The level of current transport in a given high T-c superconductor application depends upon several intrinsic microstructure-property relationships. When a magnetic field is applied, the flux vortices may shift due to the force from the current or to thermal activation, resulting in a loss of superconducting properties known as flux creep. Flux vortices may be pinned by microstructural defects such as grain boundaries or dislocations, if present in sufficient quantities, hence the importance of microstructure. In spite of significant progress in understanding vortex dynamics in high T-c superconductors our knowledge of the thermally activated flux creep is incomplete. Our experimental results indicate that the logarithmic decay of magnetization with log time is a monotonically increasing function of temperature contrary to the prediction of the widely accepted collective pinning models. The goal of this study was to characterize both current transport properties and microstructures in high T-c superconductors in order to optimize material performance. Initial research was focused on BSCCO (barium, strontium, calcium, copper oxide) tapes. Superconducting properties were measured as a function of temperature and applied magnetic field for sections of this material. Additionally, the microstructures were characterized using optical and electron microscopy and x-ray diffraction. These microstructural parameters were then correlated with the superconducting properties in order to rank their relative importance and to predict the combinations which should maximize superconductor performance. Flux creep in these materials were then predicted by a new model and shown to be in good agreement with experiments.