Multi-element co-doped bismuth ferrite multiferroic ceramic material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of novel ceramic materials, and particularly relates to a multi-element co-doped bismuth ferrite multiferroic ceramic material as well as a preparation method and application thereof. The chemical formula of the multielement co-doped bismuth ferrite multiferroic ceramic material is Bi < 1-x > (Ce < 0.2 > Sm < 0.2 > Eu < 0.2 > La < 0.2 > Pr < 0.2 >) < x > Fe < 0.70 > Ti < 0.10 > Zr < 0.10 > Zn < 0.10 > O < 3 >, according to the material, BiFeO3 ceramic is replaced by multiple elements in an equal proportion, a solid-phase reaction method is adopted for preparation, and ball milling, pre-sintering, ultrasonic dispersion, tabletting and sintering are performed to obtain the ceramic material with the high Bi < 1-x > (Ce < 0.2 > Sm < 0.2 > Eu < 0.2 > La < 0.2 > Pr < 0.2 >) < x > Fe < 0.70 > Ti < 0.10 > Zr < 0.10 > Zn < 0.10 > O3. The ceramic material has a single-phase structure, and has relatively low leakage current, relatively high ferroelectric polarization intensity and magnetization intensity and remarkably improved magnetodielectric effect; the material is simple in preparation process, low in cost, environment-friendly and harmless, and has a wide application prospect in the fields of magnetoelectric sensors, information storage, spinning electronic devices and energy converters.

Description

Technical Field

[0001] The present invention belongs to the technical field of novel ceramic materials, and particularly relates to a multi-element co-doped bismuth ferrite multiferroic ceramic material, a preparation method thereof, and an application thereof. Background Art

[0002] Multiferroic materials simultaneously possess ferroelectricity and magnetism, and the ferroelectricity and magnetism of such materials can be mutually coupled to generate new physical phenomena such as magnetoelectric coupling effects, thereby potentially enabling the mutual regulation of ferroelectricity and magnetism; as a novel multifunctional material, multiferroic materials have broad application prospects in magnetoelectric sensors, spintronics, information storage, and other fields; BiFeO3 is currently the only single-phase multiferroic material that simultaneously exhibits ferroelectricity, magnetism, and magnetoelectric coupling effects at room temperature, and its Curie temperature T c is approximately 830 °C, and the Néel temperature T n is approximately 370 °C, which provides convenience for the research on the basic physical mechanisms of multiferroic materials and also has potential important application prospects. However, for BiFeO3, there are still two problems to be solved: one is the relatively high leakage current, and the other is the relatively low magnetism. Due to the existence of both, not only is the application of this material greatly restricted, but also the magnetoelectric coupling effect in BiFeO3 is very small or even unobservable, thus affecting the exploration of microscopic mechanisms such as the mutual coupling regulation of ferroelectricity and magnetism.

[0003] In recent years, the construction of high-entropy ceramics through related technologies has become a research hotspot in the field of ceramic materials. Compared with traditional ceramics, the entropy engineering strategy brings unexpected performance optimization to ceramics through high-entropy effects, severe lattice distortion, sluggish diffusion effects, and the "cocktail" effect in performance; the Bi site and the Fe site are respectively substituted in equal proportions by introducing multiple elements, which is expected to solve the inherent problems existing in BiFeO3 and enable ceramic materials to exhibit excellent comprehensive performance. However, at present, the research and reports on the substitution of multiple elements in equal proportions at the Bi site and the Fe site of BiFeO3 ceramic materials are relatively few; at the same time, for BiFeO3 ceramics with equal-proportion substitution of multiple elements, the preparation of pure-phase materials is currently a difficulty, and the presence of impurity phases will seriously affect the magnetoelectric properties of the system. Summary of the Invention

[0004] The present invention provides a multi-element co-doped bismuth ferrite multiferroic ceramic material, a preparation method thereof, and an application thereof to solve the problems of large leakage current, weak ferroelectric polarization, weak magnetism, and weak magnetoelectric coupling in existing BiFeO3 ceramic materials.

[0005] According to the first aspect disclosed by the present invention: The present invention provides a multi-element co-doped bismuth ferrite multiferroic ceramic material, and its chemical formula is: Bi 1-x (Ce 0.2 Sm 0.2 Eu0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3, wherein x is 0.05-0.15. Preferably, x=0.05, 0.10, 0.15.

