Ferroelectric refrigeration

Ferroelectric refrigeration. Just as a ferromagnet has a spontaneous magnetic moment that can be controlled by an applied magnetic field, a ferroelectric has a spontaneous electric polarization that can be controlled by an applied electric field. And in what’s known as the electrocaloric effect, applying or removing the electric field induces a reversible temperature change in a ferroelectric. If, as part of a thermal cycle, the electric field is adiabatically raised to heat the material and lowered to cool the material, a ferroelectric can function as a heat pump for heating or cooling. Such materials thus hold promise for compact, small-scale, solid-state refrigeration. Though early work achieved temperature changes of only a few kelvin, researchers in 2006 were able to cool a 350-nm-thick ferroelectric film by 12 K. Recent experiments by Yang Bai (University of Science and Technology Beijing) and colleagues have shown that for barium titanate, the cooling effect...