PNNL

Abstract

The A-site calcium doped yttrium chromite was additionally doped with various transition metals on the B-site to improve the sintering, thermal behavior and electrical properties of these ceramics for future use as an interconnect material in high temperature solid oxide fuel cells (SOFC). With 10 % addition of Co, Cu, Ni, Fe, and Mn, the single phase orthorhombic perovskite structure remained stable over a wide range of oxygen partial pressures, as confirmed by X-ray diffraction. The substitution of Cu for chromium remarkably improved the sinterability and allowed full densification in air by sintering at 1400 degrees C. The substitution of Co and Ni significantly improved the electrical conductivity of yttrium chromites in both oxidizing and reducing environments. This was explained by the increase of charge carrier density with nickel and cobalt doping, as confirmed by Seebeck measurements. With 10% of nickel dopant, the electrical conductivity of Y0.8Ca0.2CrO3±d increased from 12 to 38 S/cm in air and from 2 to 15 S/cm in reducing atmosphere at 950 degrees C. Mn doping had a negative effect on the sintering and electrical conductivity.