Strontium migration assisted by oxygen vacancies in SrTiO3from classical and quantum mechanical simulations

Effects of dielectric film surface on oxygen diffusion

“…The gas-solid exchange (GSE) method using an oxygen isotope enriched gas, e.g., 18 O 2 , is a conventional technique for evaluating oxygen diffusivity in oxides. 5) 7) In the GSE method with oxygen isotope tracers, D v (T) is evaluated by fitting the observed oxygen isotope concentration profile, C(x, t, T), according to Eq.…”

“…Here, C(x, t, T) is the 18 O concentration at a certain depth (x) from the surface after a certain GSE reaction period (t), C bg is the background concentration of 18 O (in general, the natural abundance of 18 O µ 0.002), and C s is the surface concentration of 18 O. 8) It should also be noted that the 18 O concentration (C) is defined as the abundance of 18 O under an assumption that the abundance of 17 O is negligibly low.…”

“…8) It should also be noted that the 18 O concentration (C) is defined as the abundance of 18 O under an assumption that the abundance of 17 O is negligibly low. For evaluation of D v (T) with Eq.…”

“…For evaluation of D v (T) with Eq. (1), C s has to be constant (the same as the 18 O concentration in the gas phase) during whole GSE treatment period. In other words, the reaction rate for oxygen molecule (O 2 ) splitting at the sample surface must be high enough and the oxygen diffusivity has to be the rate-limiting process determining the C(x, t, T) profile.…”

“…Deformation of the BaTiO 3 lattice and inhibition of the oxygen diffusivity occurred simultaneously when the YSZ layer, which is assumed to be catalytic for the 18 O/ 16 O exchange reaction, was deposited on BaTiO 3 . The mechanism for the reduction in oxygen diffusivity due to the YSZ cover layer is discussed in terms of residual stress in the strained BaTiO 3 layer.…”