SINGLE-CRYSTAL GROWTH AND CHARACTERIZATION OF YBA2CU4O8 WITH T(C)SIMILAR-TO-80-K

Single-crystals of YBa2Cu4O8 with T(c) approximately 80 K have been grown from a BaO-CuO flux at 1100-degrees-C under 600 bar of O2. Unlike earlier crystals of this material that were grown in Al2O3 Crucibles, crystals grown in ZrO2 crucibles show sharp superconducting single-transitions (DELTAT(c) approximately 0.5 K) with T(c)s as high as the best polycrystalline material. The high crystal quality was confirmed by crystal X-ray diffraction. The incorporation of a small amount of aluminium in the lattice (confirmed by electron microprobe measurements) is the probable cause for the degradation of superconducting properties of crystals grown in Al2O3 crucibles.