Effect of microwave conditions on sintering of hydroxyapatite ceramics

Abstract

In this work, Hydroxyapatite (HAp) was sintered by microwave and compared with the sintered samples by conventional method. The power levels of microwave were 450, 600, 900 W and the sintering temperatures were in the range from 750 to 1000 °C without isothermal holding. It was shown that the using of higher power level at the same heating temperature increases the density of sintered samples. Samples sintered in microwave at 1000 ºC by 900 W power reached a higher density of 95 % compared to the conventional process (85 %), however in the case of using 450 W power, the densification trend was almost similar to the conventional one. HAp to TCP phase transformation was not detected at 1000 ºC; however, the preferred growth of (211) planes corresponded to circular morphology was observed. Microstructural observations showed larger grains (500 nm) and porosities (300 nm) in the traditional sintered samples compared to the samples, which were sintered by microwave (200 nm and 100 nm, respectively).