Isothermal Crystallisation of a Glass from the 3CaO.P₂O₅–SiO₂–MgO–K₂O System Studied by Impedance Spectroscopy

Abstract:

Impedance spectroscopy was used to measure the changes of electrical properties during the isothermal crystallisation of the phosphate phase in bulk samples of a glass with nominal molar composition (3CaO.P2O5)20(SiO2)35(MgO)38.354(K2O)6.646, developed for biomedical applications. Crystallization studies were performed in isothermal conditions at 800°C and 860°C, and were monitored by impedance spectroscopy. XRD shows that a stable orthophosphate phase, Ca9MgK(PO4)7 crystallizes at about 860°C, after formation of earlier phosphate precursors formed at lower temperatures, namely oxyapatite (Ca5(PO4)3O) and tricalcium phosphate (Ca3(PO4)2). The conductivity of bulk glass samples decreases at 800°C, as the phosphate precursors phases crystallize. The opposite trend is observed on crystallizing the orthophosphate phase, at 860°C.

• Periodical: Materials Science Forum (Volumes 514-516)
• Pages: 1073-1077
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.514-516.1073
• Online since: May 2006
• Authors: Carlos M. Queiroz, Maria Helena F.V. Fernandes, Jorge R. Frade
• Keywords: Electrical Conductivity, Glass Crystallization, Impedance Spectroscopy, Oxyapatite, Tricalcium Phosphate, Whitlockite

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