Thermal-mismatch induced cleaving and spontaneous healing of zirconia dispersed Co1−xO

Co1−xO embedded with yttria-partially stabilized zirconia (Y-PSZ with 6 mol.% Y2O3) particles were prepared by a sintering route at 1600 °C for 1 to 100 h. Analytical electron microscopic observations indicated that the Co1−xO matrix of the air-quenched, but not slowly cooled, specimens were cleaved predominantly along {1 0 0} and {1 1 0} planes and were spontaneously healed by crack regression, pinching and the formation of epitaxial Y-PSZ and Co3O4 precipitates with relic voids. The Co1−xO cleaving can be attributed to thermal shear stress build up around the embedded Y-PSZ particles, whereas healing due to surface diffusion, exsolution, and oxidation under the influence of capillary force upon quenching.