High-entropy rare earth ferrite ceramic material and preparation method thereof

Abstract

The application relates to a high-entropy rare earth ferrite ceramic material and a preparation method thereof, and belongs to the field of ceramic materials. The high-entropy rare earth ferrite ceramic material is a single crystal structure, and has a general chemical formula of Bi 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z wt.%MnCO3, wherein z The value range of x is 0.25-1. The high-entropy rare earth ferrite ceramic synthesized by the high-entropy rare earth ferrite ceramic material preparation method has excellent performances such as small grain size, low room-temperature dielectric loss, small leakage current density and good ferromagnetism.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials, and more particularly to a high-entropy rare-earth ferrite ceramic material and its preparation method. Background Technology

[0002] Single-phase multiferroic materials possess both ferromagnetic and ferroelectric coupling properties, making them promising candidates for spintronic devices. Currently, research on single-phase multiferroic materials primarily focuses on BiFeO3 and rare-earth ferrites. Among these, BiFeO3 exhibits excellent ferroelectric properties, but its preparation as a single-phase ceramic is extremely difficult, and it exhibits weak magnetism at room temperature. Rare-earth ferrite multiferroic materials also exhibit weak ferroelectric properties (polarization intensity of 0.01 μC·cm). -2 Furthermore, ferroelectricity exists below room temperature (< 25℃).

[0003] To address the issue of the relatively weak room-temperature polarization of rare-earth ferrites, previous studies have utilized the excellent ferroelectricity of BiFeO3 and the strong ferromagnetism of rare-earth ferrites to synthesize ferrites with relatively high polarization at room temperature (> 1 μC·cm). -2 Bi single-phase high-entropy rare-earth ferrite multiferroic material 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3. Among them, high-entropy rare-earth ferrite ceramics Bi 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3 possesses excellent properties such as small grain size, high resistivity, and low room-temperature dielectric loss. However, in high-entropy rare-earth ferrite ceramics, Bi... 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 The introduction of titanium into O3 is accompanied by a large leakage current density, which needs to be improved. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a high-entropy rare-earth ferrite ceramic material and its preparation method. The synthesized high-entropy rare-earth ferrite ceramic has excellent properties such as small grain size, low room temperature dielectric loss, low leakage current density, and good ferromagnetism.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] This application provides a high-entropy rare-earth ferrite ceramic material, which has a single crystal structure and a general chemical formula of Bi. 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z wt.%MnCO3, where z The value range is 0.25-1.

[0007] Preferred, z The value is 0.75, at which point the performance is better.

[0008] In addition, a method for preparing high-entropy rare-earth ferrite ceramic materials is also provided, the steps of which are as follows:

[0009] (1) Preparation of high-entropy rare earth ferrite powder

[0010] According to Bi 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z The stoichiometric ratio of Bi₂O₃, La₂O₃, Y₂O₃, Dy₂O₃, Tb₄O₇, Fe₂O₃, TiO₂, and MnCO₃ powders was weighed separately. The powders, anhydrous ethanol, and zirconia balls were then mixed in a nylon jar and ball-milled for 24 hours at a ball-to-liquid ratio of 10:1:5. The powders were then dried and subsequently milled in a sealed alumina crucible at 5℃·min⁻¹. -1 The temperature is increased from room temperature to 1100℃, and then held at 1100℃ for 3 hours to obtain the product.

[0011] (2) Preparation of high-entropy rare earth ferrite ceramic materials

[0012] The obtained high-entropy rare earth ferrite powder was ball-milled a second time under the same ball-milling conditions as (1), for a time of 10 hours; the ball-milled powder was dried again; granulated and pressed into a green body; then it was held at 500℃ for 4 hours in a high-temperature furnace, and then heated at 5℃·min. -1 The heating rate is increased to 1200℃, and the temperature is maintained for 2 hours to obtain the product.

[0013] Preferably, in step (2), the specific steps of granulation and pressing into a green blank are as follows: the powder and polyvinyl alcohol with a mass concentration of 5 wt.% are mixed at a mass ratio of 1:0.05 and granulated, passed through a 90-mesh sieve, and then a pressure of 382 MPa is applied to the powder, the pressure holding time is 2 minutes, and the green blank with a diameter of 10 mm is pressed into a green blank.

[0014] Preferably, in steps (1) and (2), the powder drying conditions are: drying in an oven at 80°C for 24 hours.

[0015] The advantages of this invention using the above-described solution are:

[0016] 1. Structurally: High-entropy rare-earth ferrite ceramics Bi introduced by the sintering aid MnCO3 were successfully synthesized via a high-temperature solid-state method. 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z This high-entropy rare-earth ferrite ceramic, containing wt.% MnCO3, not only possesses a stable single-phase perovskite structure but also exhibits a small grain size and high density.

[0017] 2. In terms of dielectric properties: Compared with existing high-entropy rare-earth ferrite ceramics without MnCO3, the high-entropy rare-earth ferrite ceramics with MnCO3 exhibit better frequency and temperature stability in dielectric constant. Furthermore, the dielectric loss of the former gradually decreases with increasing frequency, and it exhibits even lower room-temperature dielectric loss at high frequencies.

