Al2O3-glass composite seals are fabricated by tape casting Al2O3 and HGS glass powder mixtures with glass contents ranging from 20 to 60 wt%. Their leaking performance is evaluated for various temperatures, gas pressures and compressive loads. The seal with optimized glass content is subjected to thermal cycling and single-cell tests to investigate the viability of the seal. The sealing performance of the seal is significantly improved by increasing the glass content in the composite seal: the seal containing 50 wt% glass (AG50) shows the best sealing performance among the studied compositions. Increasing the testing gas pressure or decreasing the testing temperature and compressive load increase the leak rate of the seal. After 25 thermal cycles between 750 and 200 degrees C, the leak rate of the AG50 seal is still below 0.021 sccm cm(-1) under the conditions of 750 degrees C, a compressive load of 0.12 MPa and a testing gas pressure of 3.5 kPa to 10.5 kPa. Using the AG50 seal, a high open circuit voltage of above 1.16 V after 6 thermal cycles is achieved for a 10 x 10 cm(2) anode-supported single cell (active area of 9 x 9 cm(2)), which demonstrates the applicability of the AG50 seal in practical SOFC operations. (C) 2012 Elsevier B.V. All rights reserved.