Structural transformation and ionic transport properties were investigated on wet-chemically synthesized La1-xMnO3 (x = 0 to 0.18) compositions. Powders annealed in O/air at 1000–1080K exhibited cubic symmetry and transform to rhombohedral on annealing (1173–1573K) in air/O. Annealing above 1773K in air or in Ar/He at 1473K stabilized distorted rhombohedral or orthorhombic symmetry. Structural transformations were confirmed from X-ray diffraction and transmission electron microscopic studies. The total conductivity of sintered disks, measured by four-probe technique, ranges from 5S/cm at 298K to 105S/cm at 1273K. The ionic conductivity measured by blocking electrode technique ranges from 1.0 x 10-6S/cm at 700K to 2.0 x 10-3S/cm at 1273K. The ionic transference number of these compositions ranges from 3.0 x 10-5 to 5.0 x 10-5 at 1273K. The activation energy deduced from experimental data for ionic conduction and ionic migration was 1.03 to 1.10 and 0.80 to 1.00eV, respectively. The activation energy of formation, association and migration of vacancies ranges from 1.07 to 1.44eV.

Studies on the Structural and Ionic Transport Properties at Elevated Temperatures of La1-xMnO3±δ Synthesized by a Wet Chemical Method. H.Jena, K.V.G.Kutty, T.R.N.Kutty: Journal of Alloys and Compounds, 2003, 350[1-2], 102-12