Superconducting properties of Bi-based ceramics with column 3A elements

Abstract

Samples with the nominal composition Bi 1.8− x A x Pb 0.26Sr 2Ca 2Cu 3O y ( x=0–0.5; A=B, Al, Ga, In) were prepared. Measurements of resistivity, AC susceptibility, critical current density and magnetization have been used for characterization of the samples. All boron-substituted samples had a 2223 phase and narrow transition with the critical temperature T c≈106–108 K and the critical current density J c (77 K)≈10 5 A/m 2. The presence of aluminium caused decrease of T c. The 2212 phase became evident and J c (77 K) sharply decreased at x⩾0.3. The resistivity curves of all the samples with Ga were steeper. The T c values ranging from 103 to 60 K were considerably influenced by the amount of dopant. The volume of 2212 phase increased rapidly at x=0.2 and J c decreased to zero below 77 K. Introducing indium into the samples had a rather positive effect on T c since the resistivity–temperature curves were always shifted towards higher temperatures with the narrow transition at ∼107 K although the XRD patterns showed that the samples also contained the 2212 phase. The samples with x=0.05–0.4 had J c (77 K)≈10 5 A/m 2. The highest content of In worsened the quality of the samples and decreased the J c (77 K) to zero.