Thermal and crystallization kinetics of yttrium and lanthanum calcium silicate glass sealants for solid oxide fuel cells

The crystallization kinetics of glass sealants is an essential parameter to check the suitability of glass as a sealant. The crystallization kinetic behavior of calcium borosilicate glasses were studied by Differential thermal analysis (DTA), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). These glasses were exposed for different heat treatment durations in oxidizing atmosphere at 800 and 900 °C. XRD results indicate the presence of La2SiO5 crystalline phase which increases the thermal expansion of the glasses. However, yttria doped calcium borosilicate glass (CaY) sample could not form any crystalline phase even after 10 h heat treatment at 900 °C. Moreover, the thermal expansion coefficient (TEC), viscosity values and fragility index of the glasses indicate that lanthanum doped calcium borosilicate glass (CaLa) might be a better glass sealant for solid oxide fuel cell as compared to CaY glass.

► Yttria doped calcium borosilicate glass (CaY) sample could not form any crystalline phase even after 10 h heat treatment.
► Addition of Y2O3 prevents the crystallization and enhances the thermal properties of the glasses.
► XRD results indicate the presence of crystalline phase in CaLa glass which increases its thermal expansion.
► The heat treated glasses show maximum values of TEC near crystallization region which is also the working temperature of SOFC.