Vibrational properties of impurity substituted α′-NaV2O5

We report the polarized infrared reflectance of Ti4+-doped α′-NaV2O5 and an analysis of the frequency dependent conductivity. Impurity incorporation allows us to resolve a number of new rung-polarized vibrational features due to local symmetry breaking. Variable temperature measurements both above and below the charge ordering transition indicate that the majority of zone-folding modes in Ti4+ substituted α′-NaV2O5 are a subset of those in the pristine material; minute new folded modes are observed at 46 (E∥a), 105 (E∥a), and 636 (E∥b) cm−1. We discuss our results in terms of disruption of the rung in the vicinity of the Ti4+ defect.