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

The microstructure, dielectric properties and ferroelectric–paraelectric phase transition of non-stoichiometric (Ba0.75Sr0.25)Ti1−δO3−2δ (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 (Ba0.75Sr0.25)Ti1−δO3−2δ ceramics are single phase solid solutions with typical cubic perovskite structure. The average grain size of (Ba0.75Sr0.25)Ti1−δO3−2δ 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 VO..\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${V}_{O}^{..}$$\end{document} also contribute to the fine performance in dielectric loss of (Ba0.75Sr0.25)Ti1−δO3−2δ 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 (Ba0.75Sr0.25)TiO3 ceramic while a relaxor behavior is obtained in the non-stoichiometric (Ba0.75Sr0.25)Ti1−δO3−2δ ceramics with high non-stoichiometric level.