Sintering of translucent alumina

Alumina (Al2O3) specimens were made via powder injection moulding and then sintered, respectively, at three different temperatures, 1800 °C, 1850 °C and 1900 °C, for 30 min in a vacuum condition to achieve a desirable translucent level. The Al2O3 samples with different transparency were fabricated. The sintered polycrystalline alumina samples with desirable and undesirable transparency were characterized using an X-ray diffractometer (XRD) and a scanning electron microscope (SEM) attached with an energy dispersive X-ray microanalyzer (EDX). The relationship between the degree of transparency and the microstructure was investigated. It was found that the undesirable transparency was due to the presence of second phase along the grain boundaries, porosity and the range of pore sizes. Other properties of the samples, such as density, porosity, and Vickers hardness, were also measured. The optimum sintering temperature and time, that is 1850 °C for 30 min, were given for the fabrication of translucent alumina to achieve the highest density and minimum porosity.