Study of frequency dependent epsilon*(omega) in amorphous ferroelectrics: Modified generalized Langevin equation analysis

We studied the frequency dependent dielectric constants of amorphous LiNbO3 , KNbO3, and PbTiO3 at temperatures below the crystallization. We analyzed the real and imaginary part of dielectric constants epsilon'(omega) and eps ilon "(omega) using the generalized Langevin equation modified by the space charge effect and the phenomenological frequency scaling. With this model, we can explain the low frequency dispersion and the high frequency relaxat ion behavior of epsilon'(omega) and epsilon "(omega) simultaneously. Our ap proach is new and different from our previous equivalent circuit model. (C) 1999 American Institute of Physics. [S0021-8979(99)01301-8].