Detailed X-ray diffraction (XRD) analysis of two different Sr-doped LaFeO3 cathodes, YSZ electrolyte and two Sm/Gd-doped CeO2 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 mixtures 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 CDC 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 Sin-doped CeO2 is inserted between the cathode and electrolyte material. The best result obtained is for the half-cell prepared with LSF-40 and SDC interlayer on YSZ electrolyte. (C) 2008 Elsevier B.V. All rights reserved.