Polarization fatigue in ferroelectric polymers

Ferroelectric materials are characterized by a spontaneous polarization which can be switched by an applied electric field. In many ferroelectrics the magnitude of the reversed polarization is observed to decrease when the polarization is switched many times. In ferroelectric polymers a significant decrease in reversed polarization may be observed after /spl sim/3000 cycles, and the reduction can be /spl sim/50% of the initial value. Infrared and X-ray observations show a conversion of the non-polar /spl alpha/ crystal form to the ferroelectric /spl beta/ form in samples containing a mixture of the crystal phases. However there appear to be no crystalline changes of such a nature as would lead to fatigue. A decrease in dielectric loss at low frequencies is observed in all fatigued samples, suggesting that space charge trapping may be involved in the fatigue process.