Effect of rare-earth ions doped in BaCeO3 on chemical stability, mechanical properties, and conductivity properties

The microstructure, lattice parameters, morphology, mechanical properties, and conductivity of BaCe0.9M0.1O2.95 (M=Gd, Nd, Sm, Y) were systematically investigated under different atmospheres (in air and in wet 5%H2–95%Ar). The XRD results indicated that all of the specimens sintered in air have orthorhombic symmetry, whereas BaCeO3 and BaCe0.9Gd0.1O2.95 decomposed into CeO2 and BaCO3 in their specimens. Secondary CeO2 and BaCO3 might adversely affect the conductivity of BaCeO3-based specimens. The maximum conductivity (σtotal,800 °c=6.46×10−3 S/cm) and minimum activation energy (Ea=52.3 kJ/mol) measured in air were observed for BaCe0.9Y0.1O2.95 among the BaCeO3-based specimens, Whereas in wet 5%H2–95%Ar, the maximum conductivity (σtotal,800 °c=9.20×10−3 S/cm) and minimum activation energy (Ea=55.6 kJ/mol) were measured. The difference in conductivity between the air and wet reducing atmosphere can be explained by the chemical stability. The mechanical properties of BaCe0.9M0.1O2.95 significantly depended on the doping element with the rare-earth oxide dopants affecting the structure stability, grain size, conductivity, thermal expansion, and the mechanical properties. Based on a comprehensive evaluation, BaCe0.9Y0.1O2.95 revealed good chemical stability and high conductivity and thus it is a promising candidate for a proton-conducing electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs).