Metallization and superconducting properties of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{6.2}$${\mathrm{Br}}_{\mathit{y}}$

Low-temperature (260 °C) and short-time (>5-min) treatment of initially insulating ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{6.2}$ with ${\mathrm{Br}}_2$ gas converts the material into a 90-K superconductor. Bromine diffusion is found to be four orders of magnitude greater than oxygen diffusion at the same temperature. The crystal structure, phase purity, microstructure, thermal stability, and oxygen content have been studied using x-ray-diffraction Rietveld analysis, Raman spectroscopy, x-ray-fluorescence microprobe, and thermal gravimetric analysis. Superconducting and normal-state properties of the brominated material have been studied with diffuse infrared reflectivity and magnetization.