The Influence of Defects on Proton Diffusion in Perovskites А^IIВ^IV1_1-xR^III_xO_3-δ: Monte Carlo Study

Abstract

The tracer diffusion coefficient D* and the mobility of protons in proton-conducting oxides of the АIIВIV 1-xRIII xO3-δ family have been calculated using the Monte Carlo method as functions of temperature and concentration x of the acceptor impurity RIII. The effect of protondopant interactions (proton trapping) and the effect of protonic sites blocking caused by protonproton and proton - oxygen vacancy interactions, are analyzed. It is shown that the proton diffusivity depends significantly on the dopant content and is considerably reduced already at small x. The D* value weakly depends on the concentration of oxygen vacancies at fixed, not too large values of x. The conductivity dependence on the doping concentration σ(x) can have a maximum due to the proton-defect and proton-proton interactions. The Haven ratio deviates slightly from unity at the expected intensity of interparticle correlations. The calculated values of both the diffusivity activation energy increase (with x), and the location of the σ(x) maxima agree with the experimental data for a number of proton-conducting oxides.

Factors Constituting Proton Trapping in BaCeO3 and BaZrO3 Perovskite Proton Conductors in Fuel Cell Technology: A Review

“…The consequence of having a substituent in the host material over proton trapping was substantially investigated by various researchers through computational techniques . Atomic and density functional theory simulations conducted over diverse PCs yielded different proton and vacancy trapping energies against differing natures of dopant exhibiting wide variations. ,− In addition, Monte Carlo simulations conducted by Tsidilkovski et al . and multiple researchers revealed the fundamental aspect of such variations to be observed as a result of the varying potential well and barriers for protons within the PCs modulating proton diffusivity and conductivity as a function of dopant concentration.…”

Distribution of Oxygen Vacancies in an External Electric Field and Oxygen-Ion Conductivity in Acceptor-Doped Fluorite-Structured Ionic Conductors

“…With the field applied, oxygen ion-vacancy pairs undergo redistribution along direction E in the following manner (Δ 1): (7) We note that condition (2) for equilibrium distribution of bonds holds for the average value VO in a nonzero external field as well. From Eqs.…”

“…The procedure was repeated for x values of 0.02 to 0.4 at a step size of 0.02. A fairly detailed description of the Monte Carlo simulation diagrams and procedures used here in calculations of the carrier transport can be found elsewhere [7,8].…”

Thermodynamics of Defect Formation and Hydration of Y₂O₃

“…We showed [6] that water incorporation in yttria containing charge compensating oxygen vacancies produced by an acceptor doping is more preferable energetically than that in a pure crystal. Note also that acceptor impurities can substantially affect the behavior of proton transport coefficients in proton-conducting oxides [7].…”