SPECTROSCOPIC STUDIES ON THE EFFECT OF FIELD-STRENGTH UPON THE CURIE TRANSITION OF A VDF TRFE COPOLYMER

Infrared spectroscopic studies of the effects of field strength upon the ferroelectric phase transition behavior of a VDF/TrFE (75/25) copolymer upon heating and cooling in an electric field have revealed new findings. The paraelectric phase in the absence of an electric field resembles the alpha phase of PVDF with a trace of short trans sequences distributed randomly along the chain axis. The paraelectric phase in a high electric field is very different from that in the absence of an electric field. The paraelectric phase under an electric field has much longer trans sequences. The Curie transition temperature upon heating is a first-order transition temperature (T(c)up) and is dramatically elevated from 120 to 135-degrees-C under the field of more than 0.4 MV/cm. Upon cooling, the paraelectric phase in an electric field does not show a clear transition. The field-induced phase transition and the loss of dipole switchability observed below a cooling temperature of 120-degrees-C, and their dependence on time and field strength when exposed to a cyclic bipolar electric field are discussed. (C) 1993 John Wiley & Sons, Inc.