In this work, the effects of sintering temperature and Na subtitution on zero critical temperature (Tc,0) in Bi-Pb-Sr-Ca-Cu-O superconductors were investigated. The xNaxCu3O10+ bulk samples with x = and (BPSCCO) were prepared by using the solid state reaction technique at elevated sintering temperatures of 840 and 850oC. | VNU Journal of Science: Mathematics – Physics, Vol. 33, No. 3 (2017) 17-24 Enhancements of Critical Temperature in Bi-Pb-Sr-Ca-Cu-O Superconductors Tran Hai Duc1, Duong Thi Thanh Nhan1, Le Minh Tien1,2, Nguyen Phuc Duong3, Nguyen Khac Man3,* 1 Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Hanoi, Vietnam Faculty of Teacher Education, VNU University of Education, 144 Xuan Thuy, Hanoi, Vietnam 3 International Institute for Materials Science, Hanoi University of Science and Technology, 1 Dai Co Viet, Hanoi, Vietnam 2 Received 08 July 2017 Revised 30 August 2017; Accepted 15 September 2017 Abstract: In this work, the effects of sintering temperature and Na subtitution on zero critical temperature (Tc,0) in Bi-Pb-Sr-Ca-Cu-O superconductors were investigated. The bulk samples with x = and (BPSCCO) were prepared by using the solid state reaction technique at elevated sintering temperatures of 840 and 850 oC. To examine the improvements of structural and superconducting properties of the BPSCCO samples, the X-ray diffraction (XRD), scanning electronic microscope (SEM) and DC resistance versus temperature (R-T) measurements were carried out. The experimental findings exhibit a co-existence of the high Tc (Bi-2223) and low Tc (Bi-2212) phases in all samples. The estimated volume fraction of the Bi2223 phase was increased from to , and the average size of the Bi-2223 grains was enlarged from to m as changing the sample preparation conditions. The improved connectivities between the Bi-2223 grains were also obtained by quantitively analyzing the relation between Tc,0 and residual resistance ratio (RRR). These improvements were likely to be reasons for the enhancements of T c,0 in the BPSCCO samples. Keywords: BPSCCO, Bi-2223, Bi-2212, Tc,0, RRR. 1. Introduction Since the discovery of high temperature superconductors, a lot of intensive studies have been made to enhance the superconducting .
