Observations of Mixed-Phase Y-Ba-Cu-O Superconductors with a Scanning Electron Microscope at Low Temperatures

Abstract
The microstructure of a Y2Ba3Cu5O y superconducting mixed-phase material with a critical temperature of 88 K was examined with a scanning electron microscope from room temperature to 85 K. Two regions were observed: a dark region constituted of superconducting YBa2Cu3O y and a bright region of Y2BaCuO y . The dark region became darker and the bright region became brighter with decreasing temperature. The SEM image was reversible with respect to temperature.