Dynamics of the electrocaloric effect: high-resolution measurements on microsecond timescales

The electrocaloric effect (ECE) in ferroelectrics is a promising candidate for improved cooling technologies and small cooling devices. While direct and reliable measurements of the reversible adiabatic temperature change ΔT as a caloric key parameter are already challenging, an access to the full dynamics ΔT(t) of the ECE and the correlation with the ferroelectric properties are highly desirable for a more fundamental understanding of the ECE.

Here, we present a direct and contactless method to investigate the temperature change ΔT(t) of the ECE with mK temperature resolution and μs temporal resolution via the infrared emission of the sample. Ferroelectric properties are simultaneously recorded. Measurements on material systems with a first order and a diffuse phase transition, respectively, show characteristic changes of the field dependence of the ECE as fingerprints of the order of the phase transition. Systematic studies of the frequency dependence of the ECE allow, e.g., to separate extrinsic effects like heat transport from the pure caloric temperature change. High-frequency measurements up to kHz further allow the direct measurement of ΔT even for μm thin samples.