The diffusion couples of glass (30CaO-40SiO(2)-20B(2)O(3)-10La(2)O(3)) with high (Yttria stabilized zirconia) and low (titanium doped bismuth vanadate) temperature electrolytes have been prepared and heat-treated at 850 degrees C and 800 degrees C respectively for 5, 100 and 750 h to study the effect of heat-treatment duration on chemical reactivity and interface formation. The prepared diffusion couples have been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray dot mapping and electron probe microanalysis (EPMA). The XRD studies for coupled glass indicated different crystalline phase formation after prolonged heat-treatment duration of 750 h. Microstructural analysis of diffusion couples has not shown the presence of crystalline SiO2 (cristobalite) at the interface. In the present study, the efforts have been made to understand the interfacial reaction by considering different theoretical parameters associated with glass seal. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.043211jes] All rights reserved.