Superconducting critical current density enhanced to 285 A cm~(-2) for Sr_2VFeAsO_(3-δ) tapes fabricated by ex situ powder-in-tube process

摘要

Superconducting critical current density (J(c)) at 4.2;K for superconducting Sr2VFeAsO3?? tape fabricated by powder?in?tube process was enhanced up to 285;A;cm(?2). Cross?sectional SEM images for superconducting Sr2VFeAsO3?? wire/tapes indicated that void fraction f(void) was reduced from 12.8% for the round wire to ?2.5% for the tapes. The decrease in f(void) suppresses the so?called ?weak?links? and therefore enhances the J(c). In order to enhance J(c), the annealing condition should be optimized. The optimal annealing condition enforces the link between grains and avoids the loss of oxygen atoms in the superconducting core.