Understanding the charge carriers dynamics in the La0.55Ca0.45Mn0.8Nb0.2O3 perovskite: scaling of electrical conductivity spectra

Abstract

The present work proposes the best realistic theoretical approaches to examine the experimental conductivity data taken for La_0.55Ca_0.45Mn_0.8Nb_0.2O₃. For this purpose, we comprehensively discussed the structural, microstructural, and electrical properties of the La_0.55Ca_0.45Mn_0.8Nb_0.2O₃ perovskite. Both X-ray diffraction and Rietveld analysis show the orthorhombic structure of the ceramic. Scanning electron microscope showed the existence of well-defined irregularly shaped particles with a grain-size distribution of 0.843 μm. The X-ray photoemission spectroscopy reveals the existence of Mn³⁺ and Mn⁴⁺ states. The complicated behavior of the lanthanum states is demonstrated using the La3d line. AC-conductivity responses are related to the correlated barrier hopping contribution. At high temperatures, the compound's semiconductor behavior is attributed to the activation of the polaronic transport. At low temperatures, the occurrence of semiconductor behavior in the La_0.55Ca_0.45Mn_0.8Nb_0.2O₃ ceramic is attributed to the effect of the variable range hopping conduction process. The application of the time-temperature-superposition-principle and the Summerfield scaling formalisms leads to the superposition of the isotherms. Using the Ghosh formalism, the superposition of the spectra confirms that the number density and the hopping distance are temperature-dependent. The superposition of the spectra suggested the temperature-independent relaxation and polaronic processes. In addition, it confirms that the relaxation mechanism is independent of the microstructure response.