[0018] 3. Ferroelectric properties: The high-entropy rare-earth ferrite ceramic of this invention has a lower leakage current density. Furthermore, as the MnCO3 content increases, the leakage current density of the high-entropy rare-earth ferrite ceramic first decreases and then increases. When the mass fraction of MnCO3 is 0.75%, the leakage current density of the high-entropy rare-earth ferrite ceramic is the lowest at 9.90 × 10⁻⁶. -8 A·cm -2 (20 kV·cm) -1 ).

[0019] Studies have shown that introducing no more than 1% MnCO3 has a positive effect on improving the applied electric field strength of high-entropy rare-earth ferrite ceramics. Specifically, the high-entropy rare-earth ferrite ceramics after the introduction of MnCO3 still exhibit a large maximum polarization intensity (all greater than 1.45 μC·cm). -2 Furthermore, the applied electric field strength that achieves maximum polarization intensity has increased to 110 kV·cm. -1The applied electric field strength (45 kV·cm) of high-entropy rare-earth ferrite ceramics without the introduction of MnCO3 is compared with that of the ceramics without the introduction of MnCO3. -1 Compared to the previous method, the applied electric field strength of the high-entropy rare-earth ferrite ceramic of this invention is increased by approximately 1.5 times. This is indirect evidence that the leakage current density of the high-entropy rare-earth ferrite ceramic decreases after the introduction of MnCO3. Furthermore, the increased applied electric field strength makes the material less prone to breakdown under high electric field conditions, thus enhancing its application potential.

[0020] 4. Ferromagnetic properties: Compared with high-entropy rare-earth ferrite ceramics without the addition of sintering aid MnCO3, the high-entropy rare-earth ferrite ceramics prepared by introducing low-valence magnetic Mn ions in this application show a significant increase in remanent magnetization. M r Specifically, it can be calculated from 0.08 A·m 2 ·kg -1 Increased to 0.13 A·m 2 ·kg -1 . Attached Figure Description

[0021] Figure 1 The refined XRD patterns of high-entropy rare-earth ferrite ceramic samples 1-5 are shown.

[0022] Figure 2 SEM images of cross-sections of high-entropy rare-earth ferrite ceramic samples 1-5;

[0023] Figure 3 The statistical results of grain size distribution for high-entropy rare-earth ferrite ceramic samples 1-5 are presented.

[0024] Figure 4 EDS elemental spectra of high-entropy rare-earth ferrite ceramic samples 1-5;

[0025] Figure 5 Dielectric properties of high-entropy rare-earth ferrite ceramic samples 1-5;

[0026] Figure 6 The graph shows the relationship between the dielectric constant and temperature for high-entropy rare-earth ferrite ceramic samples 1-5.

[0027] Figure 7 Ferroelectric properties of high-entropy rare-earth ferrite ceramic samples 1-5;

[0028] Figure 8 The leakage current density of high-entropy rare-earth ferrite ceramic samples 1-5.

[0029] Figure 9 High-temperature impedance diagrams of high-entropy rare-earth ferrite ceramic samples 1-5;

[0030] Figure 10Impedance spectrum fitting curves for high-entropy rare-earth ferrite ceramic samples 1-5;

[0031] Figure 11 High-entropy rare-earth ferrite ceramic samples 1-5 Fe2 p XPS plot;

[0032] Figure 12 High-entropy rare-earth ferrite ceramic sample 1-5 O1 s XPS plot;

[0033] Figure 13 The oxygen vacancy content of high-entropy rare earth ferrite ceramic samples 1-5;

[0034] Figure 14 The room temperature hysteresis loops of high-entropy rare-earth ferrite ceramic samples 1-5 are shown. Detailed Implementation

[0035] To clearly illustrate the technical features of this solution, the invention will be described in detail below through specific implementation methods and in conjunction with the accompanying drawings.

[0036] 1. Instruments and reagents

[0037] Table 1 Experimental Raw Materials

[0038]

[0039] Table 2. Instruments required for the experiment

[0040]

[0041] 2. Preparation of high-entropy rare-earth ferrite ceramic materials

[0042] (1) Preparation of high-entropy rare earth ferrite powder

[0043] According to Bi 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z The stoichiometric ratios of Bi₂O₃, La₂O₃, Y₂O₃, Dy₂O₃, Tb₄O₇, Fe₂O₃, TiO₂, and MnCO₃ powders were weighed separately. The powders, anhydrous ethanol, and zirconium oxide balls were then mixed in a nylon jar and ball-milled for 24 hours at a ball-to-liquid ratio of 10:1:5. The powders were then dried in an oven at 80°C for 24 hours. Finally, the powders were dried in a sealed alumina crucible at 5°C / min. -1 The temperature is increased from room temperature to 1100℃, and then held at 1100℃ for 3 hours to obtain the product.

[0044] (2) Preparation of high-entropy rare earth ferrite ceramic materials

[0045] The obtained high-entropy rare earth ferrite powder was ball-milled a second time under the same ball-milling conditions (same as (1)) for 10 hours; the ball-milled powder was dried in an oven at 80°C for 24 hours; then the powder and polyvinyl alcohol with a mass concentration of 5 wt.% were mixed at a mass ratio of 1:0.05 and granulated, passed through a 90-mesh sieve, and then a pressure of 382 MPa was applied to the powder for 2 minutes to press it into a green blank with a diameter of 10 mm; then it was first held at 500°C for 4 hours in a high-temperature furnace to slowly remove the added polyvinyl alcohol, and then at 5 ℃·min -1 The temperature is increased from 500℃ to 1200℃, and then held at 1200℃ for 2 hours to obtain the product.