[0006] The beneficial effects of adopting the above technical solution are: 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 multiferroic ceramic material has a single-phase structure. Compared with the parent BiFeO3 material, it has lower leakage current, significantly improved ferroelectricity and magnetism, and exhibits a significant magneto-dielectric effect. The present invention adopts Ce, Sm, Eu, La, and Pr in the Bi position of BiFeO3, and Ti, Zr, Zn and other proportions to replace the Fe position, thereby causing lattice distortion effect, ion high disorder and cation vacancy defects, thereby inhibiting Bi volatilization and regulating Fe 3+ The spin arrangement of ions affects the interaction between ions, electronic structure, local electric field inhomogeneity, ion / electron displacement polarization and charge disorder, thereby regulating the ferroelectricity, magnetism and magneto-dielectric effect of the material. It is a kind of multifunctional ceramic material with broad application prospects.

[0007] According to a second aspect of the present disclosure, the present invention provides a method for preparing a multi-element co-doped bismuth ferrite multiferroic ceramic material, comprising:

[0008] (1) According to Bi 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 The molar ratio of metal ions in O3 is Bi2O3, Fe2O3, CeO2, Sm2O3, Eu2O3, La2O3, Pr6O3, and 2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2-(2- 11, ingredients are prepared from titanium dioxide TiO2, zirconium dioxide ZrO2 and zinc oxide ZnO;

[0009] (2) The obtained ingredients are added with an organic solvent as a medium and ground and mixed evenly, and then pre-calcined at 700 - 750 °C;

[0010] (3) The pre-calcined product is ground, ultrasonically dispersed, dried and tableted;

[0011] (4) The tablet is sintered at 800 - 1000 °C to prepare a multi-element co-doped bismuth ferrite multiferroic ceramic material.

[0012] The beneficial effects of adopting the above technical solution are as follows: Through the entropy structure regulation by substituting the ratios of various elements such as the Bi site and the Fe site in the BiFeO3 ceramic material (the substitution elements at the Bi site are five elements of Ce, Sm, Eu, La and Pr, and the substitution elements at the Fe site are three elements of Ti, Zr and Zn), the uniform mixing of elements is realized by using the ball milling process, and the pure-phase BiFeO3 multiferroic ceramic material with the ratios of various elements such as the Bi site and the Fe site substituted is prepared by the solid-phase reaction method, so as to obtain a new functional ceramic material with excellent magnetoelectric properties and suitable for applications in the fields of magnetoelectric sensing and information storage, etc.; the preparation process of the present invention is simple, the cost is low, the repeatability is good, the obtained ceramic material has a small leakage current, high ferroelectric polarization and magnetization intensity, and obvious magnetodielectric coupling characteristics, and has broad application prospects in the fields of magnetoelectric sensors, information storage, capacitors, energy converters and spin devices.

[0013] In a feasible implementation manner, according to Bi 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3, the molar ratios of metal ions are taken from bismuth trioxide Bi2O3, iron(III) oxide Fe2O3, cerium dioxide CeO2, samarium(III) oxide Sm2O3, europium(III) oxide Eu2O3, lanthanum(III) oxide La2O3, praseodymium(VI) oxide Pr6O 11 , titanium dioxide TiO2, zirconium dioxide ZrO2 and zinc oxide ZnO are vacuum-dried at 110 - 150 °C and then ingredients are prepared.

[0014] In a feasible implementation manner, the organic solvent is absolute ethanol.

[0015] In a feasible embodiment, in the step (2), the grinding rotation speed is 100 - 200 rpm, the grinding time is 20 - 28 h, the pre-sintering time is 2 - 5 h, and the pre-sintering atmosphere is air atmosphere.

[0016] In a feasible embodiment, in the step (3), the grinding can be manual grinding, and the grinding time is 1 - 3 h.

[0017] In a feasible embodiment, in the step (3), the ultrasonic dispersion frequency is 30 - 60 kHz, the power is 100 - 200 W, the time is 15 - 30 min, and the tableting pressure is 7 - 12 Mpa.

[0018] In a feasible embodiment, in the step (4), the sintering atmosphere is oxygen atmosphere, and the sintering time is 3 - 5 h. To prevent the volatilization of Bi ions, it is preferably to bury the tablet in the powder obtained by ultrasonic dispersion for sintering.

