Alkali-free bioactive diopside-tricalcium phosphate glass-ceramics for scaffold fabrication: Sintering and crystallization behaviours

The sintering and crystallization behaviours of alkali-free bioactive glass compositions designed in the diopside (CaO·MgO·2SiO2)-tri-calcium phosphate (3CaO·P2O5) binary join by varying the Di/TCP ratios were investigated by hot-stage microscopy and differential thermal analysis, respectively. The effects of non-isothermal heating for 1 h at 900, 1000 and 1200 °C on the structural changes were assessed by solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR) and crystalline phase assemblage. The influence of the heat treatment temperature on 3 point bending strength was also investigated. Diopside and hydroxyapatite formed as primary crystalline phases, accompanied by calcium silicate as secondary phase, in samples are sintered at 900 °C and 1000 °C. With further increase of the heat treatment temperature to 1200 °C, whitlockite that was stated appearing in some compositions at 1000 °C, appeared as main crystalline phase after diopside as a result of hydroxyapatite transformation. The data gathered was highly relevant towards setting the experimental conditions required for preparing well sintered and mechanically strong glass/glass-ceramic scaffolds for bone regeneration and tissue engineering applications.