In-doped BaZrO 3 (BZI) showed improved sinteractivity compared with Y-doped BaZrO 3 at the cost of reducing its total conductivity. With BZI-NiO as the anode, the fuel cell with BZI film electrolyte was fabricated and tested. Although the cell performance improved compared with the cell with thicker electrolyte, the BZI low conductivity limited the cell performance. With BZY-NiO as the anode, ionic diffusion of Y from anode to electrolyte happened and Y 3+ ions substituted the In 3+ in the electrolyte layer, which produced the final electrolyte film made of BZY instead of BZI. The ionic diffusion method took advantage of In-doped sample's high sinteractivity avoiding the negative effect of In on the electrolyte films, resulting in very promising fuel cell performance.