The Effect of Eu Substitution onto Ca Site in Bi(Pb)-2223 Superconductor Via Co-precipitation Method
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The samples with nominal composition of Bi16Pb0.4Sr2Ca2−x Eu x Cu3O y where x=0.000, 0.025, 0.050, 0.100, and 0.200 prepared by co-precipitation method (COP) have been investigated. They were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), electrical and resistivity measurement using the four-probe method. The temperature dependency on electrical resistance showed the superconducting behavior for all the samples. The critical current density (J c ) and superconductivity transition temperature (T c zero) of Eu substituted were found to be lower than those of the pure sample. T c zero varied between 100 and 73 K towards Eu concentration with the highest T c zero in the Eu substitution was found at 98 K for x=0.025 and decreased gradually for further substitution of Eu corresponding to a small change in the carrier concentration. J c decreased with increasing Eu substitution, and it was measured to be at 5.7512 A/cm2 in the Eu free sample and at 2.1223 A/cm2 for the x=0.025 sample at 77 K. XRD analyses showed the decrease of the volume fraction of Bi-2223/Bi-2212 (%) which were estimated from 78.13/21.87 for x=0.000 to 23.18/76.82 for x=0.200. The crystallographic structure was found to change slightly from tetragonal to orthorhombic in Eu substituted samples. The lattice parameter c of the Eu samples decreased due to the incorporation of Eu3+ (0.95 Å) with smaller ionic size at the Ca2+ (0.99 Å) site. From the SEM investigation, the grain connectivity became weak and the porosity increased with the increment of Eu concentration, resulting in the decrease of J c .
KeywordsBi-2223 Eu-substitution Phase formation Superconductor
The authors wish to thanks the Ministry of Higher Education (MOHE) Malaysia through Exploratory Research Grant Scheme (ERGS).
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