Date: August 09, 2008 at 09:05:12
From: Rhanie, [620_acl1.gw.smartbro.net]
Subject: @Baffe: evtl. is das was für dich: Large Electrocaloric Effect in Ferroelectric Polymers Near Room Temperature

Hallo! http://www.sciencemag.org/cgi/content/abstract/321/5890/821 Science 8 August 2008: Vol. 321. no. 5890, pp. 821 - 823 DOI: 10.1126/science.1159655 Prev | Table of Contents | Next Reports Large Electrocaloric Effect in Ferroelectric Polymers Near Room Temperature Bret Neese,1,3 Baojin Chu,1,3 Sheng-Guo Lu,1 Yong Wang,2 E. Furman,1 Q. M. Zhang1,2* 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). 1 Materials Research Institute, The Pennsylvania State University, University Park, PA 16802, USA. 2 Electrical Engineering Department, The Pennsylvania State University, University Park, PA 16802, USA. 3 Materials Science and Engineering Department, The Pennsylvania State University, University Park, PA 16802, USA. * To whom correspondence should be addressed. E-mail: qxz1@psu.edu Gruß Rhanie.