BiFeO3 / CoFe2O4 two-dimensional monocrystal heterojunction multiferroic material, hydrothermal preparation method and application

Abstract

The invention discloses a BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction multiferroic material, a hydrothermal preparation method and application. The hydrothermal preparation method comprises the following steps: 1) preparing oxyhydroxide precipitate suspension containing iron and cobalt; (2) adding bismuth ferrite single crystal nanosheets and a mineralizer into the suspension, and uniformly stirring to obtain a reaction material; (3) transferring the reaction materials into a reaction kettle inner container, adjusting the reaction materials in the reaction kettle inner container by using deionized water, and uniformly stirring; (4) putting the reaction kettle inner container into a reaction kettle, sealing, and carrying out hydrothermal treatment; and 5) naturally cooling the reaction kettle to room temperature, repeatedly washing the reaction product with deionized water and absolute ethyl alcohol, filtering and drying to obtain the BiFeO3 / CoFe2O4 two-dimensional single crystal heterojunction multiferroic material.According to the preparation method of the BiFeO3 / CoFe2O4 two-dimensional single crystal heterojunction multiferroic material, cobalt ferrite can be in a film shape on a single crystal bismuth ferrite micron sheet, so that the magnetism of bismuth ferrite is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of two-dimensional single-crystal heterojunction materials, in particular to a hydrothermal preparation method of a BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction multiferroic material and application. BACKGROUND

[0002] Bismuth ferrite (BiFeO3) is the only single-phase multiferroic material at room temperature among the currently discovered multiferroic materials, has ferroelectricity and antiferromagnetism, the ferroelectric Curie temperature is 830 DEG C, and the antiferromagnetic Neel temperature is 370 DEG C, and is one of the current research focuses of multiferroic materials. However, due to the special space modulation spiral magnetic structure of BiFeO3 at room temperature, the macroscopic performance is weak ferromagnetism, and improving the magnetoelectric performance is a prerequisite for wide application of BiFeO3.

[0003] At present, the BiFeO3 / CoFe2O4 composite material has three types of particle-substrate (0-3 type), multilayer film (2-2 type) and columnar vertical arrangement on the substrate (1-3 type), wherein the 0-3 type has problems of serious leakage and low magnetoelectric coupling effect, and the 2-2 type and the 1-3 type have reduced magnetoelectric coupling coefficients due to the clamping effect. SUMMARY

[0004] The purpose of the application is to overcome the defects of the prior art, and provide a hydrothermal preparation method of a BiFeO3 / CoFe2O4 single-crystal heterojunction multiferroic material and application.

[0005] The purpose of the application is achieved by the following technical scheme:

[0006] A BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction multiferroic material preparation method, comprising the following steps: 1) preparing a hydroxyl oxide precipitate suspension containing iron and cobalt;

[0007] 2) adding bismuth ferrite single-crystal nanosheets and a mineralizer to the suspension prepared in step 1), stirring uniformly, and obtaining a reaction material;

[0008] 3) transferring the reaction material prepared in step 2) into a reaction kettle inner container, adjusting the volume of the reaction material in the reaction kettle inner container to 70% to 90% of the volume of the reaction kettle inner container with deionized water, and stirring uniformly;

[0009] 4) placing the reaction kettle inner container in the reaction kettle, sealing, and performing hydrothermal treatment at 150 DEG C to 240 DEG C for 6 to 24 hours;

[0010] 5) after the hydrothermal reaction is completed, naturally cooling the reaction kettle to room temperature, repeatedly washing the reaction product with deionized water and anhydrous ethanol, filtering, and drying, so that the BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction multiferroic material is obtained.

[0011] In step 1), the preparation steps of the hydroxyl oxide precipitate suspension containing iron and cobalt are as follows:

[0012] S1: Prepare a 1~8 mol / L sodium hydroxide aqueous solution;

[0013] S2: Add an appropriate amount of water to ferric nitrate nonahydrate and cobalt nitrate hexahydrate, and add the sodium hydroxide aqueous solution prepared in S1 while stirring. The molar ratio of ferric nitrate nonahydrate to cobalt nitrate hexahydrate is 2:1. After stirring evenly, a suspension of hydroxyl oxide precipitates containing iron and cobalt is obtained.

