A mosaic of three twinned single crystals of were utilized in this experiment. The crystals were of extremely high quality, as characterized by low-field magnetization, ab-plane resistivity, microwave surface resistance and heat capacity measurements . For example, the superconducting transition temperature Tc, determined by magnetization measurements was found to be 93.2K with a relatively narrow transition width K.
The single crystals were grown by a flux method in yttria-stabilized zirconia crucibles. CuO-BaO flux was poured over hot (950- C) crystals initially grown from high purity Y2O3 (), CuO () and BaCO3 () compounds. To ensure each crystal had the identical oxygen concentration corresponding to the maximum Tc, all three crystals were carefully annealed prior to the experiment. For 3 days the crystals were held in 1 atmosphere of O2 at C, followed by 14 days at C before rapidly cooling to room temperature. Together the three crystals had a total mass of 53mg.