Raman spectra of niobium oxides

Raman spectra of various types of niobium oxides have been studied along with their i.r. spectra and the spectra interpreted in the light of the structures of the oxides. Besides discussing LO-TO splitting in these oxides, bands characteristic of edge-shared and corner-shared NbO6, octahedra have been assigned. Tetrahedral modes of NbO4, PO4, and VO4 units present in some of the oxides have been assigned to distinct bands in the spectra indicating negligible coupling between the tetrahedra and NbO6 octahedra. The spectra of PNb9O25 and analogues suggest that they belong to I4/m space group rather than IZ 4 - group.