Enhanced proton conductivity in zirconium-rich perovskites via barium diffusion-assisted low-temperature sintering

Abstract

This study demonstrated a Ba-diffusion-assisted sintering strategy that enables complete densification of BaCe_0.4Zr_0.4Y_0.1Yb_0.1O_3−δ (BCZYYb4411) electrolytes at substantially reduced temperatures (1200–1400 °C) compared to conventional methods (≥1600 °C). By controlling barium carbonate (BaCO₃) addition (0–6 wt%) in the anode layer, we facilitated natural diffusion of barium into the electrolyte during co-sintering, eliminating the need for external sintering aids or specialized processing techniques. Systematic microstructural analysis revealed that 2 wt% BaCO₃ addition resulted in optimal densification, with grain size increasing from ∼1 μm at 1200 °C to ∼10 μm at 1400 °C. X-ray diffraction confirmed phase purity across all sintering temperatures, while electrochemical impedance spectroscopy demonstrated significantly enhanced proton conductivity (∼5 × 10⁻³ S cm⁻¹ at 650 °C) and reduced activation energy (0.16 eV) for samples with 2 wt% BaCO₃ sintered at 1400 °C. The calculated area-specific resistance values from proton conductivity measurements reached as low as 0.2 Ω cm², representing a 67% reduction compared to reference samples without BaCO₃ addition and comparable to previously reported values for PCFCs sintered at much higher temperatures (1450–1500 °C). This processing innovation addresses fundamental challenges in zirconium-rich proton conductors while preserving their intrinsic electrochemical properties, offering a practical pathway toward more efficient and cost-effective protonic ceramic fuel cell manufacturing.