Agglomerate and Particle Size Effects on Sintering Yttria‐Stabilized Zirconia

TLDR

The study examined initial, intermediate, and final sintering stages of fine‑crystallite yttria‑stabilized zirconia using powders of varying agglomerate size, including an agglomerate‑free sample, and compared initial‑stage kinetics to a larger‑crystallite calcia‑stabilized zirconia reference to test the Herring scaling law. Agglomerates reduced attainable green density, disrupted microstructure development, slowed initial‑stage sintering, and limited the advantage of fine crystallites on final‑stage sintering, whereas an agglomerate‑free powder reached 99.5 % theoretical density in a 1‑hour 1100 °C cycle—about 300 °C lower than for an agglomerated powder of equal crystallite size.

Abstract

The initial‐, intermediate‐, and final‐stage sintering of fine crystallite yttria‐stabilized zirconia was studied. Experiments were conducted on powder lots of differing agglomerate size and one specially prepared agglomerate‐free powder. Initial‐stage sintering kinetics were compared with a sintering study on larger crystallite size calcia‐stabilized zirconia to access the Herring scaling law. It was found that agglomerates limit attainable green density, interfere with the development of microstructure, impede initial‐stage sintering kinetics, and limit the potential benefit of fine crystallites on final‐stage sintering. An gglomerate free powder centrifuge‐cast to 74% green density was sintered to 99.5% of theoretical density in a 1 h 1100°C cycle, which is ∼300°C lower than necessary for an agglomerated but equal crystallite size powder.