Dielectric properties and crystal structures of entire compositions in the ternary system Pb(Mg/sub 1/2/W/sub 1/2/)O/sub 3/-Pb(Ni/sub 1/3/Nb/sub 2/3/)O/sub 3/-PbTiO/sub 3/

Crystal structures and dielectric properties were investigated over the entire range of composition in the system Pb(Mg/sub 1/2/W/sub 1/2/)O/sub 3/-Pb(Ni/sub 1/3/ Nb/sub 2/3/)O/sub 3/-PbTiO/sub 3/(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 degrees 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.<
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