Frequency-dependent dielectric characteristics of Tl–Ba–Ca–Cu–O bulk superconductor

Abstract

A ceramic sample of a layered cuprate of Tl2Ba2Ca2Cu3Ox and Tl2Ba2Ca1Cu2Ox, so-called Tl-based 2223 and 2212 compounds, was investigated by the measurement of the dielectric constants (ε′ and ε′′), the dielectric loss (tanδ), and the conductivity (σac) as a function of temperature (80–300 K) and frequency (100 Hz–10 MHz). A negative capacitance phenomenon has been observed and it is believed that the negative capacitance effect is due to the polarization effect. The negative dielectric constant has been calculated from the negative capacitance. The dielectric constant (ε′) and the dielectric loss (tanδ) show strong dispersions at lower frequencies. The dielectric properties of the sample were found to have strong frequency and temperature dependence.

Dielectric properties of (CuO, CaO2, and BaO)y/CuTl-1223 composites

“…The charge reservoir layer, impurities, voids and grain-boundaries behave as dielectric media, which can be polarized by displacing the charge carriers from their equilibrium position with external applied field. Frequency and temperature dependent dielectric measurements are of great importance to study the induced dipolar polarization in these composites for their dielectric properties [17,18]. In this article we report the frequency and temperature dependent dielectric measurements of (CuO, CaO 2 , and BaO) y /CuTl-1223 composites.…”

“…There are few reports available in the literature on the dielectric measurements of oxides of the high temperature superconductors in which giant dielectric constants are observed [17,21,22]. …”

Dielectric properties of (Zn) x /CuTl-1223 nanoparticle-superconductor composites

“…CuTl-1223 superconducting phase has long coherence length along c-axis ( c  ) [2], low superconducting anisotropy ( / ab c     ) [3], small penetration depth (  ), high zero resistivity critical temperature ( c (0) T ), high irreversibility field ( irr H ), and high critical current density ( c J ) [4,5]. The performance of bulk high temperature superconductors can be severely affected by inter-grain voids, micro-cracks, and pores [6][7][8]. Different strategies have been exercised to minimize the voids and pores in  CuTl-1223 phase [9,10].…”

“…· Interfacial polarization ( i  ). This polarization is sensitive at low frequency range of 10 3 Hz and may extend to a few kHz [6,13,17]. Dielectric properties of Cu 0.25 Tl 0.75 Ba 2 Ca 3 Cu 4 O 12δ superconductor with addition of MgO nanoparticles were investigated in frequency range from 100 Hz to 4 MHz [7].…”

“…Increase in r   and decrease in ac  were observed up to certain optimum level of the nanoparticle content. Dielectric constants ( r   , r   ) and dielectric loss ( tan ) of Tl-based high temperature superconductors (HTSCs) were found to depend strongly on operating temperature and frequency of external applied ac-field [6]. Negative capacitance (NC) phenomenon was observed in Cu 0.5 Tl 0.5 Ba 2 Ca 3 Cu 4y Zn y O 12δ (y = 0, 3) superconductor at different frequencies and temperature [13,18].…”