[0019] The beneficial effects of the present invention adopting the above technical solutions are as follows:

[0020] Through one-time pre-sintering, the purposes of the present invention are: ① to promote the preliminary chemical reaction between raw materials to form the main crystal phase of the multiferroic ceramic; ② to make the particle size distribution of the powder more uniform, laying a foundation for the subsequent preparation of high-quality ceramics.

[0021] By ultrasonic dispersing the product after one-time pre-sintering, the present invention can break the hard agglomerates in the powder and improve the particle dispersibility, thereby providing uniform powder raw materials for the subsequent forming and sintering processes.

[0022] According to the third aspect disclosed by the present invention, the present invention provides the application of the bismuth ferrite multiferroic ceramic material with multi-element co-doping in magnetoelectric sensors, information storage, capacitors, energy converters, and spin devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 XRD patterns of the BiFeO3 and Bi 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 ceramic samples prepared in Examples 1 - 4 of the present invention.

[0024] Figure 2 XRD patterns of the BiFeO3 and Bi 1-x (Ce0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 I-V curves of the BiFeO₃ ceramic samples.

[0025] Figure 3 BiFeO₃ and Bi prepared in Examples 1-4 of the present invention 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 Room temperature ferroelectric hysteresis loops of the BiFeO₃ ceramic samples.

[0026] Figure 4 BiFeO₃ and Bi prepared in Examples 1-4 of the present invention 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 Room temperature magnetic hysteresis loops of the BiFeO₃ ceramic samples.

[0027] Figure 5 BiFeO₃ and Bi prepared in Example 1 of the present invention 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 Graph of the change of the magnetodielectric coefficient MD with magnetic field of the BiFeO₃ ceramic samples at 100 kHz. Detailed implementation manner

[0028] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0029] Example 1

[0030] BiFeO3 multiferroic ceramic material was prepared by ball milling solid phase reaction method:

[0031] (1) Bi2O3 (purity 99.999%) and Fe2O3 (purity 99.99%), which were dried in a drying oven at 120° C. for 12 hours, were mixed in a Bi:Fe molar ratio of 1:1;

[0032] (2) grinding the raw materials weighed in step (1) in a ball mill with anhydrous ethanol as a medium for 24 hours at a ball mill speed of 150 rpm, and pre-calcining the evenly ground powder in an air atmosphere at 720° C. for 3 hours;

[0033] (3) The calcined product obtained in step (2) was manually ground for 2 h to avoid agglomeration; the obtained powder was then placed in an ultrasonic dispersion device with a frequency of 40 kHz, a power of 150 W, and a time of 20 min to break up the particle agglomeration; the ultrasonically dispersed powder was then dried at 120° C. for 12 h and pressed into a tablet press at a pressure of 10 MPa;

[0034] (4) The disc obtained in step (3) is buried in the dried and ultrasonically dispersed powder, and sintered at 870° C. for 3 h in an oxygen atmosphere to obtain a BiFeO3 multiferroic ceramic material.

[0035] The XRD pattern of the BiFeO3 multiferroic ceramic material sample prepared in Example 1 is as follows: Figure 1 As shown, from Figure 1 It was observed that all the diffraction peaks in the material were the same as those in the orthorhombic perovskite structure, showing a single-phase structure without the appearance of diffraction peaks of the second phase; Figure 2 , Figure 3 , Figure 4 , Figure 5 The leakage current-electric field curve, hysteresis loop, magnetic hysteresis loop and magneto-permittivity-magnetic field curve of BiFeO3 are given respectively.

[0036] Example 2

[0037] Bi was prepared by solid phase reaction method combined with ball milling process and ultrasonic dispersion. 0.95 (Ce 0.2 Sm 0.2 Eu0.2 La 0.2 Pr 0.2 ) 0.05 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 Bi(Ce,Sm,Eu,La,Pr)FeTiZrZnO3 Multiferroic High-Entropy Ceramic Material:

[0038] (1) Put the raw materials Bi2O3 (purity 99.999%), Fe2O3 (purity 99.99%), CeO2 (purity 99.99%), Sm2O3 (purity 99.99%), Eu2O3 (purity 99.99%), La2O3 (purity 99.99%), Pr6O 11 (purity 99.99%), TiO2 (purity 99.99%), ZrO2 (purity 99.99%) and ZnO (purity 99.99%) in a vacuum drying oven and dry at 120°C for 12 hours. After drying, the raw materials Bi2O3, Fe2O3, CeO2, Sm2O3, Eu2O3, La2O3, Pr6O 11 , TiO2, ZrO2 and ZnO are proportioned according to the molar ratio of metal elements Bi, Ce, Sm, Eu, La, Pr, Fe, Ti, Zr, Zn of 0.95:0.01:0.01:0.01:0.01:0.01:0.70:0.10:0.10:0.10;

