A-site non-stoichiometric materials Sr1.5LaxMnO4 (x = 0.35, 0.40, 0.45) are prepared via solid state reaction. The structure of these materials is determined to be tetragonal. Both the lattice volume and the thermal expansion coefficient reduce with the decrease of lanthanum content. On the contrary, the conductivity increases and the maximum value of 13.9 S cm(-1) is found for Sr1.5La0.35MnO4 at 750 degrees C in air. AC impedance spectroscopy and DC polarization measurements are used to study the electrode performance. The optimum composition of Sr0.5La0.35MnO4 results in 0.25 Omega cm(2) area specific resistance (ASR) at 750 degrees C in air. The oxygen partial pressure measurement indicates that the charge transfer process is the rate-limiting step of the electrode reactions. (C) 2011 Elsevier B.V. All rights reserved.