A deficiency in the A sub-lattice of the orthorhombic perovskite-type La1−xNi0.5Ti0.5O3−δ, with a maximum at x = 0.07 to 0.08, was compensated by the formation of trivalent Ni and O vacancies. Atomistic computer simulations showed that these defects were trapped near to A-site cation vacancies, resulting in the stabilization of Ni3+ cations and limited electronic or O-ionic transport. The average thermal expansion coefficient of La0.95Ni0.5Ti0.5O3−δ ceramics, calculated from dilatometric data in air, increased from 8.6 x 10-6/K at 300 to 800K to 1.20 x 10-5/K at 1300 to 1500K. Data on the Seebeck coefficient and total conductivity, predominantly p-type electronic, suggested a broadband mechanism of hole transport. The activation energies for the hole and ionic conductivities were 89 and 430kJ/mol, respectively. The O ion transference numbers, as determined by Faradaic efficiency measurements in air, varied from 9.5 x 10−5 to 8.1 x 10−4 at 1173 to 1248K, and increased with temperature. Reducing the O partial pressure led to a moderate decrease in the conductivity, followed by phase decomposition in the PO2 range from 9 x 10−11 to 8 x 10-9atm at 1073 to 1223K. The low-PO2 stability limit of La0.95Ni0.5Ti0.5O3−δ perovskite was found to be between that of La3Ni2O7 and the Ni/NiO boundary.

Defect Formation and Transport in La0.95Ni0.5Ti0.5O3−δ . S.O.Yakovlev, V.V.Kharton, E.N.Naumovich, J.Zekonyte, V.Zaporojtchenko, A.V.Kovalevsky, A.A.Yaremchenko, J.R.Frade: Solid State Sciences, 2006, 8[11], 1302-11