[0039] (2) Take the raw materials weighed according to the stoichiometric ratio in step (1) with absolute ethanol as the medium, grind them in a ball mill for 24 h, the ball milling speed is 150 rpm, and place the uniformly ground powder in an air atmosphere at 720°C and pre-burn for 3 h;

[0040] (3) Manually grind the pre-burned product obtained in step (2) for 2 h to avoid forming lumps; then place the obtained powder into an ultrasonic dispersion device, set the frequency to 40 kHz, the power to 150 W, and the time to 20 minutes to break the particle agglomeration; then dry the ultrasonically dispersed powder at 120°C for 12 hours, and use a tablet press to press and form at a pressure of 10 MPa;

[0041] (4) Bury the wafer obtained in step (3) in the dried and ultrasonically dispersed powder, and sinter at 895°C in an oxygen atmosphere for 3 h to obtain Bi 0.95 (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.05 Fe 0.70 Ti 0.10 Zr 0.10 Zn0.10 O3 multiferroic ceramic materials.

[0042] Bi obtained in Example 2 0.95 (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.05 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 The XRD of the O3 multiferroic ceramic material sample is as Figure 1 shown. From Figure 1 it is observed that all the diffraction peaks of this material are the same as those of the orthorhombic perovskite structure, showing a single-phase structure without the appearance of diffraction peaks of the second phase; Figure 2 , Figure 3 , Figure 4 , Figure 5 respectively give the leakage current - electric field curve, polarization - electric field loop, magnetization - magnetic field loop and magnetodielectric coefficient - magnetic field curve of Bi 0.95 (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.05 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3.

[0043] Example 3

[0044] Using the solid - state reaction method combined with ball - milling process and ultrasonic dispersion, Bi 0.90 (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.10 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 is prepared as follows:

[0045] (1) The raw materials Bi2O3 (purity 99.999%), Fe2O3 (purity 99.99%), CeO2 (purity 99.99%), Sm2O3 (purity 99.99%), Eu2O3 (purity 99.99%), La2O3 (purity 99.99%), Pr6O 11(Purity 99.99%), TiO2 (purity 99.99%), ZrO2 (purity 99.99%) and ZnO (purity 99.99%) were placed in a vacuum drying oven and dried at 120 °C for 12 hours. The dried raw materials Bi2O3, Fe2O3, CeO2, Sm2O3, Eu2O3, La2O3, Pr6O 11 , TiO2, ZrO2 and ZnO were proportioned according to the molar ratio of metal elements Bi, Ce, Sm, Eu, La, Pr, Fe, Ti, Zr, Zn of 0.90:0.02:0.02:0.02:0.02:0.02:0.70:0.10:0.10:0.10;

[0046] (2) The raw materials weighed according to the stoichiometric ratio in step (1) were ground in a ball mill for 24 h with anhydrous ethanol as the medium, the ball milling speed was 150 rpm, and the uniformly ground powder was pre-sintered in an air atmosphere at 720 °C for 3 h;

[0047] (3) The pre-sintered product obtained in step (2) was manually ground for 2 h to avoid forming lumps; then the obtained powder was placed in an ultrasonic dispersion device, the frequency was set to 40 kHz, the power was 150 W, and the time was 20 minutes to break the particle agglomeration; then the ultrasonically dispersed powder was dried at 120 °C for 12 hours and pressed into shape by a tablet press at a pressure of 10 MPa;

[0048] (4) The wafer obtained in step (3) was buried in the dried and ultrasonically dispersed powder and sintered at 895 °C in an oxygen atmosphere for 3 h to obtain Bi 0.90 (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.10 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 multiferroic ceramic material.

[0049] The XRD of the Bi 0.90 (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.10 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 multiferroic ceramic material sample is as Figure 1 shown. From Figure 1All the diffraction peaks of the material were observed to be the same as those of the orthorhombic perovskite structure, showing a single-phase structure without the diffraction peaks of the second phase appearing; Figure 2 and Figure 3 and Figure 4 and Figure 5 respectively give the leakage current - electric field curve, polarization hysteresis loop, magnetic hysteresis loop and magnetodielectric coefficient - magnetic field curve of Bi 0.90 (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.10 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 material.

