Superconductive Properties of the YBa2Cu4O8 Superconductor

A bulk density of 85% of the theoretical density was achieved by sintering a powder compact of YBa2Cu4O8 (124) at 850°C in flowing oxygen at 1 atm (≅105 Pa). This value is very close to that obtained by the hot isostatic pressure technique (90%). The superconducting properties of the sample were characterized by magnetization and ac susceptibility techniques. The magnetization critical current density at 20 K in zero field was determined to be ∼5 × 104 A/cm2, and the superconducting transition temperatures were found to be 77 K for the bulk material and 82 K for the granular phase. The powder X‐ray diffraction and ac susceptibility studies revealed the sintered 124 material to be single phase.