Improved ionic conductivity of zirconia-scandia with niobia addition

Abstract The ionic conductivity and the crystalline structure of ZrO 2 −10 mol% Sc 2 O 3 - x mol% Nb 2 O 5 solid electrolytes were investigated for x=0.25, 0.5 and 1. Dense specimens with relative densities higher than 95% were prepared by solid state reaction and sintered at 1500 °C for 5 h. Full stabilization of the cubic structure at room temperature was obtained for compounds with x=0.5 and 1, whereas the cubic and rhombohedric structures coexist for x=0.25. The highest ionic conductivity in codoped system was found for specimen containing 0.5 mol% niobium pentoxide, with the same order of magnitude as that of the parent solid electrolyte (zirconia-10 mol% scandia) in the high temperature range (above 600 °C). Preliminary investigation on phase stability shows that the isothermal conductivity of the new solid electrolyte remained constant up to 100 h at 600 °C. Niobium pentoxide addition was found to improve the overall ionic conductivity of zirconia-scandia solid electrolyte.