Self-diffusion of calcium, yttrium, and zirconium in single-crystalline YSZ and CSZ ͑YSZ: yttria-stabilized zirconia; containing 10 to 32 mol % Y 2 O 3 ; CSZ: calcia-stabilized zirconia; containing 11 and 17 mol % CaO͒ was measured at temperatures between 960 and 1700°C. For zirconium and calcium diffusion, the stable isotopes 44 Ca and 96 Zr were used as tracers and the samples were analyzed with secondary ion mass spectrometry. In the case of yttrium diffusion, the radioactive tracer 88 Y was used and an abrasive sectioning technique was applied. Zirconium bulk diffusion is slower than yttrium and calcium bulk diffusion, and there is a nearly linear correlation of diffusion coefficient with cation radius. In YSZ, zirconium and yttrium bulk diffusivity are maximum for a stabilizer content of 10-11 mol %, while in CSZ both calcium and zirconium tracer diffusion are independent of the calcium content. The activation enthalpy of yttrium stabilizer bulk diffusion ͑4.2 eV͒ is, as in CSZ, slightly smaller than for zirconium bulk diffusion ͑4.5 eV͒. The yttrium dislocation pipe diffusivity is five to six orders of magnitude faster than the bulk diffusivity, and its activation enthalpy ͑3.5 eV͒ is also smaller than that of the bulk diffusion. From the activation enthalpy and from the concentration dependence of the cation bulk diffusion, it is concluded that the cation diffusion occurs either via free vacancies (V Zr 4 Ј in YSZ͒ or via bound vacancies (͓V Zr 4 ЈϪ2V O 2• ͔ x in CSZ͒.

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The diffusion of Co, Fe and Ni in single crystalline yttria stabilized zirconia (YSZ) containing 9.5 mol% Y 2 O 3 was studied in the temperature range between 1373 and 1673 K using secondary ion mass spectroscopy. Two different types of diffusion sources were used: thin oxide layers made by spin coating with a thickness of about 150 nm containing all three transition metals (Fe, Co and Ni) on YSZ single crystals and YSZ single crystals implanted with Ni (3 Â 10 16 ions cm À2 , 100 keV) at a mean depth of 45 nm. The determined diffusivities varied in the order D(Fe) < D(Co) < D(Ni). Activation energies for the diffusion of the elements were determined to be 2.7 AE 0.4 eV, 3.9 AE 0.3 eV and 3.8 AE 0.3 eV for Fe, Co and Ni (3.6 AE 0.5 eV for implanted Ni), respectively. For the latter ion, the value of the activation energy was practically independent of the type of Ni source. The values for all elements were lower by 1-2 eV than for the host cation (Y and Zr) diffusion.

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The signal to noise ratio in hyperfine spectra split by nuclear quadrupole interactions can be improved significantly by cross correlating experimental with theoretical spectra, especially for higher spins. In part I of the paper we present all technical details of this new approach and give examples for half integer and integer spins. In part I1 we elucidate the difficulties which arise in the attempt to reconstruct distribution functions of the largest component of the electric field gradient tensor V,, and the asymmetry parameter q from experimental line positions and profiles.

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