The domain configuration and ferroelectric property of mode relaxor ferroelectrics (RFEs) are investigated by performing a two-dimensional Monte Carlo simulation based on the Ginzburg-Landau theory on ferroelectric phase transitions and the defect model as an approach to the electric dipole configuration in relaxor ferroelectrics. The evolution of domain pattern and domain wall configuration with lattice defect concentration and temperature is simulated, predicting a typical two-phase coexisted microstructure consisting of ferroelectric regions embedded in the matrix of a paraelectric phase. The diffusive ferroelectric transitions in terms of the spontaneous polarization hysteresis and dielectric susceptibility as a function of temperature and defect concentration are successfully revealed by the simulation, demonstrating the applicability of the defect model and the simulation algorithm. A qualitative consistency between the simulated results and the properties of proton-irradiated ferroelectric copolymer is presented. (c) 2006 Springer Science + Business Media, Inc.