[0050] Example 4

[0051] Using the solid-state reaction method combined with ball milling and ultrasonic dispersion, Bi 0.85 (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.15 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 was prepared as follows:

[0052] (1) The raw materials Bi2O3 (purity 99.999%), Fe2O3 (purity 99.99%), CeO2 (purity 99.99%), Sm2O3 (purity 99.99%), Eu2O3 (purity 99.99%), La2O3 (purity 99.99%), Pr6O 11 (purity 99.99%), TiO2 (purity 99.99%), ZrO2 (purity 99.99%) and ZnO (purity 99.99%) were placed in a vacuum drying oven and dried at 120 °C for 12 hours. After drying, the raw materials Bi2O3, Fe2O3, CeO2, Sm2O3, Eu2O3, La2O3, Pr6O 11 , TiO2, ZrO2 and ZnO were proportioned according to the molar ratio of metal elements Bi, Ce, Sm, Eu, La, Pr, Fe, Ti, Zr, Zn of 0.85:0.03:0.03:0.03:0.03:0.03:70:10:10:10;

[0053] (2) Weigh the raw materials in step (1) according to the stoichiometric ratio, use absolute ethanol as the medium, grind them in a ball mill for 24 h, with a ball milling speed of 150 rpm, and place the evenly ground powder in an air atmosphere at 720 °C for pre-sintering for 3 h;

[0054] (3) Manually grind the pre-sintered powder obtained in step (2) for 2 h to avoid forming lumps; then place the obtained powder into an ultrasonic dispersion device, set the frequency to 40 kHz, the power to 150 W, and the time to 20 minutes to break the particle agglomeration; then dry the ultrasonically dispersed powder at a temperature of 120 °C for 12 h, and use a tablet press to press and form it at a pressure of 10 MPa;

[0055] (4) Bury the wafer obtained in step (3) in the dried and ultrasonically dispersed powder, and sinter it in an oxygen atmosphere at 920 °C for 3 h to obtain Bi 0.85 (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.15 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 multiferroic ceramic material.

[0056] The XRD of the Bi 0.85 (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.15 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 multiferroic ceramic material sample is shown as Figure 1 shown. It can be observed from Figure 1 that all the diffraction peaks of this material are the same as those of the orthorhombic perovskite structure, showing a single-phase structure without the diffraction peaks of the second phase appearing; Figure 2 , Figure 3 , Figure 4 , Figure 5 respectively give Bi 0.85 (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.15 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10Leakage current - electric field curve, ferroelectric hysteresis loop, magnetic hysteresis loop and magnetodielectric coefficient - magnetic field curve of O3 material.

[0057] In order to study the phase structure of Bi 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 multiferroic ceramic materials, X-ray diffractometer (XRD) was used to analyze the phase of the samples obtained in Examples 1 - 4, and the results are shown in Figure 1 as follows; it can be seen from Figure 1 that the prepared Bi 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 multiferroic ceramic materials have the same rhombohedral perovskite structure as BiFeO3, and no second phase is generated, indicating that the pure phase of Bi 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 multiferroic ceramic materials can be obtained; compared with BiFeO3, the diffraction peaks of Bi 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 multiferroic ceramics shift significantly towards smaller angles, indicating obvious lattice distortion in the high-entropy system.

[0058] In order to study the Bi prepared by the present invention 1-x (Ce0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 For the leakage conductance characteristics of the BiFeO3 multiferroic ceramic material, the leakage current - electric field of the samples in Examples 1 - 4 was measured using an RT 6000 ferroelectric test system, and the results are shown in Figure 2 as follows. It can be seen from Figure 2 that there is still a large leakage phenomenon in BiFeO3. After the equal - proportion substitution of multiple elements at the Bi site and the Fe site, its leakage characteristics are greatly improved. Bi 0.85 (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.15 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 has the most obvious improvement in leakage characteristics. When the test electric field is 3 kV / cm, its leakage current drops by nearly two orders of magnitude compared with the BiFeO3 matrix. The main reason is that the equal - proportion doping of multiple ions at the Bi site can effectively inhibit the volatilization of Bi, thereby suppressing the leakage current.

