Electrical and microstructural characterization of spinel phases as potential coatings for SOFC metallic interconnects

• Published in: Journal of power sources 2006-01, Vol.153 (1), p.114-124
• Main Authors: Qu, William, Jian, Li, Hill, Josephine M., Ivey, Douglas G.
• Format: Article
• Language: English
• Subjects: Applied sciences; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; Interconnect; Microstructure; Resistivity; Solid oxide fuel cell; Spinels
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2005.03.137

Several spinel samples, i.e., Mn x Cr 3− x O 4 (0.5 ≤ x ≤ 2.5), NiCr 2O 4 and CoCr 2O 4, were synthesized and studied in terms of phase analysis, density, electrical resistivity and thermal expansion behaviour. The spinel samples were generally single phase; exceptions included MnCr 2O 4 and Mn 0.5Cr 2.5O 4 with significant amounts of Cr 2O 3 and NiCr 2O 4 with trace amounts of NiO. Porosity, in general, decreased with increasing sintering temperature, except for Mn 0.5Cr 2.5O 4, which showed increasing porosity with increasing sintering temperature. NiCr 2O 4, CoCr 2O 4 and MnCr 2O 4, all had similar thermal expansion behaviour, with thermal expansion coefficients (TEC) ranging from 7.2–7.6 × 10 −6/°C. The TEC difference between the spinels and ferritic stainless steel was larger than the difference between the steel and chromia, which had a TEC of 9.6 × 10 −6/°C. The spinels and chromia exhibited semiconductor-type behaviour, with electrical resistivities decreasing with increasing temperature. Only Mn 2CrO 4 and NiCr 2O 4 had resistivities lower than Cr 2O 3 over the entire temperature range of testing (20–900 °C). For Mn x Cr 3− x O 4, resistivity decreased with increasing Mn content.