The Influence of Cu2+ and Mn2+ Ions on the Structure and Crystallization of Diopside–Calcium Pyrophosphate Bioglasses

The influence of two divalent cations, Cu2+ and Mn2+, on the structure, sintering, and crystallization of glasses and glass-ceramics in the diopside–calcium pyrophosphate system (90 wt.% diopside (CaMgSi2O6), 10 wt.% calcium pyrophosphate (Ca2P2O7)) was investigated. Glasses with 1, 3, and 5 wt% MnO or CuO additives were prepared by melt-quenching and characterized by XRD, 29Si and 31P NMR, DTA, and FTIR This revealed that the silicate network is predominantly coordinated in Q2 (Si) units for all glasses, while phosphorus tends to inhabit an orthophosphate (Q0) environment. All glasses had a high rate of bioactivity after immersion in simulated body fluid. A slight depolymerization was observed in the doped glasses leading to lower Tg values in comparison with the parent glass. All glass-ceramics exhibited the formation of diopside as the primary crystalline phase after sintering at 850°C/1 h. In comparison with the parent glass, the doped glasses featured significantly larger processing windows (∆T = Tc–Tg), ensuring good sinterability. Further, with increasing doping levels, the glasses exhibited a gradual decrease in Tp and ∆T, suggesting an increased tendency toward devitrification. All Cu- and Mn-containing glasses exhibited the formation of hydroxyapatite, making them good candidates for biomedical applications and tissue engineering.