Preparation and properties of ceramic interconnecting materials, La 0.7Ca 0.3CrO 3− δ doped with GDC for IT-SOFCs

Abstract

One of the challenges for improving the performance and cost-effectiveness of solid oxide fuel cells (SOFCs) is the development of effective interconnect materials. A widely used interconnect ceramic for SOFCs is doped lanthanum chromite. In this paper, we report a doped lanthanum chromite, La 0.7Ca 0.3CrO 3− δ (LCC) + x wt.% Gd 0.2Ce 0.8O 1.9 (GDC) ( x = 0–10), with improved electrical conductivity and sintering capability. In this composite material system, LCC + GDC were prepared by an auto-ignition process and the electrical conductivity was characterized in air and in H 2. The LCC powders exhibited a better sintering ability and could reach a 94.7% relative density at 1400 °C for 4 h in air and with the increase of GDC content the relative density increased, reached 98.5% when the GDC content was up to 10 wt.%. The electrical conductivity of the samples dramatically increased with GDC addition until a maximum of 134.48 S cm −1 in air at 900 °C when the materials contained 3 wt.% GDC. This is 5.5 times higher than pure LCC (24.63 S cm −1). For the sample with a 1 wt.% GDC content, the conductivity in pure H 2 at 900 °C was a maximum 5.45 S cm −1, which is also higher than that of pure LCC ceramics (4.72 S cm −1). The average thermal expansion coefficient (TEC) increased with the increase of GDC content, ranging from 11.12 to 14.32 × 10 −6 K −1, the majority of which unfortunately did not match that of 8YSZ. The oxygen permeation measurement presented a negligible oxygen ionic conduction, indicating that it is still an electronically conducting ceramic. Therefore, it is a very promising interconnect material for higher performance and cost-effectiveness for SOFCs.