Monte Carlo simulation on dielectric and ferroelectric behaviors of relaxor ferroelectrics

摘要

The dielectric and ferroelectric behaviors of relaxor ferroelectrics over the ferroelectric transition range are simulated using Monte Carlo simulation. The simulation is based on the Ginzburg-Landau ferroelectric model lattice in which a random distribution of two types of defects (dopants) which will suppress and enhance the local polarization, respectively, is assumed. The simulation reveals an evolution of the ferroelectric transitions from a normal first-order mode toward a diffusive mode, with increasing defect concentration. The simulated lattice configuration shows the microdipole ordered clusters embedded in the matrix of paraelectric phase over a wide range of temperature, a characteristic of relaxor ferroelectrics. The relaxor-like behaviors are confirmed by the lattice free energy, dielectric susceptibility, and ferroelectric relaxation evaluated as a function of the defect concentration. Finally, we present a qualitative comparison of our simulated results with the simulation based on the coarse-grain model C. C. Su, B. Vugmeister, and A. G. Khachaturyan, J. Appl. Phys. 90, 6345 (2001).