Thermal variation of piezoresponse in microscopically poled poly(vinylidene fluoride-trifluoroethylene) ferroelectric copolymers approaching Curie temperature

The piezoelectric and ferroelectric properties of microscopically poled poly(vinylidene fluoride trifluoroethylene) [P(VDF-TrFE)] copolymer films have been examined at different temperatures approaching Curie point using piezoresponse force microscopy in combination with dual frequency resonance tracking technique, with the amplitude, phase, quality factor, and resonance frequency of the piezoresponse simultaneously quantitatively determined. It is observed that the piezoresponse remains relatively stable up to 110 °C, and then drops rapidly to zero. The variations of the quality factor and resonance frequency with respect to the temperature change are also observed, which is consistent with thermal induced softening in films. The switching characteristics of films have also been examined, showing a characteristic hysteresis loop up to 110 °C with small asymmetries. The work helps illustrate the thermal stability of ferroelectric polymers poled at nanoscale.