Measurement of the Crystallographically Transformed Zone Produced by Fracture in Ceramics Containing Tetragonal Zirconia

During fracture of ceramics containing tetragonal zirconia particles, a volume of zirconia material on either side of the crack irreversibly transforms to the monoclinic crystal structure. Transformation zone sizes, measured using Raman microprobe spectroscopy, are presented for three sintered ceramics. In a single‐phase ZrO 2 −3.5 mol% Y 2 O 3 material, an upper bound measurement of 5 μm is obtained for the zone size. In the Al 2 O 3 /ZrO 2 composites studied, the zone size is deduced to correspond to ∼1 grain in diameter. On the basis of the monoclinic concentrations derived from the Raman spectra it is further concluded that only a fraction of the ZrO 2 grains within the transformation zone transform, providing indirect evidence for the effect of particle size on the propensity for transformation.