The effects of surface modification on electrical characteristics in bulk, grain boundary and interface (electrolyte/electrode) of BaCe0.9Y0.1O3-delta were investigated, The Surface modification was performed by means of two processes: specimen was firstly irradiated by 10 keV Ar+ ion with dose of 1 x 10(18) ions/cm(2) and then exposed to air. The modified surface was investigated by elastic recoil detection analysis (ERDA) for quantitative analysis of hydrogen concentration on the surface and alternating current (AC) and direct current (DC) conductivity measurements, respectively, The ERDA results showed that hydrogen concentration and reaction rate on the modified surface increased. The increase of hydrogen concentration was explained in terms of the increase of proton due to interaction between oxygen vacancy formed by modification and H2O. In AC and DC electrical conductivity measurements, it concluded that the proton and electronic carrier generated on the surface by modification attributed to the increase of bulk, grain boundary and interface conductivity. (C) 2009 Elsevier B.V. All rights reserved.