Person:
García Alvarado, Flaviano

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First Name
Flaviano
Last Name
García Alvarado
URI
https://hdl.handle.net/20.500.14352/83095
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Area
Química Inorgánica
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2011 - 20172
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Author: Yuste, Mercedes × Subject: 546 ×

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Now showing 1 - 2 of 2
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    New perovskite materials of the La2-xSrxCoTiO6 series
    (Dalton Transactions, 2011) Yuste, Mercedes; Pérez Flores, Juan Carlos; Romero de Paz, Julio; Azcondo Sánchez, María Teresa; García Alvarado, Flaviano; Amador Elizondo, Ulises
    Substitution of La3+ by Sr2+ in the double perovskite La2CoTiO6 yields materials of the La2-xSrxCoTiO6 series showing a significant amount of trivalent cobalt ions when prepared at ambient atmosphere. The as-prepared compounds can be reduced in severe conditions retaining the perovskite structure while inducing the formation of a large amount of oxygen vacancies. The limit of aliovalent substitution in this series was found to extend up to x = 1. For substitution of La3+ up to 15% cobalt and titanium are ordered, though the order is progressively lost as x increases; for x ≥ 0.30 no ordering is observed as evidenced by magnetic measurements. The ability of these materials to present either cobalt ions in a mixed oxidation state or large amounts of anion vacancies depending on the atmosphere makes them interesting to be further investigated regarding their electrical and electrochemical properties, and hence, their usefulness in some electrochemical devices.
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    Defect chemistry, electrical properties and evaluation of new oxides Sr2CoNb1-xTixO6-δ (0≤x≤1) as cathode materials for Solid Oxide Fuel Cells
    (ChemSusChem, 2017) Azcondo, Teresa; Yuste, Mercedes; Pérez-Flores, Juan Carlos; Muñoz Gil, Daniel; García Martín, Susana; Muñoz Noval, Álvaro; Puente Orench, Inés; García Alvarado, Flaviano; Amador, Ulises
    The perovskite series Sr2CoNb1-xTixO6-δ (0≤x≤1) is investigated in the full compositional range to assess its potential as cathode material for solid state fuel cell (SOFC). The variation of transport properties and thus, the area specific resistances (ASR) are explained by a detailed investigation of the defect chemistry. Increasing titanium content from x=0 to x=1 produces both oxidation of Co3+ to Co4+ (from 0% up to 40%) and oxygen vacancies (from 6.0 to 5.7 oxygen atom/formula unit) though each charge compensation mechanism predominates in different compositional ranges. Neutron diffraction reveals that samples with high Ti-contents lose a significant amount of oxygen on heating above 600K. Oxygen is partially recovered on cooling since the oxygen release and uptake show noticeably different kinetics. The complex defect chemistry of these compounds, together with the compositional changes upon heating-cooling cycles and atmospheres produce, a complicated behaviour of electrical conductivity. Cathodes containing Sr2CoTiO6-δ display low ASR values, 0,13 Ωcm2 at 973 K, comparable to those of the best compounds reported so far, being a very promising cathode material for SOFC.