Role of manganese on the structure, crystallization and sintering of non-stoichiometric lithium disilicate glasses

The structural role of Mn was investigated in a relatively simple non-stoichiometric lithium disilicate (Li2Si2O5) based glass composition. Glasses were prepared by partially replacing SiO2 by MnO2 from the base glass belonging to the system Li2O-K2O-Al2O3-SiO2. An overall depolymerization of the glass network was observed according to magic angle spinning nuclear magnetic resonance (MAS-NMR) and Fourier transform infrared (FTIR) spectroscopic studies, suggesting a network modifier role for Mn. However, thermal analysis, phase segregation and nucleation in the glasses suggested that Mn might also act as network former. Moreover, calculated crystal field parameters from UV-Visible spectroscopy, showing high ligand field strength (Do) and Racah inter electronic repulsion (B) indicate the possible existence of Mn as individual molecular entities in the interstitials of the glass network. This paper discusses the implications of this structural role of Mn on the crystallization of bulk glasses and on the sintering behaviour and crystallization of glass powder compacts

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, Si-29 and P-31 NMR, DTA, and FTIR This revealed that the silicate network is predominantly coordinated in Q(2) (Si) units for all glasses, while phosphorus tends to inhabit an orthophosphate (Q(0)) 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 T-g values in comparison with the parent glass. All glass-ceramics exhibited the formation of diopside as the primary crystalline phase after sintering at 850 degrees C/1 h. In comparison with the parent glass, the doped glasses featured significantly larger processing windows (T = T-c-T-g), ensuring good sinterability. Further, with increasing doping levels, the glasses exhibited a gradual decrease in T-p 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