Effect of the Mg<sup>2</sup><sup>+</sup> Substitution on the Sintering Behavior and Compressive Strength of Doped Β-TCP/CPP Ceramics

Abstract

β-Tricalcium phosphate (β-TCP) ceramics are of interest for bone requirements implants due to resoption behavior. The mechanical properties of β-TCP, however, are not yet sufficient to allow load bearing application of implants. The aim of this work was to investigate the effect of Mg2+substitution on the strength sintered TCP. Due to promotion of a liquid phase at 1200°C, Calcium pyrophosphate (CPP-C2P2O7) was used to improve the sintering of the samples. The introduction of CPP was promoted by use of a Ca/P molar ratio of 1.45. The powders were synthesized using a mixture of Ca (OH)2suspension and diluted H3PO4with addition of MgO and calcined at 750 °C, 900 °C and 1050 °C. The cold isostatic pressing compacts were sintered at 1200 °C and 1300 °C, respectively.It was shown that a small Mg content (1.5 mol%) increased both compressive strength and fractional density of the TCP material sintered at 1200 °C from 132 ± 39 MPa at 92.1 % of fractional density to 193 ± 29 MPa at 94.5 % of theoretical density. Higher amounts of Mg inhibited the grain growth provoking a increase of the boundary mobility activation energy. Abnormal grain growth (AGG) was observed after sintering at 1300°C, as result CPP - liquid phase formation. Increase of Mg content promoted AGG, due to inhibition of grain growth during normal grain growth resulting in a increase of the residual elastic energy of the system.