High-energy X-ray diffraction study of La co-ordination in lanthanum phosphate glasses

Differences in La co-ordination environments indicated in the structures of rare earth-phosphate crystals in glasses with compositions ranging from ultraphosphate to metaphosphate stoichiometries were investigated. A series of lanthanum phosphate glasses were characterized by X-ray diffraction analysis and a change of the La-O co-ordination number was extracted by Gaussian fitting of the first-neighbor distances. The decrease in co-ordination number was due to the transition of ultraphosphate glass structures to metaphosphate structures. The changes in the La environments explained the compositional dependence of glass properties.