Thermal properties and crystallization of iron phosphate glasses containing up to 25 wt% additions of Si-, Al-, Na- and U-oxides

The thermal properties (expansion, T g and T SOFT.) of glasses, having 56–66% P 2O 5, 14.8–34.2% Fe 2O 3 and 2–25 wt% additions of SiO 2, Al 2O 3, Na 2O and UO 2, were comparatively estimated from dilatometric measurements in similar conditions. The T g reversibility was clearly verified by varying the heating rates between 1 and 5 °C min −1. From linear equations fits of the various glass properties as functions of the six components it is suggested the iron, sodium and uranium oxides decrease the thermal expansion (for 50 < T ⩽ 300 °C), T g and T SOFT. From DTA/XRD analysis of three glasses it was confirmed the crystallization tendency decreased with increasing the UO 2 level in the glasses. Leaching test data for two compositions containing Na 2O suggest addition of UO 2 increases the chemical durability of the related glass. The roles of UO 2, Na 2O and Fe-oxide species as structural components of the glass network are discussed.