This study investigates the effect of composition on the atomic level structure and thermal characteristics of sealing glass for solid oxide fuel cells (SOFCs). The glass systems studied contain varying percentages of SiO2, Al2O3, SrO, La2O3, and B2O3; and the composition variables examined are SrO and B2O3. Atomic level parameters, including boron coordination number with silicon, the probability of boron coordination with silicon, and glass network connectivity are calculated. Thermal expansion coefficients, glass softening temperatures, and glass transition temperatures are measured by dilatometry. The glasses are then thermally treated at 700 degrees C for up to 1500 h in order to study their long term thermal stability at SOFC operating conditions. The resulting data show that the most desired glass composition is stable for at least 1500 h without devitrification and is a very promising sealant for solid oxide fuel cells. (C) 2013 Elsevier B.V. All rights reserved.