Zr AND STABILIZER TRACER DIFFUSION IN CALCIA- AND YTTRIA-STABILIZED ZIRCONIA

摘要

Tracer diffusion of yttrium and zirconium in single crystalline YSZ and CSZ (YSZ: yttria stabilized zirconia; containing 10 to 32 mol % Y_2O_3; CSZ: calcia stabilized zirconia; containing 11 to 17 mol % CaO) was measured at elevated temperatures. For zirconium and calcium diffusion, the stable isotopes ~(96)Zr and ~(44)Ca were used and the samples were analysed using secondary ion mass spectrometry (SIMS). In the case of yttrium diffusion, the radioactive tracer ~(88)Y was used and a sectioning technique was applied. The zirconium tracer diffusion is slower than the yttrium and the calcium tracer diffusion. The dependency of the diffusivity on the stabiliser concentration was evaluated with the following results: In YSZ, the zirconium tracer diffusivity decreases with increasing yttria content, but in CSZ it is independent of the calcium content. From the activation enthalpy (4.6 -5.4 eV) and from the concentration dependence of the cation diffusion, it is concluded that the cation diffusion occurs either via free vacancies (V_(Zr)~4 in YSZ) or via bound vacancies ([V_(Zr)~4-2V_O~(2*)]~x in CSZ).