PREPARATION AND MAGNETIC-PROPERTIES OF THE SB-DOPED BI-PB-SR-CA-CU-O SUPERCONDUCTORS

Two groups of samples were prepared by the wet method with nominal composition Bix1Pbx2Sbx3Sr2Ca3Cu4Oz. In the first group x1 + x2 + x3 = 2. Here x1 ranges from 1.2 to 1.6 with x2 varying from 0.72 to 0.12. The second group is characterized by x1 + x2 = 2. Here x1 was chosen to be 1.4 and 1.6 while x3 ranges from 0.08 to 0.16. The results show: (i) high Sb content reduces the transition temperature; (ii) for small Sb contents the transition temperature is relatively constant but the transition becomes sharper, (iii) the best sample (with x1 = 1.4, x2 = 0.48 and x3 = 0.12) exhibits a very sharp transition with a peak in the imaginary component of the ac susceptibility at 108.4 K; abd (iv) the transition of lightly Sb-doped material is strongly influenced by small external magnetic fields. © 1990.