Quantifying electrocaloric effects in multilayer capacitors (Vol. 49, No. 2)

“(a) Schematic cross-section of an MLC. (b) Photograph of three MLCs based on 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3, with active area per layer of 0.12, 0.29 and 0.42 cm2 within dashed lines. (c) Temperature change |ΔTj| measured directly using a thermocouple (solid circles) versus the ratio of active volume Vactive to total volume Vtotal. Multiplying by the ‘correction’ factor (solid squares) that would have been hitherto assumed elsewhere overestimates |ΔTj| (open circles)

Multilayer capacitors (MLCs) are now being exploited in prototype cooling devices because they show large voltage-driven changes of temperature that can be used to pump large amounts of heat. However, accurate quantification of these electrically driven temperature changes is challenging because only the core is electrocalorically active.

In a recent study, the authors investigated electrocaloric MLCs with different geometries. By increasing the active volume of the core with respect to the inactive surround, the authors were able to identify the temperature changes that could be driven in the core without thermalization due to the surround. This improves upon previous works, in which partial thermalization was assumed to be complete, leading to overestimates of temperature change.

T. Usui, S. Hirose, A. Ando, S. Crossley, B. Nair, X. Moya, and N. D. Mathur, Effect of inactive volume on thermocouple measurements of electrocaloric temperature change in multilayer capacitors of 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3, J. Phys. D: Appl. Phys. 50, 424002 (2017).
[Abstract]