بهينه سازي كاتد پيل سوختي اكسيد جامد دماي مياني بر پايه ي لانتانيوم

چكيده انگليسي :

Optimization of Lanthanum Based Cathode for Intermediate Temperature Solid Oxide Fuel cell Parisa Sohrabi p sohrabi@ph iut ac ir 2012 02 05 Department of Physics Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Dr Hadi Salamati Salamati@cc iut ac irAbstract Solid oxide fuel cells SOFCs are considered to be one of the most promising energy conversiondevices because of their high efficiency flexibility with respect to fuel consumption and low environmentalimpact At the present a major technological challenge for the development of SOFCs is the reduction oftheir operation temperature to about 600 700 C in order to reduce the costs and increase the fuel celllifetime Reduction of temperatures leads to a decrease in harmful material diffusion and evaporationprocesses in the cells and promises reduced material costs for interconnects and peripheral high temperaturecomponents Nevertheless decrease the operation temperature lead to losses in cell performance mainly dueto the ohmic drop in cell components For the reduction of the operating temperature it is necessary todecrease the overall thickness of the SOFC One of the vital SOFC components is the cathode perovskiteoxides 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 apromising way to transform the triple phase boundary into a double contact that lead to lowering thecathode polarization Using integrated oxide thin films for fuel cell design can reduce the size and cost ofcells Particularly a simple planar thin film structure for the fuel cells is expected to work at a loweroperating temperature than bulk cells due to a higher projected efficiency of ion transport Thin films notonly allow for the reduction of the operating temperature but also allow considerable miniaturization of theentire system In this thesis La based perovskite oxide cathode La 0 6Ca0 4Fe0 8Ni0 2O3 LCFN was prepared by sol gel method The X ray diffraction XRD pattern with Rietveld analysis indicates that LCFN sample had analmost single phase with orthorhombic perovskite structure and Pnma space group Electrical resistance hasmeasured by four point DC method from room temperature up to 800 C Measurement electricalconductivity of the sample versus temperature at the air atmosphere showed that it increased by increasingtemperature Activation energy for electrical conductivity has been calculated by fitting the Arrhenius plotwith 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 toinfluence of oxygen partial pressure on films Study of Phase structural and crystallinity surfacemorphology 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 thesubstrate 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 linearbehavior of curve Ln T versus 1 T show that thermally activated hopping of small polarons is responsiblefor electrical conduction of the films and bulk sample Also electrical conductivity relaxation ECR technique for determination surface exchange coefficient Kchem performed The conduction change wassharp upon the sudden switch of oxygen pressure and followed an exponential relaxation curve which fitwell with a surface exchange limited model that from it the determined Keywords Solid Oxide Fuel Cell Cathode Perovskite Pulsed Laser Deposition Thin Film ElectericalResista

سهرابي، پريسا

بهينه سازي كاتد پيل سوختي اكسيد جامد دماي مياني بر پايه ي لانتانيوم

پروسكايت , لايه نشاني ليزر تپشي , لايه نازك , مقاومت الكتريكي