Abstract
The new phases BaLa0.9M0.1InO3.95 (M = Ca2+, Sr2+, Ba2+) with a Ruddlesden-Popper structure were obtained. It was established that all investigated samples were capable for the water uptake from the gas phase. The ability of water incorporation was due to not only by the presence of oxygen vacancies, but also due to the presence of La-O blocks in the structure. The degree of hydration of the samples was much higher than the concentration of oxygen vacancies and the composition of the samples appear to be BaLaInO3.42(OH)1.16, BaLa0.9Ca0.1InO3.25(OH)1.4, BaLa0.9Sr0.1InO3.03(OH)1.84, BaLa0.9Ba0.1InO2.9(OH)2.1. The degree of hydration increased with an increase in the size of the dopant, i.e., with an increase in the size of the salt blocks. It was proven that doping led to the increase in the oxygen ionic conductivity. The conductivities for doped samples BaLa0.9M0.1InO3.95 were higher than for undoped composition BaLaInO4 at ~1.5 order of magnitude. The increase in the conductivity was mainly attributed to the increase of the carrier concentration as a result of the formation of oxygen vacancies during doping. The proton conductivities of doped samples increased in the order Ca2+–Sr2+–Ba2+ due to an increase in the concentration of protons. It was established that all doped samples demonstrated the dominant proton transport below 450 °C.
Highlights
Protonic ceramics are important materials for using as electrolytes in proton-conducting solid oxide fuel cells (H-SOFCs) [1,2,3,4,5,6]
To develop the novel proton conductors, we focused on the composition of BaLaInO4 as a parent compound, which has a Ruddlesden-Popper structure
The obtained lattice parameters for the sample BaLaInO4 were in good agreement with previously reported data [24]
Summary
Protonic ceramics are important materials for using as electrolytes in proton-conducting solid oxide fuel cells (H-SOFCs) [1,2,3,4,5,6]. The application of the proton-conducting complex oxides in comparison with oxygen-ion conductors (in oxygen ion-conducting solid oxide fuel cells O-SOFCs) has several advantages. This allows us to decrease the operating temperatures from 900–1000 ◦ C (O-SOFCs) to 500–700 ◦ C (H-SOFCs) [7]. The water vapor in the H-SOFCs is produced at the air-side electrode (the cathode side) and this avoids the dilution of fuel by steam [9], and, increases the energy conversion efficiency [10,11]
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