Fabrication processing condition for dense sintered La 0.6AE 0.4MnO 3 perovskites synthesized by the coprecipitation method (AE=Ca and Sr)

Abstract

The formation mechanisms of single perovskite phases for 40 mol% alkaline earth metal (AE)-doped lanthanum manganites (La 0.6AE 0.4MnO 3, AE=Ca and Sr), synthesized by the coprecipitation method, have been investigated. After calcining at 600°C for 1 h, X-ray diffraction patterns of both the sample powders showed them to almost be in an amorphous state, and small peaks, related to the perovskite phase, were observed. The second phases were small amounts of Ca 2Mn 3O 8, La 2O 3, La 2CO 5 and MnO 2 for the La 0.6Ca 0.4MnO 3, and SrMnO 3, La 2O 3, La 2CO 5 and MnO 2 for the La 0.6Sr 0.4MnO 3. With increasing temperature, the second phases gradually disappeared, and both powders changed into an almost single perovskite phase after calcining at 1100°C for 1 h. Using these perovskite powders, the fabricating conditions for the dense sintered specimens have been clarified. The powders showed the best sintering characteristics after calcining at 1100°C for 1 h for La 0.6Ca 0.4MnO 3 and at 1100°C for 5 h for La 0.6Sr 0.4MnO 3. The relative densities of the specimens reached ≥95% at 1500°C for 5 h for the La 0.6Ca 4MnO 3 and 1580°C for 5 h for the La 0.6Sr 4MnO 3.