Impact of A-Site Cation Deficiency on Charge Transport in La0.5−xSr0.5FeO3−δ

Abstract

The electrical conductivity of La0.5−xSr0.5FeO3−δ, investigated as a function of the nominal cation deficiency in the A-sublattice, x, varying from 0 to 0.02, has demonstrated a nonlinear dependence. An increase in the x value from 0 to 0.01 resulted in a considerable increase in electrical conductivity, which was shown to be attributed mainly to an increase in the mobility of the charge carriers. A combined analysis of the defect equilibrium and the charge transport in La0.5−xSr0.5FeO3−δ revealed the increase in the mobility of oxygen ions, electrons, and holes by factors of ~1.5, 1.3, and 1.7, respectively. The observed effect is assumed to be conditioned by a variation in the oxide structure under the action of the cationic vacancy formation. It was found that the cation deficiency limit in La0.5−xSr0.5FeO3−δ did not exceed 0.01. A small overstep of this limit was shown to result in the formation of (Sr,La)Fe12O19 impurity, which even in undetectable amounts reduced the conductivity of the material. The presence of (Sr,La)Fe12O19 impurity was revealed by X-ray diffraction on the ceramic surface after heat treatment at 1300 °C. It is most likely that the formation of traces of the liquid phase under these conditions is responsible for the impurity migration to the ceramic surface. The introduction of a cation deficiency of 0.01 into the A-sublattice of La0.5−xSr0.5FeO3−δ can be recommended as an effective means to enhance both the oxygen ion and the electron conductivity and improve ceramic sinterability.

Tuning Ternary Alloyed Nanoparticle Composition and Morphology by Exsolution in Double Perovskite Electrodes for CO2 Electrolysis

“…This possibly explains the lattice expansion with A-site non-stoichiometry. These results agree with the work by Merkulov et al They observed lattice expansion with A-site deficiency in La 0.5– x Sr 0.5 FeO 3−δ and ascribed it to the generation of oxygen vacancies in order to compensate for A-site vacancies to fulfill the electroneutrality requirements . In the literature, other studies have pointed out cation–oxygen bond rearrangement − upon creation of A-site vacancies, which can cause bond length enlargement, thus expanding the lattice.…”

“…These results agree with the work by Merkulov et al They observed lattice expansion with A-site deficiency in La 0.5−x Sr 0.5 FeO 3−δ and ascribed it to the generation of oxygen vacancies in order to compensate for A-site vacancies to fulfill the electroneutrality requirements. 40 In the literature, other studies have pointed out cation−oxygen bond rearrangement 41−43 upon creation of Asite vacancies, which can cause bond length enlargement, thus expanding the lattice. Thus, it seems that there is not a consensus on the mechanism that drives the lattice expansion upon the introduction of A-site vacancies.…”

Exploring the defect equilibrium and charge transport in electrode material La0.5Sr0.5Fe0.9Mo0.1O3−δ

“…For the sake of comparison, a similar plot for the La 0.5 Sr 0.5 FeO 3− δ composition taken from ref. 32 is presented in this figure, which demonstrates a substantially wider interval of oxygen content variation.…”

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

“…However, several grains seem to be much smaller compared to the others, which may indicate cation segregation phenomena. 44 Nevertheless, the EDX-determined elemental maps indicate all cations constituting the PBSCF compound are distributed uniformly over the sample surface. The actual chemical composition was also found to be close to the stoichiometric one: the average atomic percentages for Pr, Ba, Sr, Co, and Fe were estimated to be 22.9 ± 3.5, 12.3 ± 2.3, 11.8 ± 0.7, 41.3 ± 5.4, and 11.7 ± 3.1 atom %, respectively, which coincides (within the error limit) with the nominal metal content in PBSCF.…”