Significantly Improved Proton Conduction in LaBaGaO4through Li-Doping

The La1–xBa1+xGaO4–0.5x (x ≤ 0.2) materials were previously reported to be proton conductors, but the relatively low conductivity, e.g., ∼4.0 × 10–4 S/cm at 600 °C, hindered their further practical applications. Herein, we show that the lithium substitution for gallium could significantly improve the proton conductivity, ∼1.12 × 10–3–6.38 × 10–3 S/cm over 350–600 °C, which was more than one order of magnitude higher than La1–xBa1+xGaO4–0.5x and comparable to the state-of-the-art BaCeO3-based materials. Such significantly improved proton conductivities were attributed to the obviously improved oxygen vacancy concentration coupled with a phase transition from the noncentrosymmetric structure (P212121) to a higher symmetry centrosymmetric cell (Pcca). These Li-doped LaBaGaO4 materials with remarkably high proton conductivities present a big advance and show great application prospects for being used as electrolytes for proton-conducting fuel cells.