Microstructure, electrical and magnetic properties of polycrystalline La_(0.85)K_(0.15)MnO_3 manganites prepared by different synthesis routes

摘要

Influence of different synthesis techniques (solid state reaction, sol-gel and co-precipitation) on the structure, microstructure, magnetic and electrical properties of polycrystalline La_(0.85)K_(0.15)MnO_3 (LKMO) sintered at 900 ℃ is investigated. All the as-synthesized compounds were confirmed as single phase and hexagonal structure at room temperature. The nano-crystallite size and average grain size were increased from the sample synthesized through solid state, sol-gel and co-precipitation techniques. The electrical and magneto-transport properties of polycrystalline LKMO was relied on the synthesis method. Significant decreases in metal-insulator transition temperature (T_p) with the increment of resistivity were observed for co-precipitation synthesized sample when comparing with solid state and sol-gel synthesized samples. Magnetization was decreased while ferro-para-magnetic transition temperature (T_c) was shifted toward lower temperature from solid state synthesized sample to co-precipitation synthesized sample. Furthermore, co-precipitation synthesized sample achieved the highest negative magnetoresistance at room temperature.