Analysis of the thermal-mechanical redox stability of Nb2TiO7 and Nb1.33Ti0.67O4 for SOFC application

• Published in: Ceramics international 2018-05, Vol.44 (7), p.8691-8694
• Main Authors: Thomas, T., Qi, H., Sabolsky, E.M., Liu, X., Zondlo, J.W., Hart, R.
• Format: Article
• Language: English
• Subjects: Dilatometry; Electrical conductivity; Materials Science; Nb1.33Ti0.67O4; Nb2TiO7; Processing; XRD
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2018.01.170

Nb2TiO7 and Nb1.33Ti0.67O4 was reported as a potential anode materials for Solid Oxide Fuel Cells (SOFCs) based on their stable reversible phase transformation and high electronic conductivity. A high-temperature redox dilatometry test was developed to monitor the linear expansion or contraction of Nb2TiO7 and Nb1.33Ti0.67O4 synthesized through a solid-state route. XRD analysis confirmed the phase purity. It was found that Nb2TiO7 contracts linearly up to 0.006% in a reducing atmosphere and this contraction is reversible in nature whereas Nb1.33Ti0.67O4 expands linearly up to 1.9% in an oxidizing atmosphere which is irreversible in nature at 800 °C. In addition, the electrical conductivity of the materials was analyzed in redox atmospheres. At 800 °C, Nb2TiO7 showed an electrical conductivity of 1.35 S/cm in forming gas (5%H2/95%N2) which increases to 85 S/cm upon the reduction of Nb2TiO7 to Nb1.33Ti0.67O4. This study emphasizes the importance of high-temperature redox dilatometry in the development of SOFC electrode materials.