Fabrication processing condition for dense sintered La0.6AE0.4MnO3 perovskites synthesized by the coprecipitation method (AE=Ca and Sr)

The formation mechanisms of single perovskite phases for 40 mol% alkaline earth metal (AE)-doped lanthanum manganites (La0.6AE0.4MnO3, 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 Ca2Mn3O8, La2O3, La2CO5 and MnO2 for the La0.6Ca0.4MnO3, and SrMnO3, La2O3, La2CO5 and MnO2 for the La0.6Sr0.4MnO3. 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 La0.6Ca0.4MnO3 and at 1100°C for 5 h for La0.6Sr0.4MnO3. The relative densities of the specimens reached ≥95% at 1500°C for 5 h for the La0.6Ca4MnO3 and 1580°C for 5 h for the La0.6Sr4MnO3.