The Effects of Dopants and A:B Site Nonstoichiometry on Properties of Perovskite‐Type Proton Conductors

Investigations of perovskite‐type BaCeO 3 and SrCeO 3 with various dopants (Y, Gd, Nd, and Ni) indicate that their microstructures and electrical properties are strongly influenced by the type and amount of dopants. Grain growth and densification of sintered samples are influenced by dopant level and A:B site nonstoichiometry. The conductivity of BaCe 1 − x Y x O 3 − δ increases with the yttrium content in hydrogen and wet Ar, and exhibits a maximum in oxygen at an yttrium content of 10 to 20%. BaCe 0.8 Y 0.2 O 3 − δ has the highest conductivity in a hydrogen atmosphere: ∼ 1.54 × 10 − 2 Ω − 1 cm − 1 at 600°C, and ∼ 4.16 × 10 − 2 Ω − 1 cm − 1 at 800°C. The effect of BaO excess depends on the concentration of dopant. Compared with BaCe 0.95 Y 0.05 O 3 − δ , doped BaCeO 3 with BaO excess ( BaO ⋅ 0.90 CeO 2 ⋅ 0.025 Y 2 O 3 ) has a higher total conductivity in all atmospheres studied ( O 2 , H 2 , and wet Ar), whereas the conductivity of BaCeO 3 with excess BaO ( BaO ⋅ 0.85 CeO 2 ⋅ 0.05 Y 2 O 3 ) is lower than that of BaCe 0.9 Y 0.1 O 3 − δ . BaCeO 3 based materials have higher conductivities than those of SrCeO 3 based materials, whereas SrCeO 3 based materials show higher proton transference numbers.