Cubic phase in the Y-Ba-Cu-O system

A metastable phase in the Y-Ba-Cu-O system has been discovered. The phase is closely related to the high-${\mathit{T}}_{\mathit{c}}$ superconductors and is characterized by a simple-cubic perovskite structure with a lattice parameter of 3.897 Å. A composition Y:Ba:Cu:O=1.18:1.97:3.05:6.95 was determined using ion-backscattering spectrometry. The material is a black semiconductor and shows no transition to superconductivity down to 4 K. It is an excellent candidate for use in heteroepitaxial structures with the family of rare-earth–alkaline-earth–cuprate superconductors. The cubic phase was prepared as a thin film by excimer-laser ablation.