The dielectric properties and diffuse phase transition of non- stoichiometric barium strontium titanate based capacitor ceramics

摘要

The microstructure, dielectric properties and ferroelectric–paraelectric phase transition of non-stoichiometric (Ba~(0.75)Sr~(0.25))Ti~(1−δ)O~(3−2δ)(δ = 0 –0.03) ceramics prepared by conventional solid state method were studied with the non-stoichiometric level using XRD, SEM and LCR measuring system. It is found that the non-stoichiometric (Ba~(0.75)Sr~(0.25))Ti~(1−δ)O~(3−2δ)ceramics are single phase solid solutions with typical cubic perovskite structure. The average grain size of (Ba~(0.75)Sr~(0.25))Ti~(1−δ)O~(3−2δ)ceramics decreases with the increasing non-stoichiometric level when δ is less than 0.02. The phase transformation temperature decreases significantly with the increase of non-stoichiometric level due to the appearance of charged vacancies and the oxygen vacancies $${V}_{O}^{..}$$ V O . . also contribute to the fine performance in dielectric loss of (Ba~(0.75)Sr~(0.25))Ti~(1−δ)O~(3−2δ)ceramics. The diffuseness of ferroelectric–paraelectric phase transition resulting from the composition fluctuation is exacerbated significantly as the non-stoichiometric level increases. A normal ferroelectric behavior with relatively weak diffuse phase transition is observed for stoichiometric (Ba~(0.75)Sr~(0.25))TiO~(3)ceramic while a relaxor behavior is obtained in the non-stoichiometric (Ba~(0.75)Sr~(0.25))Ti~(1−δ)O~(3−2δ)ceramics with high non-stoichiometric level.