Citrate Method Perparation And Dielectric Properties Of Ba_1-xSr_xZr_0.2Ti_0.8O₃ Ceramics

based dielectrics appear as promising candidate materials of ceramic capacitors for energy storage usage because of their high dielectric constants, low dielectric losses and good insulation strength. This dissertation is devoted to chemical method preparation, structure and dielectric properties of Ba1-xSrxZr0.2Ti0.8O3 based composite dielectric ceramics. The powders of Ba1-xSrxZr0.2Ti0.8O3 (x=0.05-0.20) and MgO-CaO-Al2O3-SiO2 (abbreviated as MCAS) glass were prepared by citrate method synthesis. The composite ceramics with the nominal composition of Ba1-xSrxZr0.2Ti0.8O3 (x=0.05-0.20)+x wt% MCAS (x=3-8) were fabricated from the powders and the structure and dielectric properties of the composite ceramics were investigated.Ba1-xSrxZro.2Tio.803(x=0.05-0.20) powders were synthesized from a citrate route. The contributing factors to the phase purity and morphology of the powders have been examined. The powders with a pure perovskite phase and uniform particles of about 60 nm were produced at a calcination temperature of 650℃. Moreover, superfine powder of the MCAS glass with the average particle size of about 80 nm was derived from a citrate precursor at 600℃.The sinterability, structure and dielectric properties of the composite ceramics made from superfine Ba0.95Sr0.05Zr0.2Ti0.8O3 and MCAS powders were examined with respect to the content of the MCAS component. The MCAS component was found to be efficient in lowering the sintering temperatures of the composite ceramics. The composite specimens sintered at 1160℃showed fined-grained microstructures (～180 nm) and relative densities above 95%. The addition of the MCAS component led to a reduced bias-field-dependence of dielectric properties and an obvious dielectric relaxor behavior for the composite specimens.The sinterability, structure and dielectric properties of the composite ceramics with the nominal composition of Ba1-xSrxZr0.2Ti0.8O3(x=0.05-0.20)+x wt% MCAS were examined with respect to the content of the Sr component. The results indicated that the dielectric constant decreased and the loss increased with increasing Sr content. The composite specimen of Ba0.95Sr0.05Zr0.2Ti0.8O3+5wt% MCAS showed the optimum overall properties. Under the bias field of 140 kV/cm, the composite specimen displayed an energy storage density of 0.42 J/cm3 and an energy storage efficiency of 83.4%.