Study of mass transport kinetics in co-doped Ba0.9Sr0.1Ce0.85Y0.15O3 − δ by electrical conductivity relaxation

• Ba0.9Sr0.1Ce0.85Y0.15O3 − δ (BSCY) was synthesized by solid-state reaction method.
• Electrical conductivity showed monotonic relaxation during oxidation/reduction.
• But during hydration/dehydration conductivity relaxation is non-monotonic twofold.
• Long-term conductivity measurement showed a gradual decrease.
• Reason might be the gradual appearance of rhombohedral phase in orthorhombic BSCY.

In this work, Sr2 + and Y3 + co-doped BaCeO3-based perovskite Ba0.9Sr0.1Ce0.85Y0.15O3 − δ (BSCY) was synthesized by solid-state reaction method, and its mass transport behavior was studied using electrical conductivity relaxation (ECR) measurements in 600–800 °C range with respect to variations in oxygen partial pressure (pO2) and water vapor pressure (pH2O). During oxidation/reduction process, the electrical conductivity showed a monotonic relaxation behavior and in − 2.65 ≤ log(pO2/atm) ≤ − 0.67 range the values of oxygen chemical diffusivity (D˜vO) and surface exchange coefficient (κvO) varied in 10− 6–10− 4 cm2 ⋅ s− 1 and 10− 4–10− 2 cm ⋅ s− 1 range, respectively. However, during hydration/dehydration process, the electrical conductivity showed a non-monotonic twofold relaxation behavior, and hydrogen, and oxygen chemical diffusivities (D˜iH) and (D˜vH) values were in 10− 5–10− 3 and 10− 6–10− 4 cm2 ⋅ s− 1 range, respectively, whereas hydrogen and oxygen surface exchange coefficient (κiH) and (κvH) values were in 10− 3–10− 2 and ~ 10− 4–10− 2 cm ⋅ s− 1 range, respectively. The comparison of H and O diffusivities of BSCY with BaCe0.85Y0.15O3 − δ (BCY) showed that during hydration/dehydration the diffusivities of BSCY were lower than that of BCY. The long-term electrical conductivity measurement for ~ 800 h in humidified conditions showed a gradual decrease, which might be due to the gradual appearance of rhombohedral phase in otherwise orthorhombic BSCY, as confirmed by the X-ray diffraction (XRD) measurements.