Abstract
Investigations of perovskite‐type 
and 
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 
increases with the yttrium content in hydrogen and wet Ar, and exhibits a maximum in oxygen at an yttrium content of 10 to 20%. 
has the highest conductivity in a hydrogen atmosphere: 
at 600°C, and 
at 800°C. The effect of BaO excess depends on the concentration of dopant. Compared with 
, doped 
with BaO excess 
has a higher total conductivity in all atmospheres studied (
, and wet Ar), whereas the conductivity of 
with excess BaO 
is lower than that of 
based materials have higher conductivities than those of 
based materials, whereas 
based materials show higher proton transference numbers.