Dynamic temperature response of electrocaloric multilayer capacitors

Abstract

We measure and model the dynamic temperature response of electrocaloric (EC) multilayer capacitors (MLCs) which have been recently highlighted as novel solid-state refrigerators. The MLC temperature responses depend on the operation voltage waveform, thus we consider three types of voltage waveforms, which include square, triangular, and trapezoidal. Further, to implement an effective refrigeration cycle, the waveform frequency and duty cycle should be carefully chosen. First, our model is fitted to the measurements to evaluate an effective EC power and thermal properties, and calculates an effective cooling power for an EC MLC. The prediction shows that for a MLC with a thermal relaxation time for cooling, trc, a square voltage waveform with a duty cycle of 0 < d ≤ 0.3 and a period of trc < P ≤ 1.4trc provides the maximum cooling power. This work will help to improve the implementing methods for EC refrigeration cycles.

Spatially Resolved Imaging of Electrocaloric Effect and the Resultant Heat Flux in Multilayer Capacitors

“…This strongly supports the reliability of our data, and the results shown in Figures – can therefore represent the electrocaloric properties of MLC 3. In addition, previous work carried out direct measurement on MLCs using a thermocouple and reported three distinct types of electrocaloric responses depending on frequency . At a high frequency (≫1 Hz), it was shown that MLCs become hotter because of limited thermal conductivity of MLCs, which cannot afford such high frequency of heat transfer.…”

Indirect Electrocaloric Evaluation: Influence of Polarization Hysteresis Measurement Frequency

“…In practical application, if not properly designed, many factors would lead to the significant degradation of caloric effect and overall performance, such as operating frequency, flow rate, geometric parameters, and thermal conductivity . For ferroelectric materials, the influence of applied electric field frequency on ECE calculation has been reported by several researchers, and it is controversial based on the results reported in the literature . For instance, Ding et al reported that for BaTiO 3 single crystal, the ECE calculated through indirect measurement is significantly affected by the frequency of P – E loops.…”

“…Geng et al reported that frequency has an inappreciable effect on P – E loops and a negligible effect on in antiferroelectric [(Pb 0.97 La 0.02 )(Zr 0.95 Ti 0.05 )O 3 ] (PLZT) thin films . Kwon et al reported on multilayer capacitors (MLCs), with three different types of EC responses depending on frequency . At a high frequency (≫1 Hz), it was observed that MLCs become hotter due to the limited thermal conductivity, which cannot support such a high frequency of heat exchange.…”

Present and future caloric refrigeration and heat-pump technologies

“…polymers, the most recent work has been published in , and Kwon et al (2014). For ceramic electrocaloric materials, the following recent article has been published by Zhao et al (2015).…”