[0046] Prepare according to the above methods respectively z High-entropy rare-earth ferrites with intensities of 0, 0.25, 0.5, 0.75, and 1, wherein high-entropy rare-earth ferrite ceramics... z = 0 represents the control sample, denoted as Sample 1. This invention relates to high-entropy rare-earth ferrite ceramics. z = 0.25, 0.5, 0.75 and 1 are experimental samples, denoted as samples 2-5.

[0047] To test the dielectric properties, impedance characteristics, and ferroelectric properties of ceramics, the surface of the ceramics needs to be further ground and polished, and silver electrodes need to be coated on both sides for later use.

[0048] 3. Characterization methods for high-entropy rare-earth ferrite ceramic samples

[0049] (1) Crystal structure characterization: The crystal structure of the powder and ceramics was characterized by X-ray diffraction (XRD). The target material used was a copper target. The test angle range was 20-80°, the scanning speed was 8° per minute, the tube voltage was 45kV, and the tube current was 200 mA. The XRD structure refinement data were obtained using the Rietveld method with Fullprof software.

[0050] (2) Microstructure characterization: The microstructure of the high-entropy rare-earth ferrite ceramic samples was observed and recorded using a ZEISS SUPRA-55 scanning electron microscope (SEM) at a working voltage of 15 kV. Simultaneously, the distribution of microstructural elements in the high-entropy rare-earth ferrite ceramics was analyzed using an energy dispersive X-ray spectrometer (EDS). Furthermore, the grain size of the prepared high-entropy rare-earth ferrite ceramics was statistically analyzed using Nano Measurer software.

[0051] (3) X-ray photoelectron spectroscopy: X-ray photoelectron spectroscopy (XPS) is a surface-sensitive analytical technique that can be used to determine the chemical state of elements, including their valence state. The instrument used in this experiment was a Thermo Electron ESCALAB 250Xi photoelectron spectrometer for XPS analysis, utilizing C1... s The peak (284.6 eV) was used as the calibration binding energy, and the spectrum was fitted with peaks using Avantage software to determine the elemental composition and chemical state (mainly Fe and O elements) of the high-entropy rare earth ferrite ceramic.

[0052] (4) Electron Paramagnetic Resonance: Electron paramagnetic resonance (EPR) is a magnetic resonance technique used to detect and study matter with unpaired electrons. The signal characteristics generated by oxygen vacancies are usually different from other types of unpaired electron signals and can be identified by comparing known standards or theoretical calculations. The test equipment used in this experiment is the A300 test system manufactured by Bruker.

[0053] (5) Dielectric properties: The relationship between the dielectric properties of the prepared ceramics and temperature at different given frequencies (e.g., 10 kHz, 100 kHz, 1 MHz) and the relationship between the dielectric properties of the ceramics at room temperature and frequency (100 Hz to 1 MHz) was characterized using a wide temperature range dielectric test system (TZDM-RT-800).

[0054] (6) Ferroelectric properties: The hysteresis loops of different ceramics under different applied electric fields and the leakage current density curves of ceramics under a fixed applied electric field were tested using a ferroelectric analyzer (Multiferroic from Radiant Corporation, USA). The frequency of the test was 10 Hz.

[0055] (7) Impedance performance: For ceramic bulk, it can be regarded as being composed of semiconductor grains and insulating grain boundaries. In order to further analyze the conductivity contribution of grains and grain boundaries, the impedance performance of high entropy rare earth ferrite ceramics was tested using a TH2839 impedance analyzer within a certain temperature range (25-300℃).

[0056] (8) Magnetic properties: The hysteresis loop was characterized using the Quantum Design Integrated Physical Property Measurement System (PPMS-9). During testing, approximately 70 mg of ceramic powder was used to characterize the ceramic sample under an alternating magnetic field (1.7 MA·m). -1 The relationship between magnetization and magnetic field strength was investigated to evaluate key magnetic parameters of the synthesized material, such as saturation magnetization, coercivity, and remanent magnetization.

[0057] 4. Analysis of Results for High-Entropy Rare Earth Ferrite Ceramic Samples

[0058] (1) Crystal structure

[0059] Figure 1 The refined XRD patterns of high-entropy rare-earth ferrite ceramic samples 1-5 are shown. Figure 1 It can be seen that the present invention synthesized high-entropy rare-earth ferrite ceramic samples 1-5 with perovskite structures at high temperature (1200℃), and all of them have a single crystal structure. This indicates that the prepared novel high-entropy rare-earth ferrite ceramics can exist stably at high temperature, and the introduction of a certain amount of sintering aid MnCO3 can maintain its original crystal structure. In order to further analyze the influence of different MnCO3 contents on the structure of high-entropy rare-earth ferrite ceramics, the XRD of high-entropy rare-earth ferrite ceramic samples 1-5 was refined. It can be seen from the refined structure diagram that the prepared novel high-entropy rare-earth ferrite ceramic samples 1-5 all have a single-phase perovskite crystal structure, and all their refined results have good fitting degree, and the fitting results are within the error range.

[0060] Table 3 shows the cell parameters of the refined high-entropy rare-earth ferrite ceramic samples 1-5. The refined structural results show that the high-entropy rare-earth ferrite ceramic samples 1-5 have a single-phase crystal structure and the same space group (…). P (nma), with only slight differences in its unit cell parameters.

