Vibrational spectra of KNbW2O9 hexagonal tungsten bronze

Raman and IR studies were performed for the first time for a single crystal of KNbW2O9 belonging to the novel class of valence-balanced compounds crys tallizing in the structure of hexagonal tungsten bronze and exhibiting ferr oelectric properties. The observed vibrational modes were assigned to the r espective motions of atoms in the unit cell. The observation of weak bands above 900 cm(-1) was explained as a result of partial vacancy of W atoms in the hexagonal framework leading to the formation of terminal -W=O bonds. C opyright (C) 2001 John Wiley & Sons, Ltd.