Dilatation stresses and transport properties of grain boundaries in high-TC superconductors

A theoretical model is suggested which describes the effect of grain-boundary-induced dilatation stresses on the high-TC superconducting properties of grain boundaries in cuprates. In the framework of the model, the dilatation stresses cause weak deviations from bulk stoichiometry within grain boundary cores and give rise to electric-charge inhomogeneities within and near grain boundary cores. The regions with “non-ideal” stoichiometry and electric charge density suppress high-TC superconductivity, in which case the critical current density Jc across grain boundaries essentially decreases compared to the bulk. The Jc enhancement in polycrystalline cuprates due to doping is discussed in the framework of the model. The effect of grain boundary dislocations on stoichiometric inhomogeneities in vicinities of high-angle boundaries is theoretically analyzed. The specific structural and behavioral features of high-quality c-axis twist boundaries in BiSrCaCuO superconductors are discussed. Results of the suggested model are compared with experimental data reported in scientific literature.