High proton conduction in grain-boundary-free yttrium-doped barium zirconate films grown by pulsed laser deposition

Reducing the operating temperature in the 500–750 °C range is needed for widespread use of solid oxide fuel cells (SOFCs).
Proton-conducting oxides are gaining wide interest as electrolyte materials for this aim. We report the fabrication of
BaZr_0.8Y_0.2O_3−δ (BZY) proton-conducting electrolyte thin films by pulsed laser deposition on different single-crystalline
substrates. Highly textured, epitaxially oriented BZY films were obtained on (100)-oriented MgO substrates, showing the
largest proton conductivity ever reported for BZY samples, being 0.11 S cm⁻¹ at 500 °C. The excellent crystalline quality of
BZY films allowed for the first time the experimental measurement of the large BZY bulk conductivity above 300 °C, expected
in the absence of blocking grain boundaries. The measured proton conductivity is also significantly larger than the conductivity
values of oxygen-ion conductors in the same temperature range, opening new potential for the development of miniaturized
SOFCs for portable power supply.