Crystal structure of the mixed oxides La0.7Sr0.3Co1-zMnzO3 +/- y (0 <= z <= 1)

The crystal structure and nonstoichiometry of several compositions in the s ystem La0.7Sr0.3Co1-zMnzO3+/-y (0 less than or equal to z less than or equa l to 1) have been investigated by powder X-ray diffraction (PXD), powder ne utron diffraction (PND), thermogravimetry (TG), including full reduction in hydrogen, and chromatometric titration. The system formed solid solutions over the entire compositional range (0 less than or equal to z less than or equal to 1) crystallizing in the rhombohedral structure (space group R (3) over bar c). The lattice constant increased with increasing Mn content z. The cation stoichiometry (occupancy) was calculated from refinement of PXD data, and oxygen positions and occupancies were calculated from PND data. T hese results confer with the TG and chemical analysis of oxygen content in that the Go-rich compositions exhibit oxygen deficiency (oxygen vacancies), while the Mn-rich compositions exhibit oxygen excess in the form of metal vacancies. (C) 1999 Academic Press.