Cerium Doped Bismuth Based High Tc Superconductor: Synthesis and Study of Superconducting Properties

High-Tcsuperconductivity has been an emerging field for researchers since its discovery. Bismith based superconductors commonly called BSCCO have great importance among the superconducting family. It is divided into three phases among them 2223 phase is highly studied in order to investigate its superconducting properties by substitution of different elements. We have studied the substitution of cerium (Ce) on calcium site of bismuth based Bi (Pb)Sr (Ba)-2223 high-Tcsuperconductor. The nominal compositions of Bi1.6Pb0.4Sr1.6Ba0.4(Ca1-xCex)2Cu3Oxceramic superconductor were prepared by wet chemical method. Stoichiometric amounts of Bi2O3, PbO, Sr (NO3)2, BaCO3, CaCO3, CuO and CeO2were used as starting materials. Structural analysis was done by X-ray diffraction (XRD) at room temperature and different parameters were calculated. DC resistivity measurements for the transition temperature of synthesized superconducting samples were taken by the standard four-probe method, apparatus for which was developed in our laboratory. It is observed that with the substitution of cerium on calcium site the single high-Tc2223 phase is obtained.

Cu0.5K0.25Tl0.25Ba2Ca3Cu4O12-δ SUPERCONDUCTOR AND ITS DIELECTRIC PROPERTIES

Cu 0.5 K 0.25 Tl 0.25 Ba 2 Ca 3 Cu 4 O 12-δ superconductor samples were synthesized and their dielectric properties were measured between 80 K and 290 K by means of capacitance (C) and conductance (G) measurements with the test frequency (f) in the range of 10 KHz to 4 MHz. A negative capacitance (NC) occurrence was observed, which most likely arose from the superior Fermi level of ceramic superconductor samples than metal electrodes. Also the NC may be due to the space charge situated at the multiple insulator–superconductor interfaces (grain boundaries) in the materials. The negative dielectric constant (ε′) and loss factor ( tan δ) show strong dispersion at low frequencies. The lower thermal agitation at 80 K may boost the polarizability and hence the dielectric constants (ε′ and ε″).