Ceramic oxygen transport membrane (OTM) is a functional reactor medium to produce synthesis gas from carbon fuels and possibly capture CO_2 from exhaust gas. Sealants are needed to assemble OTMs with support metals to modules for their application in industrial process. Glass H based on the system BaO-CaO-SiO_2 commonly was used as a sealant at high temperatures. In this study, ceramic material BaSiO_3 (BS) was added to glass H in various amounts to increase the composite thermal expansion coefficient (CTE). Dilatometric tests were carried out to observe the influence of filler on CTE. The viscous behaviour of composite sealant was explored by hot stage microscopy to investigate optimal joining temperature. Joining tests were carried out with SrTi_(0.75)Fe_(0.25)O_(3-δ) (STF25) as OTM materials and two support metals, which were ferritic alloys Crofer22APU and Aluchrom in as-delivered and pre-oxidized condition. Helium leakage measurements were carried out for sandwiched samples joined by the composite sealant with 30 wt.% BS filler (HBS30) after different thermal treatments, and good gas-tightness was achieved on the samples joined under high temperatures 960℃ and 920℃. The analysis of x-ray computed tomography (CT) was employed and porosity with large pores was found. The cross-sections of the joints were analyzed by scanning electron microscopy (SEM). Glass sealant HBS30 displays good joining behaviour, and there is no crack at the two interfaces.
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