CN114685157A

CN114685157A - Zn + Ta co-doped TiO2Mesozoelectric dielectric ceramic, preparation method and application thereof

Info

Publication number: CN114685157A
Application number: CN202210482575.6A
Authority: CN
Inventors: 徐东; 蒋志; 李永涛; 李家茂; 王梦凡; 左如忠; 李宇佳; 赵丹; 孙志鹏
Original assignee: Anhui Polytechnic University; Anhui University of Technology AHUT; China Innovation Academy of Intelligent Equipment Co Ltd CIAIE
Current assignee: Anhui Polytechnic University; Anhui University of Technology AHUT; China Innovation Academy of Intelligent Equipment Co Ltd CIAIE
Priority date: 2022-05-05
Filing date: 2022-05-05
Publication date: 2022-07-01

Abstract

The invention relates to the technical field of dielectric ceramic preparation, in particular to Zn and Ta co-doped TiO₂The giant dielectric ceramic is prepared through flash burning process to form the composition Zn_1/ ₃Ta_2/3)_0.05Ti_0.95O₂(ZTTO) TiO₂The giant dielectric ceramic is prepared by co-doping Zn and Ta with TiO by XRD, SEM and XPS₂The microstructure, the electrical property, the rapid densification theory and the giant dielectric constant source of the giant dielectric ceramic are comprehensively researched, the rapid densification of a sample is realized by joule heat and high heating rate under different electric field strengths, the microstructure of the material is refined, the dielectric property of the material is optimized,when the electric field is 200V/cm, a giant dielectric constant (ε' to 1.32X 10)⁴) Low dielectric loss (tan delta-0.27), reduced furnace temperature by 25%, shortened sintering time by more than 90%, giant dielectric constant probably derived from electron pinning defect dipole polarization and Maxwell-Wagner relaxation type interface polarization, which is TiO₂The preparation of the giant dielectric ceramic opens up a way.

Description

Zn + Ta co-doped TiO2Mesozoelectric dielectric ceramic, preparation method and application thereof

Technical Field

The invention relates to the technical field of dielectric ceramic preparation, in particular to a Zn and Ta co-doped TiO₂Giant dielectric ceramic, preparation method and application thereof.

Background

Flash firing has become a typical representative of environmentally friendly sintering techniques in the ceramic material field. Compared with other sintering technologies, the flash sintering fully exerts the advantage that the current passes through the ceramic sample to realize rapid densification under the action of an external electric field, can obviously reduce the sintering temperature and shorten the sintering time. The prior art explains the flash combustion phenomenon caused by the internal resistance of materials through the joule heat theory, and then the flash combustion mechanism becomes a research hotspot, and various theoretical models of flash combustion are provided, such as the local thermal effect of a grain boundary, the Franker defect effect, the electrochemical reaction and the like. Simultaneously, flash-burnThe application field of the technology is gradually widened, and various system materials such as semiconductors (ZnO), insulators (Al)₂O₃) Ion conductor (3YSZ) and metalloid conductive ceramic (Co)₂MnO₄) And the like, have been successfully prepared under low-temperature short-time conditions. Therefore, flash firing is a low-temperature, high-efficiency, energy-saving and environment-friendly sintering technology and has a wide development prospect.

Although flash technology has been rapidly developed and widely used, there are still some problems to be studied intensively. Firstly, due to the influence of factors such as material components, sample shapes, flash combustion devices and the like, the internal rules among the heating temperature, the electric field intensity and the limiting current of flash combustion are not clear, and deep research is needed; secondly, the microstructure and performance of the material need to be regulated and controlled by an enhanced flash firing process. Finally, the mechanism of flash burning is still controversial, and there is no unified theory that can fully explain the complete phenomenon of flash burning. It is noted that the electric field strength is a very important parameter in the flash process, which determines the critical temperature of flash and the current density in the sample, thereby affecting the microstructure and properties of the sample. However, in the prior art, the applied electric field strength is studied as only one factor affecting the flash firing initiation temperature, but there are few reports on the influence on the internal structure and performance of the material. Therefore, the method has important significance for analyzing the relation between the electric field intensity and other flash burning parameters, researching the change of the microstructure and the performance of the material and perfecting the flash burning theory.

