Electrical characterization of highly titania doped YSZ

Andreas Kaiser, A. J. Feighery, D. P. Fagg, J. T. S. Irvine

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The defect fluorite region of the ternary system ZrO2-Y 2O3-TiO2 encompasses compositions which offer both, good electronic and oxygen ion conductivity which enable good catalytic activity for the direct oxidation of methane in a solid oxide fuel cell (SOFC). The electrical properties of compositions YxTiyZr1-(x-y)O2-x/2 (with x=0.15, 0.2, 0.25 and y=0.15, 0.18) were characterised in order to find the composition with highest ionic and electronic conductivity. High titanium dopant concentrations (Y) of 15 and 18 atom%, near the solubility limit of Ti4+ in the fluorite structure, have been introduced to achieve a high electronic conductivity at low oxygen partial pressure. The yttrium content x has been varied between 15 and 25 atom% to find the fluorite composition with the highest ionic conductivity for each titanium level. In the pO2-range from 0.21 to 10-13 atm the conductivity is predominantly ionic and constant over that range. The maximum ionic conductivity is 0.01 Scm-1 for the compositions, which contain 15 atom% yttrium. Substantial electronic conductivity is introduced into the system at low oxygen pressures below 10-3 atm via reduction of Ti4+ ions to Ti3+. The maximum electronic conductivity of 0.2 Scm-1 at 930°C has been measured for a sample with 18 atom% titanium. The slope of all log(σ) vs. log(pO2) plots follows a pO2-1/4-dependence
Original languageEnglish
Issue number3-4
Pages (from-to)215-219
Publication statusPublished - 1998
Externally publishedYes

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