CALORIMETRIC AND ELECTRICAL STUDIES ON THE POSITIONAL DISORDER OF LITHIUM IONS IN LITHIUM LANTHANUM TITANATE

Heat capacities and electrical moduli of high lithium ion conductor Li 0.35La0.51TiO2.94 Were measured below 300 K. A glass transition was ob served at T(g) = (102 +/- 2) K as due to the freezing-in of positional disorder of lithium ions. The associated heat capacity jump was found to be (0.03(+0.03/-0.01))JK-1 mol-1 at 125 K. The energy of the excit ed state as referred to the ground state was evaluated from the jump t o be ca. 9 kJ mol-1. The calorimetric and electrical relaxation times for the rearrangement of lithium ions were well fitted by a straight l ine on an Arrhenius plot, and the activation energy of the process was derived to be (32.0 +/- 0.1) kJ mol-1. A potential close relation was suggested to exist in general between the high ionic conductivity and the positional disorder of mobile ions.