A novel mica-based compressive seal concept was examined at elevated temperatures under compressive stress to evaluate its stability. The "hybrid" mica compressive seals, composed of cleaved Muscovite mica and two compliant inter-layers, were reported earlier to have very low leak rates at 800 degreesC. In the present study, we examined the mid-term (similar to350-700 h) stability of the mica-based compressive seals with three different inter-layers: a low melting borosilicate glass, a glass ceramic material, and a metallic material. The 800 degreesC leak test results showed excellent stability for the three different inter-layers in air at a compressive stress of 100 psi as the leak rates remained almost unchanged during the test. Microstructural characterization of the interfaces showed very limited interfacial reaction or glass penetration at the glass/8YSZ substrate interface. The results clearly demonstrate the applicability of the mica-based compressive seals for solid oxide fuel cells. (C) 2003 Elsevier Science B.V. All rights reserved.