Role of a sodium glassy binder on microstructure and electrical conductivity of beta-alumina-based gas sensors

Interactions between β-Al2O3 and a sodium aluminosilicate conductive glass, after thermal treatment at 900 °C, have been investigated on screen-printed gas sensors. Due to the high level of glass additions, the starting powder made of β/β″-alumina, underwent strong compositional modifications. SEM and TEM imaging, coupled with chemical analysis, evidenced the formation of nepheline and α-Al2O3 at the interface between β-Al2O3 and the glass. Impedance spectroscopy measurements revealed that the higher the glass content, the larger was the conductivity decrease because of these microstructural changes.