Annealing melt-processed Sm–Ba–Cu–O bulk superconductors under 10 atm oxygen

Abstract

Annealing melt-processed Sm–Ba–Cu–O under high pressure oxygen was studied because a long time is necessary to oxygenate a large sample under atmospheric pressure while increasing the size of bulk superconductors is important for its performance. An increase in the critical temperature of superconductivity ( T c) was observed with increasing the oxygen pressure ( pO 2) up to 10.5 atm when the sample was annealed at 400 or 500 °C, while T c decreased with increasing pO 2 when annealed at 300 °C. The estimated diffusion length of oxygen at 400 °C increased by a factor of 2.5 with increasing pO 2 from 1 to 10.5 atm. It is demonstrated that the time necessary to fully oxygenate a 30 mm diameter sample can be reduced to less than half of the period that was required for annealing a similar sample under flowing oxygen at atmospheric pressure.