Rapid pressure-less sintering of fine grained zirconia ceramics: Explanation and elimination of a core-shell structure

Abstract

Rapid pressure-less sintering of nanoparticle yttria-stabilized zirconia (YSZ) can result in the formation of a gradient structure characterized by an airtight layer at the surface and interconnected porosity inside the sintered compact. This structure constrains a sample from further shrinkage and limits its final density. In this study, we rapidly sintered green bodies prepared from four commercially available YSZ powder grades, all with a particle size of 60 nm, but with different chemical compositions. We have shown that all powders contained residual chlorine which is responsible for the above mentioned core-shell structure of rapidly sintered samples rather than low thermal conductivity of zirconia. The only sample without this gradient structure was prepared from the powder grade with an increased amount of binder that helped to reduce the chlorine content during binder burnout. The ultimate way for elimination of negative chlorine effect was annealing the sample at 1000 °C prior to rapid sintering.