Oxygen Electrode Kinetics and Surface Composition of Dense (La0.75Sr0.25)0.95MnO3 on YSZ

Abstract

Lanthanum strontium manganate (LSM) micro-electrodes with the nominal composition of (La0.75Sr0.25)0.95MnO3 were deposited on yttria stabilized zirconia (YSZ). The diameter varied from 20 – 100 μm and the thickness was kept constant at ca. 0.5 μm. Electrochemical characterization was carried out in situ at temperatures from 660 to 860 °C using controlled atmosphere high temperature scanning probe microscope (CAHT-SPM) set-up for measurements of impedance spectroscopy and potential sweep. The oxygen partial pressure, pO2, was varied. Further, ex situ surface analysis by time of flight secondary mass spectrometry (TOF-SIMS) and structure examination by scanning electron microscopy (SEM) were performed. Segregation of Sr and La oxides to LSM surfaces and Mn rich oxide to the three phase boundary (TPB) was observed. YSZ and LSM attract different oxides/impurities. The oxygen electrode kinetics are discussed in light of the surface compositions and compared with the literature on microelectrode and composite LSM-YSZ electrode kinetics.