Fabrication And Property Of Lanthanum Silicate Used For Electrolyte Of Solid Oxide Fuel Cell

Solid oxide fuel cell (SOFC) is an energy conversion device that can directly convertchemical energy into electric energy, compared to the conventional energy conversion device.The SOFC has some promising applications in various fields due to its advantages, such ashigh energy conversion efficiency, all solid state structure, low pollution, low noise andenvironment friendly. The main components of solid oxide fuel cells are cathode, anode andelectrolyte, and the electrolyte is the most critical components, its performance directlydetermines the working temperature and operation performance of the battery. Apatite-typelanthanum silicon compound has a high conductivity at low temperatures. The use ofapatite-type lanthanum silicon compound as a solid oxide fuel cell battery can increase theconversion efficiency and reduce the working temperature. It can solve the problems due tohigh temperature, i.e., battery parts connection, packaging and other issues. Therefore, recentstudies on apatite type lanthanum silicon compound as a solid electrolyte fuel cell material areof great significance and importance.In this thesis, apatite lanthanum silicate and apatite lanthanum silicate mixed withmagnesium powder were prepared via a high-temperature solid state reaction at1450℃. Thecrystal structure of the powder was determined by X-ray diffraction. The lanthanum silicateelectrolyte coating and the apatite-type lanthanum silicate electrolyte mixed with magnesiumcoating were fabricated by atmospheric pressure plasma spraying, and the coatings weresubsequently treated by annealing. The coating surface of apatite-type lanthanum silicatemixed with magnesium was treated in a strong pulsed high energy electron beam flow devicein order to investigate the change of porosity. The crystal structure and surface morphology ofthe coatings were characterized by X-ray diffraction and scanning electron microscopy (SEM).The porosity of the coating was examined by mercury injection apparatus. The conductivityof the coating was measured by AC impedance method. The conductivity of the lanthanumsilicate electrolyte coating prepared is2.83×10-3S/cm at800℃. The conductivity of Mgdoped apatite-type coating lanthanum silicate electrolyte is9.68×10-3S/cm at800℃. Theconductivities of lanthanum silicate electrolyte coating and Mg doped apatite-type lanthanumsilicate electrolyte coating treated at a strong pulsed high energy electron beam flow are 6.78×10-3S/cm and1.24×10-2S/cm at800℃, respectively.