Effect of fabrication processes on orientation growth of La/HAP crystal

Hydroxyapatite doped with lanthanum (La/HAP) was prepared using co-precipitation method in this study. The effects of the concentration of La3+, stirring, aging time, hydrothermal treatment and calcination temperature on orient growth of the La/HAP were investigated. The phase composition of the La/HAP was analyzed by means of X-ray diffraction (XRD). The parameter (c/a) values of the orient growth of the La/HAP were calculated based on XRD data. The results show that the orient growth of La/HAP crystal is slightly affected by the concentration of La3+ in reaction solution whereas the growth of the crystal is closely related to the aging time and the calcination temperature. As the calcination temperature changes from 100 °C to 750 °C, the La/HAP crystal tends to grow along a-axis. The tendency of the crystal growth in the direction of c-axis becomes obvious at 70 °C as aging time extends. However, stirring appears to restrain the growth of crystal in c-axis. The hydrothermal treatment at 125 °C seems helpful for getting a low c/a value crystal and changes the La/HAP from needle shape to rod one. The direction of the c-axis of the La/HAP lattice seems to be the same as that of the long-axis of the La/HAP nanoparticles. The as-synthesized La/HAP powder mainly consists of HAP phase with slight La2O3 phase and has good thermostability.