The temperature and oxygen vacancy effects on the diffusion coefficient and ionic conductivity in ferroelectric BaTiO_3 nanowires; A molecular dynamics study

摘要

In this work, the influence of oxygen vacancy defects on ionic conductivity and oxygen diffusion in BaTiO3 (BTO) nanowires (NWs) was investigated for different temperatures ranging from 700 K to 1000 K by molecular dynamics simulation method. The BTO NWs with cubic structure and axial directions of [001] and [110] were considered for simulation. The oxygen vacancies ranging from 0 to 4% were created by random deletion of oxygen atoms from perfect BTO NWs. The results show that ionic conductivity and diffusion constant of oxygen atoms in individual BTO NWs are at least ten times higher than those of single crystalline BTO and they enhance by increasing the oxygen vacancy percentage. The pre-exponential factor of oxygen diffusion coefficient and also oxygen activation energy of NWs were evaluated from linear least square fits to Arrhenius plots. Results also show that the activation energy of oxygen atoms reduces with increasing the oxygen vacancy percentage. The Arrhenius plots show a critical point about 850 K which at this point the slop of the fitted lines to Arrhenius plots shows a sudden change.