Raman Spectroscopy, X-Ray, SEM, and DTA Analysis of Alkali-Phosphate Glasses Containing<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mrow><mml:msub><mml:mrow><mml:mtext>WO</mml:mtext></mml:mrow><mml:mtext>3</mml:mtext></mml:msub></mml:mrow></mml:math>and Nb₂O₅

Abstract

New phosphate glasses in the quaternary system (50- x ) A 2 O- x WO 3 -10 Nb 2 O 5 -40 P 2 O 5 , with x = 0; 30 and A = Li or Na were prepared by the melt quenching method. The effect on the crystallization behaviour of the glass due to the introduction of WO 3 into the glass composition and, consequently, the diminishing of the molar amount of the alkaline oxide and the decreasing of the molar ratio between network modifiers and network formers (M/F) was studied. The prepared glasses were heat-treated in air, at 550°C, 600°C, and 650°C for 4 hours. The structure, of the obtained samples, was studied by differential thermal analysis (DTA), X-ray powder diffraction (XRD), and 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 WO 3 reduces the number of the crystallised phases. In the lithium-niobiophosphate glasses, the presence of WO 3 promotes the formation of NbOPO 4 instead of the LiNbO 3 phase and reduces the formation of ortho- and pyro-phosphate phases. The thermal treatments affect the arrangements of the network structure of the AW40-glasses.