Dielectric relaxation and order-parameter dynamics in lawsonite - art. no.024105

The results of dielectric measurements (f=10 kHz-400 MHz) of the natural mi neral lawsonite are presented in the region of the ferroelectric transition (T(2)approximate to 124 K). The dielectric behavior is characterized by a small value of the Curie-Weiss constant (C-cw=2220 K) typical for order-dis order ferroelectrics. This is consistent with the fact that the origin of f erroelectricity in lawsonite is related to the dynamical ordering of proton s. In the paraelectric phase the dielectric dispersion is characterized by a Debye relaxation with a single relaxation time taup = 4.2 x 10(-10)(T- T- 2)(-1). A broadening in the dielectric dispersion occurs in the paraelectri c phase only in a narrow temperature range (approximate to5 K) close to T-2 and can be associated with disordering processes in the lattice affected b y large polarization clusters. The dielectric relaxation in the ferroelectr ic phase includes the order parameter dynamics and the domain wall dynamics . The relaxational domain wall dynamics is characterized by an extremely br oad distribution of relaxation times. The characteristic parameters of the dielectric relaxation are determined.