Effect of ionic polarizability on oxygen diffusion in δ-Bi2O3 from atomistic simulation

Abstract

The effect of polarizability of cation dopants on oxygen diffusion in δ-Bi 2 O 3 is determined using moleculardynamics simulation in which the polarizability of the ions is treated within the shell model. It is found that the magnitude of the oxygen polarizability has no affect on diffusion. However, the high cation polarizability, associated with the lone pair of electrons in Bi, is found to be the key to achieving sustained oxygen diffusion. Consistent with earlier experimental results, the oxygen diffusion path is found to be between oxygen equilibrium sites, which are displaced from the 8c oxygen sites of the fluorite lattice.

Vacancy‐Ordered Structure of Cubic Bismuth Oxide from Simulation and Crystallographic Analysis

“…The simulations further indicate that there is a certain minimum ionic polarizability required to prevent vacancy ordering. In particular below a critical polarizability, ordering takes place on an MD‐accessible time scale (0.5 ns), while for higher polarizabilities, there is considerable diffusion, with no sign of vacancy ordering 13 …”

“…As a result, one ordering network is directly connected to another. It is important to recognize that although there are open channels of vacancies available for easy oxygen diffusion along the 〈111〉 network, the oxygen diffusion is limited by preferential oxygen diffusion in 〈100〉 directions 13 …”

Bi-doped La2ZnMnO6− and relevant Bi-deficient compound as potential cathodes for intermediate temperature solid oxide fuel cells

“…In previous studies, Bi 3+ and Bi 5+ have taken for granted in Ba 2 Bi x Sc 0.2 Co 1.8 − x O 6 − δ system [29,30], and 6s 2 lone pair electronic structure of Bi 3+ ions plays a vital role in anion migration in many Bibased oxide ion conductors [26,31]. For the sake of clarity the valence state of Bi ion in Bi 0.5 and Bi 0.5 − x , Bi 4f core levels were well fitted and shown in Fig.…”

Ultrafast collective oxygen-vacancy flow in Ca-doped BiFeO3

“…Furthermore, as the parent compound is ferroelectric, the system has a large lattice instability, and thus, a defect induces significant local deformation in the lattice 21,22 . At the same time, the high bismuth ionic polarizability, which is related to the presence of 6s lone-pair electrons, has been found to be one of the keys to promoting the migration of oxygen vacancies 23,24 . Ultimately, the compound, which contains inexpensive, abundant elements (Bi, Ca, and Fe), is likely to be a promising ionic conductor; however, the oxygen-vacancy dynamics of this compound are not well known.…”