Abnormal Dielectric Characteristics in Ph(Ni_(1/3)Nb_(2/3))O_3-PbTiO_3 System near Morphotropic Phase Boundary

x)PNN-xPT(x=0.30-0.40) ceramics were prepared by a two-steps synthesis method. Phase structure and dielectric properties were studied. Morphotropic phase boundary exists in (1-x)PNN-xPT system at about x=0.34-0.38 composition range according to XRD analysis. Di- electric properties measurments showed that the optimum value of dielectric constant was obtained and the phenomenon of dielectric dual peaks was found for composition near the morphotropic phase boundary. One dielectric peak is phase transition peak from relaxor ferroelectric phase to paraelectric phase. The other peak lying in 130-150℃ temperature range results from relaxational polarization of the valence change of Ni ion and kinds of defects in (1-x)PNN-xPT system.