into a ceramic target material. And then sputtering and depositing the ceramic target material on the LaAlO3 substrate by using a pulse laser deposition technology to prepare the Bi < 1-x > LaxFeO3 system thin film. The solvent gel method is adopted to ensure the mixing of the components at the molecular level, the ceramic target material is high in density, the epitaxial growth film is high in phase-forming purity and shows enhanced conductivity, the method is simple in process, the selected chemical reagents are low in price and easy to obtain, and the method is suitable for industrial production. According to a Bi < 1-x > LaxFeO < 3 > system thin film sample, an atomic-level morphology graph and a good ferroelectric domain overturning characteristic are observed.

The invention discloses a double-ferroelectric enhanced ferroelectric field effect transistor and a preparation method and application thereof, and belongs to the technical field of inorganic semiconductor nanomaterials. According to the invention, a ferroelectric field effect transistor electronic device based on strontium ruthenate / bismuth ferrite / hafnium oxide / diindium triselenide is prepared, wherein strontium ruthenate is used as a grid electrode, bismuth ferrite is used as a ferroelectric dielectric layer, hafnium oxide is used as a buffer layer, diindium triselenide is used as a ferroelectric semiconductor channel, and chromium and gold are used as source and drain electrode materials. The dual-ferroelectric field effect transistor prepared by the invention mainly aims to enhance the ferroelectric retention performance of the ferroelectric field effect transistor by utilizing the mutual coupling effect between ferroelectric polarization of the channel material diindium triselenide and ferroelectric polarization of the dielectric material bismuth ferrite and improve the nonvolatile storage capacity. Compared with a single ferroelectric field effect crystal, the double ferroelectric field effect transistor prepared by the invention can have longer ferroelectric retention time.

Sulfur-incorporated bismuth ferrite nanoparticles (SBFNPs) contain Bi2Fe4O9 nanoparticles doped with Fe(0) and Bi(0) and sulfur in an amount of 0.5 to 5 percent by weight. At least a portion of bismuth is bonded to at least a portion of the sulfur and at least a portion of iron is bonded to at least a portion of the sulfur. The bismuth ferrite nanoparticles have a longest dimension of 1 to 50 nm. A method of photocatalytic degradation of dyes and a method of hydrogen generation and storage using the nanoparticles.

The invention belongs to the field of piezoelectric electro-catalysis, and relates to preparation of a defect-state tungsten oxide coated bismuth ferrite nano material and piezoelectric electro-catalysis application of the defect-state tungsten oxide coated bismuth ferrite nano material. The preparation method comprises the following steps: firstly, preparing a bismuth ferrite nano-material through a coprecipitation method, then mixing the bismuth ferrite nano-material with tungstic acid, and calcining in hydrogen to prepare a defect-state tungsten oxide-coated bismuth ferrite nano-material (WO3-x / BFO), so that the sunlight absorption capacity of WO3-x / BFO is remarkably improved, and the defect-state tungsten oxide-coated bismuth ferrite nano-material has the advantages that the defect-state tungsten oxide-coated bismuth ferrite nano-material is obtained; meanwhile, the heterostructure and the piezoelectric potential effect are both beneficial to effective separation of photon-generated carriers, and the piezoelectric electro-catalytic performance is remarkably enhanced. Under the synergistic effect of ultrasound and light, efficient degradation of rhodamine B can be achieved through WO3-x / BFO, and the degradation rate constants are 2.03 times and 21.22 times that of WO3 / BFO and BFO respectively. The preparation method of the defect-state tungsten oxide coated bismuth ferrite nano material and the application of the defect-state tungsten oxide coated bismuth ferrite nano material in piezoelectric electro-catalytic degradation of organic pollutants are illustrated, the technological process is simple, and the application prospect is wide.

