FLUCTUATION CONDUCTIVITY OF POLYCRYSTALLINEY_1-xTb_xBa₂Cu₃O_7-δSUPERCONDUCTORS

Abstract

We studied the effect of superconducting fluctuations on the electrical conductivity of granular samples of Y 1-x Tb x Ba 2 Cu 3 O 7-δ superconductors. For all samples we observed that the transition proceeds in two stages. Above the critical temperature, the Gaussian and critical regimes were observed, independently of the terbium concentration. In the regime of approach to the zero resistance state, and for low concentrations of terbium, an occurrence of a coherence transition was observed. For high concentrations of Tb , the results show a strong disorder at mesoscopic levels.

Coherence transition in polycrystalline Y0.95Tb0.05Ba2Cu3O7−δ superconductors

“…Two polycrystalline samples of Y 0.95 Tb 0.05 Ba 2 Cu 3 O 7Àd were prepared by solid-state reaction technique [5], using terbium oxide (Tb 2 O 3 ), barium carbonate (BaCO 3 ), yttrium and copper oxides (YO, CuO 3 ). Appropriate amounts were mixed and calcinated in air at 850, 880 and 920 1C for 24 h at each temperature.…”