Effect of BaO addition on magnesium lanthanum alumino borosilicate-based glass-ceramic sealant for anode-supported solid oxide fuel cell Saswati Ghosh a , A. Das Sharma a , A.K. Mukhopadhyay b , P. Kundu a , R.N. Basu a, * a Fuel Cell and Battery Division, Central Glass & Ceramic Research Institute, Council of Scientific & Industrial Research (CSIR), Kolkata, India b Composite Division, Central Glass & Ceramic Research Institute, Council of Scientific & Industrial Research (CSIR), Kolkata, India article info Article history: Received 16 April 2009 Received in revised form 24 September 2009 Accepted 2 October 2009 Available online 11 November 2009 Keywords: Solid oxide fuel cell Glass sealants Crystallization Thermal expansion coefficient Leak-rate Nanoindentation abstract We report the effect of BaO addition on thermal, crystallization, electrical and mechanical behavior of the magnesium lanthanum alumino borosilicate glass-ceramics. The glass forming region has been found to be quite narrow with respect to BaO content. Casting and annealing of completely transparent and amorphous glasses within this system has been possible only at an optimum BaO content of 25 mol% without any La 2 O 3 and Al 2 O 3 . On further optimization of the developed glasses in terms of different borosilicate ratios, one of the developed compositions having MgO and BaO content of 22 and 25 mol% respec- tively, with a glass former ratio of 3 (SiO 2 :B 2 O 3 ) has been found to be quite promising in terms of its mechanical property, excellent joining, minimum chemical interaction and lowest leak-rate with the metallic interconnect such as Crofer22APU, and thus fulfills the major requirements for SOFC sealing application. ª 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. 1. Introduction Solid oxide fuel cells (SOFCs) provide advantages of high energy conversion efficiency, heat utilization and ability to use a variety of fuels due to their high operating temperature in the range between 800 and 1000  C [1,2]. However, the open circuit voltage obtained from a single cell of SOFC is only w 1 V. Therefore, for practical applications several such cells are generally stacked together to achieve a higher power output. Between the two designs (planar and tubular) for making a stack from such single cells, the anode-supported thin film electrolyte-based planar design has been adopted by most of the leading SOFC developers due to higher power density, involvement of cost-effective processing techniques, use of high chromium containing metal alloys (Ferritic steel) as its interconnect and gas manifolding and above all its operation at the intermediate temperature range of 750–800  C (IT-SOFC) [3,4]. However, for a planar SOFC stack, gas-tight seals must be applied along the edges of each cell and between the cell stack and gas manifolds in order to avoid intermixing of fuel gas (on anode side) and air (on cathode side). Development of such gas-tight and durable sealant is one of the major technological challenges for this design. Generally, the sealants for SOFC must meet the following requirements: (a) matching coeffi- cient of thermal expansion (CTE) with adjoining components, (b) high electrical resistivity to avoid short circuiting between different layers of the stack, (c) good thermo-chemical compatibility with relevant SOFC components (i.e., no harm- ful reaction with joining components), (d) high chemical stability and low vapor pressure in both reducing and * Corresponding author. Tel.: þ91 33 24733469; fax: þ91 33 24730957. E-mail address: rnbasu@cgcri.res.in (R.N. Basu). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he 0360-3199/$ – see front matter ª 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2009.10.006 international journal of hydrogen energy 35 (2010) 272–283