[0059] In order to study the ferroelectric properties of the Bi 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 multiferroic ceramic material, the ferroelectric characteristics of the samples in Examples 1 - 4 were measured using an RT 6000 ferroelectric test system, and the results are shown in Figure 3 as follows: It can be seen from Figure 3 that there is a difference between BiFeO3 and Bi 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10All O3 multiferroic ceramic materials show obvious ferroelectric hysteresis loop characteristics but are not saturated. Under the same test electric field, the ferroelectric properties of BiFeO3 are poor. After the equal-proportion substitution of multiple elements at the Bi site and Fe site, its ferroelectric properties are greatly improved, and both the maximum and remanent polarization intensities are higher than those of the BiFeO3 matrix sample, and the ferroelectricity increases with the increase of x, Bi 0.85 (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.15 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 The remanent polarization intensity of the O3 sample is 0.223 uC / cm 2 , which is 6.37 times that of undoped BiFeO3 (0.035 uC / cm 2 ). The reasons for the enhanced ferroelectricity are as follows: (1) The equal-proportion substitution of multiple elements at the Bi site and Fe site significantly reduces the leakage current in BiFeO3, thereby enhancing the polarization ability of the material; (2) The equal-proportion substitution of multiple elements at the Bi site and Fe site leads to severe lattice distortion in bismuth ferrite, destroys the symmetry of the lattice, increases the inhomogeneity of the local electric field, and thus enhances the polarization ability of the material; (3) The spontaneous polarization of BiFeO3 originates from the movement of trivalent iron ions in the iron oxygen octahedron along the diagonal direction of the trigonal perovskite, causing the center of gravity of positive and negative charges to deviate and generating a relative displacement to form an electric dipole moment to generate spontaneous polarization. The equal-proportion substitution of multiple elements at the Bi site and Fe site leads to an increase in the unit cell volume, the iron oxygen octahedron is distorted, and the dipole movement of Fe 3+ along the (111) direction is enhanced, thereby improving the ferroelectric polarization; (4) The introduction of multiple elements increases the charge disorder degree, resulting in a change in the local electron state density, thereby enhancing the ferroelectric response.

[0060] To study the magnetic properties of the Bi 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 multiferroic ceramic materials, the PPMS comprehensive physical property test system of Quantum Design Company was used to measure the magnetic temperature curve and magnetic hysteresis loop of the samples in Examples 1 - 4, and the results are as Figure 4As shown in the figure, the magnetization intensity of the BiFeO3 matrix changes linearly with the strength of the external magnetic field, showing antiferromagnetic characteristics and poor magnetic properties. When the Bi and Fe sites are replaced by multiple elements in equal proportions, the sample shows typical hysteresis loop characteristics and is a ferromagnetic structure, indicating that the Bi and Fe sites have changed the magnetic structure of BiFeO3 from antiferromagnetic to ferromagnetic, and the magnetic properties are greatly improved. The maximum and residual magnetization intensities of the sample increase gradually with the increase of x. The main reasons for the magnetic enhancement are as follows: (1) The Bi and Fe sites have caused the coexistence of ions of different radii in the lattice, causing serious lattice distortion. This distortion not only increases the disorder of the material, but also forms a local stress field, which in turn affects the arrangement of the magnetic moment. (2) The high entropy effect caused by the Bi and Fe sites has made the electronic structure of the material more complex and diversified, and the distribution of the electron cloud has changed, resulting in a change in the state of the spin electrons, thereby generating a net magnetic moment, which is manifested as enhanced magnetism on a macro scale. (3) The insertion of non-magnetic metal ions into Fe 3+ In the antiferromagnet lattice, it can break the adjacent Fe 3+ The antiparallel arrangement enables the magnetism to be manifested; (4) The substitution of high-valent Ce and Pr ions at the Bi site will generate a Bi vacancy, which will introduce an unpaired electron, which can couple with the 3d electrons of Fe, change the instantaneous magnetic moment, and generate magnetization.

