High-resolution electron microscopy of high-temperature superconductors.

We review recent results obtained at Northwestern using high-resolution electron microscopy to study high-temperature superconductors. While in general these materials form large, very perfect single crystal grains which display very few imperfections, there is also evidence of slip defects, amorphous regions, and order-disorder transformations. We also report that the gadolinium-based superconductors and in one case yttrium-based superconductors show evidence for some copper solid solubility in the form of copper-rich planar defects. The structure of a metastable trigonal polytype is also reported, as are the effects of electron beam and water vapor damage to the materials.