Thermally stimulated small polaron promoted conduction mechanism in Fe-doped La0.7Sm0.3CrO3

Abstract

In this study, nano-sized La0.7Sm0.3Cr1-xFexO3 (0 ≤ x ≤ 0.3) samples were prepared using the sol–gel process. No extra peaks were present in the X-ray diffraction patterns, which indicated their single phase nature. Orthorhombic crystal configurations with the Pnma space group were confirmed for all of the samples. The crystallite size, unit cell volume, bond lengths, and bond angles were found to increase as the Fe content increased. Scanning electron microscopy and energy dispersive X-ray (EDX) spectroscopy were used to analyze the surface morphology and chemical composition, which demonstrated the formation of uniform, homogeneous, and high purity samples with agglomerated particles. Transmission electron microscopy showed that the samples had rough surfaces where agglomerated particle were evident in the images and the particle size increased with the Fe content. Dielectric measurements were conducted for La0.7Sm0.3Cr1-xFexO3 (0 ≤ x ≤ 0.3) to determine the responses of the real and imaginary parts of the dielectric permittivity as well as the tangent loss with respect to temperature. The results demonstrated that the dielectric behavior was frequency dependent and thermally stimulated. Cole–Cole plots for all the samples indicated the existence of a non-Debye type relaxation phenomenon. The ac conductivity was found to obey the Jonscher power law according to plots of the frequency versus ac conductivity. The temperature dependence of the exponent “s” showed that the correlated barrier hopping and non-overlapping small polaron tunneling models of conduction were followed.