Synthesis and electrical conductivity of perovskite Gd1−xCaxCrO3 (0⩽x⩽0.3) by auto-ignition process

In order to develop interconnect ceramics for intermediate temperature solid oxide fuel cells (IT-SOFCs), perovskite compounds, Gd1−xCaxCrO3 (x=0∼0.3), were prepared by an auto-ignition process and characterized. XRD analysis indicated that a single perovskite phase was obtained as Ca2+ content (x value) was lower than 0.3, while a second phase appeared at x=0.4. The lattice parameters of the unit cell decrease with increasing the substitution Ca2+ for Gd3+. The particle sizes of Gd0.7Ca0.3CrO3 powders are in the range of 20∼50 nm observed by TEM. The powders exhibited better sintering ability and could reach 94.8% relative density at 1400 °C for 4 h in air. The DC four probe technique measurement indicated that the electrical conductivities of the specimens increased with increasing Ca2+ content as x⩽0.3 but remarkably dropped when x=0.4, which might be attributed to the formation of the second phase with lower conductivity in the materials. Gd0.7Ca0.3CrO3 with a density of 94% showed an electrical conductivity of 24 Scm-1 in air and 7.5 Scm-1 in H2 (99.999%) at 700 °C respectively, which is about 50% more than that of the commonly used lanthanum chromite (La0.7Ca0.3CrO3). It will be suitable to be interconnect material for IT-SOFCs.