Sintering and Characterization of Polycrystalline Monoclinic, Tetragonal, and Cubic Zirconia

Polycrystalline monoclinic ( m ), tetragonal ( t ), and cubic ( c ) ZrO₂, sintered at 1500°C, were annealed in the cubic stability field and rapidly cooled to permit the displacive c → t ' transformation to occur in compositions containing 0–6 mol% Y₂O₃. The bulk fracture toughness of coarse-grained (> 25 μm) m , t ', and c zirconias were compared with conventionally sintered, fine-grained (typically less than 1 μm) materials. The ferroelastic monoclinic and tetragonal zirconias were more than twice as tough as paraelastic cubic zirconia.