Bifurcation in alumina plates produced by a phase transformation in central, alumina/zirconia thin layers

Alumina plates with a center, thin layer composed of Al2O3 and ZrO2 (equal volume fractions) have been produced by sequential slip casting. Central layers as thin as 4 μm were fabricated using a low solid content slurry, but were observed to segregate the two oxides due to segregation of the consolidated layers during slip casting. Thicker layers were homogenous. The ZrO2 tetragonal to monoclinic transformation generated residual, compressive stresses in the thin, center layer. Edge cracking and crack bifurcation was observed when the compressive layer thickness was ⩾ 25 μm.