Processing and electrical properties of doped-LaGaO3 by gelcasting

Sr- and Mg-doped LaGaO3 (La0.8Sr0.2Ga0.8Mg0.2O2.8) powders have been successfully synthesized from carbonate and oxides based on the principle of gelcasting. X-ray diffraction patterns indicate the perovskite structure is formed without any second phases after sintering the powders at 1400°C for 6 h. Compacts of the gelcast powders heated at 1000°C were sintered to densities greater than 97% of theoretical at 1450°C for 6–18 h; then the relative density decreased to 95.5% sintered for 36 h. From the XRD patterns and SEM photographs, some impure phases were observed for long-sintering samples. The total electrical conductivity was greatly depended on the sintering time, whereas peak values were obtained when the pellet was sintered at 1450°C for 24 h. A transitional temperature T∗ (at about 675°C) in the plot of ln(σT) vs 1000/T exhibits a somewhat higher activation energy at lower temperatures, due to the trapping of vacancies by the dopant cations for all sintering conditions.