Phase composition of sputtered films from a hydroxyapatite target

Hydroxyapatite (HA) was coated onto a cellulose filter acting as a substrate from a crystalline HA powder target using radio-frequency magnetron sputtering at Ar pressure of 0.5–5.0 Pa and discharge power of 50–150 W. After coating, the films were heated to 700 °C to remove the substrate and the crystalline phases were identified using XRD. The Ca/P ratio of the films was analyzed using EDS. The films were composed of HA, β-tricalcium phosphate (TCP), β-calcium pyrophosphate (PYR) and CaO. The weight ratio of HA and the Ca/P ratio of the films decreased with increasing Ar pressure and were largest at 100 W of discharge power. After coating, the surface of the HA target was decomposed into α-TCP, β-TCP and CaO.