The effect of sintering temperature on the rolled silver-sheathed monofilament Bi,Pb-Sr-Ca-Cu-O superconducting wire

The manufacture of high critical temperature (Tc) Bi,Pb-Sr-Ca-Cu-O (HTS BPSCCO) superconductor wire fabricated by power-in-tube (PIT) is a multi-step process. The main difficulty is that the value of Tc superconductor wire is determined by various factors different for each step. The objective of this study is to analyze the effect of selected sintering parameters on the properties of final rolled material. The fabrication process of 1 m rolled-silver sheath monofilament superconductor BPSCCO wire using mechanical deformation process including rolling and drawing has been carried out. The pure silver powders were melted and formed into pure silver (Ag) tube. The tube was 10mm in diameter with a sheath material/superconductor ratio of about 6 : 1. Starting powders, containing nominal composition of Bi2-Sr2-Cam-1-Cum-Oy, were inserted into pure silver tube and rolled until it reached a diameter of 4 mm. A typical area reduction ratio of about 5 persen per step has been proposed to prevent sausaging and microcracking during cold-drawing process. The process of rolling of silver tube was subsequently repeated in order to obtain 3 samples and then they were heat-treated at 820°C, 840°C and 860°C, respectively. Surface morphology was analyzed with SEM, crystal structure of BPSCCO with XRD, whereas the superconductivity was analyzed using temperature dependence resistivity measurement with four point probe. SEM images showed porosity along cross sectional surface of the samples. The sample with low heating temperature showed porosity more than the one with high heating temperature did. The value of critical temperature (Tc) of sample with heating time of 8 hours is 70 K. At above 70K, it shows the behavior of conductor properties. However, the porosity increased as the heating time increased up to 24 hours. The critical temperature is hard to be identified due to its porosity. According to XRD results, Bi-2212 phase in all samples were detected. Seminar Internasional ICAMST 2016