Irradiation induced dislocations and vacancy generation in single crystal yttria stabilized zirconia.

摘要

A determination of the most effective method of introducing defect clusters and forming nanocrystals in single crystal Yttria Stabilized Zirconia (YSZ) to increase its oxygen ion conductivity for use in solid oxide fuel cell has been investigated using several techniques. High-energy particle irradiation using 800 keV electrons and 20 MeV protons and Ar+ and Xe ++ ion implantation promote the introduction of defects. Thermal annealing and temperature cycling were performed both ex-situ and in-situ in a TEM to study the dynamic recovery behavior of the defects introduced by irradiation and the nucleation and growth of nanocrystals.; This analysis found multiple outcomes to both light particle irradiation, with electrons and protons, and heavy charged particle irradiation, including Ar+ and Xe++. Electron irradiation produced very few vacancies, and therefore a very low dislocation density after high temperature annealing. The Xe++ and Ar+ irradiated samples show a high density of vacancy clusters. Evidence also shows nanocrystalline formation in Xe++ irradiated YSZ after a 20 minute anneal at 1040°C with grain sizes on the order of 10--50nm.; Defect clusters formed in samples exposed to 20.4 MeV protons with a fluence of 1.00 x 1013 p/cm2 and thermally annealed at temperatures between 800°C and 1000°C. The samples became polycrystalline after a 75 minute anneal with a grain size of approximately 20nm and remained polycrystalline throughout the 120 minute anneal.; Impedance spectroscopy measurements were conducted on proton irradiated samples with various annealing conditions. From the impedance results it is concluded that the minimum annealing conditions for a noticeable improvement in ionic conductivity are 1000°C for 2 hours and the 1200°C for 1 hour. These annealing conditions correspond to the conditions for nanocrystal formation as show by microstructural characterization. The proton irradiated YSZ ceramic samples annealed under these conditions were found to have slightly enhanced electrical properties compared to the baseline unmodified YSZ at high temperatures.