High-Temperature Creep of Polycrystalline CeO_2 Doped with Yttrium

摘要

High-temperature dead-load four-point creep was studied in Y-doped CeO_2 (Ce_(0.98)Y_(0. 02)O_(1.99) and Ce_(0.92)Y_(0.08)O_(1.96)) at Po_2 = 20.3 kPa and at temperatures between 1100 and 1300°C. At stress levels of 4.9-19.6 MPa, the stress exponent of the creep rate was m ≒ 1 where ε= σ~m(ε is the creep rate and σ is the stress), indicating diffusional creep. These creep rates and those reported in the literature were normalized at 4.9 MPa and 1μm and were compared with each other. As CeO_2 was doped substitutionally with Y, the creep rate decreased. The observed creep rate was several orders of magnitude smaller than the creep rate calculated from the oxygen diffusion coefficient using the Nabarro-Herring creep equation and was several orders of magnitude larger than the creep rate calculated from the expected cation diffusion coefficient. Cation grain boundary diffusion may control the creep of CeO_2 and Y-doped CeO_2 in the experimental range studied. A summary of the diffusion studies of CeO_2 is also given.