Compared with the high sintering temperature (1300-₂The base ceramic has the advantage of low-temperature and high-efficiency preparation. At the same time, the existing report shows that the TiO is codoped₂The ceramic has a high dielectric constant (> 10)⁴) And low dielectric loss (< 0.05), and has significant frequency and temperature stability, exhibiting excellent giant dielectric properties. In order to obtain excellent dielectric property, a plurality of donor impurities (Nb, Ta and Sb) and acceptor impurities (In and La) co-doped TiO are synthesized by adopting the traditional solid-phase reaction sintering₂Giant dielectric ceramic. However, the results of these studies are difficult to repeat (In, Nb) codoping TiO₂Ceramic materialSuch excellent giant dielectric properties. Co-doped TiO synthesis by flash firing technology₂The giant dielectric ceramic can refine the grain size under the low-temperature short-time sintering condition, obtain a uniform tissue structure and improve the density of the material.

At present, pure TiO is prepared by flash firing technology₂Some achievements have been made in the aspect, but only the law and mechanism of flash firing parameters are concerned, but the co-doped TiO is not prepared by flash firing₂The ceramic is reported. In fact, the doping composition has a large impact on the flash-firing process and the giant dielectric properties.

In view of the above-mentioned drawbacks, the inventors of the present invention have finally obtained the present invention through a long period of research and practice.

Disclosure of Invention

The invention aims to solve the problem that the final electrical property of a sintered sample is poor due to abnormal growth of crystal grains caused by long sintering time at high temperature, and provides a Zn + Ta co-doped TiO₂Giant dielectric ceramic, preparation method and application thereof.

In order to realize the purpose, the invention discloses a Zn + Ta co-doped TiO₂The preparation method of the giant dielectric ceramic comprises the following steps:

s1: mixing oxide powders in ZrO₂Ball milling in ethanol of the medium, and drying to obtain pre-calcined powder;

s2: calcining the pre-calcined powder obtained in the step S1 to obtain a calcined powder;

s3: carrying out secondary ball milling on the calcined powder obtained in the step S2 under the same ball milling condition with the pre-calcined powder, and drying;

s4: adding a binder to the dried powder obtained in step S3, and uniaxially pressing the mixed powder into a disk;

s5: calcining the disc obtained in step S4 to remove the binder;

s6: placing the sample obtained in the step S5 in a tube furnace, wherein a direct current power supply is arranged at two ends of the sample to provide an electric field, and the sample is heated at a heating rate of 10 ℃/min;

s7: when the temperature of the sample reaches 1000-1100 ℃, keeping the temperature for 20min, then applying an electric field of 100-500V/cm, initially presetting the current to be 1.0A, when applying the electric field, increasing the current by 0.1A every 4min until the current reaches the limit current of 1.5A, then closing the direct current power supply, and cooling the sample to the room temperature.

In the step S1, the ball milling time is 24h, the drying temperature is 80 ℃, and the drying time is 24 h.

In the step S2, the calcining temperature is 1100 ℃, and the calcining time is 4 h.

In the step S3, the drying temperature is 80 ℃, and the drying time is 24 h.

The binder in step S4 was 5 wt.% polyvinyl alcohol, and the pressing pressure was 310 MPa.

In the step S4, the disc has a thickness of 2mm and a diameter of 7 mm.

In the step S5, the calcining temperature is 650 ℃, the heating rate is 2 ℃/min, and the calcining time is 2 h.

The invention also discloses Zn and Ta co-doped TiO prepared by the preparation method₂Giant dielectric ceramic and Zn + Ta co-doped TiO₂The giant dielectric ceramic is applied to the miniaturization of a capacitor and the high energy storage density.

In view of Zn²⁺And Nb⁵⁺Co-doped TiO₂Has higher dielectric constant and low dielectric loss, and Ta with the same ionic radius⁵⁺Ion ratio Nb⁵⁺The ions have a more electron-shell structure.

