Creep in Yttria‐ and Scandia‐Stabilized Zirconia

Compression creep measurements at constant load on ZrO 2 ‐6 mol% Sc 2 O 3 (grain size ∼1 μm), ZrO 2 ‐6 mol% Y 2 O 3 (grain size ∼17 μm), and heat‐treated ZrO 2 ‐6 mol% Sc 2 O 3 (grain size ∼2 μm) yield activation energies of 89, 86, and 74 kcal/mol, respectively. The creep rates are linearly proportional to the inverse square of the grain size of the material. A stress exponent, n , of 1.5 was found for the scandia‐doped zirconia and two regimes, with n =1 and 6, were found for the yttria‐doped zirconia. These data, supported by metallographic evidence, are interpreted as showing that n =1 is associated with cation diffusion control of creep, n =6 with local propagation of inter‐crystalline cracks, and n =1.5 with a transition region.