Crystal Structure Analysis using Rietveld Refinement and Investigation of Electrical Properties of NaNbO3 Substituted CaTiO3 Ceramics

Abstract

Polycrystalline samples (1-x)CaTiO₃-xNaNbO₃ (x = 0, 0.10, 0.20, 0.30 and 0.40) were synthesized using solid state reaction method. Powder X-ray diffraction at room temperature showed that all of the samples' crystal structures were orthorhombic with Pbnm space group. Low χ² values were obtained and there was good agreement between the computed and observed XRD patterns according to the Rietveld refinement. Impedance spectroscopy of the samples was investigated over a broad frequency and temperature range. Nyquist plots of the samples depicted a thermally activated non-Debye type relaxation mechanism. A decrease in dispersive nature of dielectric constant (ɛ¢) and tangent loss (tan d) at low frequencies is noticed in the NaNbO₃ substituted samples rendering them a better stability. The samples became more resistive with NaNbO₃ substitution in CaTiO₃ lattice. Correlation between charge carriers and lattice has been established using modulus formalism. Imaginary impedance (Z¢¢) and imaginary modulus (M¢¢) have been employed to comprehend the conduction process in all the samples.