Characterization of iron oxychloride potassium phosphate glasses

Abstract

Glasses in the systems xFe2O3-(45-x)K2O-55P2O5 and yFeCl3-10Fe2O3-(35-y)K2O-55P2O5 have been prepared over a wide range of composition (x = 0-11.5 mol% and y = 0-30 mol%). The thermal expansion coefficient, glass transition temperature, density and dissolution rate in HCl (1.6 M) at 60 °C were investigated. Results indicate that increasing Fe2O3 content in potassium phosphate glasses increases the density and glass transition temperature, while the thermal expansion coefficient and dissolution rate decrease. The same behaviours were obtained when FeCl3 content was increased. These results indicate that the chemical durability of potassium phosphate glasses would be enhanced upon addition of Fe2O3 and/or FeCl3. The infra-red spectral analyses of the glasses reveal a significant structural change in the glass matrix depending on the composition. The incorporation of iron (as iron oxide or iron chloride) into the potassium phosphate matrix depolymerizes the glass structure through formation of P-O-Fe(III), P-O-Fe(II) and P-Cl bonds. The depolymerization process was found to be more sensitive for glasses with x+y<25 mol%.