Melt-quenched 15(ZnO,Fe2O3) 5OSiO2.20(CaO, P2O5) 15Na2O bioactive glass was heat treated at temperatures (TA) ranging from 550 deg C to 850 deg C for different time periods (1, 2 and 3h) to understand its devitrification characteristics. Crystallization of calcium sodium phosphate, zinc ferrite, magnetite, and hematite phases depend on heat treatment conditions. Decrease in saturation magnetizations (Ms) with increase in tA of glass heat treated at TA>750 deg C is attributed to the formation of hematite which is a weak magnetic material. Magnetic properties as functions of TA and tA are interpreted ont he basis of clustering of Fe ions, super-exchange interactions between Fe2+ and Fe3+ ions and formation of ferri-magnetic and weakly magnetic iron oxide phases with different heat treatment conditions. Electron paramagnetic resonance parameters reveal the variations in site distortions and randomness in Fe ion environment in the matrix upon heat treatment. In vitro mineralization ability of the glass-ceramics was evaluated by immersion in simulated body fluid (SBF) and monitoring both the pH variation of SBF and formation of hydroxyapatite surface layer as a function of immersion time. These studies help in assessing these glass-ceramics for hyperthermia treatment and in optimising the processing conditions for this application.
