Zinc and strontium co-substituted hydroxyfluorapatite: Synthesis, sintering and mechanical properties

Strontium and zinc co-substituted hydroxyfluorapatites with the general formula Ca9.9-xZn0.1Srx(PO4)(6)(OH)F with 0 <= x <= 1 were synthesized by an aqueous precipitation method in order to study the influence of Sr2+ and Zn2+ ions on the mechanical properties of bone replacement material. The evolutions of the morphology and size of grains on the one hand, and crystalline phases on the other hand, were made on calcined powder from 500 to 1200 degrees C, and mechanical properties were measured on apatite pellets sintered from 900 to 1200 degrees C. The simultaneous incorporation of Sr2+ and Zn2+ into the apatite structure had a strong influence on the microstructure, densification and mechanical properties of the materials. XRD analysis revealed a partial decomposition of the apatite phase with the formation of the tricalcium phosphate above 1000 degrees C. At a given temperature, the density increased continuously with increasing the strontium amount. It reached a maximum value of 93% of theoretical density at 1200 degrees C for x = 1. Mechanical properties: Vickers hardness H-v, Young's modulus E and modulus shear G were investigated in correlation with the modification of the microstructural characteristics of the sintered materials.