Investigation of the cooling rate in Bi(Pb)SrCaCuO high temperature superconductor by low field AC magnetic susceptibility
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Bi1.7Pb0.35Sr1.9Ca2.1CU3Ox samples prepared by the classical method were studied by the AC magnetic susceptibility (x = x' + ix") method. The annealing of the sample was concluded under different cooling rate conditions. The intergranular critical current densities and critical temperatures, estimated from the temperature dependence of the AC susceptibilities, are discussed by comparing with those of bulk materials. The results have been analysed in the light of the crystal structure and superconducting anisotropy. The AC susceptibility measurement was carried out at different values of AC field amplitude. The imaginary part of the susceptibility is used to calculate the intergranular J(c) using the Bean model. The calculated intergranular J, of the sample with 100 degrees C/h cooling rate is about 62 A/cm(2) at 95 K. The intergranular critical current densities at this temperature are about 30 A/cm(2) and 46 A/cm(2) for the 25 degrees C/h and 50 degrees C/h cooling rates, respectively. SEM (scanning electron microscopy) pictures give some information about the grain boundary and grain sizes.