Microwave and infrared conductivity of Naβ-alumina; evidence for collective ionic effects

Abstract

Detailed measurements of the ionic conductivity in single-crystal Na $\beta$-alumina are reported for frequencies between ${10}^7$ and ${10}^{13}$ Hz and for temperatures between 4.2 and 300 K. The quadratic temperature dependence of the conductivity at ${10}^{10}$ Hz and the large width (∼ 23 ${\mathrm{cm}}^{-1\mathrm{}}$) of the 65-${\mathrm{cm}}^{-1\mathrm{}}$ phonon mode are consistent with a model in which there is a broad distribution of collective ion modes.