Sintering and Thermal Expansion Characterization of Al-Doped and Co-Doped Lanthanum Strontium Chromites Synthesized by the Pechini Method

Abstract

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 mum, and with a surface area of 3.5 m(2)/g, calcined at 800 T for I h, were obtained, After the Co-doped samples were heated at 1600 T 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 greater than or equal to 94% when sintered at 1600 degreesC for 20 h. The average thermal expansion coefficient (TEC) of this material in the temperature range from 50 to 1000 degreesC was 10.4 x 10(-6)/degreesC in air and 11.2 x 10(-6)/degreesC in a H-2 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, (C) 2002 Elsevier Science B.V. All tights reserved.