Publication date: 10th April 2024
The topotactic phase transition of some perovskites, from perovskite ABO3−δ to brownmillerite A2B2O5, has recently attracted attention because of its potential for application in redox-induced resistance random access memories (ReRAM). The perovskite phase with its disordered vacancy distribution shows high oxide-ion mobility in contrast to the brownmillerite phase with its one-dimensionally ordered structural vacancies. The key process for the phase transition is the diffusion of oxygen point-defects, but oxygen diffusion coefficients have been obtained neither experimentally nor computationally. Furthermore, insights into the mechanisms of oxygen diffusion from atomistic simulations have been limited mainly to static calculations.
In our study, we employed molecular dynamics (MD) simulations with empirical pair potentials (i) to obtain oxygen diffusion coefficients for both the brownmillerite Sr2Fe2O5 phase and the perovskite SrFeO2.5 phase; and (ii) to elucidate the paths and mechanisms of oxygen diffusion. In particular, we investigated non-stoichiometric systems with oxygen excess or oxygen deficiency in order to study diffusion processes by means of oxygen interstitials or oxygen vacancies independently from each other. The investigation allowed us to achieve a deep and detailed description of diffusion processes in brownmillerite Sr2Fe2O5.
Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – DE 2854/20-1. Simulations were performed with computing resources granted by RWTH Aachen University under project No. p0020441 and thes1023.
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