Two-pulse phonon echo measurements were performed from room temperature to 900K in micro particles of polycrystalline and single crystalline LiNbO3 to investigate the relationship between Li ionic diffusion and decay time, T2, in a phonon echo study. The decay time depended on temperature; with a rapid decrease above 800K in the polycrystalline sample. The origin of this anomaly was interpreted in terms of a simple Debye-type relaxation due to Li ionic diffusion. The activation energy, which was evaluated as being 0.93eV in the polycrystalline samples, was comparable with reported values from ionic conductivity and nuclear magnetic resonance studies. On the other hand, single crystalline LiNbO3 exhibited no signs of Li ionic diffusion up to 900K. The contribution to T2 from Li ionic diffusion would be dominant at above 900K because of the much higher activation energy in a single crystalline sample. It was shown that the phonon echo decay time was strongly connected with ionic diffusion in the particles.

Phonon Echo Study of Lithium Ionic Diffusion in LiNbO3 Powder. K.Nakamura, Y.Michihiro, F.Katayama, T.Moriga, R.M.Mahbubar, I.Nakabayashi, T.Kanashiro: Japanese Journal of Applied Physics, 2005, 44[6A], 4043-6