Harmonic analysis of the polarization response in Pb(Mg/sub 1/3/Nb/sub 2/3/)O/sub 3/-based ceramics-A study in aging

The polarization response of a ferroelectric ceramic displays nonlinear behavior at high applied fields due to saturation effects. Weak-field dielectric aging imposes additional nonlinearity on the hysteresis loops of these materials. Harmonic analysis using a discrete Fourier transform (DFT) permitted an observation of the change in the polarization frequency spectrum as Pb(Mg/sub 1/3/Nb/sub 2/3/)O/sub 3/-based relaxor ceramics aged. It also facilitated the calculation of ac current, power, and "internal bias field". The results show that particular harmonics in the polarization signal are sensitive indications of aging behavior. The average power dissipated at weak ac fields was found to decrease with aging time; and the power dissipated at strong fields tended to increase.