Dopants Effect on Dielectric Response of (CuTl)0.5Ba2(CaMg)Cu3−xAxO10−δ Superconducting Phase

(CuTl)0.5Ba2(CaMg)Cu3−xAxO10−δ; (x = 0 and 1.5, A = Zn, Ni and Cd) superconducting phase was prepared by a two-step solid-state reaction. X-rays diffraction spectra confirmed the orthorhombic crystal structure of this phase. The ac-conduction mechanism in (CuTl)0.5Ba2(CaMg)Cu3−xAxO10−δ phase was explored via dielectric measurements in the frequency range from 40 Hz to 100 MHz at different temperatures from 77 to 287 K, respectively. The maximum values of the real part of the dielectric constant (\( \varepsilon_{{r({{\rm Max}} .)}}^{\prime } \)) and imaginary part of the dielectric constant (\( \varepsilon_{{r({{\rm Max}} .)}}^{\prime \prime } \)) at 40 Hz were increased with Zn and Cd doping, and their values were slightly decreased with Ni doping at Cu sites in CuO2 planes as compared to the undoped pure (CuTl)0.5Ba2(CaMg)Cu3O10−δ sample. But, a decreasing trend was observed in the values of \( \varepsilon_{{r({{\rm Max}} .)}}^{\prime } \) in Zn- and Cd-doped samples and an increasing trend was observed in the values of \( \varepsilon_{{r({{\rm Max}} .)}}^{\prime } \) in Ni-doped and pure samples with increase in temperature, while the opposite trend was observed with increasing temperature in the values of \( \varepsilon_{{r({{\rm Max}} .)}}^{\prime \prime } \) with respective dopants. The overall decrease in the maximum values of the tangent loss (tanδ) factor was observed in all doped samples as compared to the undoped pure sample. The maximum value of tanδ was increased in Zn- and Cd-doped samples and was decreased in pure and Ni-doped samples with increase in temperature. The maximum values of ac-conductivity {σac(Max.) (Ω cm)−1} were increased with Zn and Cd doping, and their values were slightly decreased with Ni doping at Cu sites in CuO2 planes as compared to the undoped pure sample. The values of σac(Max.) (Ω cm)−1 were observed to increase with increase in temperature in all the samples.