The invention discloses a method for constructing a polarized bubble-shaped topological domain array. The method comprises the following steps: S1, depositing a calcium-doped bismuth ferrite film through a pulse laser deposition method; s2, turning over an out-of-plane polarization direction of the thin film by using an electric field surface of a PFM needle tip, constructing an out-of-plane single domain, and performing characterization; s3, carrying out one-time point writing in the surface writing area through the PFM needle point pulse voltage, overturning the polarization, and constructing an in-plane center domain; s4, performing secondary dot-writing in the dot-writing area through the PFM pinpoint pulse voltage, and overturning the polarization; and S5, changing the position of the PFM needle tip, repeating the steps S3 and S4, and constructing the bubble-shaped ferroelectric topological domain array. The method for preparing the film sample is simple and environment-friendly, the method for preparing the polarized bubble-shaped topological domain array is simple and easy to implement, and the obtained polarized topological domain array is high in density and good in stability. The invention has potential application value in the aspect of high-density ferroelectric memories.

The invention discloses a microwave hydrothermal preparation method of a BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction multiferroic material. The microwave hydrothermal preparation method comprises the following steps: 1) preparing an oxyhydroxide precipitate suspension containing iron and cobalt; (2) adding bismuth ferrite single crystal nanosheets and a mineralizer into the suspension prepared in the step (1), and uniformly stirring to obtain a reaction material; (3) transferring the reaction material prepared in the step (2) into an inner container of a microwave reaction kettle, adjusting the volume of the reaction material in the inner container of the reaction kettle to 70-90% of the volume of the inner container of the reaction kettle by using deionized water, and uniformly stirring; (4) putting the microwave reaction kettle inner container into a microwave reaction kettle, putting the microwave reaction kettle into a microwave hydrothermal instrument for microwave hydrothermal treatment, raising the temperature to 200-240 DEG C in a staged temperature raising manner, and keeping the temperature for 5-2 hours; and 5) after the microwave hydrothermal reaction is completed, naturally cooling the microwave reaction kettle to room temperature, repeatedly washing a reaction product with deionized water and absolute ethyl alcohol, filtering and drying to obtain the BiFeO3 / CoFe2O4 two-dimensional single crystal heterojunction multiferroic material.

The invention relates to a preparation method of an ultrathin carbon nitride / bismuth ferrite piezoelectric catalytic composite material, which comprises the following steps: S1, putting a carbon nitride precursor into a crucible, calcining in a muffle furnace to obtain blocky nitrogen carbide, grinding and sieving; putting the sieved carbon nitride fine powder into a muffle furnace for secondary calcination to obtain ultrathin carbon nitride; and S2, dispersing bismuth ferrite nanosheets in deionized water, adding the ultrathin carbon nitride obtained in the step S1, magnetically stirring for 4-6 hours, washing with deionized water, and drying to obtain the ultrathin carbon nitride / bismuth ferrite piezoelectric catalytic composite material. The prepared composite material has high oxidability and reducibility, and hydrogen peroxide can be efficiently produced while hydrogen is produced in pure water. The g-C3N4 is obtained by adopting a two-step thermal stripping method, participation of other chemical reagents or long-time ultrasonic treatment is not needed, and the price and time cost are reduced.

The invention belongs to the technical field of inorganic functional film materials, and particularly relates to a lanthanum and manganese co-doped bismuth ferrite film and a preparation method thereof. The chemical general formula of the bismuth ferrite film is Bi (1 + Z-Y) LaYFe (1-X) MnXO3, X is the molar equivalent of Mn element, 0.09 < = X < = 0.13, Y is the molar equivalent of La element, 0.12 < = Y < = 0.18, the element Bi is added excessively, Z is the molar equivalent of Bi element, the film has N layers, Z in the first layer accounts for 8-11%, Z in the second layer to the (N-4) th layer accounts for 5-8%, Z in the (N-3) th layer to the Nth layer accounts for 3-5%, and Z in the second layer to the Nth layer accounts for 3-5%. Meanwhile, the invention provides a method for preparing the bismuth ferrite film. According to the method, parameter setting of a sol-gel process is optimized, lanthanum and manganese co-doping is achieved, the doping amount of doped ions is increased, and then the effects of reducing the leakage current of the thin film and improving the electrical performance are improved.