Raman and IR spectra of K4Nb6O17and K4Nb6O17·3H2O single crystals

Polarised Raman and IR spectra of K4Nb6O17 and K4Nb6O17· 3H2O single crystals were measured. The obtained spectra are discussed using the factor group approach for the orthorhombic P21nb space group and assignment of bands to the respective motions of atoms is proposed. In particular, we have shown that the bands above 770 cm−1 can be attributed to the stretching modes of short niobium–oxygen bonds, which are present in this material due to the pronounced layered structure, whereas the potassium atoms contribute to the bands observed below 180 cm−1. Our studies have revealed that intercalation of water molecules leads to shifts, broadening and changes in intensity of some bands. These changes have been attributed to slight changes in the bond lengths and angles, interactions of the water molecules with K atoms and structural disorder introduced by the intercalated water molecules. However, the main structural framework was preserved. Copyright © 2010 John Wiley & Sons, Ltd.