K. Van Den Abeelea and M. A. Breazealeb
National Center for Physical Acoustics
University of Mississippi
University, MS 38677
[a] Post-doctoral Research Fellow of the Belgian National Fund for
Scientific Research and of Los Alamos National Laboratory, EES-4, Los
Alamos, NM 87545, U.S.A. . Presently with a NATO grant at NCPA.
(Permanent address: K.U.Leuven Campus Kortrijk, Interdisciplinary
Research Center, B-8500 Kortrijk, Belgium)
[b] Senior Scientist, NCPA. Also Professor of Physics, The University of
Tennessee, Knoxville, TN 37996-1200, U.S.A.
Frequency dependence of the first ultrasonic nonlinear parameter and the abnormally high third harmonic signals measured in lead zirconate-titanate (PZT) ceramics suggest the introduction of a revised theoretical model combining higher order nonlinearity and generalized dispersion. The new nonlinear dispersive equation has been solved by perturbation theory. We find a solution in the form of a set of parameters whose magnitude is obtained from a fit of the experimental data. The parame-ters are independent of frequency and initial amplitude. The model is applied to four samples, and the results are discussed. The validity of the perturbation theory in these cases is tested.