Structure and dielectric relaxation behavior near the MPB for Pb(Mg 1/3Nb 2/3)O 3–Pb(Ni 1/3Nb 2/3)O 3–PbTiO 3 ferroelectric ceramics

Abstract

The structure and dielectric relaxation behavior of the (1 − x)Pb(Mg,Ni) 1/3Nb 2/3O 3– xPbTiO 3 (PMNN-PT with Mg/Ni=1:1) compositions close to the morphotropic phase boundary (MPB) have been systematically investigated as a function of PbTiO 3 content ( x). X-ray diffraction results demonstrate that a region with both pseudocubic and tetragonal phase lies in the composition range x = 0.30–0.36. The maximum relative permittivity of 36,000 was observed at x = 0.30 near the MPB. Three empirical relations to character the relaxor behavior were discussed respectively. The dielectric permitivities of all samples well obey the relations (1/ ε)=(1/ ε m)+(( T− T m) 2/2 ε m δ 2) and ε( T)=exp( α− βT) in a wide temperature range above T m, but ((1/ ε)−(1/ ε m)) 1/ n =(( T− T m)/ C) ( T> T m) may not be the proper parameter to characterize the dielectric behavior of this system. The results reveal that the PMNNT-PT ceramics successively transform from relaxor to normal ferroelectrics with the increasing of the PT content.