Hardening-softening transition in Fe-doped Pb(Zr,Ti)O3 ceramics and evolution of the third harmonic of the polarization response

It is shown that the phase angle of the third harmonic of polarization response (delta(3)) is very sensitive to the aging state of hard, Fe-doped lead zirconate titanate [Pb(Zr,Ti)O-3 or PZT] ceramics and may thus provide rich information on processes responsible for aging in hard ferroelectrics. When hard PZT ceramics experience hardening (aged state)-softening (deaged state) transition, delta(3) changes by about 90 degrees at subswitching fields and by about 180 degrees at switching conditions. Evolution of delta(3) with time, temperature and electric field amplitude during deaging suggests that at least two mechanisms of charge migration, one short-range and one long-range, may participate in the deaging process. (c) 2008 American Institute of Physics.