Novel wet chemical synthesis and ionic transport properties of LaGaO3 and selected doped compositions at elevated temperatures

LaGaO3, La0.9Ga0.8Mn0.1O3−δ and La0.9Sr0.05Ga0.8Li0.01O3−δ synthesized by the decomposition of metal nitrate–tartarate complex were found to yield the cubic phase on heat treatment at 1023–1273 K; above which they transformed to distorted cubic phase (orthorhombic). LaGaO3 was also synthesized by the co-precipitation of metal hydroxides and form single phase above 1623 K. The nano-crystalline powders obtained from tartarate route were examined by TEM, electron diffraction, XRD, XPS, infra-red, TG/DTA and EGA–MS techniques. Electrical conductivity measurement was carried out by dc and ac methods on the sintered pellets at 298–1273 K in air. LaGaO3 showed predominantly oxide ion conductivity above 650 K. The measured activation energy of conduction is ∼1.35 eV. La0.9Sr0.05Ga0.8Li0.01O3−δ exhibited electrical conductivity above 550 K with diminished activation energy of ∼0.97 eV. Loss of lithium from the lattice on sintering the powders above 1173 K was observed. La0.9Ga0.8Mn0.1O3−δ showed mixed ionic and electronic conduction in the temperature range 298–1273 K. The valence state of Mn in this compound was investigated by XPS.