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The ferroelectrics which possess switchable polarization below the Curie temperature can be applied as actuators and memory storage devices. Oxygen vacancies are commonly present in perovskite ferroelectrics. Besides that, in order to enhance certain properties, perovskite ferroelectrics are doped with foreign atoms (e.g. iron, copper, manganese, etc) which again results in the appearance of certain kinds of point defects. In this thesis, the model has been set up to investigate those two effects: a model that incorporates the ferroelectric and semiconducting feature of ferroelectric perovskites at the same time and a model taking the internal bias field due to the defect dipole into account. The phase field model is derived in a thermodynamically consistent way. The phase field modeling was numerically realized by finite element method using FEAP. Since the domain structure evolution is certain change in the reference configuration, one is interested in the driving force or tendency of such change by making use of the concept configurational force from Eshelby. The semiconducting feature of ferroelectrics with point defects was studied. The role of donors and electronic charge carriers in the domain structure stabilization was studied in a quantitative way. By accounting for semiconducting properties of barium titanate, the appearance of depletion layers near the electrodes was predicted. The stabilization of the head-to-head and tail-to-tail domain structures through the space charge was also demonstrated. As an indication of the stability, the driving force on the domain wall in the ead-to-head domain structure was quantitatively investigated. The …