Influence of a miscut of Y2O3-stabilized ZrO2 single crystals on the formation of La2Zr2O7 islands by a vapour-solid reaction

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 [ anti 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 [ anti 110] or [001] direction. The relative orientation and morphology of the LZO islands were investigated by AFM, XRD and TEM