In this paper, the effect of the cross-section on the critical current density (Jc) of a sample in ceramic superconductors YBa2Cu3O7-­δ (YBCO) and Bi1.6Pb0.4Sr2Ca2cu3Oy (BPSCCO) has been studied. Five orthorhombic bar samples of YBCO with cross-sections of 6.25, 7.67, 9.25, 11.76, 14.67 mm2­ and also five orthorhombic bar samples of BPSCCO with cross-section of 6.4, 9.01, 11.88, 13.86, 14.98 mm2­ with the same synthesis conditions by the solid state reaction method were prepared. After the

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... ration of the samples, the Meissner effect, the critical temperature (Tc), and the critical current density (Jc) measurements, XRD and SEM have been done on the samples. The results of XRD show that the dominant phase in YBCO and BPSCCO are 123 and 2223, respectively. The results of Jc measurements in 77 K show that in both superconductors, the Jc decreases with increasing of cross-section (A). The type of dissipation obeys a power law with the relation . For a given cross-section, Jc of the BPSCCO sample is smaller than the YBCO sample.