Infrared reflection spectra of the one-dimensional ionic conductor K— and RbAl priderites

The reflection spectra of the one-dimensional ionic conductors K_1.6Al_1.6Ti_6.4O₁₆ and Rb_1.49Al_1.65Ti_6.35O_15.92 have been measured for the polarizations E ∥ c (channel direction) and E 6 c in the frequency region 60–2000 cm^-1. The spectra of these two compounds are very similar with their features and have the same number of bands. The vibrational mode frequencies are obtained from a Kramers-Kronig analysis for each polarized reflectivity spectrum. A comparison of the corresponding mode frequencies for both priderites shows that only the lowest frequency mode observed in the E 6 c spectra is strongly associated with the alkali ion, while the others are not. The effect due to the non-stoichiometry is not found in the infrared reflection spectra.