Phase analysis of sintered yttria–zirconia ceramics by x-ray diffraction

Determination of the amount of cubic and tetragonal phase in yttria–zirconia using high-angle XRD (x-ray diffraction) has been complicated by problems of resolution and interpretation. The evidence, from electron diffraction studies, for ac→tshear transformation also needs to be taken into account. Two compositions, a 3 and a 5.7 mol % Y₂O₃−ZrO₂, were sintered and thermally treated at different temperatures between 1450°and 1700°C. X-ray diffraction traces revealed the anticipated tetragonal (400) and (004) reflections. The region of the diffraction pattern that was thought to arise from the cubic phase could be best interpreted as a second tetragonal phaset'. The original amount of cubic phase computed from thet' reflections showed good agreement with the phase diagram of Scott. The lattice parameters of thet' phase were determined, and the volume of the tetragonal (t') unit cell was calculated.