EFFECTS OF VARIOUS METAL-OXIDE ADDITIONS ON SINTERING OF β-CALCIUM ORTHOPHOSPHAPIE PREPARED BY SPRAY-PYROLYSIS

Effects of various metal-oxide additions on sintering of ƒÀ -calcium orthophosphate (ƒÀ-Ca3(PO4)2) were examined. The metal-oxide additives used in this experiment were: (i) the monovalent metal oxides Li2O, Na2O and K2O; (ii) the divalent metal oxides MgO, CaO, SrO and BaO; (iii) trivalent metal oxides Al2O3 and Fe2O3; (iv) tetravalent metal oxides SiO2, TiO2 and ZrO2. The sintering of ƒÀ Ca3(PO4)2 was promoted only by the addition of Fe2O3; the relative density of the sintered compact with 10 mol% of Fe2O3 addition fired at 1070•Ž for 5 h attained 98.7%. INTRODUCTION The calcium orthophosphate (ƒÀ-Ca3(PO4)2) ceramics may be applicable to the bone and tooth implant materials. Since the mechanical strengths of such ceramics are required to be high enough for the practical uses, our attention has been directed toward the fabrication of the dense ƒÀ-Ca3(PO4)2 ceramics, using the easily-sinterable ƒÀ-Ca3(PO4)2 powder prepared by spray pyrolysis; 1 the relative density of the powder compact fired at 1070•Ž for 5 h attained 96.1%. More information on the effects of metal-oxide additions on sintering of ƒÀ-Ca3(PO4)2 is needed to fabricate the dense ƒÀ-Ca3(PO4)2 ceramics. Although the effects of some additives on sintering of ƒÀ-Ca3(PO4)2 have been conducted by Toriyama et al., 2,3 no systematical investigation has been carried out so far. This paper describes the effects of various metal-oxide additions on sintering of ƒÀ-Ca3(PO4)2. EXPERIMENTAL PROCEDURES The starting ƒÀ-Ca3(PO4)2 powder was prepared by spray-pyrolysing the mixed solutions of 0.9 mol•Edm-3 Ca(NO3)2 and 0.6 mol•Edm-3 (NH4)2HPO4 at 600•Ž, using an airliquid nozzle. The spray-pyrolysed powder was heated at 600•Ž for 1 h and then was