Diffusion von Yttrium und Scandium in stabilisierten Zirkoniumdioxid

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Lower valence cations like Y3 (YSZ), Sc3 (ScSZ) or Ca2 (CSZ) on Zr4 sites introduce oxygen vacancies in zirconia and enlarge the stability range of the cubic phase in the concentration-temperature space down to low temperatures. This feature makes stabilised zirconia an oxygen ion conductor of prime interest for technical applications in solid oxide fuel cells. In the oxides with fluorite structure the slow cation diffusion governs diffusion creep and long-term ageing of the electrical (anionic) conductivity. The scope of this project is the study of the diffusion of yttrium in YSZ and of scandium and zirconium in ScSZ. Since both yttrium and scandium have only one stable isotope (89Y and 45Sc), it is impossible to use stable isotope techniques: Only radiotracer methods can be used in order to study the diffusion of yttrium or scandium. The materials for investigation should be both single crystalline and polycrystalline cubic YSZ (containing 8, 10, 18 and 24 mol % Y2O3) and polycrystalline tetragonal YSZ (containing 3 mol % Y2O3). In the case of ScSZ, only polycrystalline material containing 4 to 18 mol % Sc²O³ is available. The radioisotopes 88Y, 46Sc and 95Zr should are implanted and then diffused at temperatures between 1000 and 1800°C. The depth distribution of the radiotracer is analysed using classical sectioning techniques.