The surface Of Y2O3-stabilized ZrO2 (YSZ) is implanted with Cu and Mn in order to turn it into a mixed ionic electronic conductor (MIEC). Ar is implanted in order to examine the effect of damage only on the electrical properties. Mixed conductivity appears in the Cu- and Mn-implanted layers and is high enough to short-circuit the much thicker non-implanted YSZ layer, at T<250 degreesC. The electronic conductivity is due to hopping in the impurity band. There are two possible paths for hopping, one via the interstitial impurities and one via the substitutional ones. The faster path with an activation energy of similar to0.25 eV is attributed to the interstitials. It is, however, unstable and disappears under annealing at elevated temperatures. A relatively fast exchange of oxygen with YSZ is observed at temperatures as low as 215 degreesC through the implanted layer, where equilibrium is obtained, upon annealing, within similar to60 min. (C) 2004 Elsevier B.V. All rights reserved.