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      Electronic Percolation Threshold of Self-Standing Ag-LaCoO 3 Porous Electrodes for Practical Applications

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          Abstract

          Perovskite LaCoO 3 materials have various applications, from selective permeable membranes and gas sensing devices to water splitting applications. However, the intrinsic electrical resistivity of the perovskite limits the applicative potential. To overcome that, Ag powder was used with LaCoO 3 to obtain porous composite electrodes with enhanced conductivities. For that, a series of composite Ag-LaCoO 3 powders were prepared into pellets and pre-sintered at various temperatures up to 1000 C. Their structural properties and morphology were investigated by X-ray diffraction and scanning electron microscopy. The electronic transport of compacted specimens was studied by impedance spectroscopy. The results indicate that the presence of Ag acts as pre-sintering additive to obtain porous electrodes, with porosity values as high as 40% at 50 vol. % Ag. Moreover, the overall electrical resistivity of the composite electrodes varied well over four orders of magnitude. The results are discussed within the generalized Bruggeman theory for effective media comprising arbitrarily shaped metallic and semiconducting inclusions.

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          Most cited references 44

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          Giant negative magnetoresistance in perovskitelike La2/3Ba1/3MnOx ferromagnetic films.

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              Charge-Carrier Dynamics in Organic-Inorganic Metal Halide Perovskites.

               Laura Herz (2016)
              Hybrid organic-inorganic metal halide perovskites have recently emerged as exciting new light-harvesting and charge-transporting materials for efficient photovoltaic devices. Yet knowledge of the nature of the photogenerated excitations and their subsequent dynamics is only just emerging. This article reviews the current state of the field, focusing first on a description of the crystal and electronic band structure that give rise to the strong optical transitions that enable light harvesting. An overview is presented of the numerous experimental approaches toward determining values for exciton binding energies, which appear to be small (a few milli-electron volts to a few tens of milli-electron volts) and depend significantly on temperature because of associated changes in the dielectric function. Experimental evidence for charge-carrier relaxation dynamics within the first few picoseconds after excitation is discussed in terms of thermalization, cooling, and many-body effects. Charge-carrier recombination mechanisms are reviewed, encompassing trap-assisted nonradiative recombination that is highly specific to processing conditions, radiative bimolecular (electron-hole) recombination, and nonradiative many-body (Auger) mechanisms.
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                Author and article information

                Journal
                Materials (Basel)
                Materials (Basel)
                materials
                Materials
                MDPI
                1996-1944
                25 July 2019
                August 2019
                : 12
                : 15
                Affiliations
                [1 ]National Research and Development Institute for Cryogenics and Isotopic Technologies—ICIT Rm. Vâlcea, 4th Uzinei Str., P.O. Box 7 Râureni, 240050 Vâlcea, Romania
                [2 ]Acad. Evgeni Budevski Institute of Electrochemistry and Energy Systems, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl.10, 1113 Sofia, Bulgaria
                Author notes
                Article
                materials-12-02359
                10.3390/ma12152359
                6696329
                31349536
                © 2019 by the authors.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

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