Competition between relaxation kinetics and heat transfer in the dynamics of phase transition fronts

Abstract. The velocity of the interphase boundary motion caused by latent heat transfer at ferroelectric phase transitions is calculated. The criterion for separating of two mechanisms for the front motion- the latent heat transfer and the relaxation of the order parameter- is obtained for ferroelectrics. Electric field dynamics of interphase boundaries have been studied. The expression for the front velocity of the threshold field type is derived. The transition from a metastable phase to a thermodynamically stable phase takes place via fluctuations leading to the formation of nuclei of the new phase (heterophase fluctuations) [I]. In order to describe systems which undergo a symmetry-breaking first-order phase transition, the nucleation and growth processes must be accounted for. The growth is associated with the propagation of interphase boundaries separating the high-temperature parent phase and the low-temperature product phase. In solid diffusiohless transformations the growth may be slow enough for the observation by polarization microscope technique. In particular, in ferroelectrics sharp interphase boundaries can be observed [2-121. Crystals with sharp interfaces most often have kinetically controlled rather than diffusion-limited growth. Usually the interphase dynamics are governed entirely by the time evolution of the order parameter [13-201, and the temperature can be considered to be a constant. Thu