Dielectric Relaxation Dynamics and Polaronic Tunneling Conduction Mechanism of Electrical Conductivity of Fe_2O_3-Doped PbO–ZrO_2–SiO_2 Glass Ceramics

摘要

This study consists of comprehensive investigations on dielectric permittivity (ε'), electric moduli (M',M"), impedance (Z), and conductivity (σ_(ac_) spectra over broad regions of frequency and temperature of lead zirconium silicate glass ceramics mixed with different concentrations of Fe_2O_3. The observed increase in dielectric permittivity with the content of Fe_2O_3 is attributed to the increasing presence of iron ions in octahedral positions. Electric moduli plots with frequency (ω) and temperature (T) exhibit dipolar effects. These effects are quantitatively analyzed by Cole–Cole plots; the analysis indicates the distribution of relaxation times. Probable dipoles for these effects are identified and discussed. AC conductivity (σ_(ac)) shows a rising trend with an increase in Fe_2O_3 beyond 0.2 mol%, and this increase is attributed to the polaron exchange among Fe~(2+) and Fe~(3+) ions. The conduction mechanism is well explained using a polaron tunneling model in the middle-frequency and high-temperature regions.