Direct measurement of electrocaloric effect based on multi-harmonic lock-in thermography

TL;DR

This paper introduces a novel lock-in thermography technique for directly measuring the electrocaloric effect in dielectric materials, allowing accurate, single-measurement temperature change detection even with nonlinear responses.

Contribution

It presents a new measurement method using multi-harmonic lock-in thermography to accurately quantify electrocaloric effects in various dielectric materials.

Findings

Successfully measured temperature changes in Sr-doped BaTiO3 systems.

Able to separate electrocaloric contribution from heat losses and Joule heating.

Method applicable to diverse dielectric materials.

Abstract

In this study, we report on a direct measurement method for the electrocaloric effect, the heating/cooling upon application/removal of an electric field in dielectric materials, based on a lock-in thermography technique. By use of sinusoidal excitation and multi-harmonic detection, the actual temperature change can be measured by a single measurement in the frequency domain even when the electrocaloric effect shows nonlinear response to the excitation field. We have demonstrated the method by measuring the temperature dependence of the electric-field-induced temperature change for two Sr-doped BaTiO$_3$ systems with different ferroelectric-paraelectric phase transition temperatures, where the procedure for extracting the pure electrocaloric contribution free from heat losses and Joule heating due to leakage currents is introduced. This method can be used irrespective of the type of dielectric materials and enables simultaneous estimation of the polarization change and power dissipation during the application of the electric field, being a convenient imaging measurement method for the electrocaloric effect.