Crystallization and microstructure analysis of calcium phosphate-based glass ceramics for biomedical applications

Abstract

Calcium phosphate glasses and glass ceramics (CaO/P 2O 5=1.25 in molar ratio) modified by small amounts of additives such as Na 2O, MgO, TiO 2 and ZrO 2 were prepared after appropriate heat treatment for nucleation and crystallization. Based upon differential thermal analysis (DTA) results, a two-step heat treatment was used for crystal nucleation and growth. X-ray diffraction (XRD) analysis demonstrated that bioresorbable β-Ca 2P 2O 7 (β-DCP), β-Na 2CaP 2O 7, Na 2Mg(PO 3) 4 phases were formed in the glass matrix depending upon the relative contents of the additives. By adding higher contents of Na 2O and TiO 2 and using CaO/P 2O 5=1.5–2.0, crystallization of β-DCP and Ca 3(PO 4) 2 (β-TCP), and the formation of a dense structure in the glass ceramics were obtained. The precipitation of these crystals could be well distinguished at a magnification of 4000× and phases were dispersed in areas of micron size. A porous structure may be easily formed after the soluble phases are dissolved in physiological media. These glass ceramics with high CaO/P 2O 5 ratio, modified by the above mentioned additives are expected to find use as implants for bone replacement/regeneration and drug delivery carriers synergistically, because the soluble phases may act as drug delivery carriers and the porous structure will allow for bone ingrowth.