Effect of Preform Compaction Pressure on the Final Microstructures and Superconducting Properties of YBa2Cu3O7−δ Superconductors Fabricated by Directionally Solidified Preform Optimized Infiltration Growth Process

Abstract

Bulk YBa2Cu3O7−δ (YBCO, Y-123) superconductors with reasonable critical current densities J c are successfully fabricated in relatively short-time durations employing Directionally Solidified Preform Optimized Infiltration Growth Process (DS-POIGP). The effect of preform compaction pressure, applied to Y2BaCuO5 (Y-211) preform prior to the infiltration of liquid phases, on the end microstructures and current densities is investigated. It is found that a preform compaction pressure of 460 MPa resulted in samples with superior microstructures and superconducting properties. YBCO sample fabricated by DS-POIGP under optimized conditions revealed presence of fine-sized Y-211 particles distributed uniformly in the matrix of Y-123 causing large interfacial defect density (Y-211/Y-123). Extensive twinning on a nano-scale with twins in the size range of 40–100 nm is observed in the optimized sample. These microstructural parameters enabled a considerable improvement in the field dependence of J c . Irreversibility fields greater than 5.5 Tesla even at 77 K are achieved in the optimized sample fabricated by DS-POIGP.