Thermal cycle stability is very important for glass seals in planar solid oxide fuel cell (pSOFC) applications. in the present study. thermal cycle stability of a thermally stable sealing glass is investigated using a sealing fixture from 150 degrees C to 700 degrees C. SS410 alloy with the TEC (thermal expansion coefficient) of 12.2 x 10(-6) K-1 (room temperature to 700 degrees C) is used to evaluate the effect of TEC mismatch on the thermal cycle stability. The leak rates increase with thermal cycles and appear to be two different stages. Microstructure examinations are performed to investigate the degradation mechanism of the thermal cycle stability. It is found that the sealing glass interacts chemically with the SS410 alloy and the formation of BaCrO4 new phase results in the rapid increase of the leak rates. (C) 2009 Elsevier B.V. All rights reserved.