Effect of thermal strain on the formation of the nanostructure in YBCO films with doped nanorods

Abstract

For superconducting YBCO coated films, introducing artificial nanopinning has been proven to be the effective methodologies to effectively enhance the critical current density (Jc). In order to precisely control the nanostructure of YBCO-nanopinning composite films, it is most important to accurately understand the mismatch strain and its effect in YBCO nanocomposite films. In this article, on the base of elastic theory we derived a theoretical model of describing the elastic energy of the superconducting YBCO film doped with artificial nanorods (usually BZO nanorods) due to the temperature change during the cooling process. On this model, the total strains of the film and nanorods were analytically calculated through solving the equilibrium equations, and further the thermal strain and its influence on the diameter of nanorods arranged along the c-axis in the YBCO film were comprehensively discussed by calculating the elastic energy density of the YBCO film and nanorods. These calculated results show that the thermal strain due to temperature change has a great effect on the YBCO nanocomposite structure, while this effect gradually weakens when the dopant concentration increases to a certain value.