[0014] The molar ratio of cobalt nitrate hexahydrate to bismuth ferrite single-crystal nanosheets is 0.025~0.5:1;

[0015] This invention provides a BiFeO3 / CoFe2O4 single-crystal heterojunction multiferroic material, prepared using the method described above: wherein cobalt ferrite is attached to single-crystal bismuth ferrite nanosheets in a cubic or thin-film form. This BiFeO3 / CoFe2O4 multiferroic material exhibits a distinct hysteresis loop and can be used as a magnetoelectric storage material.

[0016] The perovskite phase bismuth ferrite single-crystal nanosheets used in this invention can be prepared using the method authorized by Chinese Patent CN102877130B.

[0017] The composite multiferroic materials prepared in this invention have potential applications in magnetic sensors, magnetic storage, and energy harvesting devices. Compared to other magnetic materials besides rare-earth ferromagnetic materials, CoFe2O4 exhibits a very large magnetostrictive effect and is used in magnetic, magneto-optical recording, electromagnetic, and spintronic devices. BiFeO3 / CoFe2O4 nanocomposites possess excellent magnetoelectric coupling effects and unprecedented physicochemical properties. Ferromagnetic properties within the composite material can be controlled by an electric field, bringing many practical applications to next-generation electronic devices. Furthermore, due to the unique photocatalytic properties of BiFeO3 / CoFe2O4, its low overpotential, and good stability in alkaline media, it has the potential for use in next-generation photovoltaic, photocatalytic, and electrocatalytic devices. The free-state magnetoelectric composite material can eliminate the substrate clamping effect and improve the magnetoelectric coupling effect. Therefore, the construction of BiFeO3 / CoFe2O4 single-crystal heterojunction materials is beneficial for characterizing the intrinsic magnetoelectric coupling effect of BiFeO3, making it an ideal material for studying the physical properties of composite systems and showing potential applications in next-generation photovoltaics, photocatalysis, electrocatalysis, and magnetic storage.

[0018] The present invention has the following advantages:

[0019] 1. Choosing a composite of bismuth ferrite and cobalt ferrite is beneficial. On the one hand, cobalt ferrite relies on bismuth ferrite as a substrate and is epitaxially grown on its surface to obtain an interface structure, which can promote the rearrangement of electrons and spins, so that bismuth ferrite can exhibit stronger magnetism under an external magnetic field and can be used as a magnetoelectric storage material.

[0020] 2. During the implementation of the process of this invention, no other impurities are introduced, and after the hydrothermal reaction, it is only necessary to wash with deionized water.

[0021] 3. In the BiFeO3 / CoFe2O4 single-crystal heterojunction multiferroic material prepared by hydrothermal method in this invention, bismuth ferrite as a substrate material can provide epitaxial growth conditions for cobalt ferrite. Bismuth ferrite and cobalt ferrite have good lattice matching, which allows cobalt ferrite to form a thin film on single-crystal bismuth ferrite microsheets, thereby improving the magnetism of bismuth ferrite.

[0022] 4. The BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction material prepared by the hydrothermal method in this invention is low in toxicity and relatively environmentally friendly. Attached Figure Description

[0023] Figure 1 This is the X-ray diffraction (XRD) pattern of the BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction material prepared in Example 4 of this invention;

[0024] Figure 2 This is a scanning electron microscope (SEM) image of the BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction material prepared in Example 4 of this invention;

[0025] Figure 3 This is the energy dispersive spectroscopy (EDS) diagram of the BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction material prepared in Example 3 of this invention;

[0026] Figure 4 The MH hysteresis loop is the BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction material prepared in Example 2 of this invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0030] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0031] The bismuth ferrite single-crystal nanosheets used in the following examples can be prepared using the method authorized by Chinese Patent CN102877130B.

