Influence of Al doping and oxygenation on the superconducting properties of TSMG YBCO bulks

YBCO bulk single-grain samples with the nominal composition Y1.5Ba2(Cu1-xAlx)3Oy were fabricated by the Top – Seeded Melt – Growth process. Aluminium was found to be a suitable chemical dopant in Y1Ba2(Cu1-xAlx)3O7/Y2BaCuO5 bulk superconductors, which introduces effective nanosized pinning centres. An increase of the critical current density, Jc, and the appearance of a peak effect were observed at intermediate magnetic fields below the critical temperature, Tc. A significant increase of the critical current density was observed in Al doped samples after high pressure oxygenation (16 MPa oxygen pressure) at 750 °C, i.e. by a factor of 3 compared to samples subjected to standard oxygenation at 400 °C at ambient oxygen pressure.