Compared with the prior art, the invention has the beneficial effects that: the invention adopts a flash firing method under different electric fields to successfully prepare (Zn)²⁺，Ta⁵⁺) Co-doped TiO₂The giant dielectric ceramic utilizes XRD, SEM and XPS to comprehensively research the microstructure, electrical properties, rapid densification theory and giant dielectric constant source of the ZTTO ceramic. Under different electric field strengths, the rapid densification of the sample is realized by joule heat and high heating rate, the microstructure of the material is refined, and the dielectric property of the material is optimized. When the electric field is 200V/cm, a giant dielectric constant (. epsilon.' -1.32X 10) is obtained⁴) Low dielectric loss (tan delta-0.27) and high non-linear coefficient (5.8), reduced furnace temperature by 25%, and high sintering efficiencyThe time is shortened by more than 90 percent. The giant dielectric constant may be due to electrically pinned defective dipole polarization and Maxwell-Wagner relaxation type interface polarization, which is TiO₂The preparation of the giant dielectric ceramic opens up a way.

Drawings

FIG. 1 is a plot of flash parameters versus time for ZTTO samples at different electric fields: (a) the electric field strength; (b) current density; (c) power density; (d) estimating a temperature;

FIG. 2 is an XRD pattern of flash-fired ZTTO samples at different electric fields;

FIG. 3 is an SEM micrograph and elemental distribution plot of ZTTO ceramic at different electric fields (a) 100V/cm; (b) 200V/cm; (c) 300V/cm; (d) 400V/cm; (e) 500V/cm; (f) elemental mapping of 200V/cm samples;

FIG. 4 is a graph of the average grain size and relative density of ZTTO ceramics under different electric fields;

FIG. 5 is a schematic view at 10²～10⁶The frequency dependence of the dielectric constant and dielectric loss of the ZTTO sample at Hz and room temperature;

FIG. 6 is a graph showing the variation of dielectric constant and dielectric loss with applied electric field at a test frequency of 1 kHz;

FIG. 7 is the temperature dependence of dielectric constant and dielectric loss for the ZTTO sample: (a)1kHz and (b) 200V/cm;

FIG. 8 is a representation of the valence states of elements in a flash-burned sample with an electric field intensity of 200V/cm by CasaXPS software.

Detailed Description

The above and further features and advantages of the present invention are described in more detail below with reference to the accompanying drawings.

First, green body preparation

TiO₂(rutile, 99.99%), Ta₂O₅(99.99%) and ZnO (99.9%) were used as raw materials, and dried in an oven at 80 ℃ for 24 hours. According to (Zn)_1/3Ta_2/3)_0.05Ti_0.95O₂Respectively weighing raw material powder according to a stoichiometric ratio, putting the raw material powder into a polyethylene ball milling tank, and ball milling the raw material powder, ethanol and ZrO for 24 hours at a speed of 200r/min₂The mass ratio of the balls is 1:8: 20. The slurry after ball milling is at 80 DEG CDrying in an oven, and calcining at 1100 deg.C for 4 hr to obtain Zn²⁺And Ta⁵⁺Solid solution into rutile TiO₂A crystal lattice. After calcination, the powder was ball milled and dried twice according to the same procedure.

Then, the mixture was sieved through a 150 mesh sieve, and 5 wt% polyvinyl alcohol (PVA) was added thereto to carry out granulation. The molding was carried out under a uniaxial pressure of 300MPa to obtain a cylindrical test specimen having a thickness of about 2.0mm and a diameter of 7.0 mm. The binder was removed from the green sample by calcining at a ramp rate of 2 ℃/min to 650 ℃ for 2 hours to give a green relative density of about 57% to 60%.

Second, sintering process

The ZTTO ceramics were sintered using a tube furnace (OTF-1200XS, science crystal group, china) with the assistance of different electric fields. First, the green sample was connected to an external power source through a platinum wire electrode, and a nickel plate was used to improve the contact performance of the sample with the platinum electrode. Secondly, the tube furnace is heated to 1000-. Finally, an electric field generated by a direct current power supply (DLM300-10E, Sorensen, USA) was applied to the sample at an electric field intensity ranging from 100V/cm to 500V/cm. Samples were labeled FS1, FS2, FS3, FS4, and FS5, respectively. For each sample, the limiting current was increased stepwise from 1.0A to 1.5A, each step wide ranging from 0.1A, and held for 4 min. Finally, the oven and power were turned off and the sample was cooled to room temperature in a tube furnace.