[0032] Example 1

[0033] A method for preparing a BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction multiferroic material includes the following steps:

[0034] 1) Preparation of a hydroxyl oxide precipitate suspension containing iron and cobalt;

[0035] 2) Add bismuth ferrite single crystal nanosheets and mineralizing agent to the suspension prepared in step 1), stir evenly, and obtain the reaction material;

[0036] 3) Transfer the reactants prepared in step 2) into the inner liner of the reactor and adjust the volume of the reactants in the inner liner to 70% to 90% of the inner liner volume with deionized water, and stir evenly;

[0037] 4) Place the inner liner of the reactor into the reactor, seal it, and perform hydrothermal treatment at 150~240℃ for 6~24h;

[0038] 5) After the hydrothermal reaction is completed, allow the reactor to cool naturally to room temperature. Wash the reaction product repeatedly with deionized water and anhydrous ethanol, filter and dry to obtain BiFeO3 / CoFe2O4 two-dimensional single crystal heterojunction multiferroic material.

[0039] In step 1), the preparation steps of the hydroxyl oxide precipitate suspension containing iron and cobalt are as follows:

[0040] S1: Prepare a 1~8 mol / L sodium hydroxide aqueous solution;

[0041] S2: Add an appropriate amount of water to ferric nitrate nonahydrate and cobalt nitrate hexahydrate, and add the sodium hydroxide aqueous solution prepared in S1 while stirring. The molar ratio of ferric nitrate nonahydrate to cobalt nitrate hexahydrate is 2:1. After stirring evenly, a suspension of hydroxyl oxide precipitates containing iron and cobalt is obtained.

[0042] The molar ratio of cobalt nitrate hexahydrate to bismuth ferrite single-crystal nanosheets is 0.025~0.5:1.

[0043] Example 2

[0044] A method for preparing a BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction multiferroic material includes the following steps:

[0045] 1) Preparation of a hydroxyl oxide precipitate suspension containing iron and cobalt;

[0046] 2) Add bismuth ferrite single crystal nanosheets and mineralizing agent to the suspension prepared in step 1), stir evenly, and obtain the reaction material;

[0047] 3) Transfer the reactants prepared in step 2) into the inner liner of the reactor and adjust the volume of the reactants in the inner liner to 80% of the inner liner volume with deionized water, and stir evenly;

[0048] 4) Place the inner liner of the reactor into the reactor, seal it, and keep it at 200℃ for 6 hours for hydrothermal treatment;

[0049] 5) After the hydrothermal reaction is completed, allow the reactor to cool naturally to room temperature. Wash the reaction product repeatedly with deionized water and anhydrous ethanol, filter and dry to obtain BiFeO3 / CoFe2O4 two-dimensional single crystal heterojunction multiferroic material.

[0050] In step 1), the preparation steps of the hydroxyl oxide precipitate suspension containing iron and cobalt are as follows:

[0051] S1: Prepare a 4 mol / L sodium hydroxide aqueous solution;

[0052] S2: Add an appropriate amount of water to ferric nitrate nonahydrate and cobalt nitrate hexahydrate, and add the sodium hydroxide aqueous solution prepared in S1 while stirring. The molar ratio of ferric nitrate nonahydrate to cobalt nitrate hexahydrate is 2:1. After stirring evenly, a suspension of hydroxyl oxide precipitates containing iron and cobalt is obtained.

[0053] The molar ratio of cobalt nitrate hexahydrate to bismuth ferrite single-crystal nanosheets is 0.025:1.

[0054] The samples prepared in Example 2 were subjected to XRD tests, such as... Figure 1As shown, the diffraction peaks of the sample can be identified as rhombohedral BiFeO3 (JCPDS 86-1518) and cubic CoFe2O4 (JCPDS 22-1086), indicating that a BiFeO3 / CoFe2O4 composite multiferroic material was obtained.

[0055] The samples prepared in Example 2 were characterized by SEM, such as... Figure 2 As shown in the figure, CoFe2O4 plates are embedded on the surface of BiFeO3, and some particles are agglomerated on the surface of BiFeO3.

