Preparation of YBa2Cu4O8 Superconducting Bulk at Ambient Oxygen Pressure via Oxalate Gel Route

The superconducting bulk YBa2Cu4O8 compound was prepared by a modified sol-gel method via an oxalate route. In this route, metal nitrates were used as the starting ingredients, added with and without Na(NO3), respectively. The 124 bulk could be straightly produced by sintering the as-pelletized bulk in flowing oxygen at 800°C for 1–5 days. The obtained bulk YBa2Cu4O8 compound showed a nearly phase-pure 124, examined by X-ray diffraction, and a Tc(zero) of 80K by resistivity measurement. Ac and DC magnetic susceptibilities were also shown the identical onset temperature of superconducting state. Results reveal that the addition of Na(NO3) could prominently speed up the formation of the 124 phase.