Hindawi Publishing Corporation Advances in Materials Science and Engineering Volume 2012, Article ID 346280, 6 pages doi:10.1155/2012/346280 Research Article Development of Alternative Glass Ceramic Seal for a Planar Solid Oxide Fuel Cell P. Lemes-Rachadel, 1 H. Birol, 1, 2 A. P. N. Oliveira, 1 and D. Hotza 3 1 Department of Mechanical Engineering (EMC), Federal University of Santa Catarina (UFSC), 88040-900 Florian´ opolis, SC, Brazil 2 CSEM Brasil Innovation Center, 30170-020 Belo Horizonte, MG, Brazil 3 Department of Chemical Engineering (EQA), Federal University of Santa Catarina (UFSC), 88040-900 Florian´ opolis, SC, Brazil Correspondence should be addressed to D. Hotza, dhotza@gmail.com Received 16 July 2012; Revised 12 September 2012; Accepted 29 September 2012 Academic Editor: Meilin Liu Copyright © 2012 P. Lemes-Rachadel et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. LZSA glass ceramic (LiO 2 -ZrO 2 -SiO 2 -Al 2 O 3 ) was tested for its thermomechanical compatibility as a sealing material with a stainless steel interconnect (AISI 430) of a planar SOFC. With this purpose, the densification and crystallization behavior of LZSA were investigated initially. It was observed that the material reached maximum relative density and shrinkage, respectively 95% and 17%, at 800 ◦ C, which corresponded approximately to the crystallization temperature of the material as evidenced by DTA analysis. In the next step, LZSA tapes were cast from slurries and prepared either as LZSA laminates or LZSA-steel bilayers. The densification behavior and microstructural features of cofired LZSA laminates and LZSA-steel bilayers were analyzed at 800 and 900 ◦ C. Maximum relative density and defect-free interfaces were observed for laminates and bi-layers cofired at 800 ◦ C, whereas increased porosity and detached bi-layer were the characteristics of the samples fired at 900 ◦ C. 1. Introduction Seal is one of the most critical components of a SOFC as it prevents the mixture of the fuel and the oxidizing gas in the cell, fuel leakage from the stack, and the possibility of short circuit with the metallic interconnect [1–5]. Therefore, an ideal seal is expected to be hermetic, electrically insulating, thermomechanically and chemically compatible with other cell components at high temperatures and over long periods of time [1–9]. Glass ceramics are so far the most common seal materials, not only since they fulfill the aforementioned requirements but also due to their modifiable compositions, by which the critical properties such as glass transition temperature (T g ), viscosity, coefficient of thermal expansion (CTE), and dielectric strength can be optimized [6–9]. Glass ceramic seals are a rigid type of seals, which are bonded to interconnector and electrodes by a chemical reaction unlike the compressive type of seals requiring an external force applied [1, 3, 9]. Therefore, adherence, cracking, and thermal expansion match are considered as the critical issues at the interfaces, which are strongly related to glass transition, crystallization, sintering temperatures (T g , T c , T s ), and CTE of glass ceramic seals [3]. Ideally, the seal is expected to wet the surface after glass transition (or glass softening) temperature and to reach to full density prior to crystallization [3]. Crystallization preceding complete wetting or densification is extremely undesired as it results in poor adherence and porosity; whereas its insufficiency also results in lack of mechanical integrity of the seal that is enhanced by the crystalline phase [3, 8, 9]. The major difficulty in developing glass ceramic seals for a specific application is the selection of proper glass composition, which is usually composed of network form- ers, network modifiers, and intermediate oxides [9]. Glass network formers are the main glass formers and the stable ones at/above 800 ◦ C are SiO 2 ,B 2 O 3 , or P 2 O 5 [10]. Glass network modifiers are alkali metal oxides such as Li 2 O, Na 2 O, K 2 O and they increase the thermal expansion, while reducing the glass softening temperature of the glass [9]. They should, however, be selected with utmost attention as they react with other cell components due to their high diffusion coefficients at SOFC operation temperatures [9].