Here, for the first time, we present data on proton conductivity of high-entropy, single-phase perovskites. The BaZr0.2Sn0.2­Ti0.2Hf0.2Ce0.2O3−δ, BaZr0.2Sn0.2­Ti0.2Hf0.2­Y0.2O3−δ, BaZr1/7Sn1/7­Ti1/7Hf1/7­Ce1/7Nb1/7Y1/7O3−δ, and BaZr0.15Sn0.15­Ti0.15Hf0.15­Ce0.15Nb0.15­Y0.10O3−δ single-phase perovskites were synthesized. Before electrical measurements, materials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The following experimental results demonstrated that studied high-entropy perovskites are proton conductors: (1) The observed mass increase upon the switch from dry to wet atmosphere confirmed the water incorporation into materials structure. (2) The electrochemical impedance spectroscopy (EIS) revealed that the total conductivity increased while its activation energy decreased in the presence of water vapor in the atmosphere. (3) The conductivity in atmosphere humidified with H2O and D2O differed one from another, showing typical of proton conductors isotope effect in high-entropy oxides.

The structure and thermomechanical properties of As-substituted lanthanum orthoniobates are presented and an in-depth analysis of a broad range of other substituents is performed.

In this work, Fe-doped strontium titanate SrTi1−xFexO3−x/2−δ, for x = 0–1 (STFx), has been fabricated and studied. The structure and microstructure analysis showed that the Fe amount in SrTi1−xFexO3−x/2−δ has a great influence on the lattice parameter and microstructure, including the porosity and grain size. Oxygen nonstoichiometry studies performed by thermogravimetry at different atmospheres showed that the Fe-rich compositions (x > 0.3) exhibit higher oxygen vacancies concentration of the order of magnitude 1022–1023 cm−3. The proton uptake investigations have been done using thermogravimetry in wet conditions, and the results showed that the compositions with x < 0.5 exhibit hydrogenation redox reactions. Proton concentration at 400 °C depends on the Fe content and was estimated to be 1.0 × 10−2 mol/mol for SrTi0.9Fe0.1O2.95 and 1.8 × 10−5 mol/mol for SrTi0.5Fe0.5O2.75. Above 20 mol% of iron content, a significant drop of proton molar concentrations at 400 °C was observed. This is related to the stronger overlapping of Fe and O orbitals after reaching the percolation level of approximately 30 mol% of the iron in SrTi1−xFexO3−x/2−δ. The relation between the proton concentration and Fe dopant content has been discussed in relation to the B-site average electronegativity, oxygen nonstoichiometry, and electronic structure.

Lanthanum orthoantimonate was synthesized using as olid-state synthesis method.T oe nhancet he possible protonic conductivity,s amples with the addition of 1mol %C ai nL a-site were also prepared. The structure was studied by the meanso fX-ray diffraction, which showedt hat both specimens weres ingle phase. The materials crystallized in the space group P2 1 /n. Dilatometry revealedt hat the materiale xpanded non-linearly with the temperature. The nature of this deviation is unknown; however,t he calculated linearf raction thermal expansion coefficient was 9.56 10 À6 K À1 .E lectrical properties studies showedt hat the material is ap rotonc onductor in oxidizing conditions, which was confirmed both by temperature studiesi nw et in dry air,b ut also by the H/D isotopee xchangee xperiment. The conductivity was rather modest, peakinga tt he order of 10 À6 Scm À1 at 800 8C, but this could be further improved by microstructure and doping optimization.T his is the first time protonic conductivity in lanthanum orthoantimonates is reported. Proton conducting ceramics (PCCs) are materials exhibiting ionic conductivityi nw hichp roton (H +)i sacharge carrier. [1] This class of materials has gathered interest over the years for their potential applications.E specially the so-called triple conductingo xides, that is, materials with three mobile charge carriers (protons, oxygen ions, and electron/electron holes) were discovered and studied as potential electrode materials. [2-5] The increased interest led to developing highly-efficient fuel cells [5-7] and steam electrolyzers. [8] This interest stems from the fact that PCC-based devices can operate with high efficiencies while being cost-competitive in comparison to traditional solid oxide fuel cells. [5, 9] Apart from that, new typeso fe lectrochemical devices have been developed. Such devicesc an be used for the synthesis of ammonia, [10, 11] conversion of methane into aromaticsi namembraner eactor, [12] or thermo-electrochemical production of hydrogen from methane. [13]