Investigation on Mechanical Behavior and Bioactivity of Fluorohydroxyapatite Toughened by Zirconium–Cerium ions Additions

Ceria stabilized zirconia (CSZ) in fluorohydroxyapatite (FHA) are prepared by sol-gel method, their phase transition, mechanical and biological properties are reported in this technical paper. Powder samples of pure HA, YZr/5Ce-FHA (where Y=5, 15, 40 mol% of Zirconium ions (Zr)) and 40Zr / XCe –FHA (where X = 5, 10, 20 mol% of Cerium ions (Ce)) compositions are prepared. The powders are uniaxially pressed at 100MPa to form pellets and sintered at 1200°C for 2 hrs. Mechanical properties such as Vickers microhardness [Hv], fracture toughness [K1c] and brittleness index [Hv / K1c] are evaluated through Vicker’s microhardness testing. Microhardness of pure HA was found to be 4.16 GPa, further additions of Zr-Ce ions in FHA increased the Hv value to 7.4 GPa. Sample 40 Zr/10Ce-FHA recorded the highest fracture toughness as 1.87 MPa m1/2, which is 2.8 times higher than pure HA. The lowest brittleness index 4.2 μm-0.5 for this sample confirms the transformation into tough material. The XRD pattern confirmed the presence of t-ZrO2 and m-ZrO2 phases. The characteristic of the surface that favours osteogenic bone formation was analysed in vitro, by immersing the sample in simulated body fluid (SBF) solution for 14 days. The apatite layers on the surface prove the osteoconductive nature and is analysed by FESEM-EDAX. Experimental results suggest that the addition of CSZ in FHA increased the toughness of the material suitable for load-bearing applications and confirmed the osteoconductivity.