Our lab uses magnetron sputter to deposit thin film electrolyte for solid oxide fuel cells (SOFCs) or protonic ceramic fuel cells (PCFCs). The perovskite structure of yttrium-doped barium zirconate (BZY) has higher ionic conductivity than yttria-stabilized zirconia (YSZ), the well-known electrolyte used in conventional SOFCs. The nanometer-thick BZY electrolyte reduces ionic resistance. The high proton conductivity enables operation in the mid-temperature region (≤ 600°C), resulting in increased efficiency and performance.