Advanced ceramic interconnect material for solid oxide fuel cells: Electrical and thermal properties of calcium- and nickel-doped yttrium chromites

The structural, thermal and electrical characteristics of calcium- and nickel-doped yttrium chromites were studied for potential use as the interconnect material in high temperature solid oxide fuel cells (SOFCs) and other high temperature electrochemical and thermoelectric devices. The Y0.8Ca0.2Cr1−xNixO3±δ compositions with x = 0–0.15 showed single phase orthorhombic perovskite structures between 25 and 1200 °C over a wide range of oxygen partial pressures. Nickel doping remarkably enhanced sintering behavior of otherwise refractory chromites, and densities 94% of theoretical density were obtained after sintering at 1400 °C in air with 15 at.% Ni. The thermal expansion coefficient (TEC) was increased with nickel content to closely match that of an 8 mol% yttria-stabilized zirconia (YSZ) electrolyte for 0.05 ≤ x ≤ 0.15. Nickel doping significantly improved the electrical conductivity in both oxidizing and reducing atmospheres. Undesirable oxygen ion “leakage” current was insignificant in dual atmosphere conditions. No interfacial interactions with YSZ were detected after firing at 1400 °C.