Pyroelectric or piezoelectric compensated ferroelectric composites

The matrix and inclusions of 0-3 composites of lead titanate (PT) in polyvi nylidenefluoride trifluoroethylene (P(VDF-TrFE)) have been independently po led by a special poling method. The polarization states of both constituent s are investigated by the measurement of the dynamic pyroelectric coefficie nts of the composites in the temperature range of 20-90 degrees C, within w hich the copolymer matrix undergoes a ferroelectric-paraelectric phase chan ge. The pyroelectric coefficients of PT and P(VDF-TrFE) have the same sign, while their piezoelectric coefficients have opposite signs. This allows th e preparation of composites with enhanced pyroelectric but reduced piezoele ctric activity when the matrix and inclusions are polarized in the same dir ection, or vice versa if the constituents are oppositely polarized. For a P T volume fraction of 27% it was possible to prepare a pyroelectric composit e with vanishing piezoelectric activity or a piezoelectric composite with v anishing pyroelectric activity by poling the matrix and inclusions in paral lel or antiparallel directions. (C) 2000 American Institute of Physics. [S0 003-6951(00)04719-7].