Structure and physical properties of sodium antimony germanate glasses

The structure and physical properties of sodium antimony germanate glasses with compositions 10Na(2)O - x Sb2O3 - (90 - x)GeO2, x = 10-30 mol%, prepared by the melt-quenched route have been studied. It is observed from x-ray diffraction, SEM, density and oxygen molar volume, infrared (IR), differential thermal analysis (DTA), and optical absorption that single phase homogeneous glasses with a random network structure can be obtained in this system. The strength and connectivity of the glass network increase with GeO2 content. The main Ge-O stretching vibration also shifts to higher wavelength side. Two oxidation states of antimony, Sb3+ and Sb5+, are present, while the so-called ''germanate anomaly'' is absent in these glasses. This study discusses the probable structural reasons behind this type of behavior of these glasses.