Effect of ZnO on phase emergence, microstructure and surface modifications of calcium phosphosilicate glass/glass–ceramics having iron oxide

The effect of ZnO on phase emergence and microstructure properties of glass and glass–ceramics with composition 25SiO2–50CaO–15P2O5–(10 − x)Fe2O3–xZnO (where x = 0, 2, 5, 7 mol%) has been studied. They have been characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Surface modifications of these glass–ceramics in simulated body fluid have been studied using Fourier transform infrared reflection spectroscopy (FTIR), XPS and SEM. Results have shown a decrease in the fraction of non-bridging oxygen with increase in zinc oxide content. Emergence of crystalline phases in glass–ceramics at different heat treatment temperatures was studied using XRD. When glass is heat treated at 800 °C calcium phosphate, hematite and magnetite are developed as major phases in the glass–ceramics samples with ZnO up to 5 mol%. In addition to these, calcium silicate (Ca3Si2O7) phase is also observed when glass is heat treated at 1000 °C. The microstructure of the glass–ceramics heat treated at 800 °C exhibits the formation of nano-size (40–50 nm) grains. On heat treatment at 1000 °C crystallites grow to above 50 nm size and more than one phase are observed in the microstructure. The formation of thin flake-like structure with coarse particles is observed at high zinc oxide concentration (x = 7 mol%). In vitro studies have shown the surface modifications and formation of Ca–P-rich layer on the glass–ceramics when immersed in simulated body fluids (SBF) for different durations. The bioactive response was found to depend on ZnO content.