Successful seal design relies on good understanding of glass network structure and the corresponding impact on glass thermophysical properties. This study is focused on effects of nickel replacement of glass formers SiO2 and B2O3 and glass modifier SrO on SrO-La2O3-Al2O3-B2O3-SiO2 glass network structure and thermal properties. Glass structure local ordering was studied by Raman spectroscopy. Glass network connectivity was formulated to compare glass structure evolution with nickel addition for different compositions. Glass transition temperature and dilatometric softening temperature were evaluated by dilatometry. Glass thermal stability was studied by X-ray diffraction. Nickel behaves as a glass modifier in the studied glass system and decreases glass network connectivity. However, nickel can increase or decrease glass transition temperature and dilatometric softening temperature depending on the specific composition. Overall, nickel addition degrades glass thermal stability by increasing the amount of non-bridging oxygen atoms and devitrification. (c) 2008 Elsevier B.V. All rights reserved.