Effect of silicon and heat-treatment temperature on the morphology and mechanical properties of silicon - substituted hydroxyapatite

The precipitation method was used to synthesize silicon-substituted hydroxyapatite with different Si contents of 0.4, 0.8 and 1.6 wt.% (0.4, 0.8 and 1.6Si-HA) using silicon acetate [Si(OCOCH3)4] as a Si source. As-synthesized hydroxyapatite (HA) and Si-HA powders/bulks were heat-treated at different temperatures of 1150, 1200 and 1250 °C for 1 h. Pure 0.4Si-HA and 1.6Si-HA were obtained after heat-treatment at all temperatures, whilst α-TCP phase was formed in the 0.8Si-HA sample after heat-treatment at 1250 °C. SEM observation clearly showed that the substitution of Si in HA inhibited the grain growth of Si-HA even at high heat-treatment temperatures (1200 or 1250 °C). The highest diametral tensile strength (DTS) of 15.93 MPa was obtained in the 1.6Si-HA sample after heat-treatment at 1250 °C.