Rare earth effect on conductivity and stability properties of doped barium indates as potential proton-conducting fuel cell electrolytes

► BaIn0.6Ti0.2Ln0.2O2.6 (Ln = Gd, Dy, Ho, Er, Yb, Lu) react with water vapor to form proton conductors BaIn0.6Ti0.2Ln0.2O2.6-n/2(OH)n. ► Preliminary stability tests show that the Ln compounds are stable under 3% CO2 atmosphere at 600 °C. ► BaIn0.6Ti0.2Yb0.2O2.6 shows the highest proton conductivity level at 400 °C (σH+ = 1.7 10− 3 S cm− 1).