Pore coalescence as an inherent problem in the sintering of zirconia nanoparticles

Abstract

This article investigates the densification behaviour of zirconia nanoparticle compacts sintered at high temperatures. It was shown that zirconia nanoparticle compacts exhibited pore growth and related density decrease after sintering at temperatures above 1100 °C. Extensive analytical testing was performed to elucidate this behaviour. The de-densification effect was explained as pore coalescence and swelling. Intensive grain growth at high sintering temperatures induced coalescence of residual pores that remained in the dense structure. The overpressure of a non-diffusing gas entrapped in coalesced pores resulted in their expansion and ceramics swelling. The ceramics swelling was modelled and compared with experimental data. This de-densification behaviour seems to be inherent to all nanozirconia compacts accompanied by large grain coarsening in a dense structure.