Combined effect of oxygen annealing and La-doping in broadening the phase transition of Ba(Zr0.2Ti0.8)O3 ceramics

Abstract

The present study focuses on a novel approach to broaden the phase transition in Ba(Zr0.2Ti0.8)O3 by the combined effect of oxygen annealing and La-doping. The (Ba1-xLax)(Ti0.8Zr0.2)O3, Pb-free ceramics, with nominal compositions (x = 0.00, 0.01, 0.02 and 0.03) are synthesized in oxygen annealing atmosphere at 1673 K for 11 h using solid-state reaction method. While the X-ray diffraction confirmed the single phase formation, the secondary electron images revealed inhibited grain growth at a low concentration of La-doping but intermediate 2-dimensional grain growth at higher La-doping. The Raman peak appearing at 836 cm−1 indicates La-substitution at Ba-site and vacancies at Ti-sites. The temperature dependent dielectric permittivity exhibits a broad diffuse phase transition at Tm = 230 K with a full width at half maxima (FWHM) of 289 K for 3 atomic % La-doped sample. The combined effect of oxygen annealing and La-doping results in an extremely broad diffuse phase transition. Such an extremely broad phase transition close to room temperature due to La-doping and oxygen annealing is useful for capacitor applications.