Does the pelletization pressure modify the effective anisotropy of the grains in (Bi,Pb)2223 bulk system?

Abstract

In this paper we present a new method to determine separately inter and intragranular magnitudes of polycrystalline superconducting materials, such as: intrinsic effective anisotropy, t= ρc/ ρa b, the slope of the linear part in the temperature dependence of the ab-planes resistivity, Aa b= Δ ρa b/ Δ T, the weak links resistivity, ρw l, and the orientation probability of the grains’ a-axes along a certain preferential direction, γx a. Here, ρa b, ρc and T are the main values of the resistivitity tensor and the measurement temperature, respectively. The application of the method, illustrated by two (Bi,Pb)2223 polycrystalline samples, allows comparing the parameters obtained for the grains with those reported in single crystals. Moreover, we have demonstrated that different compacting pressures in the fabrication of the pellets change not only the inter, but also the intragranular properties of the ceramics. The method could be used to follow the different steps during the synthesis of polycrystalline high Tc superconductors in order to optimise the process.