Microstructure, chemistry, phase composition, and stress-induced transformability of abnormal grains in DC flash sintered 3 mol% yttria-stabilized zirconia

Document Type

Article

Publication Date

10-1-2026

Abstract

Abnormal grain growth was triggered by DC flash sintering in 3 mol% yttria-stabilised zirconia (3YSZ). The abnormal grains exceeded 100 µm in size and exhibited a tetragonal structure, as confirmed by X-ray diffraction and Raman spectroscopy. No spontaneous transformation to the monoclinic phase was observed in the sintered samples. Transmission electron microscopy revealed that the abnormal grains consisted of thin Y-lean and Y-rich lamellae, similar to those previously reported in the early stages of high-temperature decomposition of the non-transformable tetragonal ( t’ ) phase in zirconia with higher yttria contents. Electrochemically reduced 3YSZ is considered to mimic the behaviour of zirconia compositions with higher yttria contents. The coherency and small domain size of the lamellar structure provide additional stability, preventing spontaneous transformation of the abnormal grains to the monoclinic polymorph. Nevertheless, it is shown that transformation to the monoclinic phase can still be triggered by stress associated with an indentation crack.

Publication Source (Journal or Book title)

Journal of the European Ceramic Society

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