The effect of Ti addition on the electrical conductivity of Sr- and Mg-doped LaAlO3

Ti was added into acceptor-doped LaAlO3 to enhance the mixed electronic and ionic conductivity at low Po2. Electrical conductivities of [La0.9Sr0.1Al0.9Mg0.1O3]1−x[La2 / 3TiO3]x (LAT) for x = 0–0.30 were measured using 4-probe d.c. method at temperatures between 1000 and 1300 °C and as a function of oxygen partial pressure (Po2 = 1∼10− 15 atm) at 1200 °C. Electrical conductivities in air decreased with increasing Ti contents (x) for 0 < x < 0.15, and increased for 0.15 < x < 0.30 after showing minimum values at x = 0.15. The activation energy in air showed percolative change near x∼0.13. LAT samples for 0 ≤ x ≤ 0.10 were oxygen ion conductors in low Po2 and mixed (p-type and ionic) conductors in high Po2. However, for x ≥ 0.15, n-type conductivity was dominant in low Po2. For x ≥ 0.20, the p-type conductivity in high Po2 disappeared and the n-type conductivity was dominant in all Po2 range and increased with increasing Ti concentration.