EFFECT OF FE ON THE CRYSTAL-GROWTH MORPHOLOGY OF BI-SR-CA-CU-O

The effect of Fe on the crystal growth of Bi2.1Sr1.9Ca(Cu1-yFey)(2)O-x was studied by a floating zone method. The result shows that the plan ar solid-liquid growth interface breaks down into a cellular growth in terface with increasing Fe substitution in the feed rods of Bi2.1Sr1.9 Ca(Cu1-yFey)(2)O-x. The size of the single crystals decreases with the increase in Fe substitution in the feed rods. When Fe substitution co ntent y is 0.06 in a feed rod, the Bi-2212 single crystals in an as-gr own bar are too small to be visible. The maximum thickness along the c -axis of the pure Bi-2212 single crystals is as large as 2 mm. The sol ubility limit of Fe in Bi-2212 crystals is 0.025. The Fe substitution in Bi-2212 crystals depress sharply not only the superconductivity tra nsition temperature but also the homogeneity of the superconducting ph ase in the crystals.