Effects of Ag-Doping on Microstructure and Mechanical Properties of Hydroxyapatite Films

Ag-doped hydroxyapatite films were deposited on a ZrO2 substrate using r.f. magnetron sputtering to improve the bioaffinity and mechanical properties of the hydroxyapatite. The resulting hydroxyapatite films exhibited a variation in their microstructure and mechanical properties relative to the Ag content. The variation in the (Ca, Ag)/P ratios suggested that some of the Ca2+ ions in the hydroxyapatite were replaced with Ag+ ions. After annealing at 800oC, the hydroxyapatite films showed a microstructure with crystalline nano-grains, whereas the Ag-doped hydroxyapatite films revealed the formation of crystallites embedded in the amorphous matrix. The hydroxyapatite films showed an average roughness of about 3~4nm, very smooth surface, and dense microstructure. The hardness and modulus of the films decreased with an increasing Ag content.