[0061] Table 3. Cell parameters of high-entropy rare-earth ferrite ceramic samples 1-5 after refinement.

[0062]

[0063] (2) Microscopic morphology

[0064] Figure 2 The images show cross-sectional SEM images of high-entropy rare-earth ferrite ceramic samples 1-5; where (a)z = 0, (b) z = 0.25, (c) z = 0.5, (d) z = 0.75, (e) z = 1. From Figure 2 It can be seen that the grains of high-entropy rare-earth ferrite ceramic samples 1-5 are irregularly blocky, with relative densities of 95.1%, 96.1%, 95.3%, 95.9%, and 96.3%, respectively. Among them, high-entropy rare-earth ferrite ceramic sample 1 without the addition of sintering aid MnCO3 has obvious grain boundaries and contains trace amounts of pores; high-entropy rare-earth ferrite ceramic samples 2-5 with the addition of sintering aid MnCO3, which has a lower decomposition temperature, not only have fewer pore defects, but also have tighter grain bonding and a more compact structure. Figure 3 This presents the statistical results of grain size distribution for high-entropy rare-earth ferrite ceramic samples 1-5. Figure 3 It can be seen that the average grain sizes of the high-entropy rare-earth ferrite ceramic samples 1-5 are 1.02, 1.02, 0.98, 1.03, and 1.05 μm, respectively. The above results of microstructure and grain size distribution indicate that the high-entropy rare-earth ferrite ceramic samples 2-5 prepared in this invention not only have high density but also maintain a small grain size.

[0065] (3) Element distribution

[0066] Figure 4 The following are the EDS elemental spectra of high-entropy rare-earth ferrite ceramic samples 1-5, where (a) z = 0, (b) z = 0.25, (c) z = 0.5, (d) z = 0.75, (e) z = 1. According to the elemental spectrum results, with the addition of sintering aid MnCO3, each element (Fe, O, Bi, La, Dy, Tb, Y, Ti and Mn) is uniformly distributed in the high-entropy rare earth ferrite ceramic samples 2-5, and there is no obvious segregation or aggregation. This indicates that the synthesized high-entropy rare earth ferrite ceramic samples 1-5 have a uniform elemental distribution on a macroscopic scale, which is beneficial to the stability of material properties.

[0067] (4) Dielectric properties

[0068] Figure 5 The dielectric properties of high-entropy rare-earth ferrite ceramic samples 1-5 are shown, where (a) is the dielectric spectrum and (b) is the dielectric loss. Figure 5(a) It can be seen that the high-entropy rare-earth ferrite ceramic samples 2-5 of this invention, which incorporate an appropriate amount of MnCO3, all exhibit good frequency stability in their dielectric constants. At a frequency of 0.1 kHz, the dielectric constants of the high-entropy rare-earth ferrite ceramic samples 1-5 are 543, 103, 65, 58, and 62, respectively. The high-entropy rare-earth ferrite ceramics with introduced MnCO3 have relatively low dielectric constants, which may be related to the introduced manganese valence state. Different stable Mn compounds exist in different temperature ranges, as shown in equation (1-1):

[0069] (1-1)

[0070] The low decomposition temperature of MnCO3 results in high density in the synthesized single-phase high-entropy rare-earth ferrite ceramic samples 2-5. The synthesis temperatures (1200℃) of the high-entropy rare-earth ferrite ceramics with different MnCO3 contents prepared in this study were all higher than 1080℃, therefore the Mn ions existed in +3 and +2 valence states (see Equation (1-1)). Compared to the dielectric constant of high-entropy rare-earth ferrite ceramic sample 1 (0.1 kHz, 543), the dielectric constant of high-entropy rare-earth ferrite ceramic samples 2-5 is smaller, which may be related to the introduction of low-valence manganese (+2 valence). The introduced Mn... 2+ It may enter the crystal lattice and replace Fe. 3+ Mn 2+ Fe replacement 3+ The relationship is shown in equation (1-2):

[0071] (1-2)

[0072] The introduction of low-valence manganese (+2 valence) into high-entropy rare-earth ferrite ceramics increases the number of oxygen vacancies in the crystal. Oxygen vacancies and... The presence of these defects (see equation (1-2)) may lead to the generation of more defect dipoles inside the synthesized high-entropy rare-earth ferrite ceramics. The presence of defect dipoles within high-entropy rare-earth ferrite ceramics not only enhances the pinning effect on domain walls but also increases their stability. The above analysis indicates that the introduction of low-valence manganese ions makes domain flipping in high-entropy rare-earth ferrite ceramics more difficult, thus reducing their dielectric constant under the same testing conditions.

[0073] The introduction of MnCO3 also caused significant changes in the dielectric loss of high-entropy rare-earth ferrite ceramic samples 2-5, such as... Figure 5 As shown in (b), at a frequency of 0.1 kHz, the introduction of manganese ions significantly increased the dielectric loss of high-entropy rare-earth ferrite ceramic sample 2 compared to high-entropy rare-earth ferrite ceramic sample 1. The increase in dielectric loss of high-entropy rare-earth ferrite ceramic sample 2 at low frequencies is due to the presence of defect dipoles in the crystal. The number of defect dipoles (MnCO3) is relatively small. With increasing MnCO3 content, the number of defect dipoles in high-entropy rare-earth ferrite ceramics (samples 3-5) increases. As the number of elements increases, the dielectric loss gradually decreases. At a frequency of 100 kHz, the room temperature dielectric losses of high-entropy rare-earth ferrite ceramic samples 1-5 are 0.82, 0.04, and 3.4 × 10⁻⁵, respectively. -3 1.4×10 -3 and 1.3×10 -3 Furthermore, with the increase of MnCO3 content, the room temperature dielectric loss of high-entropy rare-earth ferrite ceramics at high frequencies gradually decreases, which further indicates that the high-entropy rare-earth ferrite ceramics maintain low dielectric loss performance after the introduction of manganese ions.

