A-site-deficient (La(0.3)Sr(0.7))(1-x)TiO(3-delta) materials were synthesized by conventional solid-state reaction. The A-site deficiency limit in (La(0.3)Sr(0.7))(1-x)TiO(3-delta) was below 10 mol% in 5%H(2)/Ar at 1500 degrees C. A-site deficiency level promoted the sintering process of (La(0.3)Sr(0.7))(1-x)TiO(3-delta). The ionic conductivity increased but the electronic conductivity decreased with increasing A-site deficiency level. The ionic conductivity of (La(0.3)Sr(0.7))(0.93)TiO(3-delta) sample was as high as 0.2-1.6 x 10(-2) S/cm in 500-950 degrees C and 1.0 x 10(-2) S/cm at 800 degrees C, over twice of La(0.3)Sr(0.2)TiO(3-delta). Its electrical conductivity was in the range of 83-299 S/cm in 50-950 degrees C and 145 S/cm at 800 degrees C. A-site deficiency improved the thermal stability of (La(0.3)Sr(0.7))(1-x)TiO(3-delta) and ensured the material with a stable electrical performance in different atmospheres. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.