New experimental approach to nonlinear dielectric effects in the static limit

We present a nonlinear dielectric technique that measures the real and imaginary component of permittivity in a time resolved fashion for a sequence of high field amplitudes. Data is recorded within a few milliseconds of exposing the sample to sinusoidal fields without dc-bias. This short exposure time and a sample thickness of only 10 μm greatly reduces heating effects. The Piekara factor quantifying the nonlinear dielectric effect can be derived from analyzing the response at both the fundamental and the third harmonic frequency, and for both quantities the near quadratic field dependence is verified. The small deviations from the expected field dependence are ascribed to a resolved fifth harmonic response. In this manner, the nonlinear dielectric effect of the polar glass-forming liquid propylene glycol is determined in the static limit, and it is found that the Piekara factor changes from −2.9 × 10⁻¹⁶ V⁻² m² to −1.4 × 10⁻¹⁶ V⁻² m² when the temperature is raised from 204 K to 235 K.