Effects of Adding Transition Metal-Substituted Polyoxotungstates on the Frequency and Temperature-Dependent Dielectric Properties of (Bi1.8Pb0.4)Sr2Ca2Cu3O10+δ Superconducting Phase

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 (Tan??) and ac conductivity (??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 ??ac showed a decreasing trend with an increase in temperature in contrast to the increasing trend shown by $$\varepsilon^{\prime\prime}$$ and Tan??. 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 $$61.449$$  (??.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.