Large Electrocaloric Effect in Ferroelectric Polymers Near Room Temperature

• Published in: Science (American Association for the Advancement of Science) 2008-08, Vol.321 (5890), p.821-823
• Main Authors: Neese, Bret, Chu, Baojin, Lu, Sheng-Guo, Wang, Yong, Furman, E, Zhang, Q.M
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cooling; Copolymers; Dielectric polarization; Dielectric, piezoelectric, ferroelectric and antiferroelectric materials; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Electric fields; Electrical, magnetic and optical properties; Entropy; Exact sciences and technology; Material films; Materials; Materials science; Organic polymers; Physicochemistry of polymers; Physics; Polymers; Polymers; organic compounds; Properties and characterization; Room temperature; Temperature; Transition temperature
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1159655

Applying an electrical field to a polar polymer may induce a large change in the dipolar ordering, and if the associated entropy changes are large, they can be explored in cooling applications. With the use of the Maxwell relation between the pyroelectric coefficient and the electrocaloric effect (ECE), it was determined that a large ECE can be realized in the ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer at temperatures above the ferroelectric-paraelectric transition (above 70°C), where an isothermal entropy change of more than 55 joules per kilogram per kelvin degree and adiabatic temperature change of more than 12°C were observed. We further showed that a similar level of ECE near room temperature can be achieved by working with the relaxor ferroelectric polymer of P(VDF-TrFE-chlorofluoroethylene).