The electrocaloric effect is a phenomenon in which a material shows a reversible temperature change under an applied electric field. It is often considered to be the physical inverse of the pyroelectric effect. It should not be confused with the

Thermoelectric effect The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when ...

(specifically, the

Peltier effect The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when ...

), in which a temperature difference occurs when a current is driven through an electric junction with two dissimilar conductors. The underlying mechanism of the effect is not fully established; in particular, different textbooks give conflicting explanations. However, as with any isolated (adiabatic) temperature change, the effect comes from the voltage raising or lowering the

entropy Entropy is a scientific concept, as well as a measurable physical property, that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynam ...

of the system. (The

magnetocaloric effect Magnetic refrigeration is a cooling technology based on the magnetocaloric effect. This technique can be used to attain extremely low temperatures, as well as the ranges used in common refrigerators. A magnetocaloric material warms up when a m ...

is an analogous, but better-known and understood, phenomenon.) Electrocaloric materials were the focus of significant scientific interest in the 1960s and 1970s, but were not commercially exploited as the electrocaloric effects were insufficient for practical applications, the highest response being 2.5 degrees Celsius under an applied potential of 750

volt The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827). Defin ...

s. In March 2006 it was reported in the journal ''

Science Science is a systematic endeavor that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earli ...

'' that thin films of the material

PZT Lead zirconate titanate is an inorganic compound with the chemical formula (0≤''x''≤1), commonly abbreviated as PZT. Also called lead zirconium titanate, it is a ceramic perovskite material that shows a marked piezoelectric effect, meaning t ...

(a mixture of

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

titanium Titanium is a chemical element with the Symbol (chemistry), symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resista ...

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

and

zirconium Zirconium is a chemical element with the symbol Zr and atomic number 40. The name ''zirconium'' is taken from the name of the mineral zircon, the most important source of zirconium. The word is related to Persian '' zargun'' (zircon; ''zar-gun'' ...

) showed the strongest electrocalorific response yet reported, with the materials cooling down by as much as ~12 K (12 °C) for an electric field change of 480 kV/cm, at an ambient temperature of 220 °C (430 °F). The device structure consisted of a thin film (PZT) on top of a much thicker substrate, but the figure of 12 K represents the cooling of the thin film only. The net cooling of such a device would be lower than 12 K due to the heat capacity of the substrate to which it is attached. Along the same lines, in 2008, it was shown that a ferroelectric polymer can also achieve 12 K of cooling, nearer room temperature. With these new, larger responses, practical applications may be more likely, such as in

computer cooling Computer cooling is required to remove the waste heat produced by computer components, to keep components within permissible operating temperature limits. Components that are susceptible to temporary malfunction or permanent failure if over ...

or batteries.

References

Further reading