[0074] To further investigate the changes in dielectric constant of high-entropy rare-earth ferrite ceramic samples 1-5 at high temperatures before and after the introduction of the sintering aid MnCO3, the relationship between their dielectric constant and temperature was analyzed, such as... Figure 6 As shown, when the temperature is below 300℃, the dielectric constant of the synthesized high-entropy rare-earth ferrite ceramics increases with increasing test temperature. At a frequency of 10 kHz, the dielectric constants of high-entropy rare-earth ferrite ceramic samples 1-5 at 300℃ are 1368, 953, 400, 243, and 216, respectively. Furthermore, with increasing MnCO3 content, the dielectric constant of the high-entropy rare-earth ferrite ceramics at high temperatures gradually decreases, which is related to the introduction of low-valence manganese ions (+2). With further increases in test temperature (> 300℃), the resistance of high-entropy rare-earth ferrite ceramic samples 2 and 3 decreases at high temperatures, leading to a decrease in their dielectric constant. However, no decreasing trend was observed in the dielectric constants of high-entropy rare-earth ferrite ceramic samples 4 and 5 within the test temperature range.

[0075] In summary, with the addition of sintering aid MnCO3, the high-entropy rare earth ferrite ceramic samples 2-5 prepared by this invention have smaller dielectric losses, thereby giving their dielectric constant better frequency and temperature stability.

[0076] (5) Ferroelectric properties

[0077] Figure 7 Ferroelectric properties of high-entropy rare-earth ferrite ceramic samples 1-5 at 0.01 kHz. When the applied electric field strength is 45 kV·cm... -1 At that time, the high-entropy rare-earth ferrite ceramics prepared z The maximum polarization intensity at 0 is 2.5 μC·cm. -2 (like Figure 7 (as shown in (a)). When the maximum applied electric field strength is 110 kV·cm -1 At that time, high-entropy rare-earth ferrite ceramics zThe maximum polarization intensities for 0.25, 0.5, 0.75, and 1 are 2.34, 1.59, 1.45, and 1.50 μC·cm, respectively. -2 .

[0078] With the introduction of the sintering aid MnCO3, the maximum polarization intensity of high-entropy rare-earth ferrite ceramics decreases. This is due to the defect dipoles within the crystal ( With the increase in the number of domains, the pinning effect of domain walls is enhanced, making domain flipping more difficult. The introduction of MnCO3 leads to higher entropy rare-earth ferrite ceramics... z The applied electric field strengths of 0.25, 0.5, 0.75, and 1 are increased to 110 kV·cm. -1 High-entropy rare-earth ferrite ceramics z = 0 applied electric field strength (45 kV·cm) -1 Compared to high-entropy rare-earth ferrite ceramics, z The applied electric field strengths of 0.25, 0.5, 0.75, and 1 increased by approximately 1.5 times. The increase in the applied electric field strength of high-entropy rare-earth ferrite ceramics is due to the presence of... This resulted in the formation of more defect dipoles within the crystal. In high-entropy rare-earth ferrite ceramics, the increased number of defect dipoles can strengthen the pinning effect of domain walls and reduce dielectric loss, thereby increasing the applied electric field strength. Analysis of the ferroelectric properties shows that introducing no more than 1% MnCO3 can improve the ferroelectric performance of high-entropy rare-earth ferrite ceramics. 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z The applied electric field strength of wt.%MnCO3 has a positive effect.

[0079] To investigate the effects of introducing the sintering aid MnCO3 on high-entropy rare-earth ferrite ceramics z The reasons for the changes in ferroelectric properties of 0, 0.25, 0.5, 0.75 and 1 were investigated, and their leakage current densities were analyzed. Figure 8 The leakage current density is for high-entropy rare-earth ferrite ceramic samples 1-5.

[0080] Depend on Figure 8 It is known that the leakage current density of high-entropy rare-earth ferrite ceramics increases with the increase of the applied electric field strength. Compared with high-entropy rare-earth ferrite ceramics without the introduction of MnCO3, the high-entropy rare-earth ferrite ceramics of this invention have a smaller leakage current density. When the applied electric field strength is 20 kV·cm... -1 At that time, high-entropy rare-earth ferrite ceramics z= 0, 0.25, 0.5, 0.75 and 1 leakage current densities are 3.87 × 10 -6 1.15×10 -7 1.09×10 -7 9.90×10 -8 and 2.24×10 -7 A·cm -2 Furthermore, in the high-entropy rare-earth ferrite ceramic of this invention, as the MnCO3 content increases, the leakage current density of the high-entropy rare-earth ferrite ceramic first decreases and then increases. Among them, the high-entropy rare-earth ferrite ceramic... z The increased number of defect dipoles in the MnCO3 concentrations of 0.25, 0.5, and 0.75 gradually decreases the leakage current density, which is consistent with the ferroelectric performance analysis results. When the introduced MnCO3 mass fraction is 0.75%, the high-entropy rare-earth ferrite ceramic exhibits the lowest leakage current density, with a value of 9.90 × 10⁻⁶. -8 A·cm -2 As the previous analysis showed, Mn ions in high-entropy rare-earth ferrite ceramics exist in both +2 and +3 valence states. When the introduced MnCO3 mass fraction is 1%, the high-entropy rare-earth ferrite ceramic... z An increase in oxygen vacancy defects in =1 will lead to insufficient defect dipoles to fix oxygen vacancies under an applied electric field, resulting in an increase in leakage current density.