[0061] In order to study the Bi prepared by the present invention 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 The magnetic and dielectric properties of O3 multiferroic ceramic materials were measured using a precision impedance analyzer produced by Agilent and connected to the PPMS of Quatum Design to measure the magnetic and dielectric properties of samples of Examples 1 to 4. The results are shown in Figure 5 shown; from Figure 5 It can be seen that all samples have magneto-dielectric effect; when the external magnetic field is less than 1000Oe, the magneto-dielectric coefficient (MD = (ε(H)-ε(0)) / ε(0), ε(H) is the dielectric constant under the external magnetic field, and ε(0) is the dielectric constant under zero field) increases with the increase of the external magnetic field. When the external magnetic field is higher than 1000Oe, the MD change is not obvious. The magneto-dielectric coefficient of the ceramics with equal proportions of Bi and Fe elements is significantly higher than that of BiFeO3 samples. When the external magnetic field is 1000Oe, Bi 0.85 (Ce 0.2 Sm0.2 Eu 0.2 La 0.2 Pr 0.2 ) 0.15 Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 The MD of the O3 sample is 10.58%, which is 4.35 times that of the doped BiFeO3 (2.43%). This is related to the lattice distortion and high ion disorder caused by the equal-proportion substitution of multiple elements at the Bi site and Fe site, which together lead to an increase in the magnetoelectric coupling effect. The experimental results show that the high-entropy effect caused by the equal-proportion substitution of multiple elements at the Bi site and Fe site enhances the magnetodielectric effect of bismuth ferrite.

[0062] In summary, the Bi 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3 multiferroic ceramic material can well optimize the ferroelectric, magnetic and magnetodielectric properties of BiFeO3 ceramic materials through the lattice distortion and high ion disorder effects caused by the equal-proportion substitution of multiple elements at the Bi site and Fe site, and is a new type of multiferroic ceramic material with great application prospects.

[0063] Finally, it should be noted that the embodiments described here are only used to illustrate the technical implementation solutions of this material and not to limit. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A multi - element co - doped bismuth ferrite multiferroic ceramic material, characterized in that, Its chemical formula is: Bi 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 O3, where x is 0.05 - 0.

15.

2. The multielement co-doped bismuth ferrite multiferroic ceramic material according to claim 1, characterized in that, x＝0.05、0.10、0.15。 3. A preparation method of a multi - element co - doped bismuth ferrite multiferroic ceramic material, characterized in that, Comprising: (1) According to Bi 1-x (Ce 0.2 Sm 0.2 Eu 0.2 La 0.2 Pr 0.2 ) x Fe 0.70 Ti 0.10 Zr 0.10 Zn 0.10 The molar ratio of metal ions in O3 is based on bismuth trioxide Bi2O3, iron(III) oxide Fe2O3, cerium(IV) oxide CeO2, samarium(III) oxide Sm2O3, europium(III) oxide Eu2O3, lanthanum(III) oxide La2O3, praseodymium(III) oxide Pr6O 11 , titanium(IV) oxide TiO2, zirconium(IV) oxide ZrO2 and zinc oxide ZnO for batching; (2) Adding the obtained ingredients with an organic solvent as a medium and grinding and mixing them evenly, and then pre-sintering at 700 - 750 °C; (3) Grinding, ultrasonic dispersing, drying and tabletting the pre-sintered product; (4) Sintering the tablet at 800 - 1000 °C to obtain a multi-element co-doped bismuth ferrite multiferroic ceramic material.

4. The preparation method of the multi-element co-doped bismuth ferrite multiferroic ceramic material according to claim 3, characterized in that, In the step (2), the organic solvent is absolute ethanol.

5. The preparation method of the multi-element co-doped bismuth ferrite multiferroic ceramic material according to claim 3, characterized in that, In the step (2), the grinding speed is 100 - 200 rpm, and the grinding time is 20 - 28 h.

6. The preparation method of the multi-element co-doped bismuth ferrite multiferroic ceramic material according to claim 3, characterized in that, In the step (2), the pre-sintering time is 2 - 5 h.

7. The preparation method of the multi-element co-doped bismuth ferrite multiferroic ceramic material according to claim 3, characterized in that, In the step (3), the grinding time is 1 - 3 h.

8. The preparation method of the multi-element co-doped bismuth ferrite multiferroic ceramic material according to claim 3, characterized in that, In the step (3), the ultrasonic dispersion frequency is 30 - 60 kHz, the power is 100 - 200 W, the time is 15 - 30 min, and the tabletting pressure is 7 - 12 Mpa.

9. The preparation method of the multi-element co-doped bismuth ferrite multiferroic ceramic material according to claim 3, characterized in that, In the step (4), the sintering time is 3 - 5 h.

10. Application of the multi-element co-doped bismuth ferrite multiferroic ceramic material according to claim 1 or 2 in magnetoelectric sensors, information storage, capacitors, energy converters and spin devices.

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