La0.hSro.hMnO~ thin films were prepared by a pyrosol technique. Films were characterized by x-ray diffraction and scanning electron microscopy analysis. Their electrical resistance was measured, and they showed a semiconductive behavior. The ~(i) curves were drawn at 800 and 900~ and impedance spectroscopy was performed during polarization. At low polarization, the oxygen reduction takes place at the triple contact points and is progressively delocalized over the whole surface of the electrode. At high polarizations, two components of the impedance have been identified. The first, at high frequency, is correlated with an atomic rearrangement of the electrode (either in the bulk or at the surface), which favors the electrode reaction. At low frequencies, the impedance has been attributed to a concentration impedance due to at least two adsorbed species.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 155.33.16.124 Downloaded on 2014-11-02 to IP
The ionic and electronic transport properties of La 0 gSr,,Ga,_MeO 3 _ (with Me = Fe or Cr and x = 0, 0.05, or 0.20) were studied by impedance spectroscopy in air (250 to 1000°C), high temperature (700 to 1000°C) ac conductivity measurements as a function of oxygen partial pressure (Po 2 ranging from air to about 10 -5 Pa), and ion blocking measurements (800 to 1000°C). Combination of data for the p-type and n-type conductivity contributions, obtained with the latter technique with ionic conductivities measured by impedance spectroscopy allowed us to estimate the ionic transport numbers of these materials as a function of Po 2 . Small Fe and Cr additions (5%) were found effective in increasing the p-type conductivity in air'with respect to the base material (x = 0), but large ionic domains could still be identified. For the 20% Fe or Cr doped samples the p-type conductivity in air is about the same or even exceeds the ionic conductivity. Tailoring of mixed ionic-electronic conductivity by compositional effects can be easily achieved in this family of materials.
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