Non-isothermal crystallization in BaO–Fe₂O₃–P₂O₅ glasses

Crystallization behaviour in 10 and 20 mass% BaO-loaded iron phosphate glasses was studied using differential thermal analysis technique under non-isothermal conditions. Activation energy of crystallization was estimated from the experimental data by applying isoconversional method of kinetic analysis. Activation energy of crystallization was found to increase in 10 mass% BaO-loaded iron phosphate glass, whereas the activation energy showed a decreasing trend as a function of fraction of crystallization (α) in 20 mass% BaO-loaded iron phosphate glass. Fe₃(P₂O₇)₂ was found to be the major product of crystallization in both the BaO-loaded iron phosphate glasses, and other products of crystallization varied depending on the composition of the glass. The concentration of Fe²⁺ was estimated based on the contribution of various identified products of crystallization and composition of the parent glass. The estimated concentration of Fe²⁺ ions was 19 and 22% after the heat treatment of 10 and 20 mass% BaO-loaded iron phosphate glasses, respectively. The crystallization behaviour of BaO-loaded iron phosphate glass is compared with iron phosphate glass and iron phosphate glass containing equivalent concentration of Cs₂O. The activation energy of crystallization of BaO-loaded glasses was relatively higher than that of Cs₂O-loaded iron phosphate glass. The results and comparison on crystallization of these glasses are presented in this paper.