Influence of Grinding Particle Size on Structure and Electrical Properties of La0.67Sr0.33MnO3-δ Compound

In this article, the influences of grinding particle size on the structure and electrical transport properties of La0.67Sr0.33MnO3- compound have been investigated. The compound was prepared by gel combustion process followed by grinding for different duration time. It was found that the lattice parameters, unit-cell volume, strain, oxygen deficiency, and temperature dependence of resistivity -T increase with decreasing particle size. The -T growth can be explained by the increasing contribution of the grain boundary effect, strain, and even oxygen deficiency. The electrical transport mechanism over the whole temperature range of 100-400K was thoroughly described by applying the phase separation model around the phase transition temperature T-P. This model was subsequently employed to calculate the -T at high temperature up to 1000K. The result showed there was a second phase transition at a typical temperature T*>T-P, which could be attributed to the relaxation of small polarons to large ones. This relaxation occurred at lower temperatures when the particle size decreased. It might be due to the decrease in conduction bandwidth caused by the defects arisen during the grinding.