Low-frequency-dispersion of Pb(Fe1/2Nb1/2)O3 single crystal in the region of its paraelectric ferroelectric phase transition

An empirical equation at low frequency regime is derived for a part of the spectrum of the complex dielectric constant ϵ∗=ϵ′−iϵ″ of Pb(Fe1/2Nb1/2)O3 single crystal with a linear relationship between real dielectric constant ϵ′ and imaginary dielectric constant ϵ″. This equation is used to find the relaxation time and other relaxation parameters and to investigate their temperature dependences in the phase transition region. The low frequency dispersion in the polar phase can be understood in terms of irreversible motion of domain walls in polydomain crystal. The reasons for the inconsistency between the observed dispersion of ϵ∗ and the dielectric dispersion of the Debye type are discussed.