Analysis of a Bi-2223/Ag multi-layered bulk sample with an R–L equivalent circuit

The J c of a sintered Bi-2223/Ag multi-layered bulk sample increases as the number of Ag layers is increased. The sample used in this experiment was placed next to the bifilarly wound coil consisting of two coils having the same properties located at the same place. With the sample fixed, a current was applied to the two coils in the same and then in the opposite direction so as the fluxes augment or counteract each other, and the difference in the synthetic impedance of the two coils ( ΔZ ) was measured. First, the temperature dependence of ΔZ for Ag and Bi-2223 samples, and Bi-2223/Ag multi-layered sample pellets were measured at 10 kHz. Next, each sample was treated as a serial circuit having the same resistance and inductance, and a formula for obtaining ΔZ for each bifilarly wound coil was derived. The calculated values of the temperature dependence of ΔZ obtained by substituting the sample and coil constants into the formula corresponded fairly well with the measured ones.