Many coating methods of hydroxyapatite (HAp) on mechanically strong materials as substrates have been studied for increasing the mechanical strength of bioactive HAp. In this paper, coating of HAp on 3mol% Y2O3 partially stabilized zirconia (PSZ) substrate, a bioinert and highly strong and fracture-resistant material was studied utilizing a new plasma spraying method of a radio-frequency (r. -f.) thermal plasma. High contents of HAp in the coated layer were obtained by using larger HAp powders at smaller plasma powers and at lower substrate temperatures. The decomposition of the HAp phase was suppressed below the substrate temperature of about 1500°C. Adhesive strength of the coated HAp layer to the substrate was measured to be 5-14MPa. The surface of the coated layer had many pores. Thus, a possibility of coating HAp on the PSZ utilizing a r. -f. thermal plasma process was indicated. The HAp coated layer on the PSZ can be used as a mechanically strengthened and biocompatible material.
