Abstract
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″).
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