Structural evolution and electrical characteristics of Sn-doped Ba0.8Sr0.2TiO3 ceramics

(Ba0.8Sr0.2)(Ti1−xSnx)O3 (BSTS) perovskite structure ferroelectric ceramics with different compositions (x=0; 0.03; 0.05; 0.07; 0.10 and 0.20) were synthesized by a conventional high temperature solid-state reaction. X-ray diffraction (XRD) study allowed the identification of a pure solid solution with average tetragonal symmetry for x≤0.05 and cubic for x≥0.07 at room temperature (RT). Especially, for the composition x=0.05, a coexistence of tetragonal (P4mm) with dominating fraction close to 88.84% and cubic (Pm3¯m) (11.16%) phases was determined in powder by Rietveld refinement. The local structures of the BSTS samples were studied by Raman spectroscopy, which shows a small fraction of rhombohedral phases for Sn-rich compositions (x≥0.05) at RT. Dielectric analysis show a diffuse phase transition for x≤0.10, the dielectric permittivity become three time better than that of pure (Ba0.8Sr0.2) TiO3 and when x=0.20, the material change from normal ferroelectric to a typical relaxor ferroelectric. Macroscopic Polarization-field loops measured at RT illustrate a decreasing of the polarization at the maximum field of 3 kV/mm from 14.31 to 1.35 µC/cm2 confirming XRD and dielectric studies.