Comparison of directly and indirectly measured electrocaloric effect in relaxor ferroelectric polymers

We report the directly measured electrocaloric effect (ECE) (the adiabatic temperature change Delta T) of relaxor ferroelectric poly (vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer and its blend with poly (vinylidene fluoride-chlorotrifluoroethylene). The results show that the directly measured Delta T in the relaxor terpolymer is much larger than that deduced from Maxwell relation and that the relaxor terpolymer possesses a giant ECE at room temperature. The large difference between the directly measured Delta T and that deduced indicates that the Maxwell relation, which is derived for ergodic systems, is not suitable for deducing ECE in the relaxor ferroelectric polymers, which are nonergodic (polar-glass) material systems. (C) 2010 American Institute of Physics. [doi:10.1063/1.3514255]