Dielectric properties and crystal structures of entire compositions in the ternary system Pb(Mg1/2W1/2)O3-Pb(Ni1/3Nb 2/3)O3-PbTiO3

Crystal structures and dielectric properties were investigated over the entire range of composition in the system Pb(Mg_1/2W _1/2)O₃-Pb(Ni_1/3 Nb_2/3)O₃-PbTiO₃(PM A morphotropic phase boundary (MPB) was found on the compositional line with 45 to 50 mol.% PT content. The PT-rich composition with Tc>100°C showed a steep temperature dependence of the dielectric constant. The PMW-rich composition with Tc around room temperature or below showed a diffuse phase transition. Superlattice reflections due to the ordering of Mg and W ions in the perovskite B-site were observed in the X-ray diffraction patterns of the PMW-rich composition. The results obtained indicate that PMW-rich compositions were relaxor ferroelectric. A downward Curie temperature shift as a function of PMW content was saturated in the PMW-rich compositional region, which suggests that the PMW-rich region is not a simple solid solution but a nanometer composite of an ordered region and a disordered region