[0056] Example 3

[0057] A method for preparing a BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction multiferroic material includes the following steps:

[0058] 1) Preparation of a hydroxyl oxide precipitate suspension containing iron and cobalt;

[0059] 2) Add bismuth ferrite single crystal nanosheets and mineralizing agent to the suspension prepared in step 1), stir evenly, and obtain the reaction material;

[0060] 3) Transfer the reactants prepared in step 2) into the inner liner of the reactor and adjust the volume of the reactants in the inner liner to 70% of the inner liner volume with deionized water, and stir evenly;

[0061] 4) Place the inner liner of the reactor into the reactor, seal it, and keep it at 180℃ for 10 hours for hydrothermal treatment;

[0062] 5) After the hydrothermal reaction is completed, allow the reactor to cool naturally to room temperature. Wash the reaction product repeatedly with deionized water and anhydrous ethanol, filter and dry to obtain BiFeO3 / CoFe2O4 two-dimensional single crystal heterojunction multiferroic material.

[0063] In step 1), the preparation steps of the hydroxyl oxide precipitate suspension containing iron and cobalt are as follows:

[0064] S1: Prepare a 2 mol / L sodium hydroxide aqueous solution;

[0065] S2: Add an appropriate amount of water to ferric nitrate nonahydrate and cobalt nitrate hexahydrate, and add the sodium hydroxide aqueous solution prepared in S1 while stirring. The molar ratio of ferric nitrate nonahydrate to cobalt nitrate hexahydrate is 2:1. After stirring evenly, a suspension of hydroxyl oxide precipitates containing iron and cobalt is obtained.

[0066] The molar ratio of cobalt nitrate hexahydrate to bismuth ferrite single-crystal nanosheets is 0.05:1.

[0067] Energy dispersive spectroscopy (EDS) analysis was performed on the samples prepared in Example 3, such as...Figure 3 As shown, Fe, Bi, Co, and O elements were present at the detection point. Combined with the XRD results, it can be determined that the particles on the BiFeO3 micron sheet are CoFe2O4.

[0068] Example 4

[0069] A method for preparing a BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction multiferroic material includes the following steps:

[0070] 1) Preparation of a hydroxyl oxide precipitate suspension containing iron and cobalt;

[0071] 2) Add bismuth ferrite single crystal nanosheets and mineralizing agent to the suspension prepared in step 1), stir evenly, and obtain the reaction material;

[0072] 3) Transfer the reactants prepared in step 2) into the inner liner of the reactor and adjust the volume of the reactants in the inner liner to 75% of the inner liner volume with deionized water, and stir evenly;

[0073] 4) Place the inner liner of the reactor into the reactor, seal it, and keep it at 240℃ for 6 hours for hydrothermal treatment;

[0074] 5) After the hydrothermal reaction is completed, allow the reactor to cool naturally to room temperature. Wash the reaction product repeatedly with deionized water and anhydrous ethanol, filter and dry to obtain BiFeO3 / CoFe2O4 two-dimensional single crystal heterojunction multiferroic material.

[0075] In step 1), the preparation steps of the hydroxyl oxide precipitate suspension containing iron and cobalt are as follows:

[0076] S1: Prepare a 1 mol / L sodium hydroxide aqueous solution;

[0077] S2: Add an appropriate amount of water to ferric nitrate nonahydrate and cobalt nitrate hexahydrate, and add the sodium hydroxide aqueous solution prepared in S1 while stirring. The molar ratio of ferric nitrate nonahydrate to cobalt nitrate hexahydrate is 2:1. After stirring evenly, a suspension of hydroxyl oxide precipitates containing iron and cobalt is obtained.

[0078] The molar ratio of cobalt nitrate hexahydrate to bismuth ferrite single-crystal nanosheets is 0.1:1.

