Ab initio thermodynamic study of proton conductivity in BaZrO3


Ab initio thermodynamic study of proton conductivity in BaZrO3

Raja, N.; Murali, D.; Posselt, M.; Satyanarayana, S. V. M.

BaZrO3 (BZO) is a potential candidate material for electrode in solid oxide fuel cells (SOFL) because of its excellent reported proton conductivity [1, 2]. It is suggested that presence of intrinsic point defects such as O vacancies act as sinks for O atoms produced upon hydrogenation of water molecule and promote proton conductivity. For this, the formation energy of O atom should be lower and its migration should be suppressed [3]. Since these materials are used at high temperature, it is very important to consider effects of phonons on the defect chemistry [4, 5, 6]. In this work, first, we identify thermodynamically favorable conditions for the formation of BZO by free energy calculations of bulk phases using Density Functional Theory. Next, we study the free energy of formation of both neutral and charged O vacancies of stable BZO phase and discuss significance of these results for experimental growth conditions. Initial results show that phonon contributions to free formation energy of charged vacancy is significantly high compared to neutral vacancy due to large lattice distortion and negative formation entropy for charged vacancy. Studies also show that acceptor doping both at A and B site lowers the formation energy of O vacancy in the vicinity of dopant atoms resulting in increase of proton conductivity [7, 8]. In order to understand the mechanism of this enhancement, we study the free energy of formation of O clusters in reducing conductions for acceptor doping at A and B sites.

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Keywords: DFT; proton conductivity; solid oxide fuel cells

  • Lecture (Conference)
    International Conference on Advances in Functional Materials, 06.-08.01.2017, Chennai, Madras, India

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Publ.-Id: 25336