Effects of Adding Transition Metal-Substituted Polyoxotungstates on the Frequency and Temperature-Dependent Dielectric Properties of (Bi1.8Pb0.4)Sr2Ca2Cu3O10+δSuperconducting 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 capacitanceCp 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 (epsilon ' and epsilon ''), loss tangent (Tan delta) and ac conductivity (sigma(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,epsilon ' and sigma(ac)showed a decreasing trend with an increase in temperature in contrast to the increasing trend shown by epsilon '' and Tan delta. Additionally,epsilon '' has decreased upon increasing temperature at low frequencies. Accordingly, low {MnSiW11} addition at 0.12 wt% exhibited the highest dielectric constant 1.99x107 and ac conductivity61.449 (omega.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 mml:mfenced close=")" open="("1.654 <= S <= 1.759 for all the prepared samples.