Piezoelectric hydrostatic coefficients of PVDF and P(VDF-TrFE) copolymer foils at high hydrostatic pressures

Pressure dependence of the hydrostatic piezoelectric coefficient d(h) was m easured for PVDF and P(VDF-TrFE) polymer foils in the range up to 60MPa. Th e hydrostatic strain coefficient d(h), the hydrostatic voltage coefficient g(h) and figure of merit d(h).g(h) were determined using the static method. Electric charge induced across samples was measured by Keithley 6517 elect rometer and the pressure in the measuring chamber was changed by using a ho me made hydraulic press. The pressure dependences of hydrostatic coefficien ts were measured for several cycles. A pressure hysteresis was observed the re. Permittivity of the polymer foils was measured as a function of pressur e using an HP 4192A Impedance Analyser. Experimental dependences of the cha rge on pressure and temperature were fitted by multi parameter function. Th e pressure and temperature dependences of the hydrostatic d(h) and pyroelec tric p(3) coefficients were determinated. It was found the hydrostatic stra in coefficient d(h) decreased and pyroelectric coefficient p(3) increased w ith pressure at constant temperature.