GROWTH, SUPERCONDUCTIVITY AND ANISOTROPY IN THE ELECTRICAL-RESISTIVITY OF PB2SR2HO0.5CA0.5CU3O8 SINGLE-CRYSTALS - THE EFFECT OF CONTAMINATION FROM THE CRUCIBLE ON T(C)

Single crystals of Pb2Sr2Ho0.5Ca0.5Cu3O8 have been grown in Pt, Al2O3 and Au crucibles by means of the flux method. The effect of contaminat ion from the crucible on T(c) has been investigated by studing the eff ects of Cu-site substitution on T(c) and magnetic properties for sinte red polycrystals of Pb2Sr2R0.5Ca0.5(Cu1-yMy)3O8 with R=Ho or Y and M=P t or Al. Consequently, it has been found that use of a Pt crucible lea ds to growth of single crystals of the best quality with high T(c) val ues and that Al2O3 and Au crucibles contaminate the single crystals to decrease T(c). Anisotropy in the electrical resistivity of the single -crystal Pb2Sr2Ho0.5Ca0.5Cu3O8 has been found to be comparable to that of YBa2Cu3O7 in spite of its thick blocking layer, suggesting that th e wave functions of conduction electrons moderately overlap along the c-axis in Pb2Sr2Ho0.5Ca0.5Cu3O8.