Pressure Dependence of Ferroelectric Transition and Anomaly in Bulk Modulus in Copolymer of Vinylidende Fluoride and Trifluoroethylene

Thermal expansion of copolymer of 52.8 mol-% vinylidene fluoride and 47.2 mol-% trifluoroethylene under varied hydrostratic pressure p up to 100 MPa was observed over a temperature range of 30 to 110°C. Pressure dependence of the ferroelectric transition T t was evaluated as 0.318 K MPa -1 from the abrupt change in thermal expansion at the transition. This considerably large value of d T t /d p was in good agreement with that found in the dielectric measurements. The bulk modulus vs temperature curve exhibited a conspicuous minimum at the transition of 337 K as is the case with ferroelectric crystals.