Solid oxide fuel cells (SOFCs) are considered to be one of the most promising energy conversion devices because of their high efficiency, flexibility with respect to fuel consumption and low environmental impact. At the present, a major technological challenge for the development of SOFCs is the reduction of their operation temperature to about 600-700 ?C in order to reduce the costs and increase the fuel cell lifetime. Reduction of temperatures leads to a decrease in harmful material diffusion and evaporation processes in the cells and promises reduced material costs for interconnects and peripheral high-temperature components. Nevertheless decrease the operation temperature lead to losses in cell performance mainly due to the ohmic drop in cell components. For the reduction of the operating temperature it is necessary to decrease the overall thickness of the SOFC. One of the vital SOFC components is the cathode. perovskite oxides are appropriate candidate because of their good features as solid oxide fuel cell SOFC cathodes. Concerning the cathode material, using a mixed ionic and electronic conducting material appears to be a promising way to transform the triple-phase boundary into a double contact that lead to lowering the cathode polarization. Using integrated oxide thin films for fuel cell design can reduce the size and cost of cells. Particularly, a simple planar thin film structure for the fuel cells is expected to work at a lower operating temperature than bulk cells due to a higher projected efficiency of ion traort. Thin films not only allow for the reduction of the operating temperature, but also allow considerable miniaturization of the entire system. In this thesis, La based perovskite oxide cathode, La 0.6 Ca 0.4 Fe 0.8 Ni 0.2 O 3 (LCFN), was prepared by sol-gel method. The X-ray diffraction (XRD) pattern with Rietveld analysis indicates that LCFN sample had an almost single phase with orthorhombic perovskite structure and Pnma space group. Electrical resistance has measured by four-point DC method from room temperature up to 800 ?C. Measurement electrical conductivity of the sample versus temperature at the air atmosphere showed that it increased by increasing temperature. Activation energy for electrical conductivity has been calculated by fitting the Arrhenius plot with experimental data. Then, LCFN thin films have been deposited on single crystal SrTiO 3 (100), (STO) substrates by Pulsed laser deposition in different pressures of oxygen flux 100, 200, 300, 400 mTorr to influence of oxygen partial pressure on films. Study of Phase structural and crystallinity, surface morphology and electrical properties of films with analysis X-Ray diffraction, atomic force microscopy (AFM) and electrical resistance measurements with four point method, respectively have been performed. The results from X-Ray diffraction films, indicated all films are epitaxial with preferential direction of the substrate. The AFM images of films showed a very smooth surface, with a RMS roughness of 2-3 nm . Increasing the partial pressure of oxygen lead to increase topography of nano-meter islands. The linear behavior of curve Ln?T versus 1/T, show that thermally activated hopping of small polarons is responsible for electrical conduction of the films and bulk sample. Also electrical conductivity relaxation (ECR) technique for determination surface exchange coefficient (K chem ) performed. The conduction change was sharp upon the sudden switch of oxygen pressure and followed an exponential relaxation curve, which fit well with a surface exchange-limited model that from it the determined. Keywords: Solid Oxide Fuel Cell, Cathode, Perovskite, Pulsed Laser Deposition, Thin Film, Electerical Resistance