Nonstoichiometry, Defect Chemistry and Oxygen Transport in Fe-Doped Layered Double Perovskite Cobaltite PrBaCo2−xFexO6−δ (x = 0–0.6) Membrane Materials

Abstract

Mixed conducting cobaltites PrBaCo2−xFexO6−δ (x = 0–0.6) with a double perovskite structure are promising materials for ceramic semi-permeable membranes for oxygen separation and purification due to their fast oxygen exchange and diffusion capability. Here, we report the results of the detailed study of an interplay between the defect chemistry, oxygen nonstoichiometry and oxygen transport in these materials as a function of iron doping. We show that doping leads to a systematic variation of both the thermodynamics of defect formation reactions and oxygen transport properties. Thus, iron doping can be used to optimize the performance of mixed conducting oxygen-permeable double perovskite membrane materials.

Correlating High-Temperature Defect and Magnetic Structures with Anomalous Chemical Expansion in an Outstanding PrBa0.5Sr0.5Co1.5Fe0.5O6−δ Positrode

“…Another important influence of Fe dopants can be associated with the variable enthalpy of reaction depending on the actual cation coordination of the resulting oxygen vacancy . Still, the results of the recent work have proved that this phenomenon can influencenonstoichiometry variations in PrBaCo 2– x Fe x O 6−δ oxides only at quite low (<900 K) temperatures. Therefore, the only modification introduced into the defect formation model developed earlier for PBC was the site balance correction accounting for the presence of trivalent iron ions in the lattice, which do not exchange their electrons with other cations.…”

Thermodynamics of Formation and Disordering of YBaCo2O6-δ Double Perovskite as a Base for Novel Dense Ceramic Membrane Materials

“…In contrast with the double perovskite cobaltites RE BaCo 2 O 6-δ ( RE = La, Pr, Nd, Sm, Eu) with larger rare-earth ions, both YBC and GBC are characterized by somewhat lower cobalt disproportionation enthalpy of around 20 kJ∙mol −1 (as compared with ≈35 kJ∙mol −1 for RE BaCo 2 O 6-δ ). In addition, YBC and GBC possess significantly lower enthalpy of oxygen vacancy localization in the rare-earth layers of the double perovskite structure, around −100 kJ∙mol −1 against ≈−50 kJ∙mol −1 for RE BaCo 2 O 6-δ [ 13 , 27 ]. The strongly negative values of the localization enthalpy fitted for YBC are in line with the trend revealed recently in [ 27 ] which shows increasing preference for localization in the rare-earth layers with decreasing radius of the rare-earth cation.…”

“…The latter, on condition that the p O 2 - T -δ data set is sufficiently large and accurate, allows validating the defect structure model and evaluating the thermodynamics of defect interactions. Defect structure models are indispensable for describing and controlling many, if not most, target properties of nonstoichiometric oxides for energy applications, including the oxygen transport properties [ 13 , 14 ]. As with any kind of model, the best way of answering, with any certainty, the question of aptness of the defect structure model lies in finding the correlations between the modeling results and various physicochemical properties of complex oxides.…”

“…Most of the previous studies of RE BaCo 2 O 6-δ concerned their crystal structure [ 16 , 17 , 18 ], magnetic [ 17 , 19 , 20 ] and transport [ 21 , 22 ] properties, while their oxygen content, defect structure and thermodynamic properties were investigated primarily at high temperatures [ 15 , 23 , 24 , 25 , 26 ], with only a few recent works focused on the intermediate-temperature range [ 13 , 15 , 27 , 28 ]. In this respect, the object of this work, YBC, is no exception.…”

Progress in Developing LnBaCo2O5+δ as an Oxygen Reduction Catalyst for Solid Oxide Fuel Cells

“…Over the past few years, owing to its unique crystal structure, considerable efforts have been directed towards investigating the MIEC double perovskite oxides LnBaCo 2 O 5+δ (Ln = Lanthanide). These materials find potential applications across a multitude of domains, such as magnetism [15][16][17], SOFCs, proton-conductive ceramic fuel cells [18][19][20][21][22][23][24][25], water electrolysis [26][27][28], CO 2 electrolysis [29], chemical sensors [30][31][32], ceramic semi-permeable membranes [33][34][35], metal-air batteries [36,37], soot combustion [38], supercapacitors [39], photocatalysis [40], and solar-driven thermal storage [41,42]. Given the diverse requirements in terms of physicochemical properties for each application, this article will exclusively focus on novel strategies employed in advancing double perovskites for use as cathode catalysts in SOFCs.…”