Layered Perovskites BaM2In2O7 (M = La, Nd): From the Structure to the Ionic (O2−, H+) Conductivity

Abstract

The design of new oxide compounds that can be used as oxygen- or proton-conducting electrolytes for solid oxide fuel cells is actively in progress. Despite the intensive research activities regarding electrolytes with perovskite/fluorite structures, the search for other structural alternatives is of paramount importance. In this study we focus on a novel material with significantly improved properties for the electrochemical purposes. The two-layered BaNd2In2O7 perovskite with a Ruddlesden–Popper structure was investigated as a protonic conductor for the first time. In detail, its local structure, water uptake, and the ionic (O2−, H+) conductivity were comprehensively studied. The nature of rare-earth elements (M = La, Nd) in the structure of BaM2In2O7 on the structural and transport properties was revealed. The presented analysis showed that the composition of BaNd2In2O7 is nearly pure proton conductor below 350 °C. This work opens up a new way in the design of protonic conductors with double-layered perovskite structure.

Oxide Ion Conduction, Defect Chemistry, and the Conducting Mechanism in Ruddlesden–Popper La2–xMxBaIn2O7–0.5x (M = Ca, Sr, Ba)

“…As reported in Tarasova et al’s work, , protonic conduction was evidenced for the parent La 2 BaIn 2 O 7 material under 400 °C. In the present work, to study the proton conduction properties of these acceptor-doped La 2 BaIn 2 O 7 materials, the electrical conductivities of the selected composition of La 1.7 Ba 1.3 In 2 O 6.85 were also recorded under the wet condition at high oxygen partial pressures, and the results are provided in Figure S3a–d.…”

“…Then, numerous studies applying a doping strategy to further improve its oxide ion conductivity have been carried out by different research groups. − As to the La 2 BaIn 2 O 7 material, the La 3+ and Ba 2+ cations also have ordered distributions in the rock salt layer and the perovskite layer, respectively, as shown in Figure d, due to the large ionic radius difference between La 3+ (1.216 Å) and Ba 2+ (1.47 Å) for CN = 9, and this material was reported even more early than NdBaInO 4 . However, until more recently, the protonic conduction was reported for the parent (La/Nd) 2 BaIn 2 O 7 materials by Tarasova et al , They claimed that the (La/Nd) 2 BaIn 2 O 7 materials demonstrated nearly pure protonic conductivity below 350 °C, and no obvious oxide ion conductions were observed.…”

Heterovalent and isovalent doping of bilayer proton-conducting perovskite SrLa2Sc2O7

“…Figure 6 Temperature dependencies of conductivity under dry air for the compositions SrLa2ScInO7 (1), SrLa2Sc2O7 (2), BaLa2In2O7[41] (3), BaNd2In2O7[43] (4).…”