[0081] (6) Resistance characteristics

[0082] To analyze the source of the variation in leakage current density in high-entropy rare-earth ferrite ceramics introduced by MnCO3, the Bi content of high-entropy rare-earth ferrite ceramics with different MnCO3 contents was characterized. 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z The high-temperature impedance diagram of wt.%MnCO3 is as follows: Figure 9 As shown, at high temperatures, the impedance curve is an irregular semicircle. With increasing test temperature, due to thermal motion, the impedance of the synthesized high-entropy rare-earth ferrite ceramic gradually decreases.

[0083] When the test temperature is 200℃, the impedance spectrum of the high-entropy rare-earth ferrite ceramic is an arc-shaped curve. When the test temperature increases to 250℃, with the increase of MnCO3 content, the high-entropy rare-earth ferrite ceramic... zThe impedance of high-entropy rare-earth ferrite ceramics decreases and then increases at values ​​of 0, 0.25, 0.5, 0.75, and 1. The impedance is lowest when the mass fraction of MnCO3 is 0.25%. When the mass fraction of MnCO3 is greater than 0.25%, the impedance of high-entropy rare-earth ferrite ceramics... z The impedance values ​​gradually increase from 0.5 to 0.75 and from 1.

[0084] Ceramics can be viewed as consisting of semiconductor grains and insulating grain boundaries, and their impedance curves can be fitted to two parts: grains and grain boundaries. To clarify the contributions of grains and grain boundaries to impedance, impedance curves of high-entropy rare-earth ferrite ceramics were fitted. At a test temperature of 250℃, the impedance curves of high-entropy rare-earth ferrite ceramics with different MnCO3 contents were compared. 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z The impedance spectrum fitting curve of wt.%MnCO3 is as follows: Figure 10 As shown. After fitting the impedance curve, the resistance of the synthesized high-entropy rare-earth ferrite ceramic grains and grain boundaries can be calculated, thereby analyzing the reason for the impedance change of the high-entropy rare-earth ferrite ceramic after the introduction of MnCO3. From the impedance fitting curve, it can be seen that the high-entropy rare-earth ferrite ceramic… z The lowest resistance value is 0.25. With further increases in MnCO3 content, high-entropy rare-earth ferrite ceramics (… z The impedance values ​​of (= 0.5, 0.75, and 1) gradually increase. A magnified view near the zero point shows that the impedance curve of the synthesized high-entropy rare-earth ferrite ceramic passes through the zero point, indicating that the impedance spectrum is a result of the interaction between grains and grain boundaries.

[0085] To investigate in more detail the reasons for the impedance changes in the prepared high-entropy rare-earth ferrite ceramics, the impedance of high-entropy rare-earth ferrite ceramics with different MnCO3 contents (Bi) was analyzed. 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z The impedance fitting parameters for wt.% MnCO3 are shown in Table 4. C g Table 4 shows the grain capacitance of the synthesized high-entropy rare-earth ferrite ceramics, with the unit of capacitance being nF. As can be seen from Table 4, the high-entropy rare-earth ferrite ceramics... zThe grain boundary resistivities of 0, 0.25, 0.5, 0.75, and 1 are 255.72, 25.884, 180.69, 203.46, and 200.02 kΩ, respectively. With the introduction of MnCO3, high-entropy rare-earth ferrite ceramics... z The grain boundary resistivity decreases to 0.25, which may be due to the presence of some manganese ions at the grain boundaries. As the MnCO3 content continues to increase, the high-entropy rare-earth ferrite ceramic... z The grain boundary impedances of 0.5, 0.75, and 1 increased by approximately one order of magnitude. This is because the introduction of low-valence manganese ions generates defect dipoles within the grains of high-entropy rare-earth ferrite ceramics (see Equation (1-2)), reducing their dielectric loss and leakage current density, thereby increasing the impedance at the grain boundaries. High-entropy rare-earth ferrite ceramics z The grain boundary resistance fluctuation of 1 is likely due to an increase in oxygen vacancy defects in the crystal, which is consistent with its leakage current density analysis results. High-entropy rare-earth ferrite ceramics z The grain capacitances for 0, 0.25, 0.5, 0.75, and 1 mF are 43.1, 4.87, 0.37, 0.16, and 0.13 nF, respectively. With increasing MnCO3 content, the generated defect dipoles reduce the intragranular capacitance of the high-entropy rare-earth ferrite ceramic. Meanwhile, the high-entropy rare-earth ferrite ceramic... z The grain boundary capacitances for 0, 0.25, 0.5, 0.75, and 1 are 1.10, 1.58, 1.02, 0.34, and 0.20 nF, respectively. With the introduction of MnCO3, high-entropy rare-earth ferrite ceramics... z The grain boundary capacitances of 0.5, 0.75, and 1 also decreased synchronously, indicating that the defect dipole ( This also acts at the grain boundaries, maintaining low dielectric loss and leakage current density. High-entropy rare-earth ferrite ceramics... z The presence of some manganese ions at the grain boundary with a capacitance of 0.25 increases the grain boundary capacitance.

