Effect Of Ion Doping On Performance Of Colossal Permittivity And Low Dielectric Loss For SrTiO₃ Ceramics

With the rapid development of social science and technology,the demand for colossal permittivity ceramic materials in electronic industry is becoming higher.Many colossal permittivity ceramic materials have been developed through the efforts of some researchers.However,the simultaneous realization of colossal permittivity(>104),low dielectric loss(<0.05),and the requirements for good frequency and temperature stability in a single ceramic material is challenging.And with the idea of sustainable development,the research on the multi-function of colossal permittivity ceramic materials has gradually become a hot spot SrTiO3 ceramics with perovskite structure(ABO3)are excellent dielectric materials with low dielectric loss,wide band gap,high insulation resistivity,and good structural and dielectric stability.The literature indicates that SrTiO3 ceramics can be used as giant dielectric materials or high energy storage materials by modification,and have the potential to develop into various properties.In addition,the properties of SrTiO3 ceramics are strongly correlated with modified ions and methods,and the origin of their mega dielectrics is controversial.Therefore,this paper takes SrTiO3-based ceramics as the research object,through designing experiments,doping modification,defect control and other ways to improve the dielectric properties of SrTiO3 ceramics and analyze its influence mechanism.The study of the correlation between different defect types,micro structure and dielectric property optimization provides experimental support for the study of the versatility and theoretical analysis of SrTiO3-based ceramics,which is of great significance to the development of electronic components.The SrTi1-xTaxO3-2wt%SiO2(0.000?x?0.014)(STTO)ceramic samples were prepared by the conventional solid-phase method and nitrogen atmosphere sintering.The effect of doping amount on its structure,microstructure and dielectric properties was discussed.The results show that appropriate amount of Ta ions(B-site donor doped ions)can be dissolved in ST structure and obviously promote the growth of grain size.When x=0.010,the permittivity(22790@1 kHz,22063@1 MHz)of the ceramic sample,low dielectric loss(0.01@1 kHz,0.025@1 MHz),good frequency stability(20-106 Hz)and temperature stability(25-350?)were obtained.Based on the sintering of different atmospheres as well as the XPS analysis,the mechanism of realizing the large dielectric constant and low dielectric loss under wide band is discussed in depth.It is found that proper amount of TiTi'-Vo-TiTi' defect dipoles and Vo-3TiTi'-TaTi' defect clusters are the main reason for the excellent dielectric properties,which will hinder the long-range transition of electrons and lead to the electrons moving within the local area.High-performance LaxSr1-xTiO3(0.000?x?0.018)(LST)ceramic samples were prepared by solid-phase and nitrogen atmosphere sintering.The phase structure and microscopic morphology of the ceramic samples were analyzed by XRD and SEM,respectively.It is found that there are no second phase generation and a small amount of La ions(A-site donor doped ions)doping promoted the growth of ceramic grains.The La0.010Sr0.099TiO3 ceramic samples exhibit good dielectric properties.The permittivity is 26897 and the dielectric loss is 0.005 at 1 kHz,and it is 26072 and the dielectric loss is 0.031 at 1 MHz,also with good frequency(20-2×106 Hz)and temperature(25-300?)stability.In addition,its insulation resistivity is up to 3.10×109 ?·cm at DC 100 V.The mechanism of A-site donor doped SrTiO3 ceramics to obtain excellent dielectric properties is discussed based on the treatment of different atmospheres,XPS and impedance analysis.Eventually,TiTi'-VO-TiTi' defect dipoles and VO-3TiTi'-LaSr defect dipole clusters are considered to be the main cause of the huge dielectric constant and ultralow dielectric loss.The high DC resistivity of ceramic samples is mainly caused by the grain boundary with high insulation.High-performance Sr1-xDyxTiO3(0.000?x?0.018)(SDT)ceramic samples were prepared by solid-phase method and sintering in different atmospheres.The defect type and concentration in the ceramic were further adjusted by Dy ion(amphoteric ion)doping modification and different atmosphere treatments.The Sr0.99Dy0.008TiO3 ceramic embryo body can be prepared by different treatments for excellent colossal permittivity ceramic materials and high energy storage density ceramic material,respectively.On the one hand,the permittivity of 23134(1 kHz)and 22069(1 MHz)of x=0.008 ceramic samples,dielectric loss of 0.0098(1 kHz)and 0.028(1 MHZ),insulation resistance of 1.52×109 ?·cm(DC 100 V)and excellent temperature stability(25-400?)were obtained by reduction and reoxidation.The excellent dielectric properties are mainly determined by the defect dipoles associated with oxygen vacancies and the highly insulating grain boundary layer.On the other hand,for x=0.008 ceramic samples sintered in oxygen,a high energy storage density of 4.00 J/cm3,a high energy storage efficiency of 89.49%and a transmittance of 65%were achieved.Meanwhile,the x=0.008 ceramic samples exhibit excellent thermal stability(20-120?,120 kV/cm)and frequency stability(20 Hz-1 kHz,400 kV/cm)under different electric fields.The increase of energy storage density is mainly due to the easy attraction of oxygen vacancies to form defect dipoles,resulting in the decrease of oxygen vacancy content and oxygen vacancy mobility,as well as the increase of relative density and the decrease of grain size.In addition,the current density of the x=0.008 ceramic sample at 120 kV/cm electric field is 420.1 A/cm2 and the discharge rate of the power density of 19.2 MW/cm-3 and 20 ns,which indicates that it is a lead-free high-power capacitor with strong application potential.The conversion of large dielectric constant behavior and high energy storage density by adjusting the defect concentration.The idea of"one formula,two sintering processes,multiple properties" is proposed,which is helpful to the sustainable development of colossal permittivity ceramic materials.According to comparative studies of dielectric properties of B-site donor ions(Ta5+),A-site donor ions(La3+),and amphoteric ions(Dy3+)doped SrTiO3 ceramic samples,which can be found that the main reason for the large dielectric and low loss of SrTiO3 ceramic samples is due to a moderate amount of defect dipoles related to oxygen vacancies,in which the main defect dipoles are TiTi'-VO-TiTi' and other defects are secondary factors.Whereas the retention of high insulation resistivity of SrTiO3 ceramic samples with colossal permittivity mainly depends on the insulation of grain boundaries.While the generation of oxygen vacancies is mainly affected by ion doping,oxygen partial pressure,sintering temperature,and the insulation of grain boundaries is mainly affected by oxygen vacancy migration and the grain size.