Experimental and theoretical study of transport properties in uniaxially pressed [formula omitted] ceramic samples

Abstract

Experimental and theoretical studies on the magnetic field dependence of the electrical resistance R ( B a ) and the transport noise (TN) in polycrystalline high- T c superconductors subjected to different uniaxial compacting pressures were conducted. X-ray diffraction rocking curves were performed in different surfaces of the samples in order to investigated the degree of texture. The results indicated an improvement of the degree of texture with increasing the uniaxial compacting pressure. In theoretical simulations of the data, the polycrystalline superconductors were described as a series-parallel array of Josephson devices. The intergranular magnetic field is described within the framework of the intragranular flux-trapping model and the distribution of the grain-boundary angles is assumed to follow the Rayleigh statistical function. The proposed model describes well the experimental magnetoresistance R ( B a ) data. We have found that the behavior of the R ( B a ) curves changes appreciably when different uniaxially compacting pressures are applied to the sample and such a changes are reproduced by the model when different grain-boundary angles distributions are used. In addition, changes in the R ( B a ) dependence have their counterparts in the experimental transport noise signals.