Tuning proton kinetics in BaCo<sub>0.4</sub>Fe<sub>0.4</sub>Zr<sub>0.2–<i>X</i></sub>Y<sub><i>X</i></sub>O<sub>3–<i>δ</i></sub> triple ionic-electronic conductors <i>via</i> aliovalent substitution
Journal of materials chemistry. A