降温速率对Bi-2223/AgAu带材微观结构和传输性能的影响

采用PIT工艺制备了单芯Bi-2223/AgAu带材,系统地研究了第二次热处理阶段(HT2)降温速率对带材相组成、微观结构和传输性能的影响。结果表明：随着降温速率的减小,富铅相3321不断增加,CuO颗粒尺寸逐渐增大。当冷却速率从600°C/h减小到1°C/h时,临界电流密度Jc从7 kA/cm₂增加到11.5 kA/cm₂,增加了64%。由于晶间连接性能和磁通钉扎性能的提高,在较低的降温速率下,Bi-2223/AgAu带材在磁场下的临界电流密度也得到了提高。

Effects of cooling rate on the microstructures and transport properties of AgAu sheathed Bi-2223 tapes

Monofilament AgAu sheathed Bi-2223 tapes were fabricated by powder in tube (PIT) process. The influences of cooling rate during the second heat treatment process (HT2) on the phase composition, microstructures and transport properties of Bi-2223/AgAu tapes were systematically investigated. It was noticed that after the HT2 process, the content of Pb-rich Pb₃Sr_2.5Bi_0.5Ca₂CuO_y (3321) phase increased with the decreasing cooling rate, while the size of CuO phase particles became bigger. With the cooling rate decreasing from 600 °C /h to 1 °C /h, the critical current density, J_c increased from 7 kA/cm₂ to the maximum value of 11.5 kA/cm₂, which increased for 64%. Meanwhile the current capacities in magnetic field of these Bi-2223/AgAu tapes have also been enhanced with slow cooling process, attributed to the improvements of both the intergrain connectivity and the flux pinning properties.