Third, characterize

The relative density of the ZTTO flash-fired samples was determined using a standard archimedes method. The temperature of the sample was estimated by a Black Body Radiation (BBR) model, which assumes no heat loss during thermal radiation, and the temperature difference between the tube furnace and the sample depends only on thermal diffusion. The temperature of the sample can be expressed by the following equation:

in the formula T₀Is the furnace temperature, and the unit is K; w is the electric energy dissipated by the sample and the unit is W; a is the sample surface area m²(ii) a σ is the Stefan-Boltzmann constant, valueIs 5.67X 10^-8W·m^-2·K^-4. X-ray diffraction (XRD, brueck, germany D8 Advance) was used to analyze the phase structure of the samples. After grinding and polishing, the flash-burned sample is subjected to thermal corrosion treatment at 1200 ℃ for 30 min. Facilitates better observation of the microstructure of the sample, and the microstructure and elemental distribution were characterized by field emission scanning electron microscopy (FE-SEM, NANO SEM430, FEI inc., USA) and energy dispersive X-ray analysis (EDX). The particle size of the sample was calculated using the nano-measurement software. After silver electrodes were coated on both sides of the sample, a precision impedance analyzer (Dekochman E4990A, USA) and a high temperature dielectric temperature Spectroscopy test System (TZDM-RTA-10C, China) were used at 10 deg.C²～10⁶And testing the dielectric property of the sample in a frequency range of Hz and a temperature range of 30-500 ℃. X-ray photoelectron spectroscopy (XPS, Kratos AXIS Ultra DLD, Japan) was used to analyze the chemical valence states of the elements in a sample.

Fourthly, the result

FIG. 1 shows the electric field strength, current density, power density and estimated temperature as a function of sintering time at applied electric field strengths of 100V/cm, 200V/cm, 300V/cm, 400V/cm and 500V/cm, respectively. The dashed line area is partially enlarged in the form of an internal illustration to more clearly show the change of each physical quantity at the moment of flash. In the figure, the time before the zero point is the incubation period, and the flash-over occurs instantaneously in the vicinity of the zero point of the abscissa and then tends to stabilize, corresponding to the three stages of flash-over, respectively.

As can be seen from FIG. 1, the flash firing was well performed while limiting the current passing through the sample at different electric field strengths. In the early sintering stage, the incubation period of flash firing is gradually shortened along with the increase of the electric field intensity, and the incubation period is reduced to zero when the electric field is increased to 300V/cm. As the electric field strength continued to increase, the ZTTO samples flash immediately without the incubation period.

In the incubation period, under the driving of the electric field force, electron gas is formed in the sample and is diffused, so that the sample is suddenly converted from an insulator to a conductor, and the electric conductivity is gradually enhanced. When the current reaches a preset value, the flash combustion is changed from a constant voltage control mode to a cross current control mode, the electric field intensity is sharply reduced, the power density reaches the maximum value, and meanwhile, the BBR model estimates that the temperature reaches the highest peak value (the corresponding time axis value in the figure is zero). At this stage, the electric field strength has a great influence on the parameters of flash firing. With the increase of the electric field intensity, the electrical parameters of the flash combustion electric field intensity, the power density, the estimated temperature and the like are increased and then reduced, and when the electric field intensity is 300V/cm, the value is the highest. According to a BBR model, the estimated temperature of a sample can reach 1568 ℃ at the moment of flash burning, and the temperature value is 500 ℃ higher than the furnace temperature, which has important significance for the rapid densification of the ZTTO giant dielectric ceramic. Of course, the stabilization phase of flash combustion is also necessary to further increase the density of the sample due to the high melting point of the rutile structure. In summary, flash firing technology shows significant advantages in low temperature high efficiency sintering due to the joule heating effect and extremely high heating rate. Compared with the traditional solid reaction sintering, the furnace temperature of flash firing is obviously reduced (about 25 percent), and the sintering time is obviously shortened (up to 90 percent).

