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 800°C, 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.