A stable bilayer electrolyte with high ionic conductivity was developed for intermediate-temperature solid oxide fuel cell operation. The bilayer structure improved the limited thermodynamic stability of bismuth oxides and prevented electronic conductivity of ceria-based oxides in reducing atmosphere. Bilayer electrolytes were formed by depositing thin and thick layers of erbia-stabilized bismuth oxide (ESB) on samaria-doped ceria (SDC) substrates, via pulsed laser deposition and dip-coating techniques. Scanning electron microscope (SEM) images of the ESB/SDC samples showed dense ESB layers and excellent adherence between both ESB and SDC phases. Interdiffusion between the two phases was not detected by X-ray diffraction and EDX. Measurements of the conductivity of SDC coated with ESB exhibited slightly higher total conductance than SDC.