The effect of Sn for Ti substitution on the average and local crystal structure of BaTi1−xSnxO3 (0 ≤x≤ 0.20)

The effect of Sn for Ti substitution on the crystal structure of a perovskite, barium titanate stannate (BTS), BaTi1−xSnxO3 for x = 0, 0.025, 0.05, 0.07, 0.10, 0.12, 0.15 and 0.20, was investigated. The powders were prepared by the conventional solid-state reaction technique. The structural investigations of the BTS powders were done at room temperature by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected-area electron diffraction (SAED) and Raman spectroscopy analyses. Rietveld refinement of XRD data indicates that gradual replacement of titanium by tin in BaTiO3 provokes a phase transition from tetragonal for 0 ≤x≤ 0.07 to cubic for x = 0.12, 0.15 and 0.20. The coexistence of tetragonal (P4mm) and cubic (Pminline imagem) crystal phases was established in powder with nominal composition BaTi0.9Sn0.1O3. The crystal phases determined by Rietveld refinement were confirmed by HRTEM and SAED analyses. The crystal structures of the BTS powders at short-range scale were studied by Raman spectroscopy, which shows tetragonal (P4mm) and a small fraction of orthorhombic (Pmm2) crystal phases for all the examined BTS powders, implying a lower local ordering when compared to the average symmetry