Structural and electrical transport properties of (La0.7-xYx)Ca0.3MnO3 manganites

The effect of yttrium (Y) substitution at La-site on structural, microstructural and electrical transport properties of (La0.7-xYx)Ca-0.3 MnO3 (x = 0.00, 0.05, 0.10, 0.15 and 0.20) were investigated. Samples were prepared by conventional solid state reaction method and structural properties of the samples were obtained using the Rietveld refinement of X-ray diffraction data. X-ray diffraction patterns show orthorhombic distorted perovskite structures. Resistivity measurement results of the LaYCaMnO3 compounds show that metal-insulator transition temperature, T-MI, shifts to lower temperature while the resistivity increases by increasing Y3+ substitution. In the metallic region (T < T-MI), experimental resistivity data were fitted to electron-electron and electron-magnon scattering mechanism while in the insulator region (T > T-MI), resistivity data were fitted to model of small polaron hopping conduction mechanism and the activation energy, E-a, increased as Y substitutions increases.