Frequency dependence of the dielectric properties of La-doped Pb(Zr0.35Ti0.65)O3 thin films

Abstract

Frequency dependence of the dielectric properties of La-doped lead zirconate titanate thin films with Pt and Ir electrodes and two different La doping levels is studied by impedance spectrometry between ${10}^{\text{−3}}$ and ${10}^4\hspace{0.17em}\mathrm{Hz}.$ A constant phase element with an impedance of ${\mathrm{Z=A}}_0{\mathrm{(j\omega )}}^{\mathrm{-\alpha }}$ is introduced into the equivalent circuit, which fits very well both the real and imaginary components of the measured impedance over the full frequency range, including the resonance, using a single α $\text{(0≪α<1).}$ Our analysis shows that α is not related to the ferroelectric properties of the films, but it has a monotonic correlation with the real dielectric constant. The close resemblance to the well-known butterfly-shaped $\mathrm{C–V}$ curve shown by α with the applied dc bias $\mathrm{(\alpha -V)}$ suggests that α may be affected by the density of the domain walls in the film, in addition to various dielectric relaxation processes.