[0086] Table 4. Impedance fitting parameters of high-entropy rare-earth ferrite ceramic samples 1-5

[0087]

[0088] The addition of low-valence manganese ions to high-entropy rare-earth ferrite ceramics generally increases the valence state of cations or creates anion vacancies. To further understand the existence state of defects in high-entropy rare-earth ferrite ceramics, tests were conducted on Bi high-entropy rare-earth ferrite ceramics with different MnCO3 contents. 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3-z wt.%MnCO3 Fe 2 p XPS plots, such as Figure 11 As shown. XPS spectra can be used to study the surface chemical composition and chemical state of materials. From the XPS spectrum of Fe, it can be seen that Fe... 3+ 2 p 3 / 2 and Fe 3+ 2 p 1 / 2 The double peaks are located near 710.8 eV and 724.4 eV. Additionally, a satellite peak near 718.8 eV also belongs to Fe. 3+ Characteristic peaks. With increasing MnCO3 content, high-entropy rare-earth ferrite ceramics exhibit... z = 0.25, 0.5, 0.75 and 1 Fe 2 p The absence of peak shift indicates that the valence state of Fe is relatively stable and there is no increase.

[0089] High-entropy rare earth ferrite ceramics Bi with different MnCO3 contents 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z wt.%MnCO3 O 1 s XPS plots, such as Figure 12 As shown. High-entropy rare-earth ferrite ceramics. z = 0, 0.25, 0.5, 0.75 and 1 for O 1 s The spectrum can be divided into two peaks: the characteristic peaks at 529.5 eV and 531 eV correspond to lattice oxygen (O) and adsorbed oxygen (O1) in the metal oxide, respectively, indicating the presence of oxygen vacancies.

[0090] High-entropy rare earth ferrite ceramics Bi 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z wt.%MnCO3 ( z The oxygen vacancy content of (= 0, 0.25, 0.5, 0.75 and 1) can be obtained by the area of ​​the characteristic peaks of adsorbed oxygen and lattice oxygen, as shown in equation (1-3):

[0091] (1-3)

[0092] In the formulaS O1 and S O These are the characteristic peak areas of adsorbed oxygen and lattice oxygen test peaks, respectively. Calculations show that high-entropy rare-earth ferrite ceramics... z The oxygen vacancy contents for MnCO3 values ​​of 0, 0.25, 0.5, 0.75, and 1 are 0.37, 0.55, 0.71, 0.64, and 0.64, respectively. The oxygen vacancy content of high-entropy rare-earth ferrite ceramics increases with the introduction of MnCO3.

[0093] When MnCO3 is introduced, high-entropy rare-earth ferrite ceramics z The oxygen vacancy content within the crystals changed with increasing MnCO3 content (0.25, 0.5, 0.75, and 1). To further analyze the change in oxygen vacancy content in high-entropy rare-earth ferrite ceramics with increasing MnCO3 content, their EPR was tested. High-entropy rare-earth ferrite ceramics with different MnCO3 contents (Bi) 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z Oxygen vacancy content of MnCO3 by weight (wt.%), such as Figure 13 As shown in the figure, the trend of the curves indicates that with the increase of MnCO3 content, the high-entropy rare-earth ferrite ceramics... z The peak intensities of oxygen vacancies gradually increase at values ​​of 0, 0.25, 0.5, 0.75, and 1, indicating a gradual increase in the content of oxygen vacancies. The coexistence of oxygen vacancies and... More defect dipoles can be formed ( This further reduces the entropy of high-entropy rare-earth ferrite ceramics. z = Dielectric losses of 0.25, 0.5, 0.75 and 1.

[0094] (5) Magnetic properties

[0095] The addition of MnCO3 alters the electrical properties of high-entropy rare-earth ferrite ceramics and may also affect their magnetic properties. High-entropy rare-earth ferrite ceramics Bi 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z The room temperature hysteresis loop of wt.%MnCO3, such as Figure 14 As shown. With the gradual increase of the applied magnetic field, high-entropy rare-earth ferrite ceramics... zThe magnetization intensities of 0, 0.25, 0.5, 0.75, and 1 gradually saturate. Furthermore, the magnetization curve exhibits a thin, saturated hysteresis loop and does not pass through the origin (e.g., ...). Figure 14 (b) shows that the synthesized high-entropy rare-earth ferrite ceramic exhibits a ferromagnetic structure. The electron configuration of the transition metal element Mn is [Ar]4. s 2 3 d 5 In high-entropy rare-earth ferrite ceramics z In the values ​​of 0.25, 0.5, 0.75, and 1, manganese has a mixed valence of +2 and +3. In these cases, Mn... 2+ / Mn 3+ 3 d The presence of unfilled single electrons in the layer may create new magnetic centers inside the crystal, resulting in Mn-O-Mn superexchange interactions.

