Glass formation and structure of glasses in the WO3–ZnO–Nd2O3–Al2O3 system

Abstract

Glass formation ability in three different sections: WO3–ZnO–Nd2O3; (100-x) (0.8WO3·0.1ZnO·0.1Nd2O3)·xAl2O3, x=5–30mol% and 90(xWO3·yZnO·zNd2O3)·10Al2O3 from WO3–ZnO-Nd2O3–Al2O3 system is investigated by melt quenching technique. Glasses are obtained from the compositions with a high WO3 content (65–75mol%). According to DTA data the glass transition temperature (Tg) is in the range 508–525°C and the glass crystallisation temperature (Tx) is around 600°C. Neodymium tungstates, Al2(WO4)3, ZnWO4 and WO3 are identified in the XRD patterns of quenched samples beyond the glass formation region. The structure of glasses is studied by IR, Raman and DR-UV–Vis spectroscopies. It is established that the amorphous network is built up mainly by WO6 octahedra, connected by W–O–W bridges. This structure does not satisfy the classical concept for the formation of an amorphous network which is built up by MeO4 tetrahedra.