Effect of strontium on crystallization characteristics and properties of ZnO-Fe2O3-B2O3-P2O5 glass-ceramics for biomedical applications

The synthesis, crystallization, thermal, and magnetic properties of the glass-ceramics based on ZnO-SrO- B ₂O ₃-Fe ₂O ₃-P ₂O ₅ glasses were studied. The impact of the SrO/ZnO replacements in the crystalline phases formed, the thermo-magnetic properties, and density of the crystalline materials were analyzed. Adding strontium to replace zinc in the glasses led to an increase in the glass transition temperature (Tg) and the crystallization peak (Tc). However, the thermal stability ΔT of the glasses decreased. SEM micrographs have revealed that the addition of SrO instead of ZnO in the glasses led to the formation of a fine-grained microstructure. As major phases, Zn ₂P ₂O ₇, SrZnP ₂O ₇, and α-Sr ₂P ₂O ₇ crystallized in glass-ceramic while, two minor phases Fe ₃(PO ₄) ₂ and SrFe ₂(P ₂O ₇) ₂ were also formed after the controlled heat-treatments process. The magnetic parameters improved with increasing SrO instead of ZnO, which was attributed to the formation of strontium-based crystalline phases. The prepared glass-ceramics have good magnetic properties with saturation magnetization of 0.682–0.852 emu/g, the coercivity force of 26.87–41.77 G, and remanence magnetization of 1.54–4.02 emu/g. The coefficients of thermal expansion (CTE) at 500 °C of the glass-ceramic increased to 10.4 × 10 ⁻⁶ °C ⁻¹ from 5.2 x 10 ⁻⁶ °C ⁻¹ for the base specimen due to SrO/ZnO replacements. The density values of the glass-ceramic specimens were 3.34 –3.46 g/cm ³. Depending on the physical, magnetic, and thermal properties of prepared glass-ceramic, these materials can be potentially used as magnetic materials for biomedical applications.