Development of rare earth element-doped Ni–Ba(Ce/Zr)O3 cermets for hydrogen-permeable membranes

Substitution of the rare earth element in Ni–Ba(Ce/Zr)O3 cermets (i.e., ceramic-metal composites) is considered a promising method for improving their hydrogen permeability, which could potentially improve the quality of cermet membranes. Microstructure and chemical properties of a rare earth element-doped cermet strongly depend on the type and content of the rare earth element. In this study, Ni–BaCe0.5Zr0.3M0.2O3 (M = Er, Sm) cermets were prepared by a citrate–nitrate gel combustion method. Analyses based on X-ray diffraction, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy indicated that Er and Sm have rather different solubilities in the Ni–Ba(Ce/Zr)O3 cermet and that when the amount of Sm exceeds the solubility limit, it reacts with the cermet, forming an impurity phase. Thermogravimetric analysis showed that the substitution of rare earth dopants in Ni–Ba(Ce/Zr)O3 improved the chemical stability of the cermets against CO2 and that Ni–BaCe0.5Zr0.3Er0.2O3 is chemically more stable than Ni–BaCe0.5Zr0.3Sm0.2O3 below 670 °C.

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