The effects of calcium-to-phosphorus ratio on the densification and mechanical properties of hydroxyapatite ceramic

• Main Authors: Tan, C.Y., Singh, R., Teh, Y.C., Tan, Y.M., Yap, B.K.
• Published: 2018
• Online Access: http://dspace.uniten.edu.my/jspui/handle/123456789/8774

In this work, hydroxyapatite (HA) powders were synthesized using calcium hydroxide Ca(OH)2 and orthophosphoric acid H3PO4 via wet chemical precipitation method in aqueous medium. Calcium-to-phosphorus (Ca/P) ratio was set to 1.57, 1.67, 1.87 that yield calcium-deficient HA, stoichiometric HA, and calcium-rich HA, respectively. These synthesized HA powders (having different Ca/P ratio) were characterized in terms of particle size and microstructural examination. Then, the densification and mechanical properties of the calcium-deficient HA, stoichiometric HA, and calcium-rich HA were evaluated from 1000 to 1350°C. Experimental results have shown that no decomposition of hydroxyapatite phase was observed for stoichiometric HA (Ca/P = 1.67) and calcium-deficient HA (Ca/P = 1.57) despite sintered at high temperature of 1300°C. However, calcium oxide (CaO) was detected for calcium-rich HA (Ca/P = 1.87) when samples sintered at the same temperature. The study revealed that the highest mechanical properties were found in stoichiometric HA samples sintered at 1100-1150°C, having relative density of ∼99.8%, Young's modulus of ∼120 GPa, Vickers hardness of ∼7.23 GPa, and fracture toughness of ∼1.22 MPam1/2. © 2014 The American Ceramic Society.