Electrical study of cathodic activation and relaxation of La_0,80Sr_0,20MnO₃

International audienceThe effect of cathodic activation of sprayed La0.8Sr0.2MnO3 (LSM) films has been studied by electrochemical spectroscopy impedance (EIS). LSM powder was prepared by a citrate route and X-ray diffraction analyses show a complete LSM crystallization without La2O3 or La(OH)3 as side products. Porosity and grain size estimated from scanning electronic microscopy gave values of 33% and 100 nm, respectively. EIS measurement was performed on a Pt/yttria-stabilized zirconia/LSM cell before and after a cathodic current load (300 mA/cm2) on LSM electrode. The relaxation process, which is time-dependent, has been investigated. A drastic decrease of the electrode resistance was noticed just after applying the cathodic current, but after 9 h at optimized valence configuration in air at 850 °C, the recorded polarization resistance gradually enhanced until it almost reached the initial value. The resulting diagrams have been fitted using a Gerischer associated with a resistor and constant phase elements. This simple method has permitted us to observe that only the electrode interfaces are modified by a cathodic activation and the microstructure remains nearly constant