Two members of the solid solution Li3xLa(2/3)-xTiO3, with x = 0.06 and 0.167, were studied by means of X-ray diffraction, nuclear magnetic resonance and impedance spectroscopy. In the orthorhombic sample, x = 0.06, La and vacancies adopt an ordered disposition in alternating ab-planes producing the c-axis doubling of the perovskite. In the tetragonal sample, x = 0.167, superstructure peaks become considerably broadened, indicating the existence of an important disorder in the distribution of vacant sites. 7Li nuclear magnetic resonance spectra of ordered samples display the presence of 2 types of Li with different mobility. In the orthorhombic sample, an analysis of the relaxation rates, T1-1 and T2-1, indicated the bi-dimensional motion of Li ions between 200 and 270K. This became progressively tri-dimensional as the temperature was increased. In the tetragonal sample, tri-dimensional motion of Li was favored. Conductivity measurements indicated that Li motions were strongly correlated; displaying a non-Arrhenius behavior between 160 and 500K. The electrical relaxation behavior was independent of the composition of the sample, indicating that the long-range motion of Li ions was not greatly affected by structural distortions.

Li3xLa(2/3)-xTiO3 Fast Ionic Conductors - Correlation between Lithium Mobility and Structure. A.Rivera, C.León, J.Santamaría, A.Varez, M.A.Paris, J.Sanz: Journal of Non-Crystalline Solids, 2002, 307-310, 992-8