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

Polycrystalline monoclinic ( m ), tetragonal ( t ), and cubic ( c ) ZrO 2 , 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% Y 2 O 3 . 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.