Influence of Mg-substitution on the physicochemical properties of calcium phosphate powders

Tricalcium phosphate based ceramics (TCP) are bioresorbable and thereby considered to be promising bone replacement materials. The differences in crystal structure between α and β-TCP phases gives rise for different dissolution rates in vitro and in vivo, which may alter the bioresorbable behavior of TCP ceramics. It is suggested that the addition of magnesium ions, which are also present in biological tissues, stabilizes β-phase to higher temperatures and thus enables the sintering of β-TCP at elevated temperatures compared to Mg free TCP.In this paper, Mg-substituted TCP, with the general formula (Ca1−xMgx)3(PO4)2 and 0.01 ≤ x ≤ 0.045, were produced by wet chemical synthesis from Ca(OH)2, H3PO4 and MgO, after calcinations at three different temperatures between 750 and 1050 °C. The influence of different amounts of Mg substitution on the physical properties, microstructure, and sintering behavior of calcium phosphate powders was evaluated. Thermal analytical techniques, together with X-ray diffraction analysis, were successfully combined in order to characterize the occurring phase transformations during annealing of the powders. The results show that the addition of small amounts of Mg (up to 1.5 mol%) are adequate to postpone the β–α TCP phase transformation to 1330 °C and to accelerate the densification process during sintering of β-TCP ceramics.