The TEC of the commercially-available SOFC sealant used in this study is 12.6 ppm K−1, which is reasonably-matched with that of the main cell structure: YSZ (10.5 ppm K−1), Ni-YSZ (12.5 ppm K−1), LSTN-based layer (11–12 ppm K−1) and STS (11.2 ppm K−1)29,30.