Thermal Properties of Na₂O-MgO-TiO₂-Al₂O₃-B₂O₃-SiO₂ Glasses and Prospects for Their Use for Sealing Solid Oxide Fuel Cells

Abstract

A series of Na₂O-MgO-TiO₂-Al₂O₃-B₂O₃-SiO₂ glasses promising as sealants for solid oxide fuel cells are prepared. The glassy state is confirmed by X-ray diffraction analysis, and the elemental composition is determined by inductively coupled plasma atomic emission spectroscopy. The coefficient of thermal expansion (CTE) is calculated from the dilatometric data; it varies within (69–77) × 10⁻⁷ K⁻¹ and increases with the MgO to Al₂O₃ concentration ratio. The CTE calculation by the Appen method gives the results that are underestimated by 5–8% relative to the experimental data. The temperature dependences of the heat capacity of the glasses are determined by differential scanning calorimetry and calculated using the Kopp-Neumann rule. Comparison of the calculated values with the experimental data shows that the Kopp-Neumann rule is observed for the systems under consideration with relatively high accuracy. The sensitivity of different methods in determination of the glass transition point has been evaluated.