[0096] To investigate the effect of introducing magnetic Mn on the magnetic properties of high-entropy rare-earth ferrite ceramics, their magnetic property parameters were analyzed. High-entropy rare-earth ferrite ceramics with different MnCO3 contents and Bi... 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z Magnetic properties of wt.% MnCO3 ( M s , M r and H c As shown in Table 5. High-entropy rare-earth ferrite ceramics z = 0, 0.25, 0.5, 0.75 and 1 M s The values ​​are 0.5, 1.7, 1.7, 1.5, and 1.3 A·m, respectively. 2 ·kg -1 With the introduction of MnCO3, the magnetic manganese ions in the synthesized high-entropy rare-earth ferrite ceramics introduce new magnetic centers, reducing their magnetic domains and thus leading to a decrease in magnetic domain size under the same magnetic field. M s Increase. Meanwhile, high-entropy rare-earth ferrite ceramics... z = 0, 0.25, 0.5, 0.75 and 1 M r The values ​​were 0.08, 0.13, 0.12, 0.13, and 0.13 A·m, respectively. 2 ·kg -1 The introduction of MnCO3 enables high-entropy rare-earth ferrite ceramics...z = 0.25, 0.5, 0.75 and 1 increase the magnetic properties. Compared with high-entropy rare earth ferrite ceramics without the addition of sintering aid MnCO3. z Compared to 0, the introduction of low-valence magnetic Mn ions makes high-entropy rare-earth ferrite ceramics ( z Defect dipoles were generated within the ranges of 0.25, 0.5, 0.75, and 1). These defect dipoles in high-entropy rare-earth ferrite ceramics hinder domain flipping, thereby increasing the ceramic's... M r In addition, high-entropy rare-earth ferrite ceramics z = 0, 0.25, 0.5, 0.75 and 1 H c The values ​​were 3.71, 3.29, 3.05, 3.15, and 2.96 kA·m, respectively. -1 With the introduction of MnCO3, high-entropy rare-earth ferrite ceramics ( z The magnetic domains with values ​​of 0.25, 0.5, 0.75, and 1 decrease, causing their... H c All are lower than those of high-entropy rare-earth ferrite ceramics without the introduction of MnCO3. z = 0.

[0097] Table 5 Magnetic property parameters of high-entropy rare earth ferrite ceramic samples 1-5

[0098]

[0099] A comprehensive analysis of impedance characteristics, dielectric properties, ferroelectric properties, and magnetic properties reveals that MnCO3 introduces high-entropy rare-earth ferrite ceramics. z = 0.75 has a small grain size (1.03 μm) and a low room temperature dielectric loss (1.4 × 10⁻⁶ at 100 kHz). -3 ), and a relatively small leakage current density (20 kV·cm). -1 At that time, it was 9.90 × 10 -8 A·cm -2 ) and larger M r (0.13 A·m) 2 ·kg -1 It has excellent characteristics such as ).

[0100] The specific embodiments described above should not be construed as limiting the scope of protection of this invention. Any alternative modifications or variations made to the embodiments of this invention by those skilled in the art will fall within the scope of protection of this invention. All aspects not detailed in this invention are well-known to those skilled in the art.

Claims

1. A high-entropy rare-earth ferrite ceramic material, characterized in that, The high-entropy rare-earth ferrite ceramic material has a single crystal structure and its general chemical formula is Bi. 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z wt.%MnCO3, where z The value range is 0.25-1; the introduction of low-valence manganese ions causes the formation of [something] within the grains of high-entropy rare-earth ferrite ceramics. Defect dipoles; MnCO3 is used as a sintering aid; The preparation method of the high entropy rare earth ferrite ceramic material includes the following steps: (1) preparing high entropy rare earth ferrite powder According to Bi 0.2 La 0.2 Y 0.2 Dy 0.2 Tb 0.2 Fe 0.975 Ti 0.025 O3- z The stoichiometric ratio of Bi₂O₃, La₂O₃, Y₂O₃, Dy₂O₃, Tb₄O₇, Fe₂O₃, TiO₂, and MnCO₃ powders was weighed separately. The powders, anhydrous ethanol, and zirconia balls were then mixed in a nylon jar and ball-milled for 24 hours at a ball-to-liquid ratio of 10:1:

5. The powders were then dried and subsequently milled in a sealed alumina crucible at 5℃·min⁻¹. -1 The temperature is increased from room temperature to 1100℃, and then held at 1100℃ for 3 hours to obtain the product. (2) Preparation of high-entropy rare earth ferrite ceramic materials The obtained high-entropy rare-earth ferrite powder was ball-milled a second time under the same ball-milling conditions for 10 hours; the ball-milled powder was dried again; granulated and pressed into green blanks; then held at 500℃ for 4 hours in a high-temperature furnace, and then heated at 5℃·min. -1 The heating rate is increased to 1200℃, and the temperature is maintained for 2 hours to obtain the product.

2. The high-entropy rare-earth ferrite ceramic material according to claim 1, characterized in that, z The value is 0.

75.

3. The high-entropy rare-earth ferrite ceramic material according to claim 1, characterized in that, In step (2), the specific steps for granulation and pressing into a green blank are as follows: the powder and polyvinyl alcohol with a mass concentration of 5 wt.% are mixed at a mass ratio of 1:0.05 and granulated, passed through a 90-mesh sieve, and then a pressure of 382 MPa is applied to the powder for a holding time of 2 minutes to press into a green blank with a diameter of 10 mm.

4. The high-entropy rare-earth ferrite ceramic material according to claim 1, characterized in that, In steps (1) and (2), the powder drying conditions are: drying in an oven at 80°C for 24 hours.

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