Fig. 2 shows the X-ray diffraction patterns of ZTTO flash-burned samples at different electric field strengths. All ZTTO samples consisted of pure tetragonal rutile structure (PDF #21-1276) and no second phase, according to the crystallographic indices of the diffraction peaks, indicating that the Zn and Ta co-doped ions were completely substituted into the lattice. It is clear that there is no precipitation of solute atoms during the flash firing process, and the electric field strength has little effect on the crystalline phase of the ZTTO sample, despite the sharp rise in sample temperature due to joule heat.

FIG. 3 shows SEM microstructure and element bitmap of ZTTO hot corrosion sample, all flash-fired samples obtain compact polygonal grain structure, the grain size is uniform, the arrangement is ordered, no obvious air hole exists, and the density of the sample can be improved. According to the elemental bitmap analysis of the flash-burned sample at an electric field strength of 300V/cm, Ti, O, Zn and Ta elements were almost uniformly distributed (FIG. 3 (f)). With increasing electric field, there is always a first growth of single grains, followed by a decrease of smaller grains, with larger grains. As shown in fig. 4, the higher the electric field, the larger the average grain size. Depending on the power consumption and estimated temperature of the flash-burned sample, nucleation and growth of grains should be a more complex non-equilibrium dynamic process.

The grain size depends on the number of nucleation sites, and during the flash inoculation phase, the current through the sample is relatively small and the joule heating is low, where the mass transfer by diffusion provides the driving force mainly by the heat of the furnace temperature. The longer the incubation period, the greater the number of nucleation and the smaller the grain size. The grain growth should occur in the stable stage of flash firing, with the power consumption increasing with the increase of the electric field and the grain size increasing with the increase of the energy. Due to the short flash time, it is inevitable that the grain growth is asynchronous and uneven. However, the relative density of the flash-burned samples at different electric fields was relatively high, with values in the range of 93% to 96% (fig. (4)).

In combination with the SEM microstructure (fig. 3) and the average grain size (fig. 4), the grain sizes of the flash-fired samples were slightly different, but the microstructures had almost no defects such as pores, and thus the relative densities of the samples were both high. Compared with the traditional sintering, the flash firing technology can refine the grain size, reduce air holes and improve the density. This demonstrates that flash firing techniques can produce high density ZTTO giant dielectric ceramics at lower heating temperatures and short sintering times.

Is obviously at 10²-10⁶Each sample exhibited excellent giant dielectric properties and low dielectric loss over the Hz test frequency range. High dielectric constant (. epsilon.' > 10)³) Low dielectric loss and a maximum dielectric constant of 3.85X 10⁴. For all samples, the dielectric properties were not greatly affected by the frequency of detection, and the dielectric constant decreased with increasing frequency. At detection frequencies above 10⁵After Hz, there is a point of inflection on the dielectric constant curve, and relaxation of the polarization results in a rapid increase in dielectric loss as the polarization of the particles in the material lags behind the applied electric field at higher frequencies. The dielectric constant of the sample showed a tendency to increase with increasing electric field strength, but the dielectric loss decreased first and then increased (fig. 6). The overall electrical properties of the samples were best when the electric field strength was 200V/cm.

The dielectric constant and dielectric loss versus temperature are shown in fig. 7. The dielectric constant and the dielectric loss of the flash-burned sample can be kept stable well within the testing temperature range of 30-500 ℃. The dielectric properties of the ZTTO sample are not greatly influenced by the testing temperature, and the dielectric constant and the dielectric loss only slightly increase along with the increase of the temperature. All flash sintered samples had a small valley at a dielectric constant of about 300 c at different electric fields when the test frequency was 1 kHz. Meanwhile, the dielectric loss shows a rising peak in the temperature range of 200-300 ℃ (FIG. 7 (a)).

This can be explained by a change in the polarization mechanism. In the low temperature region, polarization of the local defect dipole cluster plays a major role, and dielectric loss is also low since long-range migration of electrons is suppressed. As the temperature increases, the thermal motion of the particles increases, the defective dipoles become unstable, leading to dissolution and rotation, dielectric losses increase, and peaks due to energy consumption. After the particle flipping process is over, the dielectric loss is reduced. FIG. 7(b) shows the temperature dependence of the dielectric properties of the sample with an electric field strength of 200V/cm. The giant dielectric constant remains stable over the test temperature range and decreases with increasing frequency. However, as the test frequency increases, the dielectric loss decreases and then increases, the peak value of the dielectric loss becomes smaller, and the dielectric loss tends to be flat and stable. This is due to the reduced polaron migration distance at higher frequencies, resulting in reduced dielectric losses. Within the whole detection temperature range, the dielectric constant of the sample is increased and then reduced along with the increase of the electric field, and when the electric field strength is close to 200V/cm, the sample shows good electrical properties of high dielectric constant and low dielectric loss.

