Co-doped La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3 ͑LSGMC͒ thin films were deposited on Pt͑200͒ substrates by pulsed laser deposition, and the crystal phases and microstructure properties of the films were examined using X-ray diffraction and scanning electron microscope. Depending on the deposition conditions of substrate temperature and oxygen partial pressure, the LSGMC thin films exhibited different phases and microstructures. Especially, the oxygen partial pressure strongly influenced the formation of secondary phases. The single phase of the LSGMC thin film with high density and no cracks was obtained at the optimum condition of substrate temperature of 750°C and at the oxygen pressure of 150 mTorr.Fuel cells are devices which convert the chemical energy stored in the atomic bonds of molecules into electrical energy that can be used to drive motors, illuminate light bulbs, charge batteries, or operate portable electronic devices. Solid oxide fuel cells ͑SOFCs͒, in particular, have attracted much attention because of their high energy conversion efficiency, flexibility in fuel selection, and clean operation with low NO x . 1,2 The principal components of SOFC are electrolyte, cathode, and anode. 3,4 The most extensively studied solid electrolyte for SOFCs are those based on yttria-stabilized zirconia ͑YSZ͒, which operates near 1000°C. Nowadays, decreasing the operating temperature of SOFC is one of the most important issues. Lower operating temperatures would have the advantages of a longer lifetime and cost reduction in fabrication and total system operation. There are two possible approaches to be considered: One is to reduce the thickness of the YSZ electrolyte layer, 5 and the other is to search for alternative electrolyte materials with higher oxygen ion conductivities. Therefore, a solid electrolyte with a high conductivity and in the form of a thin film is essential to achieve high power density at decreased temperature. 6,7 Nowadays, the two promising alternative electrolytes to YSZ which have been intensively studied in recent years are gadolinadoped ceria 8,9 and lanthanum gallate-based perovskite. 10-12 Doped LaGaO 3 with Sr for La and Mg for Ga ͑LSGM͒ has especially attracted considerable attention in recent years as a promising alternative electrolyte for lowering the operating temperature to ϳ600 to 700°C, which are currently too low to obtain adequate power densities with YSZ-based SOFCs. 6,10,11,13 However, there are problems associated with the stability of certain compositions of LSGM. It has also proved difficult to prepare pure single phase electrolytes of LSGM, in which additional phases including LaSrGaO 4 , La 4 Ga 2 O 9 , and SrLaGa 3 O 7 have been detected. 10,14-16 In addition, such phases raise doubts over the long-term durability of SOFCs with doped LaGaO 3 electrolytes, calling for much further research into this material. Meanwhile, some authors 11,17 found that additional doping of LSGM with smaller concentrations of transition metal ions of Co or Fe on the Ga site generate increased ion...
