The influence of Zn on the superconducting properties of 30 mm diameter melt-texturedDy–Ba–Cu–O bulk superconductors

Abstract

Single-domain, c-axis-oriented 30 mm diameter Zn-doped Dy–Ba–Cu–O/Ag (DyBCO) bulk superconductorshave been successfully grown by the top-seeded melt growth method from precursors ofDyBa2Cu3Oy (Dy123),Dy2BaCuO5 (Dy211)and Ag2O in air and their position-dependent superconducting and magneticproperties studied. The Zn-free DyBCO sample exhibits an onsetTc of 91.9 K with a sharp superconducting transition. The onsetTc decreased monotonically from 91.9 to 87 K as the ZnO contentincreased from 0 to 0.1 wt%. The value of the critical current density(Jc) under the seed, namely, at position A1, for the undoped DyBCO sample was increased from 4 to5.8 × 104 A cm−2, and at position D1, i.e., 7.5 mm from the centre of the seed, it increased from 5.3 to6.5 × 104 A cm−2 for an optimally Zn-doped DyBCO sample. The highest value of the irreversibility field(Birr) was found at position D1 for all the compositions. A prominent peakeffect was observed both in undoped and optimally Zn-doped DyBCOsamples. Furthermore, the maximum trapped magnetic flux densities(Bmax) of Zn-free and optimally Zn-doped DyBCO samples were foundto be 0.77 and 0.83 T at 77 K, respectively. We also synthesizedCeO2-doped DyBCO bulk samples in order to refine the size of theDy211 particles and studied the trapped field distribution ofCeO2-doped Zn–DyBCO samples. It was found that the value of trapped field was enhancedfrom 0.77 to 0.95 T for the undoped and from 0.83 to 1.08 T for the optimally Zn-dopedDyBCO sample. As a result, the Dy–Ba–Cu–O sample with the addition of Zn andCeO2 exhibits the most enhanced superconducting properties.