Journal of Power Sources 185 (2008) 401–410 Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour Reactivity between La(Sr)FeO 3 cathode, doped CeO 2 interlayer and yttria-stabilized zirconia electrolyte for solid oxide fuel cell applications Ana Martínez-Amesti a , Aitor Larra ˜ naga a,∗ , Lide M. Rodríguez-Martínez b , Andrés T. Aguayo a , Jose L. Pizarro a , Maria L. Nó a , Ander Laresgoiti b , Maria I. Arriortua a a University of the Basque Country (UPV/EHU), Faculty of Science and Technology, B. Sarriena S/N, 48940 Leioa, Vizcaya, Spain b Ikerlan-Energía, Centro Tecnológico, Parque Tecnológico de Alava, Juan de la Cierva 1, 01510 Mi˜ nano, Spain article info Article history: Received 14 February 2008 Received in revised form 21 May 2008 Accepted 8 June 2008 Available online 26 June 2008 Keywords: SOFC Reactivity Interlayer Doped ceria Lanthanum ferrite abstract Detailed X-ray diffraction (XRD) analysis of two different Sr-doped LaFeO 3 cathodes, YSZ electrolyte and two Sm/Gd-doped CeO 2 interlayer and their mixtures were used to evaluate the formation of undesired secondary reaction compounds. The analysis of room temperature X-ray diffraction data of the mix- tures indicates the crystallization of strontium and/or lanthanum zirconates between the cathode and the electrolyte materials and no detected reaction between the cathode and the interlayer materials. For all the ferrite mixtures a significant shift in the diffraction peaks is observed, which is the result of the unit cell volume expansion and contraction of the cathode (LSF) structures mixed with electrolyte (YSZ), and with interlayers (SDC, GDC), respectively. On the other hand, a complete solid solution was observed between the crystal structures of YSZ electrolyte and SDC or GDC interlayers. The observed cell modifications for the ferrite mixtures were the result of the incorporation of Zr and Ce, in the B and A type positions of the perovskite structure, respectively. The electrolyte/interlayer interface shows the presence of intermediate compositions at high temperature. The electrochemical studies show better results when a Sm-doped CeO 2 is inserted between the cath- ode and electrolyte material. The best result obtained is for the half-cell prepared with LSF-40 and SDC interlayer on YSZ electrolyte. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Solid oxide fuel cells (SOFC) are electrochemical devices that directly convert chemical energy, through an electrochemical reac- tion between a fuel and an oxidant, into electrical energy. The basic elements of the typical fuel cell consist of an electrolyte phase in intimate contact with a porous anode and cathode. SOFCs have exceptional potential as electric power generation systems, because of their high-energy conversion efficiency, which can reach up to 65%. In addition, SOFCs have many advantages such as multi-fuel capability or the simplicity of the system design. Actually, reasonably high power densities and long-term stability ∗ Corresponding author at: University of the Basque Country (UPV/EHU), Faculty of Science and Technology, Department of Mineralogy and Petrology, B. Sarriena S/N, 48940 Leioa, Vizcaya, Spain. Tel.: +34 946012599; fax: +34 946013500. E-mail address: aitor.larranaga@ehu.es (A. Larra ˜ naga). have been achieved for high temperature SOFC single cells using La(Sr)FeO 3 (LSF) as cathode and yttria-stabilized zirconia (YSZ) as electrolyte [1]. Some studies show an improved performance of the power densities with the incorporation of a Sm or Gd-doped CeO 2 layer between the Sr-doped lanthanum ferrite cathode and YSZ elec- trolyte [2]. One potential reason for this development is the enhanced oxy- gen surface exchange kinetics of ceria compared to zirconia [1] and another is that for LSF perovskites, the ceria acts as a reaction bar- rier, preventing the formation of poorly conducting phases (SrZrO 3 , SrFe 12 O 19 , and La 2 Zr 2 O 7 ) [3]. Preliminary studies show that the inclusion of Sm or Gd-doped CeO 2 (SDC, GDC) interlayer prevents the formation of strontium and lanthanum phases [4,5]. However, closer examination of the X-ray diffraction (XRD) data for the reacted LSF–(SDC/GDC)–YSZ mixtures revealed different small shift in the LSF peak positions, correspond- ing to an increase of LSF–YSZ or a decrease of LSF–(SDC/GDC) in the 0378-7753/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2008.06.049