Properties of mixed Na2O and K2O iron phosphate glasses

Glass formation and properties of iron phosphate glasses containing Na2O and K2O have been investigated to determine the suitability of these glasses for disposing of certain types of nuclear wastes that contain one or more alkali oxides. Two series of glasses of the general composition xK2O–(20−x)Na2O–20Fe2O3–60P2O5 and xK2O–(20−x)Na2O–32Fe2O3–48P2O5, mol%, with x=0, 5, 10, 15 and 20, were chosen for this investigation. The properties that have been measured include density, molar volume, chemical durability, electrical resistivity, dielectric constant and IR spectra. No typical mixed alkali effect, namely, a minimum or maximum in the properties as a function of the ratio of two alkali ions, was observed for these glasses. The present results show that iron phosphate glasses can be suitable for vitrifying nuclear wastes that contain amounts of one or more alkali oxides ⩽20 mol%. An Fe/P ratio of the compositions at about 0.67 and the O/P ratio between 3.5 and 3.7 are desirable to obtain the maximum chemical durability of the wasteforms.