New Gd-Zn co-doping enhanced mechanical properties of BaZrO3 proton conductors with high conductivity for IT-SOFCs

Highlights: • BZGZn was synthesized by a citric acid – EDTA combustion method. • BZGZn exhibited excellent chemical stability in CO₂ and water vapor. • Sinterablility and mechanical properties have a great improvement by co-addition. • The minor modification results in an enhancement of the total conductivities. - Abstract: We report here the synthesis and characterization of Gd-Zn co-doped BaZrO₃ proton conducting oxides, developed for IT-SOFCs. BaZr_0.8Gd_0.2−xZn_xO_3−δ (BZGZn, x = 0, 0.02, 0.04, and 0.06) samples were prepared and then sintered at 1300–1500 °C for characterization of chemical stability, sinterability, mechanical properties, and proton conductivity. Gd-Zn co-doping significantly improved the mechanical performance of BaZrO₃-based proton conductors: hardness and compressive strength increased, mainly resulting from improved relative density and the enhancement in grain boundary bonding strength. Importantly, Gd-Zn co-doping dramatically improved the total conductivity, which can achieved a higher conductivity of 2.54 × 10⁻³ S·cm⁻¹ at 750 °C. A typical anode-supported single cell with Gd-Zn co-doped BaZrO₃ electrolyte was tested using humidified hydrogen(∼3% H₂O) as fuel, presenting a high maximum power density of 282 mW·cm⁻² at 700 °C. Preliminary results demonstrated that Gd-Zn co-doping is an effective way and has a great improvement in sinterability, mechanical properties and conductivity, leading to high electrochemical performance of IT-SOFC.