Influence of sintering temperature on the structure and electrical transport properties of La_0.7Ba_0.1Sr_0.2Mn_0.85Cu_0.15O₃ manganites

A systematic study of the La_0.7Ba_0.1Sr_0.2Mn_0.85Cu_0.15O₃ manganites have been conducted, mainly to understand the influence of sintering temperature on structure, microstructure, and electrical transport properties in the materials. Polycrystalline sample of La_0.7Ba_0.1Sr_0.2Mn_0.85Cu_0.15O₃ were prepared using sol-gel method and sintered at 1100 °C and 1200 °C. X-ray diffraction result shows that sintering temperature does not affect the crystal structure of the materials which remain rhombohedral with R-3c space group. a more detailed examination shows that sintering temperature change the unit cell volume, <Mn-O-Mn> bond length, and <Mn-O> bond angle of the samples. The electrical resistivity decreases followed by the decrease in the grain size with the increase in sintering temperature. Analysis using theoretical model shows that both samples can be well explained using percolation model. Fitting result suggests that the transport properties of the materials at low temperature were governed by the scattering and interaction between electron, phonon, and magnon. At high temperature, the electrical transport of the samples was governed by the hopping of polarons.