An applied electric field can reversibly change the temperature of an electrocaloric material under adiabatic conditions, and the effect is strongest near phase transitions. We demonstrate a giant electrocaloric effect (0.48 kelvin per volt) in 350-nanometer PbZr _0.95 Ti _0.05 O ₃ films near the ferroelectric Curie temperature of 222°C. A large electrocaloric effect may find application in electrical refrigeration.

The authors have recently observed a giant electrocaloric effect (12K in 25V) in 350nm sol-gel PbZr0.95Ti0.05O3 films near the ferroelectric Curie temperature of 242°C. Here the authors demonstrate a giant electrocaloric effect (5K in 25V) in 260nm sol-gel films of the relaxor ferroelectric 0.9PbMg1∕3Nb2∕3O3–0.1PbTiO3 near the Curie temperature of 60°C. This reduction in operating temperature widens the potential for applications in cooling systems.

Permittivity measurements of a 0.93PMN-0.07PT thin film show a broad maximum near 35 °C, and an anomaly at the depolarizing temperature Td=18 °C on heating only, suggesting a dipolar glass-relaxor phase transition. No structural phase transition at 18 °C is apparent from ferroelectric hysteresis loops taken on field cooling and field heating. These loops show the thermal hysteresis expected for ferroelectric relaxors, which has not hitherto been experimentally verified in PbMg2/3Nb1/3O3-PbTiO3 thin films. Our data suggest the intriguing possibility of a giant electrocaloric effect (ΔT=9 K, ΔE=720 kV cm−1) at and near room temperature.

The physics of pyroelectric infra red detectors as it applies to the selection of detector materials is briefly reviewed and the properties of a number of the more commonly used materials are compared. The use of ferroelectrics in the region of the Curie temperature as dielectric bolometers with an applied bias field is assessed and the properties of barium strontium titanate and lead magnesium niobate for use in this mode are reported and their potential compared with the conventional pyroelectrics.

Next-generation electrocaloric and pyroelectric materials for solid-state electrothermal energy interconversion - Volume 39 Issue 12 - S. Pamir Alpay, Joseph Mantese, Susan Trolier-McKinstry, Qiming Zhang, Roger W. Whatmore