Ferroelectric to paraelectric phase transition mechanism in poled PVDF-TrFE copolymer films

Direct experimental insights into the structural and dynamical mechanisms for ferroelectric \ensuremath{\beta} to paraelectric \ensuremath{\alpha} phase transition in a poled PVDF-TrFE copolymer is obtained from in situ x-ray diffraction and quasielastic neutron scattering measurements at high temperatures. It is observed that the \ensuremath{\beta}-to-\ensuremath{\alpha} phase transition proceeds through two energetically distinct processes, which are identified here as the nucleation and growth of an intermediate \ensuremath{\gamma} phase with random skew linkages followed by a \ensuremath{\gamma}-to-\ensuremath{\alpha} transition. The two energetically distinct microscopic processes can explain the stages of evolution for \ensuremath{\beta}-to-\ensuremath{\alpha} phase transition observed from heat flow measurements.