Effect of Uniaxial Strain on Oxygen Diffusion in Grain Boundaries of Polycrystalline YBa2Cu3O7-Coated Conductors

Abstract

For polycrystalline YBa2Cu3O7 (YBCO)-coated conductors, the diffusion behavior of oxygen ions during the preparation process, especially in grain boundaries (GBs), results in the motion of oxygen vacancies, and finally has a strong impact on the critical current density (Jc) of YBCO conductors. Such the oxygen diffusion in GBs has been found to be very sensitive to applied strain. In order to deeply understand the strain effect, in this article, we have studied the oxygen diffusion in polycrystalline YBCO conductors under uniaxial strain by molecular dynamic simulation. On the two different bicrystal structural models, the calculated results display that the oxygen diffusion in the grain boundary region shows a downward trend with the loading of the uniaxial tensile or compressive strain. And also, we found that applied strain leads to the variation of the microstructure of GBs, and thus results in reducing the oxygen vacancy concentration. As our previous study concluded, the high diffusion of oxygen can be regarded as a medium for analyzing the supercurrent through grain boundary. This paper further illustrates that the relation between the activation energy of oxygen diffusion and the strain loading has an almost similar form as that between the critical current density and the strain. This indicates that the activation energy of oxygen diffusion in the grain boundary region could be closely related to the critical current density, which arouses our interest to further explore whether or not it can be used as an index of predicting the current-carrying capability of YBCO conductors.