Lybye, D.

Mogensen, Mogens Bjerg

Zirconia compounds stabilised with rare-earth metal oxides like yttria, ytterbia and scandia are known to be good oxide ion conductors suitable as electrolyte material in solid oxide fuel cells. However. stabilised zirconia with high oxide ion conductivity is often only metastable at fuel cell operation temperatures and changes in temperature or oxygen partial pressure together with long-term operation are seen to induce partial destabilisation and even phase changes. In order to avoid these effects co-doping has proven helpful. Based on experimental data available in literature, we discus the effect of co-doping with smaller transition metal ions such as Ti-, Fe- and Mn-ions. Many of the ionic radii of the transition metal ions are too small compared to the host lattice ionic radius of zirconium. Here we explore the effect of a) the small ionic radii compared to the large ionic radii of the host lattice and b) the preferred six coordination compared to the desired eight-fold coordination of the fluorite structure. Particular interest is paid to the solubility of the transition metal ions and to the conductivity of the resulting material.Indium is not a transition metal but due to the size of the ionic radius of the metal, the effect of doping with In is also explored

Effect of transition metal ions on the conductivity and stability of stabilized zirconia

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