Thermal, mechanical, and electrical properties of LSCo/mullite composite contact materials for solid oxide fuel cells. Issue 5 (28th June 2020)

• Record Type: Journal Article
• Authors: Chou, Yeong‐Shyung; Canfield, Nathan; Bonnett, Jeff F.; Hardy, John S.; Stevenson, Jeffry W.
• Is Part Of: International journal of applied ceramic technology. Volume 17:Issue 5(2020)
• Page Start: 2051
• Page End: 2061
• Publication Date: 2020-06-28
• Subjects: contact materials -- contact strength -- CTE -- electrical conductivity -- LSCo -- mullite; Ceramics -- Periodicals; Ceramics -- Technological innovations -- Periodicals; 620.1405
• DOI: 10.1111/ijac.13536
• Languages: English
• ISSNs: 1546-542X

Abstract

Abstract: Lanthanum strontium cobaltite (LSCo) is considered as a good candidate cathode contact material for solid oxide fuel cells, due to high electrical conductivity. However, LSCo has a very large coefficient of thermal expansion (CTE) than the cells and metallic interconnects. As a result, poor mechanical stability is expected during thermal cycling. To minimize the CTE mismatch, we investigate a composite approach involving mixing LSCo with an inert material of low CTE, such as mullite at volume fractions from 0.1 to 0.4. Composite's CTE shows a decreasing trend with increasing mullite volume fractions and is consistent with model predictions. X‐ray powder diffraction analysis of sintered LSCo/mullite composites exhibits no presence of other phases for samples aged for 500 hours at 800°C, indicating chemical compatibility. Electrical conductivity by a 4‐pt method shows a decreasing trend with increasing mullite content. Contact strength of as‐sintered and thermally cycled samples show that only the composite with 0.4 volume fraction has a measurable strength; the other composites have no strength. Overall, the composite approach is demonstrated in the LSCo/mullite system to lower the CTE and hence achieve thermal cycle stability. The addition of the inert phase to the LSCo matrix, however, also reduces the electrical conductivity.