Electrical Response of Mixed Regions in the Pb(Mg_(1/3)Ta_(2/3))O_3 and the Pb(Mg_(1/3)Nb_(2/3))O_3 Complex Perovskites

摘要

The dielectric properties of the Pb(Mg_(1/3)Ta_(2/3))O_3-Pb(Mg_(1/3)Nb_(2/3))O_3-PbTiO_3 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(Mg_(1/3)Ta_(2/3))O_3-(0.6-x)Pb(Mg_(1/3)Nb_(2/3))O_3-0.4PbTiO_3 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 PbTiO_3. From the dielectric data for xPb(Mg_(1/3)Ta_(2/3))O_3-(0.7-x)Pb(Mg_(1/3)Nb_(2/3))O_3-0.3PbTiO_3, 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(Mg_(1/3)Ta_(2/3))O_3 to 29227 for 0.5Pb(Mg_(1/3)Ta_(2/3))O_3 for the xPb(Mg_(1/3)Ta_(2/3))O_3- (0.6-x)Pb(Mg_(1/3)Nb_(2/3))O_3-0.4PbTiO_3 systems. However, the dielectric constant maxima between 32626 at 0.1Pb(Mg_(1/3)Ta_(2/3))O_3 and 28757 at 0.3Pb(Mg_(1/3)Ta_(2/3))O_3 decreased with increasing mole fraction x for the xPb(Mg_(1/3)Ta_(2/3))O_3-(0.7-x)Pb(Mg_(1/3)Nb_(2/3))O_3-0.3PbTiO_3 systems. The value of the diffuseness component varied from 1.56 to 1.74 in Pb(Mg_(1/3)Ta_(2/3))O_3-Pb(Mg_(1/3)Nb_(2/3))O_3- PbTiO_3 ternary systems at different Pb(Mg_(1/3)Ta_(2/3))O_3 ratios.