Preparation and study of magnetic properties of silico phosphate glass and glass-ceramics having iron and zinc oxide

The magnetic properties of 25SiO₂–50CaO–15P₂O₅–(10−x)Fe₂O₃−xZnO (where x=0, 2, 5 mol%) glass and glass-ceramics have been studied. These glasses are prepared by melt quench technique and heat treated at 800 °C for 6 h. Electron Spectroscopy for Chemical Analysis (ESCA) revealed that the fraction of non-bridging oxygen decreases with the increase in zinc oxide content. Evolution of crystalline phases in glass-ceramics has been studied by X-ray diffraction (XRD). The microstructure as seen by scanning electron microscopy (SEM) exhibits formation of nanosize particles. Effect of controlled heat treatment on magnetic properties was studied by means of a Superconducting Quantum Interference Device (SQUID) magnetometer. Mössbauer spectroscopy at room temperature was also carried out to determine the state of iron ions in glasses and glass-ceramics. Isomer shift values of the glasses suggest that Fe³⁺ and Fe²⁺ are in tetrahedral coordination. The analysis of the glass without ZnO shows about 58 wt% of total iron ions is in the Fe³⁺ state. The samples on heat treatment show improved magnetic properties due to the formation of magnetic nanoparticles. Magnetic studies revealed the relaxation of magnetic particles and the increase in saturation magnetization with addition of 2 mol% ZnO. Increase in ZnO content results in decrease in the strength of dipolar interactions.