Effect of neodymium and lanthanum oxides on alumino phosphate vitreous and devitrified states

Alumino phosphate glasses containing up to 25 mole % of oxides of neodymium and lanthanum have been prepared using the melt quenching method and their devitrified states were obtained using heat treatment. X-ray diffraction, FTIR, Raman and EXAFS were employed to examine the materials both in the vitreous and devitrified states. The density of the glasses is found to be lower by 5% to 10% than that for the corresponding devitrified states depending on the rare-earth inclusion. The network connectivity was found to decrease in the mixed rare earth glass as compared to the glass containing either oxide of Nd or La. Deconvolution of Raman peaks was used to quantify the presence of the Q0, Q1, Q2 and Q3 structural units in the glass samples. The main structural units in both the glasses and devitrified states were found to be the Q1 and Q2 tetrahedral units. For the mixed Nd-La, these units appear as an average of the numbers appearing in the single rare-earth included materials. The main structural vibrations present in the devitrified state are found to have survived in the glassy state. The EXAFS study indicates that the coordination number of oxygen around the rare earth ion increases by about 5% in going from the vitreous to the devitrified state.