Electrical response of mixed regions in the Pb(Mg1/3Ta2/3)O3 and the Pb(Mg1/3Nb2/3)O3 complex perovskites

The dielectric properties of the Pb(Mg1/3Ta2/3)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ternary systems were examined as a function of temperature. The split (002) or (200) X-ray diffraction patterns were in the 2θ range of 43.5 ∼ 45.5° for xPb(Mg1/3Ta2/3)O3-(0.6-x)Pb(Mg1/3Nb2/3)O3-0.4PbTiO3 indicating the formation of a tetragonal phase at room temperatures. The reciprocal dielectric constant spectra were analyzed further in terms of normal and relaxor ferroelectrics. The frequency dispersion of the dielectric constant maxima was decreased by PbTiO3. From the dielectric data for xPb(Mg1/3Ta2/3)O3-(0.7-x)Pb(Mg1/3Nb2/3)O3-0.3PbTiO3, two major anomalies corresponding to the rhombohedral → tetragonal → cubic phase transitions were observed. At a temperature of about 160 ∼ 190 °C, the dielectric constant deviates from the Curie-Weiss law and the deviation temperature for normal ferroelectrics. The maximum values of the dielectric constant increased from 21151 for 0.1Pb(Mg1/3Ta2/3)O3 to 29227 for 0.5Pb(Mg1/3Ta2/3)O3 for the xPb(Mg1/3Ta2/3)O3-(0.6-x)Pb(Mg1/3Nb2/3)O3-0.4PbTiO3 systems. However, the dielectric constant maxima between 32626 at 0.1Pb(Mg1/3Ta2/3)O3 and 28757 at 0.3Pb(Mg1/3Ta2/3)O3 decreased with increasing mole fraction x for the xPb(Mg1/3Ta2/3)O3-(0.7-x)Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 systems. The value of the diffuseness component varied from 1.56 to 1.74 in Pb(Mg1/3Ta2/3)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ternary systems at different Pb(Mg1/3Ta2/3)O3 ratios.