Synthesis, structural, electrical and thermal properties of Ti-doped Bi2Sn2O7 pyrochlore

Polycrystalline ceramic samples of Bi2Sn2-xTixO7 (x = 0.0, 0.2, 0.4, 0.6, 0.8) have been synthesized by conventional solid-state reaction method. The effect of homovalent cation (titanium) substitution on the Sn-site on the structural, morphological, electrical and thermal properties of the pure Bi2Sn2O7 ceramics have been studied by X-ray diffraction (XRD) followed by scanning electron microscopic techniques, dc conductivity and modulated differential scanning calorimetry. The XRD analysis carried out by performing the Rietveld refinement using the space group Fd3m indicates that the increase of titanium contents do not lead to any secondary phase. The grain size distributions of all the samples were investigated by SEM. It was found that the grain sizes are strongly influenced by the addition of titanium to the system. The frequency and temperature dependent dielectric studies have been carried out. The dc conductivity measurement was carried out for all the compounds and the activation energies were calculated using the relation sigma = sigma 0 exp(-E-a/kT). The modulated differential scanning calorimetry has been used to investigate the effect of substitution on the specific heat, heat flow and other thermal parameters of the compounds. The results are discussed in detail.