Dielectric relaxation in granular metal-dielectric nanocomposites

The paper presents the research of dielectric properties on alternating current of (FeCoZr)(PZT)100-${x}$ metal-dielectric nanocomposites. Tested samples with ${X}1$=51.7 at.% and ${X}2$=57.6 at.% have been prepared by using of ion beam sputtering technique using technological gases of argon and oxygen. After films manufacturing they were subdued to 15-min isochronous annealing in temperature of $T_{\mathrm {a}}$=573 K. Alternating current (AC) electrical parameters of the nanocomposites: dissipation factor tg$\delta $, capacity ${C}$, resistance ${R}$ and phase shift angle $\varphi $ have been measured for the temperature range 77 K-373 K using frequencies of 50 Hz$--\text{l}$ MHz. Based on the measurement results complex values of conductivity $\sigma $, dielectric permeability $\varepsilon $, electrical modulus ${M}$ and their real and imaginary components have been calculated. Nonlinear dependence of conductivity $\sigma \mathrm {v}\mathrm {s}$. angular frequency have been observed for each samples. This indicates the hopping type of electrical conduction in the materials. Moreover, in both cases for angular frequencies $(j) \lt 10^{5}\mathrm {r}\mathrm {a}\mathrm {d}\cdot \mathrm {s}^{-1}$ the ionic polarization takes place. This type of polarization is associated to the simultaneous movement of many atoms linked together by chemical bonds in the crystal lattice. On the other hand in case of frequencies $(j)\geq 10^{5}\mathrm {r}\mathrm {a}\mathrm {d}\cdot \mathrm {s}^{-1}$ the orientation (dipole) polarization is observed. In case of $X1$ sample one time $\tau $ dipole relaxation under Debye’s conditions is registered. For the other sample ${X}2$, non-Debye relaxation can be observed. Values of the imaginary part of permittivity $\varepsilon^{\prime\prime}$ increases when the real component $\varepsilon^{\prime\prime}$ increases as well. In such a case, the dielectric response to the impact of external electric field ${E}$ can be determined using the formalism of the electric modules ${M}$, which is a conventional method for analyzing of the dynamic aspects of charge transport in materials.