High electromechanical coupling factor and electrostrictive strain over broad frequency range in electrostrictive poly(vinylidene fluoride-trifluoroethylene) copolymer films

Electromechanical coupling factor is one of the most important parameters for measuring the performance of materials for electromechanical transduction applications. In this paper, we will show that a transverse electromechanical coupling factor k₃₁ of more than 0.45 can be achieved in poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer under certain electron irradiation treatment conditions. In addition, the effective piezoelectric coefficients of the irradiated copolymer have been found to increase markedly in comparison to non-irradiated copolymers. Experimental evidences also indicate that the improved electrostrictive strains in irradiated copolymer films can be maintained over a broad frequency and temperature range.