X-Ray Diffraction and Raman Spectroscopic Studies of Glasses and Glass-Ceramics Inside the A2O-MoO3-Nb2O5-P2O5 (A= Li, Na) Systems

Phosphate glasses in the system (50-x)A 2 O-xMoO 3 -10Nb 2 O 5 -40P 2 O 5 (AMo-40), with x=0; 30 and A=Li or Na were prepared by the melt quenching method. The effect in the crystallization behaviour of the glass due to the introduction of MoO 3 in the glass composition and varying the molar ratio between network modifiers and network formers (M/F) was studied. The prepared glasses were heat-treated in air, at 550, 600 and 650 ºC for 4 hours. The structure, of the obtained samples, was studied by differential thermal analysis (DTA), X-ray powder diffraction (XRD), Raman spectroscopy and the morphology by scanning electron microscopy (SEM). It was found that the replacement of Li 2 O or Na 2 O by MoO 3 reduces the number of the crystallised phases. In the lithium-niobiophosphate glasses the presence of MoO 3 promotes the formation of NbOPO 4 and reduces the formation of ortho- and pyro-phosphate phases. The thermal treatments affect the arrangements of the network structure of the AMo-40-glasses.