Growth of YBa2Cu3Ox Single Crystals with Superconducting Transition above 90 K

Single crystals of high-temperature superconductor YBa₂Cu₃O_x have successfully been prepared using a CuO flux method. Two types of crystals of a mm-size are obtained: irregular blocks with the (001) habit and thin plates with the well-developed (001) plane. EPMA shows that the ratio Y/Ba/Cu is 1.0/1.9/2.9 and no apparent difference in metal composition is observed between the two. Electrical resistivity measurements show that the block crystals are metallic and exhibit a sharp superconducting transition at 91.3 K, whereas the plates are semiconducting and show no superconducting behavior above 4.2 K.