IMPROVEMENT IN SUPERCONDUCTIVITY OF TLBA2CACU2OY SYSTEM BY INTRODUCTION OF OXYGEN LOSS

The Tc and oxygen content of TlBa2CaCu2Oy have been investigated by quenching experiments, in which the heat-treated samples were dropped into liquid nitrogen. The oxygen loss, v, of TlBa2CaCu2Oy was determined by thermogravimetry in a nitrogen atmosphere using an oxygen-annealed specimen of TlBa2CaCu2Oy and also by measurements of the weight differences before and after quenching. Tc increased from 80 K of the oxygen-annealed specimen up to about 110 K with increasing oxygen loss up to v = 0.035 by annealing at 500°C in a nitrogen atmosphere. Judging from the high Tc above 110 K achieved by a small oxygen loss about v = 0.035, the as-sintered oxygen-annealed TlBa2CaCu2Oy specimen was in the over-doping state and probably has an oxygen vacancy of 7 - yo0. © 1990.