Entrapped Gas Effect in the Fast Firing of Yttria-Doped Zirconia

Compared to conventional sintering of Y₂O₃-doped ZrO₂ using a slow heating rate of 10°C/min, microwave sintering and fast firing using a rapid heating rate of about 500°C/min resulted in lower final sintered densities. It is attributed to the residual chlorine in commerical zirconia powders manufactured by the chloride process. By calcining at 1100°C for 1 h to remove residual chlorines from the powder compacts, near full densities (>99% of theoretical) could be obtained by both fast firing and microwave sintering.