Electronic structure, electrical and dielectric properties of BaSnO₃ below 300 K

Abstract

The electronic structure, electrical and dielectric properties of barium stannate, a semiconducting perovskite oxide prepared by solid state ceramic route were studied by employing X-ray photoelectron spectroscopy (XPS), Mössbauer and impedance spectroscopic techniques in the temperature range 77–300 K. X-ray diffraction (XRD) pattern of BaSnO₃ confirms the cubic structure. Scanning electron microscopy (SEM) images show high porosity in the sample and the average grain size was found to be about 1.85 μm which corroborates with the particle size obtained through XRD line broadening analysis. Mössbauer spectra, at 298 and 78 K reveal that tin exists mainly in tetravalent, Sn⁴⁺ state. XPS study also shows the same results but it indicates the existence of a trace amount of Sn²⁺. Electrical conductivity and dielectric constant of this system have been measured in the temperature range 298 to 148 K and in the frequency range 10-2 to 106 Hz. Frequency and temperature dependent electrical conductivity/dielectric properties have been used to separate the contributions of grains and grain boundaries to the total observed conductivity and dielectric constant. Orientational polarisation and space charge polarisation contributes to the observed dielectric properties of the system.