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

Glass formation ability in three different sections: WO 3 –ZnO–Nd 2 O 3 ; (100-x) (0.8WO 3 ·0.1ZnO·0.1Nd 2 O 3 )·xAl 2 O 3 , x = 5–30 mol% and 90(xWO 3 ·yZnO·zNd 2 O 3 )·10Al 2 O 3 from WO 3 –ZnO-Nd 2 O 3 –Al 2 O 3 system is investigated by melt quenching technique. Glasses are obtained from the compositions with a high WO 3 content (65–75 mol%). According to DTA data the glass transition temperature (T g ) is in the range 508–525 °C and the glass crystallisation temperature (T x ) is around 600 °C. Neodymium tungstates, Al 2 (WO 4 ) 3 , ZnWO 4 and WO 3 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 WO 6 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 MeO 4 tetrahedra. [ABSTRACT FROM AUTHOR]