Characterization of Strontiumapatite Powders Prepared by Ultrasonic Spray-Pyrolysis Technique.

Abstract

Strontiumapatite (Sr10(PO4)6(OH)2; SrAp) powder was prepared by the ultrasonic spray-pyrolysis technique and was characterized. Three kinds of starting solutions with a Sr/P molar ratio of 1.67 were prepared by mixing Sr(NO3)2, (NH4)2HPO4 and HNO3; the concentrations of Sr2+ and PO43- were in the ranges of 0.10 to 0.50mol·dm-3 and 0.06 to 0.30mol·dm-3, respectively. These solutions were sprayed into the heating zone to prepare the SrAp powders. The heating zone was composed of two electric furnaces; the lower furnace served for the evaporation of the solvent from the droplets (400°C), the upper furnace for the pyrolysis of the precipitated metal salts (850°C). Easily sinterable SrAp powder was prepared by spray-pyrolysis from a starting solution containing 0.10mol·dm-3 of Sr2+ and 0.06mol·dm-3 of PO43-. The resulting powder was composed of spherical and solid particles filled with fine primary particles. This SrAp powder was thermally stable up to 1200°C. Even without calcination and grinding operations, the relative densities of the compacts fired at 1200°C for 5h attained maxima of -96%. The microstructure of the sintered compacts appeared to be uniform; the average grain size was -2μm.