Highly dense and thermally stable BaCe0.5Zr0.3Y0.1A0.05 Zn0.05O3−δ (A = Gd, Sm) electrolyte for intermediate temperature solid oxide fuel cell (IT-SOFC)

Abstract

Perovskite-type polycrystalline proton-conducting BaCe_0.5Zr_0.3Y_0.1A_0.05Zn_0.05O_3-δ (A = Gd, Sm) has been synthesized using a solid-state reaction method for the application in intermediate temperature solid oxide fuel cell (IT-SOFC). These materials were characterized by X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and electrochemical impedance analysis (EIS). Rietveld analysis of the XRPD data shows that these materials crystallize in the cubic symmetry in the Pm-3 m space group. SEM image analysis confirms the well-crystallized high-density materials, and TGA shows these as thermally stable up to 900 °C. EIS measurements at 700 °C show the beneficial ionic conductivities. In wet 5% hydrogen, the ionic conductivities were 1.29 × 10⁻³ Scm⁻¹ and 5.95 × 10⁻⁵ Scm⁻¹ for BaCe_0.5Zr_0.3Y_0.1Gd_0.05Zn_0.05O_3-δ (BCZYGdZn) and BaCe_0.5Zr_0.3Y_0.1Sm_0.05Zn_0.05O_3-δ (BCZYSmZn), respectively. In contrast, the ionic conductivities of BaCe_0.5Zr_0.3Y_0.1Gd_0.05Zn_0.05O_3-δ (BCZYGdZn) and BaCe_0.5Zr_0.3Y_0.1Sm_0.05Zn_0.05O_3-δ (BCZYSmZn) in dry hydrogen were 1.30 × 10⁻³ Scm⁻¹ and 4.71 × 10⁻⁵ Scm⁻¹, respectively. The calculated activation energies in wet 5% hydrogen were 0.38 eV and 0.40 eV for BCZYGdZn and BCZYSmZn, respectively. Hence, both materials are promising electrolytes in IT-SOFC.