[0079] Example 5

[0080] The magnetic properties of the BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction multiferroic material prepared in Example 2 were tested, such as... Figure 4 As shown. From Figure 4As can be seen, the remanent magnetization of this material is 2.942 emu / g, and the coercive field is 170.80 Oe, which is a significant improvement over the magnetic properties of pure phase BiFeO3 reported in related studies. For example, Yang Xin prepared pure-phase BiFeO3 material with a remanent magnetization of only 0.000332 emu / g and a coercivity of 63 Oe (Yang Xin. Zhejiang University [Doctoral Dissertation], 2014); Ozdilek C et al. prepared pure-phase BiFeO3 by hydrothermal method, and the obtained material had a remanent magnetization of 0.002 emu / g and a coercivity of 186 Oe, showing a weak magnetoelectric coupling effect (Ceramics International, 2020, 46(17):27800); H. Shokrollahi et al. prepared nano BiFeO3 powder by coprecipitation method, and the magnetic performance test results showed that the material was weakly ferromagnetic, and the coercivity and remanent magnetization were very small (Powder Technology, 2013, 235:953). Furthermore, the magnetic properties of the samples prepared in this invention were compared with those of BiFeO3 / CoFe2O4 materials prepared in the prior art, as follows: Ge Qingyang prepared BiFeO3 / CoFe2O4 composite materials using a scraping method, with a remanent magnetization of 1.86 emu / g (Ge Qingyang, Hubei University [Master's Thesis], 2024); Dabas S et al. prepared BiFeO3 / CoFe2O4 composite materials using a solid-state method, with a remanent magnetization of only 0.1012 emu / g and a coercive field of 740 Oe (Mater Sci: Mater Electron, 2019, 30, 2837); Lin Y et al. synthesized BiFeO3 / CoFe2O4 composite materials using a sol-gel method, and magnetic test results showed that its remanent polarization was 1.091 emu / g (Mater Sci: Mater Electron, 2015, 26, 2019). (1102) In comparison, the BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction material prepared in this study exhibits superior magnetic properties, demonstrating its potential application value as a magnetoelectric storage material.

[0081] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hydrothermal preparation method for a BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction multiferroic material, characterized in that, Includes the following steps: 1) Preparation of a hydroxyl oxide precipitate suspension containing iron and cobalt; 2) Add bismuth ferrite single-crystal nanosheets and mineralizer to the suspension, stir evenly, and obtain the reaction material; 3) Transfer the reactants to the inner liner of the reactor, add a certain volume of deionized water, and stir until homogeneous; 4) Place the inner liner of the reactor into the reactor, seal it, and perform hydrothermal treatment at a certain temperature; 5) After the hydrothermal reaction is completed, allow the reactor to cool naturally to room temperature. Wash the reaction product repeatedly with deionized water and anhydrous ethanol, filter and dry to obtain BiFeO3 / CoFe2O4 two-dimensional single crystal heterojunction multiferroic material.

2. The hydrothermal preparation method according to claim 1, characterized in that, In step 1), the preparation steps of the hydroxyl oxide precipitate suspension containing iron and cobalt are as follows: S1: Prepare a 1~8 mol / L sodium hydroxide aqueous solution; S2: Add an appropriate amount of water to ferric nitrate nonahydrate and cobalt nitrate hexahydrate, and while stirring, add the sodium hydroxide aqueous solution prepared in S1 in a molar ratio of ferric nitrate nonahydrate to cobalt nitrate hexahydrate of 2:

1. After stirring evenly, a suspension of hydroxyl oxide precipitates containing iron and cobalt is obtained.

3. The hydrothermal preparation method according to claim 1, characterized in that, In step 2), the molar ratio of cobalt nitrate hexahydrate to bismuth ferrite single-crystal nanosheets is 0.025~0.5:

1.

4. The hydrothermal preparation method according to claim 1, characterized in that, In step 3), adding a certain volume of deionized water means transferring the reactants into the inner liner of the reactor and adjusting the volume of the reactants in the inner liner to 70% to 90% of the inner liner's volume using deionized water.

5. The hydrothermal preparation method according to claim 1, characterized in that, In step 4), the hydrothermal treatment is carried out at 150~240℃ for 6~24h.

6. The hydrothermal preparation method according to claim 1, characterized in that, The remanent magnetization of the BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction multiferroic material is 2.942 emu / g, and the coercive field is 170.80 Oe.

7. A BiFeO3 / CoFe2O4 multiferroic material, characterized in that, It is prepared by the hydrothermal preparation method according to any one of claims 1-6.

8. The BiFeO3 / CoFe2O4 multiferroic material according to claim 7, characterized in that, in, Cobalt ferrite is attached to single-crystal bismuth ferrite nanosheets in the form of cubes or thin films.

9. The application of the BiFeO3 / CoFe2O4 two-dimensional single-crystal heterojunction material according to claim 7 or 8 in the fabrication of magnetoelectric storage materials.

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