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Friday, December 14

Beyond The Traditional Polarization Response in Polar-polymers:
Some Amazing Properties of The Ferrorelaxor Polymers

Q. M. Zhang, The Pennsylvania State University,
CNMS Discovery Seminar Series
11:00 AM — 12:00 PM, Central Laboratory and Office Building (SNS), Building 8600, Iran Thomas Auditorium
Contact: Dave Geohegan (geohegandb@ornl.gov), 865.742.8995

Abstract

The direct and efficient coupling between the electric signals and the elastic, thermal, optical and magnetic signals in ferroelectric based electroactive polymers makes them attractive for exploiting a broad range of cross-coupling phenomena and applications which have great promise for new device technologies (see the figure). This talk will present the recent advances in developing electroactive polymers and nanocomposites for solid state cooling. One major engineering challenge in this century is to develop alternative cooling technology to replace the century old vapor compression cycle (VCC) based cooling which employs strong greenhouse gases as the refrigerants and to provide efficient thermal management of microelectronic components and computers. Electrocaloric effect (ECE), which is the temperature and entropy change of insulating dielectric materials under electric fields, is attractive to realize efficient cooling devices. However, the relatively small ECE observed in dielectrics in the last century make it unimpressive for any practical applications. By making use of phase transitions and the high dipolar entropy in these polymers in the dipolar disordered state we demonstrated that a giant ECE can be achieved in a class of ferroelectric polymers. Moreover, by employing defects modifications to convert the normal ferroelectric into a ferroelectric relaxor, which is a self-organized nanocomposite, a large ECE over a broad temperature range about room temperature can be obtained. This talk will also discuss considerations on further enhancing the ECE and chip-scale solid state EC cooling devices, exploiting the newly discovered large ECE in ferroelectric polymers.