From the above discussion, the ZTTO samples prepared by rapid sintering exhibited excellent giant dielectric properties. However, the source of the huge dielectric constant of the ZTTO flash-burned samples still needs further investigation. To clearly explain the mechanism of the giant dielectric and the transition of the valence state of the element, a flash sintered sample having an electric field strength of 200V/cm was characterized by XPS measurement, and the result is shown in FIG. 8. The chemical valence of each element in the sample was analyzed using Casaxps software.

As shown in FIG. 8(a), Ta4f doublets were obtained at binding energies of 24.7eV and 26.7eV, with the energy level difference for spin-orbit splitting of 2.0eV, which is almost the same as reported in the literature. The spectrum of Ta4f shows that the chemical valence of Ta element is only +5 without any reduction. In addition, XP of zinc elementThe results of S are shown in FIG. 8 (b). At binding energies of 1021.3eV and 1044.0eV, there were two energy peaks corresponding to the Zn 2p1/2 and Zn 2p3/2 electron orbitals, and a spin orbit split of 22.7eV was formed, indicating Zn²⁺Is present.

The XPS plot of Ti2p is shown in FIG. 8(c), with two energy peaks observed at 457.6eV and 464.5eV binding energies, corresponding to Ti2p3/2 and Ti2p1/2 electron orbitals, respectively. Furthermore, at binding energies of 460.8eV and 466.9eV, there are two additional energy peaks corresponding to Ti³⁺2p3/2 and Ti ³⁺2p 3/2. Thus, in the process of solid-dissolving the doped Ta ion into the rutile lattice, Ti⁴⁺Is reduced to Ti³⁺Wherein Ta⁵⁺Is greater than Ti⁴⁺One more electron and the additional electrons respond to the charge conversion of the Ti ion as shown in the equation. (2) And (3):

2TiO₂+Ta₂O₅→Ti_Ti+2Ta^· _Ti+7O_O+O₂………………(2)

………………Ti⁴⁺+_e ^-→Ti³⁺………………(3)

reduction of Ti³⁺The ratio of ions can be determined by the Ti in the XPS pattern³⁺And Ti⁴⁺The area under the peak curve is estimated. Reduced Ti in flash-fired samples compared to common sintered samples in other references³⁺The proportion of ions is higher, up to 12%. Notably, Ta as the donor ion⁵⁺By substitution of Ti in the lattice⁴⁺And generates additional electrons, which are very important for generating a giant dielectric constant.

From the fitting results of the XPS spectrum in fig. 8(d), three energy peaks of O1s electrons were observed at binding energies of 530.0eV, 531.5eV, and 533.3eV, corresponding to an oxygen vacancy, an oxygen lattice, and an oxygen hydroxyl group, respectively. The oxygen lattice is derived from Ti-O bonds in rutile lattice, and H is absorbed on the surface₂O may generate an oxyhydroxy group. It is emphasized that the oxygen vacancy is in Zn²⁺Formed during the process of ion solid solution. Due to Zn²⁺Ion into lattice to substitute Ti⁴⁺Two electrons are absent in the ion, so the charge balance should beIs broken. To maintain charge balance of the system, an oxygen vacancy is created which carries two positive charges.

Thus, TiO₂The lattice system remains charge balanced because electrons are bound by oxygen vacancies. According to the literature, all of these Ti³⁺、Ta⁵⁺、Zn²⁺The ions can combine with each other to form a defective dipole cluster in the shape of a triangle or a rhombus, called an electron-pinned defective dipole (EPDD). The interaction between the electrons and the oxygen vacancies limits the long-distance diffusion of the electrons, thereby avoiding overlarge dielectric loss and improving the dielectric property.

