| In this thesis, the main focus is to understand the electronic transport properties of grain boundaries (GBs) in perovskite materials from an atomic scale viewpoint. Often the controlling the overall bulk properties, GBs in perovskites are becoming widely studied, In particular, GBs in the cuprate superconductors, which drastically reduce the critical current capacity, have been especially enigmatic. In this work, extra attention will be directly towards YBa2Cu3O7 (YBCO), a commonly studied cuprate superconductor.; The general outline of this thesis is as follows. First, in order to obtain the necessary atomic scale data to develop such an understanding, the experimental techniques of Z-contrast imaging in the scanning transmission electron microscope (STEM) correlated with electron energy loss spectroscopy (EELS) were used to acquire information on the atomic and electronic structure of GBs in perovskite materials. As an example, a study using STEM will be performed on both pure and Ca-doped GBs in YBCO. Next, using this data, an atomic scale model will be developed to explain the transport properties of GBs in YBCO. The results of this model fit very well with experimental transport measurements obtained elsewhere. Finally, to show the generality of using these experimental and theoretical methods to explain transport properties in perovskite GBs, a different perovskite system La1−xCa xMnO3 (LCMO) is investigated. Overall, the methodology presented in thesis serves well to explain the transport properties of GBs in perovskites. |
