Percolation effects in the diamagnetic response of polystyrene-YBa 2Cu 3O 7−δ superconductor composites

Abstract

Polystyrene compositions with the high- T c superconductor (HTSC) YBa 2Cu 3O 7−δ were prepared and a study of their diamagnetic responses was carried out at the frequency f=50 kHz, depending on HTSC content (c=0–100 vol.% with 5% steps) and temperature (T=77–300 K). The results presented allow us to conclude that the diamagnetic behaviour of composites is of percolation character, and the critical volume fraction of HTSC is in the region of 0.20< c<0.30. The increase of the diamagnetic response in composites with increasing c is the results of formation and merging of a winding superconductive labyrinth consisting of YBa 2Cu 3O 7−δ grains. The electrical resistance ϱ of composites shows a sharp decrease from 10 14 to 10 4 Ω cm, which depends on c in the region of 0.20< c<0.30.