In fact, defective bi-crystal films are unstable and can diffuse when they are subjected to external environments (e.g., electric field and temperature). If the defective dipole diffuses to the grain boundary, twin boundary or sample surface and is blocked and concentrated, the positive and negative charges on both sides of the interface will inevitably produce a polarization effect similar to that of a capacitor, called Inner Boundary Layer Capacitor (IBLC) effect, Surface Barrier Layer Capacitance (SBLC) effect, which also results in (Zn, Ta) co-doping of TiO₂The large dielectric effect of ceramics. Thus, co-doping of TiO₂The large dielectric constant of the ceramic may result from the combined action of EPDD and SBLC.

The (Zn, Ta) codoped TiO is quickly prepared by quick sintering at a lower sintering temperature (1050 ℃) and a shorter sintering time₂Giant dielectric ceramic. The flash firing process parameters, the microstructure and the giant dielectric property under different electric fields are systematically researched, and the results are shown in table 1, wherein the maximum peak value of the sample temperature is 1568 ℃ which is 49% higher than the hearth temperature. All ZTTO ceramic samples had fine grains (1.5-3.0 μm) and high relative density (93-96%) at an electric field strength of 100-500V/cm. When the electric field intensity is 200V/cm, the (Zn, Ta) codope TiO₂The ceramic has a high dielectric constant (epsilon)>10⁴) Lower dielectric loss (tan. delta.)<0.27). The excellent dielectric property of the dielectric material is derived from the combined action of the defect dipole polarization and Maxwell-Wagner relaxation type interface polarization. Therefore, the electric field auxiliary flash-firing technology is used for preparing co-doped TiO with low temperature and high efficiency₂A promising technology for giant dielectric ceramics。

TABLE 1 estimated temperature, relative density and average grain size of ZTTO samples at different electric field strengths

Sample(s)	Electric field strength (E, V/cm)	Predicted temperature (T)_s,℃)	Relative compactness (RD,%)	Average grain size (AG, μm)
					FS1	100	1337	95.9	1.50
FS2	200	1457	94.8	2.52
					FS3	300	1568	93.4	2.6
FS4	400	1460	95.4	2.97
					FS5	500	1398	95.8	3.02

The foregoing is merely a preferred embodiment of the invention, which is intended to be illustrative and not limiting. It will be understood by those skilled in the art that various changes, modifications and equivalents may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. Zn + Ta co-doped TiO₂The preparation method of the giant dielectric ceramic is characterized by comprising the following steps of:

s1: mixing oxide powders in ZrO₂Ball milling in ethanol as medium, and drying to obtain pre-calcined powder;

s5: calcining the disc obtained in step S4 to remove the binder;

2. The Zn + Ta co-doped TiO of claim 1₂The preparation method of the giant dielectric ceramic is characterized in that in the step S1, the ball milling time is 24 hours, the drying temperature is 80 ℃, and the drying time is 24 hours.

3. The Zn + Ta co-doped TiO of claim 1₂The preparation method of the Mesoxazole dielectric ceramic is characterized in that the calcining temperature in the step S2 is 1100 ℃, and the calcining time is 4 h.

4. The Zn + Ta co-doped TiO of claim 1₂The preparation method of the gigantic dielectric ceramic is characterized in that the drying temperature in the step S3 is 80 ℃, and the drying time is 24 hours.

5. The Zn + Ta co-doped TiO of claim 1₂The method for preparing the gigantic dielectric ceramic is characterized in that the binder in the step S4 is 5 wt.% polyvinyl alcohol, and the pressing pressure is 310 MPa.

6. The Zn + Ta co-doped TiO of claim 1₂The preparation method of the gigantic dielectric ceramic is characterized in that the disc in the step S4 is 2mm thick and 7mm in diameter.

7. The Zn + Ta co-doped TiO of claim 1₂The preparation method of the Mesozoelectric ceramic is characterized in that in the step S5, the calcination temperature is 650 ℃, the heating rate is 2 ℃/min, and the calcination time is 2 h.

8. Zn and Ta co-doped TiO prepared by the preparation method of any one of claims 1-7₂A giant dielectric ceramic.

9. The Zn + Ta co-doped TiO of claim 8₂The giant dielectric ceramic is applied to the miniaturization of a capacitor and the high energy storage density.