Structure and properties of reduced LaCoO3

Changes occurring in the chemical state, and the crystallographic and electronic structure of LaCoO3 in a reducing atmosphere were determined. These determinations involved the use of thermogravimetric and calorimetric techniques, x-ray diffraction, and magnetic property measurements. It was shown that the reduction process proceeded through the formation of a series of oxygen-deficient structures. In the 0–3.25 wt% weight-loss region, corresponding to the general formula LaCo1−xO3−y, where 0.0<x≤0.08 and 0.0<y≤0.5, the structure is monoclinic. In this structure, the cobalt ion exists as either high-spin Co2+ or low-spin CoIII. At a weight loss of approximately 3.25 wt% the structure reverted to the original rhombohedral symmetry with a loss of lanthanum and cobalt. The chemical formula was again LaCoO3. Samples reduced to greater than 3.25 wt% possessed a different crystal structure than was previously observed.