Crystal Structure, Hydration, and Two-Fold/Single-Fold Diffusion Kinetics in Proton-Conducting Ba0.9La0.1Zr0.25Sn0.25In0.5O3−a Oxide

Abstract

Abstract:In this work, hydration kinetics related to the incorporation of water into proton-conducting Ba 0.9 La 0.1 Zr 0.25 Sn 0.25 In 0.5 O 3−a perovskite-type oxide are presented, with a recorded transition on temperature from a single-fold to a two-fold behavior. This can be correlated with an appearance of the electronic hole component of the conductivity at high temperatures. The collected electrical conductivity relaxation data allowed to calculate chemical diffusion coefficient D and surface exchange reaction coefficient k, as well as respective activation energies of their changes on temperature. Presented results are supplemented with a systematic characterization of the structural properties of materials synthesized at different temperatures, amount of incorporated water after hydration in different conditions, influence of water content on the crystal structure, as well as electrical conductivity in dry, H 2 O-and D 2 O-containing air, which enabled to evaluate proton (deuterium) conductivity.

Charge Transport in High-Entropy Oxides

“…The values of transport coefficients are comparable to the previously reported barium–zirconium system. For example, for Ba 0.9 La 0.1 Zr 0.25 Sn 0.25 In 0.5 O 3– a , the coefficient D OH • is in a range from 10 –8 to 10 –5 cm 2 s –1 at a 300–600 °C temperature range and the chemical surface exchange coefficient k OH • is from 10 –6 to 10 –2 cm s –1 in the same range. Additionally, these values are higher than those published for some other proton-conducting perovskites such as indium-doped SrCeO 3 for which D OH • is in the range of 10 –6 –10 –7 cm 2 s –1 and k OH • is 10 –5 –10 –6 cm s –1 at 500–700 °C.…”

Ceramic Conductors

“…Among them, electronic-, ionic-, as well as mixed electronic-ionic-conducting ceramics are very important groups of materials. Proton conductivity may be observed in acceptor-doped perovskite oxides such as Ba 0.9 La 0.1 Zr 0.25 Sn 0.25 In 0.5 O 3−a , as studied by Skubida et al [2], and terbium-substituted lanthanum orthoniobate [3]. Oxygen ions are mobile charge carriers in materials such as substituted bismuth vanadate [4] and doped cerium oxide [5,6], as studied by Ring and Fuierer, and to a minor extent and at high temperature, they are also mobile charge carriers in ceramic proton conductors.…”

“…The most often used method of ceramic materials preparation, which is usually used as a first-trial method, is the solid-state reaction method. This method was used for the preparation of doped barium indate Ba 0.9 La 0.1 Zr 0.25 Sn 0.25 In 0.5 O 3−a [2], terbium-doped lanthanum orthoniobate [3], and doped strontium titanate [8]. On the other hand, the solid-state reaction route often does not allow the achievement of single-phase ceramics with expected properties.…”

“…La-doped strontium titanate was studied as a ceramic component of a composite current collector in a metal-supported SOFC [8]. Similarly, the development of proton-conducting ceramics [2,3] is aimed at future applications in SOFCs with proton-conducting electrolytes. SOFCs both with oxygen ionand proton-conducting electrolytes operate at high temperatures, i.e., between 600 • C and 800 • C. Even the YF 3 -SrF 2 solid solutions are considered as electrolytes for high-temperature all-solid-state fluorine batteries [7].…”

Proton surface exchange kinetics of perovskite triple conducting thin films for protonic ceramic electrolysis cells: BaPr0.9Y0.1O3−δ (BPY) vs. Ba1−xCo0.4Fe0.4Zr0.1Y0.1O3−δ (BCFZY)

“…For example, multiple conductivity relaxations in opposite directions can be superimposed, requiring careful tting and analysis. 14,15 Therefore, a geometrically well-dened electrode structure that avoids diffusion contributions to the kinetic response is preferred.…”