Influence of Bi 2 O 3 on Crystalline Phase Content and Thermal Properties of Åkermanite and Diopside Based Glass-Ceramic Sealant for SOFCs Pornchanok Lawita 1, a , Apirat Theerapapvisetpong 1, 2, b and Sirithan Jiemsirilers 1, 2, c * 1 Research Unit of Advanced Ceramics, Department of Materials Science, Faculty of Science, Chulalongkorn University, Bangkok, 10330 Thailand 2 Center of excellence on Petrochemical and Materials Technology, Chulalongkorn University, Bangkok, 10330 Thailand a p.lawita@gmail.com, b apirat.t@chula.ac.th, c sirithan.j@chula.ac.th Keywords: SOFC, Sealant, Glass-ceramics, Barium-free Abstract. Solid oxide fuel cell (SOFC) is an electrochemical energy conversion device which is considered as clean energy source generator with reliability and relatively inexpensive production cost. One of the most important components for planar design SOFC is the hermetic seal that prevents fuel from leaking out of the assembled fuel cell stack. Glass-ceramics are attractive materials as sealing materials for this device. The expected coefficient of thermal expansion (CTE) of the glass-ceramic sealants should be between 9 and 13 x 10 −6 K −1 . Glass – ceramics based on åkermanite (Ca 2 MgSi 2 O 7 ) phase are reported their high CTE in the range of 10 to 11.3 x 10 −6 K −1 . In this study, glass compositions in the CaO-MgO-B 2 O 3 -Al 2 O 3 -SiO 2 system with varying amounts of Bi 2 O 3 from 0 to 10 wt. % were prepared by conventional melting and investigated their properties. The selected compositions were derived from ternary åkermanite–forsterite–anorthite phase diagram. Phase composition and quantitative phase analysis of glass–ceramics were examined by X-ray diffractometer. The onset of crystallization (T x ) and crystallization temperature (T c ) were measured by DTA. The thermal properties of bulk glass samples and heat treated samples at 900 ºC for 2 h which were glass transition temperature (T g ), dilatometric softening temperature (T s ), and coefficient of thermal expansion (CTE) were determined by dilatometer. Furthermore, the long-term stability of their CTE was investigated. The samples were continued to soak at 800 ᵒ C for 100 h and observed their change in CTE value. The results found that the åkermanite phase tended to increase with increasing amount of Bi 2 O 3 content. Introduction Solid oxide fuel cells (SOFCs) is a very efficient and clean source of energy. The primary function of a fuel cell is to produce an electricity by the electrochemical reaction between a fuel and an oxidant. Among the different designs of SOFCs, the planar design offers improved performance and power density relative to other designs. This design also offers simple fabrication and more structural reliability [1, 2]. Therefore, it requires hermetic sealing at the edge of different plates. Sealing is required along the interfaces between each cell and adjacent separator plate. Any leakage from the seal leads to decrease system performance and service life. It can also cause a local hot spot and widespread internal combustion within the stack, which leads to degradation of the device. Glass and glass-ceramics are considered as most suitable sealant because they are compatible with other components of SOFCs. They also exhibit good chemical stability in reducing and oxidizing atmosphere [3]. Moreover, the coefficient of thermal expansion of glass and glass- ceramics can be tailored to match with other fuel cell components, both of yttria stabilized zirconia (YSZ) and the metal interconnect. Many glass systems have been studied to develop glass-ceramics sealants for SOFCs [4, 5]. To develop a suitable glass-ceramic sealant, it is necessary to understand the sealing properties and the chemical interactions with other components of the cell. Several Key Engineering Materials Submitted: 2017-01-04 ISSN: 1662-9795, Vol. 751, pp 483-488 Revised: 2017-03-23 doi:10.4028/www.scientific.net/KEM.751.483 Accepted: 2017-04-11 © 2017 Trans Tech Publications, Switzerland Online: 2017-08-23 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (#91201475-09/06/17,09:20:12)