A high performance interconnecting ceramics for solid oxide fuel cells (SOFCs)

In order to improve the electrical conductivity and sintering capability of doped lanthanum chromite, the well-known interconnecting ceramic for solid oxide fuel cells (SOFCs), the composite material system La0.7Ca0.3CrO3–δ (LCC) + x wt.%Sm0.2Ce0.8O1.9 (SDC) (x = 0–10) has been investigated. The high sintering activity LCC and SDC powders used in this study were prepared by an auto-ignition process and the composite materials were made by pressing the mixture of LCC and SDC powders and then firing. The relative density of pellets sintered at 1400 °C for 4 h in air was 97.4% for only LCC powder and increased with the increase of SDC content, reaching 98.7% when the SDC content was up to 10%. The electrical conductivity of the samples dramatically increased with SDC addition and reached maximal value of 687.81 S cm− 1 in air at 800 °C for the sample with 5% SDC content, which is 38.7 times higher than that of pure LCC (17.77 S cm− 1). The conductivity in pure H2 at 800 °C was 3.57 S cm− 1, which is also higher than the pure LCC ceramics (2.5 S cm− 1). The average thermal expansion coefficient (TEC) at 30–1000 °C in air increased slightly with SDC content, ranging from 11.12 × 10− 6 K− 1 to 12.46 × 10− 6 K− 1. We assume that there is negligible oxygen ion conduction. Such an assumption makes us state that it is still an electronically conducting ceramic. The above results demonstrate that it is a very promising interconnect material for intermediate temperature SOFCs.