The oxygen tracer diffusion coefficient (D*) has been measured for 9 mol% scandia 2 mol% yttria co-doped zirconia solid solution, (Y2O3)(2)(Sc2O3)(9)(ZrO2)(89), using isotopic exchange and line scanning by Secondary Ion Mass Spectrometry. as a function of temperature. The values of the tracer diffusion coefficient are in the range of 10(-8)-10(-7) cm(2) s(-1) and the Arrhenius activation energy was calculated to be 0.9 eV; both valid in the temperature range of 600-900 degrees C. Electrical conductivity measurements were carried Out using 2-probe and 4-probe AC impedance spectroscopy. and a 4-point DC method at various temperatures. There is a good agreement between the measured tracer diffusion coefficients (D*, Ea = 0.9 eV) and the diffusion coefficients calculated from the DC total conductivity data (D-sigma Ea = 1.0 eV). the latter calculated using the Nernst-Einstein relationship. (C) 2009 Elsevier B.V. All rights reserved.