Dresden 2020 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 11: Ferroics - Domains and Domain Walls (joint session KFM/MA)

KFM 11.2: Talk

Wednesday, March 18, 2020, 15:20–15:40, TOE 317

Dielectric nonlinearity in 0.5(Ba_0.7Ca_0.3)TiO₃–0.5Ba(Zr_0.2 Ti_0.8)O₃ ferroelectric thin film capacitors — •Maximilian Becker^1,2, Claus Burkhardt¹, Reinhold Kleiner², and Dieter Koelle² — ¹NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, Germany — ²Physikalisches Institut and Center for Quantum Science (CQ) in LISA⁺, University of Tübingen, Germany

We use the recently developed Rayleigh analysis based on impedance spectroscopy to investigate dielectric nonlinearity caused by irreversible motion of domain walls in lead-free ferroelectric 0.5(Ba_0.7Ca_0.3)TiO₃–0.5Ba(Zr_0.2Ti_0.8)O₃ (BCZT) thin films. Impedance spectra from 10 Hz to 1 MHz were collected at different excitation fields on pulsed laser deposited polycrystalline and epitaxial BCZT thin film capacitors. Rayleigh plots were created by fitting the measured complex impedance to an equivalent-circuit model containing the Rayleigh element. For a polycrystalline film, we observed nonlinear behavior in good agreement with the Rayleigh law at a threshold field E_T≈55 kV/cm with Rayleigh constant α′=0.407±0.035 cm/kV. For the epitaxial counterpart, we found Rayleigh-like behavior which is not in full agreement with the Rayleigh law at E_T≈3.75 kV/cm with α′=1.836±0.031 cm/kV, indicating a significantly higher domain wall mobility. Our results demonstrate the superiority of Rayleigh analysis based on impedance spectroscopy over the commonly used single-frequency approach.

This work was partly funded by the BMBF (Grant No. 13GW0123E).