Effects of calcium doping on the superconducting properties of top-seeded melt growth processed Y1.5Ba2−xCaxCu3Oy superconductors

The effect of calcium doping on the superconducting properties of top seeded melt growth (TSMG) processed Y1.5Ba2−xCaxCu3Oy superconductors was studied in terms of calcium content (Xca). YBa2−xCaxCu3O7−δ (Xca = 0, 0.005, 0.01, 0.02, 0.04, 0.1, 0.3) powders were synthesized by the powder calcination method. YBa2−xCaxCu3O7−δ powders were mixed with 0.25 mole Y2O3 powder and 1 wt.% CeO2 as Y2BaCuO5 (Y211) refiner, and finally made into Y1.5Ba2−xCaxCu3Oy (Y1.5) + 1 wt.% CeO2 composition. The single Y123 growth on the top surface was observed up to Xca = 0.1, while the multiple Y123 growth was observed at Xca ⩾ 0.1. The superconducting transition temperature (Tc) and critical current density (Jc) of TSMG processed Y1.5 samples were inversely proportional to Xca. The Y211 size increased with increasing Xca due to the enhancement of Y211 coarsening by calcium doping. No Y211 refining effect by CeO2 was observed in the calcium doped samples. The Tc and Jc decrease by calcium doping are likely to be due to the calcium incorporation with the Y123 lattice and formation of coarse Y211 particles.

► We study effects of calcium doping in melt processed Y123 superconductors.
► We examin a superconducting transition temperature and current density.
► A transition temperature and current density decreases by calcium doping.
► Calcium doping leads to coarseing of Y211 particles.
► Y211 refining effect by CeO2 is disappreared by calcium doping.