Room temperature mechanosynthesis of the La 1-xSr xMnO 3±δ (0≤x≤1) system and microstructural study

Abstract

Monophase nanocrystalline powders belonging to the La 1-xSr xMnO 3±δ system (0≤x≤1) with a perovskite structure have been obtained by mechanochemistry synthesis using a planetary ball milling equipment from La 2O 3, SrO, and Mn 2O 3 mixtures. The solid state reaction was complete after one hour of milling treatment. For all the compositional range, the diffraction domain was very small and the structure appeared as a pseudo cubic perovskite. After annealing at 1100 °C under static air, the symmetry evolution due to the La substitution by Sr was analyzed by X-ray and electron diffraction. Samples with x=0, 0.25, 0.5, and 0.75 were assigned to R-3c space group (1 6 7) in the rhombohedral system and perovskite structure. However, the symmetry of the last term of the system (x=1), SrMnO 3±δ sample, changed to P6 3/mmc space group (1 9 4) in the hexagonal system. The terms with x=0.8, 0.85, and 0.9 presented mainly rhombohedral symmetry