Atomistic simulations of ion migration in sodium bismuth titanate (NBT) materials: towards superior oxide-ion conductors. Issue 19 (1st May 2018)

• Record Type: Journal Article
• Authors: Zhang, Haiwu; Ramadan, Amr. H. H.; De Souza, Roger A.
• Is Part Of: Journal of materials chemistry. Volume 6:Issue 19(2018)
• Page Start: 9116
• Page End: 9123
• Publication Date: 2018-05-01
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c8ta02545b
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : Fabricating (111)-ordered NBT and avoid any A -site vacancies will yield even higher oxide-ion conductivities. Abstract : Ion migration in Na0.5 Bi0.5 TiO3 (NBT) was investigated by molecular dynamics (MD) simulations and molecular static (MS) simulations. In MD simulations (>10 4 ions), performed for simulation times of t sim = 0.3 ns and at simulation temperatures in the range 1200 ≤ T /K ≤ 2400, oxide ions exhibited appreciable diffusivity, with derived activation enthalpies lower than 0.8 eV, whereas sodium and bismuth cations displayed no diffusion at the temperatures and on the time scale of the simulations. MS calculations yielded high activation barriers (>2 eV) for the migration of these cations. These results strongly suggest that the contribution of A -site cations to the total ionic conductivity is negligible. Bismuth vacancies and sodium vacancies were found to be detrimental to the rate of oxygen diffusion. The effect of ordered arrangements of Bi 3+ /Na + cations on oxygen tracer diffusion was also examined by MD simulations. The (111)-ordered structure was seen to display higher rates of oxygen diffusion than the (100)- and (110)-ordered structures. MS calculations of the individual barriers for oxygen-ion jumps provided insights into this behavior. Our simulation results thus suggest design rules for developing superior low-temperature oxide ion conductors based on NBT perovskites and related materials.