Electric field induced effect on the optical, dielectric and ferroelectric properties of Pb(Fe_2/3W_1/3)O₃ single crystals

Single crystals of the complex perovskite Pb(Fe_2/3W_1/3)O₃ [PFW], synthesized from high temperature solution growth, have been studied by optical and dielectric characterizations at zero field and under an electric bias field. It was found that at zero electric field the PFW crystals remain optically isotropic down to 10 K, and that the diffuse maximum of the permittivity near 178 K results from a typical dielectric relaxation with strong frequency dispersion. Application of an electric field can induce a macroscopically polar phase, which remains metastable when removing E at low temperatures. Reversing the polarity of the applied field leads to a reversal of the induced polarization P_ind, giving rise to the dielectric hysteresis loop of ferroelectric character. Thus the ferroelectricity in PFW results in reality from the induction of the macropolar phase. The coercive field for the establishment of the induced polarization increases sharply with decreasing temperature. The switching of the induced polar states have been evidenced and the induced birefringence measured by means of simultaneous optical examinations with polarized light microscopy. It is expected that the magnetoelectric effect can be detected in such an induced ferroelectric phase in PFW.