Structure and dissolution behavior of orthophosphate MgO–CaO–P2O5–Nb2O5 glass and glass-ceramic

• Published in: Materials letters 2016-07, Vol.175, p.135-138
• Main Authors: Lee, Sungho, Maçon, Anthony L.B., Kasuga, Toshihiro
• Format: Article
• Language: English
• Subjects: Biomaterials; Dissolution; Durability; Glass; Glass ceramics; Glassy; Magnesium; Niobates; Niobium; Orthophosphate; Phases; Phosphate invert glass; Phosphates; Structure
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2016.04.027

The aim of this work is to investigate the effect of lowering the phosphate content, from 27 to 20mol%, in calcium-phosphate invert glass/glass-ceramic containing magnesia and niobia (MgO-CaO-P2O5-Nb2O5) on the structure and dissolution properties. According to 31P solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies, glass containing 20mol% of P2O5 was exclusively composed of orthophosphate (QP0), whereas orthophosphate and pyrophosphate (QP1) coexisted in 27mol% P2O5 glass. Tetrahedral niobate was detected by Raman spectroscopy with 20mol% phosphate, suggesting that niobate acts as a network former and therefore cross-links orthophosphate groups together (P-O-Nb bonds). The equivalent glass-ceramic consisted of crystalline phases (β-Ca3(PO4)2, Mg3(PO4)2 and Mg3Ca3(PO4)4), which did not contain niobate, and a residual glassy phase. The glass with 20mol% P2O5 showed a lower chemical durability than the glass with 27mol% P2O5, which was likely due to the formation of P-O-Mg bonds, which favor hydrolysis. The glass-ceramic chemical durability was improved after crystallization, probably because of an increase in the niobate concentration of the residual glassy phase. •A glass based on a network consisting of orthophosphate group was prepared.•Niobate tetrahedra and magnesium crosslink orthophosphate groups in the glass.•The glass-ceramic included orthophosphate crystal phases.