Li sub(0.33)La sub(0.55)TiO sub(3) solid electrolytes with a pure phase were synthesized by the citric acid-supported sol-gel method and then sintered under controlled redox atmospheres of air, argon and hydrogen. Although of similar morphology and relative density, Li sub(0.33)La sub(0.55)TiO sub(3) samples sintered under reduction atmosphere such as argon and hydrogen exhibited a tetragonal structure with lattice distortion. The distortion and volume expansion of the crystal lattice was identified as originating from the transformation of the Ti valence state, and this was more clearly observed under sintering of the hydrogen atmosphere. The qualitative analysis of the Ti valence state using an X-ray Photoelectron Spectroscopy experiment was performed and indicated that the largest amount of Ti super(3+)(18.6%) was formed in the Li sub(0.33)La sub(0.55)TiO sub(3) samples sintered under hydrogen atmosphere. The relationship between the lattice distortion and the lithium ion conductivity of the Li sub(0.33)La sub(0.55)TiO sub(3) sintered under different atmospheres is also discussed on the basis of the lattice distortion.