Fast Oxygen Transport in Bottlelike Channels for Y-Doped BaZrO₃: A Reactive Molecular Dynamics Investigation

Abstract

Yttrium-doped barium zirconate (BZY) has emerged as an attractive candidate of oxygen ion (O2–) conducting solid electrolyte because of its high ionic conductivity and excellent chemical stability. In this work, the O2– transport properties and mechanisms of BZY coexisting oxygen vacancies, dopants, and edge dislocations are simulated by reactive molecular dynamics for the first time, and the yttrium concentration (Y%) and temperature (T) dependences of thermodynamic and kinetic properties are studied for the bulk and dislocation (Bulk and Disl) systems, respectively. It is concluded that the Y% under 20 mol % for Bulk BZY can promote O2– conduction, while 30 mol % Y-doped Disl BZY has the highest O2– diffusion coefficient. Besides, dislocations will accelerate O2– diffusion when T is less than 1173.15 K due to the formation of double-bottle diffusion channels that enables facile reorientation of oxygen polyhedron. Therefore, it is feasible to introduce line defects to enhance ion conductivity at low temperature in the practical applications of BZY electrolytes.

Optimizing the Proton Conductivity with the Isokinetic Temperature in Perovskite‐Type Proton Conductors According to Meyer–Neldel Rule

“…From experiment, T iso may be determined by computational simulations. [52] For proton conductivity in perovskites, some other simple descriptors, such as ionic radii and basicity, are already known. Very likely, these descriptors turn out to be included in the concept of proton-phonon interaction.…”

Recent progress in the experimental and theoretical studies on the barium zirconate proton conductors: A review

“…Through incorporating reactive force eld potentials, the oxygen vacancies, doping effect, and edge dislocations have been explored for the BZO system with or without edge dislocations, and calculations on radial distribution function, expansion coe cient, and ionic self-diffusion coe cient. The MD calculations on the aforementioned entities have been carried out employing the dependencies of temperature and doping percentage [186]. These results manifest that a mole fraction of yttrium can increase oxygen transport which can be characterized by the oxygen transport coe cient.…”

Dislocation-Mediated Conductivity in Oxides: Progress, Challenges, and Opportunities

“…Although less numerous, similar studies have been conducted to determine the effects of dislocations on ionic transport in BaZrO 3 (BZO). − For BZO, two experimental studies, both on BZO thin-films on NdGaO 3 substrates, showed significant increases in proton conductivity as a result of misfit dislocations that form due to the lattice mismatch between BZO and NdGaO 3 . , Although the authors found similar results, the explanations they proposed are different. Felici et al .…”

“…determined that the effect was due to the incorporation of hydroxyl groups at dislocations, which required protons to be integrated to provide charge balance, whereas Liu et al . proposed that the increase in both barium and oxygen vacancies could have enabled the higher conductivity. , For oxygen diffusion in these systems, simulations by Li et al propose pipe diffusion as the mechanism, so the explanations for dislocation-modified transport can vary greatly based on the study, carrier in question, processing route, including impurity incorporation (if experimental), and types of dislocations present . For a simplified summary of reported effects of dislocations on transport in oxides, where diffusivity or conductivity was directly measured or simulated, refer to Table .…”

“…53,54 For oxygen diffusion in these systems, simulations by Li et al propose pipe diffusion as the mechanism, so the explanations for dislocation-modified transport can vary greatly based on the study, carrier in question, processing route, including impurity incorporation (if experimental), and types of dislocations present. 55 For a simplified summary of reported effects of dislocations on transport in oxides, where diffusivity or conductivity was directly measured or simulated, refer to Table 1.…”