AC losses and determination of some superconducting parameters of Ag2O added Bi2223 superconductors

Abstract

The effects of Ag2O addition on electromagnetic properties in a Bi2223 superconductor have been investigated by means of AC susceptibility measurements and theoretical analysis. Intergranular critical current density was found to be decreased with increased amount of Ag2O addition (0, 15, 30 wt.%). The effective volume fractions of the grains were estimated as a function of Ag2O amount. The field and temperature dependence of the intergranular critical current density for each sample has been accounted by the function J(cm) (T) = (J(0)/B-n) (1 - T/T-cm)(P), where alpha(0) denotes the pinning strength parameter at T = 0. The field exponent n, temperature exponent p, and maximum intergranular loss peaks, which are determined from the comparison of the experimental and calculated curves, increased with increasing amount of Ag2O addition. Experimental isothermal hysteresis losses as a function of field amplitude are also seen to adequately be reproduced by model calculation using the same fitting parameters as for AC susceptibility chi(n)(T) data.