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

The thermal properties (expansion, Tg and TSOFT.) of glasses, having 56-66% P2O5, 14.8-34.2% Fe2O3 and 2-25 wt% additions of SiO2, Al2O3, Na2O and UO2, were comparatively estimated from dilatometric measurements in similar conditions. The Tg 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), Tg and TSOFT. From DTA/XRD analysis of three glasses it was confirmed the crystallization tendency decreased with increasing the UO2 level in the glasses. Leaching test data for two compositions containing Na2O suggest addition of UO2 increases the chemical durability of the related glass. The roles of UO2, Na2O and Fe-oxide species as structural components of the glass network are discussed.