A key problem in the fabrication of planar solid oxide fuel cells is the sealing of the metallic interconnect to the ceramic electrolyte. The sealing material must be gas-tight, stable in different atmospheres at high temperature, chemically compatible with the other cell components and resistant to thermal stresses. Glass-ceramic sealants are good candidates because of their high mechanical properties and the possibility to use a wide range of chemical compositions to control some physical properties like viscosity or coefficient of thermal expansion (CTE). In this work, glass sealants were synthesized using a sol-gel route, which generally allows to obtain both homogeneity at a nanoscale and reduction of the processing temperature. The studied glasses were based on the system BaO-B2O3-Al2O3-SiO2 with varying amounts of CaO and MgO additions. Dilatometry, differential thermal analysis and hot-stage microscopy were the techniques used to determine optimal thermal treatment for sealing operation (880 A degrees C with a dwell time of 10 h). The thermomechanical properties of the sealants were improved after sealing by a thermal treatment transferring the sealant into a favourable partially polycrystalline state. Gas-tightness tests performed after joining and 100 h ageing treatment at 800 A degrees C under air of steel-sealant-steel assemblies highlighted that 4 of the selected glass chemical compositions remained impermeable. Joining degradations, crystalline phases evolution and CTE of these glasses were analysed. Electrical resistivities were larger than 10(5) Omega cm at 700 A degrees C. On the basis of these results, four glasses were identified as promising candidates for this application.