Preparation And Modification Of SrTiO₃-based Ceramics For Energy Storage Application

In order to meet the development trend of portability and miniaturization for energy storage electronic components,higher requirements have been put forward for dielectric ceramics used in energy storage electronic components,and research of the energy storage ceramics with both high dielectric constant and high insulation properties at the same time can be a major project in today’s dielectric field.SrTiO₃ceramics were selected as the study material in this thesis.By doping rare earth elements Er,the Er_xSr_1-3x/2TiO₃（Er-ST）ceramics were prepared by conventional solid state method.The physical models were established to discuss the intrinsic physical mechanism of SrTiO₃ ceramics with high dielectric constant by Er doping.Composition of the best comprehensive performance Er_0.02Sr_0.97TiO₃ was chosen as research matrix.HfO₂ additives and ZnO-B₂O₃-SiO₂ glass additives were put into it.Improvement of the dielectric constant and optimization of the insulation properties for grain boundary were obtained so as to increase the effective energy storage density by controlling the amount of additives.Er_xSr_1-3x/2TiO₃ ceramics with dielectric constant of 2810⁷200 and dielectric loss of not more than 3.5%were prepared by using the traditional solid state method and adjusting the doping amount x of rare earth Er in the range of 0.01⁰.03 at the same time.When the doping amount x=0.02,the dielectric constant of the samples reached the maximum（⁷200）,which is about 20 times higher than that of pure SrTiO₃ ceramics.The sintering performance analysis showed that the addition of rare earth element Er increased the optimum sintering temperature of the system by 20℃and inhibited the growth of ceramic grains.The crystal structure analysis showed that samples of Er_xSr_1-3x/2TiO₃ had a single cubic perovskite structure at room temperature,and the lattice parameters of the ceramics were increased due to the substitution of Er³⁺ions for Sr²⁺ions.Two dielectric relaxation peaks Peak 1 and Peak 2 appeared in the temperature dependence of dielectric loss spectra for the doped ceramics.The relaxation peak Peak 1 was generated by the motion of the defect associate(V_Sr′-V_O^··),and the generation of the relaxation peak Peak 2 was related to the motion of oxygen vacancies.Oxygen vacancy ionization polarization mechanism accounted for high dielectric constant in rare-earth doped SrTiO₃ ceramics.Composition of the best comprehensive performance Er0.02Sr0.97TiO3 was chosen as research matrix.（1-y wt%）Er_0.02Sr_0.97TiO₃—y wt%HfO₂ ceramic system with dielectric constant of 415¹071 and dielectric loss of not more than 2%was prepared by adjusting the additive amount y of HfO2 in the range of 2.0⁸.0 wt%.With the increase of HfO₂ addition,the breakdown strength of the sample varied from 8.40kV/mm to 21.55 kV/mm,and the hysteresis loop became slender.In addition,the energy storage efficiency increased from 71.22%to 95.56%,and the effective energy storage density increased first and then decreased.When the addition amount y=6.0wt%,the comprehensive performance of the sample was optimized,whose dielectric constantε_r=470,dielectric loss tanδ=1.0%,and the breakdown strength E_b=20.20kV/mm.The effective energy storage density of the sample reached the maximum value of 0.878 J/cm³,which was 2.4 times that of pure SrTiO₃ ceramics.（1-z wt%）Er_0.02Sr_0.97TiO₃—z wt%（ZnO-B₂O₃-SiO₂）ceramic system with dielectric constant of 300⁶96 and dielectric loss of not more than 2.5%was prepared by adjusting the additive amount z of ZnO-B2O3-SiO2 glass in the range of 2.0⁸.0wt%.With the increase of the glass content,the effective energy storage density increased first and then decreased.When the glass content z=4.0 wt%,the comprehensive performance of the sample was optimized,whose dielectric constantε_r=551,dielectric loss tanδ=1.78%,and the breakdown strength E_b=19.44 kV/mm.The effective energy storage density of the sample reached the maximum value of 0.869 J/cm³.