Effect of Sintering Temperature on Microstructure, Electrical and Magnetic Properties of La0.85K0.15MnO3 Prepared by Sol-Gel Method

The influence of sintering temperature on the microstructure and transport properties of polycrystalline La0.85K0.15MnO3(LKMO) samples via sol-gel method is studied. Powder X-ray diffraction (XRD) shows that all the LKMO samples have single phase with hexagonal structure. The data obtained from XRD were analyzed by using the Rietveld refinement technique. The increase of the sintering temperature considerably promotes grain growth and improves grains connectivity. The increase of the average grain size throughout the sintering temperatures has affected the transport properties of LKMO samples. The magnetization is improved with the reduction of coercivity. The Curie temperature (T (c)) was obtained from AC susceptibility data and the results were inversely proportional to the sintering temperature of the samples because the ferromagnetic properties are reduced by the increase of unit cell volume and Mn-O bond length. The electrical resistance is decreased and the metal-insulator transition temperature (T (p)) is shifted towards the high temperature side, due to the improvement of grain connectivity. A phase diagram based on the measurement of T (p) and T (c) is constructed. All the LKMO samples are in the ferromagnetic-insulator phase at room temperature.