Effect of inactive volume on thermocouple measurements of electrocaloric temperature change in multilayer capacitors of 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3

On increasing the active/total volume ratio of 0.9Pb( Mg1/3Nb2/3)O-3-0.1PbTiO(3) multilayer capacitors (MLCs), the electrocaloric temperature change measured using a thermocouple near the centre increases, until saturating to reveal the nominally adiabatic limit (vertical bar Delta T vertical bar similar to 2.7 K for rapid field changes of vertical bar Delta E vertical bar = 28.8 V mu m(-1)). For all MLCs that we studied, the practice of multiplying the measured temperature change by the total/active heat capacity ratio causes the adiabatic temperature change to be overestimated by a small numerical factor. These findings highlight the challenge associated with quantifying electrocaloric effects in MLCs of the type that are currently being used as working bodies in prototype cooling devices.