Structure-properties relationship study in niobium oxide containing GaO3/2-LaO3/2-KO1/2 gallate glasses
Abstract The investigation has been devoted to the effect of the KNbO 3 in a gallate based glasses of composition (100-x) (69GaO 3/2 -11LaO 3/2 -20KO 1/2 ) – x KNbO 3 with x varying from 0 to 20 mol.% allowing the use of standard melt technique. The thermal and optical properties were characterized and the local structure has been investigated by Raman spectroscopy. The gallium ions are mostly found in tetrahedra thanks to charge balancing of potassium and lanthanum ions. The continuous increase of the KNbO 3 concentration gives rise to the progressive formation of a niobate subnetwork composed of corner shared NbO 6 octahedra which does not depolymerize the gallate glass network. This addition has a limited impact on the multiphonon edge in the infrared while it causes a significant increase of the refractive index. For KNbO 3 concentrations above 14 mol.% a phase separation occurs due to the absence of formation of a mixed gallo-niobate glass skeleton.