INFRARED AND TRANSPORT-PROPERTIES OF THE LAYERED PEROVSKITE RELATED OXIDE BA5NB4O15 AND ITS OXYGEN-DEFICIENT PHASES

Ba5Nb4O15-x oxides were studied by infrared, electrical resistivity an d thermogravimmetric analysis (TGA). FIR reflectivity measurementsreve al a strong ionic compound that has well defined features in groups th at we assign to oxygen stretching, bending and lattice phonons splitte d by the lower symmetry of this layered compound. For the sample with x = 0.56, oxygen vacancies do not affect phonon band profiles, indicat ing that carriers are not free enough to interact with longitudinal mo des. Electrical resistivity vs. temperature measurements show that the oxygen deficient compounds, for low values of x, are small band gap s emiconductors.