Water Uptake and Transport Properties of La1−xCaxScO3−α Proton-Conducting Oxides

Abstract

In this study, oxide materials La1−xCaxScO3−α (x = 0.03, 0.05 and 0.10) were synthesized by the citric-nitrate combustion method. Single-phase solid solutions were obtained in the case of calcium content x = 0.03 and 0.05, whereas a calcium-enriched impurity phase was found at x = 0.10. Water uptake and release were studied by means of thermogravimetric analysis, thermodesorption spectroscopy and dilatometry. It was shown that lower calcium content in the main phase leads to a decrease in the water uptake. Conductivity was measured by four-probe direct current (DC) and two-probe ascension current (AC) methods at different temperatures, pO2 and pH2O. The effects of phase composition, microstructure and defect structure on electrical conductivity, as well as correlation between conductivity and water uptake experiments, were discussed. The contribution of ionic conductivity of La1−xCaxScO3−α rises with decreasing temperature and increasing humidity. The domination of proton conductivity at temperatures below 500 °C under oxidizing and reducing atmospheres is exhibited. Water uptake and release as well as transport properties of La1−xCaxScO3−α are compared with the properties of similar proton electrolytes, La1−xSrxScO3−α, and the possible reasons for their differences were discussed.

Effect of irradiation with Ar ions on properties of proton conductors on the base of LaScO3

“…It should be noted that the mass loss of powders occurs at a lower temperature compared to solid ceramics. The weight loss in solid samples observed at the temperatures above 700°C is due to the water release, which follows from the results of earlier experiments on thermal desorption [4]. It should be noted that the mass loss spectra of powders of irradiated ceramics differed from similar spectra of powders of the non-irradiated samples, which is apparently associated with the formation of new active centers in powders of irradiated samples, while the maximum mass loss was observed for the non-irradiated powders.…”

“…In this work the ceramic samples of La 1-x (Ca,Sr) x ScO 3-δ (х = 0.05 and 0.1) and La 1-х ScO 3-δ (х = 0.03, 0.05, 0.1) synthesized by the citric-nitrate combustion method have been studied. The chosen technique made it possible to obtain the practically non-porous ceramics with a density of at least 98% [4]. The samples of the following compositions La 0.9 Sr 0.1 ScO 2.95 , La 0.9 Ca 0.1 ScO 2.95 and La 0.9 ScO 2.85 were irradiated with Ar ions at the energy of 100 keV to a fluence of 10 16 cm -2 at the DC-60 accelerator, Nur-Sultan.…”

Crystal Structure, Electrical Conductivity and Hydration of the Novel Oxygen-Deficient Perovskite La2ScZnO5.5, Doped with MgO and CaO

“…This situation is typical for many perovskites. For example, the concentration of protons was measured in oxides based on La 2 O 3 : La 0.9 Sr 0.1 MO 3−δ (M = Al, Sc, In, Yb, Y) [53], La 0.9 Sr 0.1 (Yb 1−x M x )O 3−δ (M = Y, In) [54], La 0.9 M 0.1 YbO 3− δ (M = Ba, Sr, Ca, Mg) [55], La 1−x Ba x YbO 3−δ [56], La 1−x Ca x ScO 3−α [33], and La 1−x Sr x ScO 3−δ [34]. The authors point out that the concentration of protons does not reach the concentration of oxygen vacancies.…”

“…The well-studied orthorhombic-doped perovskite LaScO 3 exhibits high oxygen-ionic and proton conductivities. This complex oxide has been successfully doped into various sublattices [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]. In a dry atmosphere, acceptor-doped LaScO 3 is a mixed oxygen ion and hole conductor.…”

Membrane Technologies for Decarbonization

“…In this regard, attempts are being made to create similar materials containing no alkaline earth metals. Among them are promising systems based on complex oxides of lanthanum with titanium, zirconium, tin, cerium, or niobium [249][250][251][252], as well as lanthanum oxides with trivalent elements LaXO 3 with a perovskite structure [253][254][255]. However, the practical application of these materials is currently constrained by the relatively high ohmic losses of FCs based on them [256][257][258].…”