Structural and Transport Studies on Mixed Valent Rare Earth Manganite Ceramics

Abstract

ABSTRACTLa0.5Pr0.2Ca0.3–xBaxMnO3 (LPCBMO) (x = 0.05, 0.10, 0.15, 0.20, 0.25, 0.30) ceramic manganites have been successfully synthesized by conventional solid state reaction method. Structural studies have been carried out by performing X-ray diffraction measurements and Rietveld refinements. Obtained value of crystallite size varies from 76 nm in lower doped sample (x=0.05) to 13 nm in the sample doped with x=0.30. Variation in crystallite size with x has been discussed in the context of size mismatch at A-site cationic lattice and structural disorder. In addition, all the samples exhibit metal to insulator transition at TP which gets increased with increase in Ba-content (x). Effect of crystallite size and other structural parameters on the transport properties of LPCBMO samples has been discussed in detail in the light of competition between the structural disorder and tolerance factor and shown that the tolerance factor can effectively modify the transport behaviour in manganites. Below 50 K, all the R-T plots of LPCBMO system show resistivity minimum behaviour which gets modified by Ba-content. This behaviour has been discussed in detail on the basis of electronelectron interaction having the form: ρ = [1/(σ0+BT1/2)]+ρnTn.