Hydroxyapatite (HAp Ca 10 (PO 4 ) 6 (OH) 2 ) is very known to be a biomaterial and an absorbent for chromatography. In this study, HAp was agglomerated with anatase TiO 2 to manufacture thermal spray powders to improve the absorption activity of TiO 2 and then improve its photocatalytic activity. The microstructures and compositions of plasma sprayed TiO 2 , TiO 2 -10%HAp, TiO 2 -30%HAp and HAp coatings were investigated. Due to the low thermal conductivity of HAp compound, not all HAp particles fully melted even under the arc current of 800 A. Low temperature stable β-Ca 3 (PO 4 ) 2 was detected in the sprayed HAp coatings. The addition of HAp inhibited the phase transformation of anatase TiO 2 to rutile. Under the arc current of 600 A, the anatase content in the TiO 2 , TiO 2 -10%HAp and TiO 2 -30%HAp coatings was 10.6%, 20% and 42%, respectively. Although slightly decomposition of HAp to α-Ca 3 (PO 4 ) 2 was found in the TiO 2 -30%HAp coatings, it did not decompose to CaO and P 2 O 5 according to the XRD and EDAX analysis. With the increasing of the spraying distance from 70 mm to 110 mm, the anatase content in the TiO 2 -30%HAp coatings decreased from 34% to 17% under arc current of 700 A. The addition of the secondary gas of helium has no significant influence on the melting state of the TiO 2 -HAp feedstock powders.

The compositions and photocatalytic activity of plasma sprayed TiO 2 , TiO 2 -30%FeTiO 3 , TiO 2 -50%FeTiO 3 and FeTiO 3 coatings were investigated. The influence of FeTiO 3 compound on the photocatalytic activity of TiO 2 coating was clarified. The TiO 2 -30%FeTiO 3 coating sprayed under the arc current of 400 A had good photocatalytic activity because the coating did not contain the unfavorable Fe 2 TiO 5 phase. The relative deposition speed of TiO 2 -30%FeTiO 3 powder under the arc current of 400 A was approximate to 4 µm/pass. Although pure FeTiO 3 compound nearly did not show photocatalytic performance, the existence of FeTiO 3 could improve the photocatalytic activity of anatase TiO 2 if FeTiO 3 contacts coherently with it, which was explained using two-steps electron transfer model.