Thermal stability of Ln 2 NiO 4Dd (Ln: La, Pr, Nd) and their chemical compatibility with YSZ and CGO solid electrolytes Alejandra Montenegro-Herna ´ ndez a,b , Jesu ´ s Vega-Castillo a,b , Liliana Mogni a,b , Alberto Caneiro a,b,c, * a Instituto Balseiro - Centro Ato ´mico Bariloche, 8400 San Carlos de Bariloche, Rı´o Negro, Argentina b Consejo Nacional de Investigaciones Cientı´ficas y Te ´cnicas CONICET, Argentina c Comisio ´n Nacional de Energı´a Ato ´mica CNEA, Argentina article info Article history: Received 22 June 2011 Received in revised form 16 August 2011 Accepted 20 August 2011 Available online 6 October 2011 Keywords: Ln 2 NiO 4þd SOFC Cathode YSZ CGO Reactivity abstract Thermal stability and chemical compatibility with electrolyte materials for Solid Oxide Fuel Cells (SOFC) have been studied on Ruddlesden-Popper nickelates Ln 2 NiO 4þd with Ln: La, Pr and Nd. Samples of each composition prepared by three different routes, were charac- terized by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Different microstructures were achieved by each preparation method. The thermal stability of these compounds was analyzed by annealing all the samples at 700 and 900  C in air. Pr 2 NiO 4þd (PNO) decomposes after 24 h of annealing at 700  C confirming its instability at these conditions. Evidences of chemical reaction between La 2 NiO 4þd (LNO) and both Ce 0.9 Gd 0.1 O 1.96 (CGO) and Zr 0.92 Y 0.08 O 1.96 (YSZ) were observed at 700 and 900  C, respectively. No decomposition or chemical reaction with YSZ or CGO were found for Nd 2 NiO 4þd (NNO) below 900  C. Nevertheless, reactivity with both electrolytes was found for this compound at 1000  C. The kinetics of these reactions strongly depends on the microstructure of Ln 2 NiO 4þd . Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction The search of new electrode materials is an active field of research. In particular, cathodes electrode materials for Solid Oxide Fuel Cells (SOFC) must fulfill several requirements such as high catalytic activity for oxygen reduction [1,2], and both thermal and chemical compatibility with solid electrolytes [3e6]. The most commonly used solid electrolytes are Zr x Y 1x O (xþ3)/2 for SOFC and Ce x Gd 1x O (xþ3)/2 for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC) [7e9]. La 0.8 Sr 0.2 MnO 3 (LSM) electronic conductor is the current cathode material compatible with Zr x Y 1x O (xþ3)/2 electrolyte [10,11], while mixed conductors such as cobaltites, (La,Sr) CoO 3d and and ferrocobaltites (La,Sr)Co 1x Fe x O 3d , are implemented on Ce x Gd 1x O (xþ3)/2 electrolytes [12,13]. LSM has the drawback of a low catalytic activity at temperatures around 500  C [14]. Despite the high catalytic activity for oxygen reduction of cobaltites and ferrocobaltites, their Thermal Expansion Coefficients (TEC) values are too high compared to those of YSZ and CGO electrolytes. In the last years, nickelates with chemical formula Ln 2 NiO 4þd (Ln: La, Nd, Pr) have received much attention because they display high oxygen exchange coefficient and similar TEC than Zr x Y 1x O (xþ3)/2 and Ce x Gd 1x O (xþ3)/2 [15e18]. These compounds belong to the Ruddlesden-Popper series * Corresponding author. Instituto Balseiro - Centro Ato ´ mico Bariloche, 8400 San Carlos de Bariloche, Rı ´o Negro, Argentina. Tel.: þ54 2944445274; fax: þ54 2944445299. E-mail address: caneiro@cab.cnea.gov.ar (A. Caneiro). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 36 (2011) 15704 e15714 0360-3199/$ e see front matter Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2011.08.105