Structural Investigations on Na2O – CaO-V2O5- SiO2 Bioglass Ceramics

All as obtained glasses in the system 24.5 Na2O-24.5 CaO-6 P2O5- xV2O5 (45-x) SiO2 (x ranges from 0-15 mole %) are transparent and have an amorphous network structure. Glasses containing up to 6 mol% V2O5 still transparent upon heat treatment at 660°C for 4 hours. On the other hand, heat sintered glasses containing higher V2O5 concentration are transformed to opaque white glass ceramic characterized by their highly crystalline network structure. Crystalline apatite (calcium phosphate, Ca3(PO4)2), wollastonite (calcium silicate, CaSiO3), and sodium vanadate (Na2VO3) are the main well-formed crystalline species played the major role in material bioactivity. The advantage of V2O5 containing glasses is that it can easily be crystallized, since the high crystallinity is obtained by lowering sintering temperature when compared with that of glasses free from V2O5. Crystalline clusters containing vanadate species and both apatite and wollastonite phases are evidenced to be present. A hydroxyapatite (HA) formation is confirmed by the in vitro test of bioactivity. Processes of degradation and ion exchange between sample and phosphate solution and HA precipitation are evaluated. It is found that V2O5 can speed up the rate of reaction between the tested sample and phosphate solution. Glass ceramics containing V2O5 is highly active than that of vanadium free silicate glasses.