Effects of Adding Transition Metal-Substituted Polyoxotungstates on the Frequency and Temperature-Dependent Dielectric Properties of (Bi_1.8Pb_0.4)Sr₂Ca₂Cu₃O_10+δ Superconducting Phase

Abstract

In the search for highly responsive dielectric materials, superconducting samples of type (Bi,Pb)-2223 were prepared using the standard solid-state reaction technique, with the addition of three different concentrations of ferrato and mangano-undecatungstosilicate (0.04, 0.12, and 0.20 wt%). The dielectric studies were performed by measuring the parallel capacitance $C_{p}$ as well as the dielectric loss factor using LCR HiTESTER. The studies were performed at temperature and frequency ranges starting from room temperature down to 98 K and from 50 kHz up to 5 MHz, respectively. The dielectric behavior was investigated by calculating both dielectric constants ($\varepsilon^{\prime}$ and $\varepsilon^{\prime\prime}$), loss tangent (Tanδ) and ac conductivity (σ_ac) as a function of frequency, temperature and addition concentrations of the {FeSiW₁₁} and {MnSiW₁₁} polyoxometalates. The results revealed that the dielectric parameters decrease with increasing frequency at each temperature for all the {FeSiW₁₁}_x(Bi,Pb)-2223 and {MnSiW₁₁}_x(Bi,Pb)-2223 prepared samples. Moreover, $\varepsilon^{\prime}$ and σ_ac showed a decreasing trend with an increase in temperature in contrast to the increasing trend shown by $\varepsilon^{\prime\prime}$ and Tanδ. Additionally, $\varepsilon^{\prime\prime}$ has decreased upon increasing temperature at low frequencies. Accordingly, low {MnSiW₁₁} addition at 0.12 wt% exhibited the highest dielectric constant $\left( {1.99 \times 10^{7} } \right)$ and ac conductivity $61.449$ (Ω.m)⁻¹ with minimum dissipation (1.078). Furthermore, the ac conductivity was studied according to the power law, and the frequency exponent was found greater than one $\left( {1.654 \le S \le 1.759} \right)$ for all the prepared samples.