New viscous sealing glasses for electrochemical cells

Sealing is an ongoing concern for the development of pSOFC and pSOEC systems, mainly because gas tightness largely drives performance and is a critical key to develop these technologies. The main difficulties are due to the fact that gas tightness must be achieved at high temperature (≈800 °C) between metal/metal components, brittle ceramic/ceramic materials or combination of both. To tackle this question, we report on compliant glassy seals, which represent an interesting alternative to rigid seals. Indeed, their thermal properties, especially a suitable thermoplasticity, enable to prevent damages that occur during thermal cycling due to an intrinsic self-healing effect. In this context, a series of compliant sealing glasses based on K2O–Na2O–La2O3–B2O3–ZrO2–SiO2 system has been developed. These glasses have suitable viscosities around bonding (107.6 dPa·s at 900 °C) and operating temperature (106 dPa·s at 800 °C). They show also high resistance to crystallization and low interactions with the other cell components in spite of the low thermal characteristics. However, the viscosity has a great influence on the glass stability. This correlation has been investigated to get interesting compromise.