Alternating-current conductivity measurements were performed on ionically conducting Li0.18La0.61TiO3 at 100Hz-30MHz, and temperatures ranging from 8 to 300K. The power-law frequency dependence, which was usually attributed to ionic hopping, changed to a linear frequency dependence as the temperature was decreased. This was due to a near-constant loss contribution to the alternating-current conductivity. The cross-over was thermally activated, and the activation energy was related to the energy barrier which ions had to overcome in order to jump outside of their wells. This was considered in terms of the vibrational mean-square displacement of ions within their wells; which was sometimes shorter than the onset of the intersite hopping process. This indicated a vibrational origin for the near constant loss term.

Low Temperature AC Conductivity in the Fast Ionic Conductor Li0.18La0.61TiO3. A.Rivera, A.Várez, J.Sanz, J.Santamaría, C.León: Journal of Alloys and Compounds, 2001, 323-324, 545-8