非線形共鳴現象を利用した超イオン導電体の物性測定

Lithium transition metal oxides are attractive as the positive electrode of secondary battery.
In this study, the phonon-echo measurements have been performed to study Li+ ionic motion
in piezoelectric LiNbO3 powder. The phonon-echo is generated by propagating waves coupling
through the anharmonicity of lattice vibrations. The decay time of the echo, T2 is connected
with the internal friction within each particle, which is functional as an acoustic oscillator.
The decrease in T2 observed above 800 K in the polycrystalline powder is explained in terms of
a Debye-type relaxation model based on Li+ ionic motion. The activation energy is estimated
as about 0.93 eV, which is in good agreement with those reported from NMR and ionic
conductivity measurements. The present study indicates that the phonon-echo measurement
is useful to elucidate the ionic motion in ionic conductors.