Berlin 2008 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 23: Poster session

MM 23.12: Poster

Tuesday, February 26, 2008, 14:45–18:00, Poster B

Influence of a miscut of Y₂O₃-stabilized ZrO₂ single crystals on the formation of La₂Zr₂O₇ islands by a vapour-solid reaction — •Markus Andreas Schubert, Stephan Senz, and Dietrich Hesse — Max Planck Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany

The La₂Zr₂O₇-forming solid state reaction between ZrO₂ and La₂O₃ is of significance in view of solid oxide fuel cells degrading during operation by a reaction of this type, if ZrO₂ is the solid electrolyte and if a La₂O₃-containing ternary oxide cathode is used. In model experiments, La₂O₃ vapour at 1200 ^∘C directly reacts with an yttria-stabilized ZrO₂ single crystal (YSZ) forming La₂Zr₂O₇ (LZO) pyrochlore islands. Islands on YSZ(001) are square shaped and consist of four or eight slightly tilted domains. On YSZ(110), islands have a long edge along [110] and a short edge along [001] and four tilted domains. The tilt of the islands is a consequence of the misfit accommodation mechanism for a vapour-solid reaction with a large positive misfit of +5 %.

New experiments were performed to investigate the influence of the miscut angle on the favoured formation of special domains. YSZ(001) and YSZ(110) single crystals with a miscut angle of 4^∘ were used. For YSZ(001) substrates the surface was rotated around a [100] or [110] direction, respectively, and for YSZ(110) it was rotated around the [110] or [001] direction. The relative orientation and morphology of the LZO islands were investigated by AFM, XRD and TEM.