Sintering and thermal expansion characterization of Al-doped and Co-doped lanthanum strontium chromites synthesized by the Pechini method

The air-sintering and thermal expansion characteristics of Al-doped and Co-doped lanthanum strontium chromites synthesized by the Pechini method have been discussed as interconnect materials in high-temperature solid oxide fuel cells (SOFC). Fine perovskite powders with an average particle size of 0.24 μm, and with a surface area of 3.5 m2/g, calcined at 800 °C for 1 h, were obtained. After the Co-doped samples were heated at 1600 °C for 10 h, surface analysis showed the materials to have a densely packed structure with little sign of porosity. It was, however, found that large pores remained inside the samples. By energy dispersive X-ray analysis, it was clarified that the composition on the surface shifted to a B-site lean region by cobalt-vaporization. The La0.9Sr0.1Cr0.95Al0.02Co0.02O3 sample with a slight chromium-deficiency enhanced bulk diffusion sintering, and showed the relative densities to be ≥94% when sintered at 1600 °C for 20 h. The average thermal expansion coefficient (TEC) of this material in the temperature range from 50 to 1000 °C was 10.4×10−6/°C in air and 11.2×10−6/°C in a H2 atmosphere. The La0.9Sr0.1Cr0.95Al0.02Co0.02O3 powder synthesized by the Pechini method is the one that is suitable for use as the interconnect material for solid oxide fuel cells.