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Compositional variation within the Pb(MgInNb2,3)03-PbTi03 -(Ba,Sr)Ti03 (hereafter PMN-PT-BT,ST) ternary (6.4% 5 PT% 5 14.1%, 1.25% 5 BT,ST% 5 2.5%) results in major changes in induced strain and hysteresis. For the 1.25% BT family, the increase in strain correlates with an increase in Tma,, while the dielectric loss is uncorrelated with hysteresis and strain. In addition, weakfield aging (which is not reset by application of field) shows little effect on strain and hysteresis for drive fields of > 0.2 MV/m. The vary narrow polarization-field loops (virgin curves nearly indistinguishable from subsequent cycles) show that weak-field permittivity is a good approximation to the high-field permittivity. Although these data clarify the frequency (T,,,,, is linearly dependent on the logarithm of the frequency) effect on weak-field dielectric behavior, they do not directly address the question of meaningful extrapolation of high-field strain with frequency. In particular, the question remains as to whether the high-field permittivity and strain are frequency dependent. In future papers we will address this question by a combination of measurement techniques as functions of frequency. [Key words: lead magnesium niobate, electromechanical properties, dielectric properties, aging, strain.]

Compositional change within the Pb (Mg,,,Nb,,)O,-PbTiO,-(Ba,Sr)TiO, ternary, hereafter known as PMN-PT-BT,ST, results in major variations in properties. When coupled with the temperature and processing dependence of the relaxor materials near their diffuse phase transition, the compositional dependence significantly complicates the selection of an optimum composition for transducer use. Noncompositional variations in dielectric and electromechanical properties with temperature and processing are easily noted among the many publications on the PMN family of relaxors. In this work, we concentrate on the effects of composition on the electromechanical properties over the 0'40°C range. The specific compositions include a total of 17 compositions within the PMN-PT-BT,ST family (6.4% I PT% 5 14.1%, 1.25% I BT,ST% I 2.5%). By careful processing of matched pairs of BT-and ST-containing compositions, we demonstrate compositional effects on the properties without an associated processing effect. In this work, we present weak-field (relative permittivity and dielectric loss) and high-field (induced strain, polarization, and hysteresis) data for a total of 17 compositions synthesized by a modified columbite precursor route. As previously reported on a more limited compositional suite, the shift in weak-field T,,, with the logarithm of frequency is nearly linear. There is a minor departure from linearity at low frequencies. Strontium additions are shown to be more effective at reducing T,,, than the equivalent barium addition. All compositions showed dielectric aging which was easily reset by short exposure to elevated temperature. A method for selecting a composition for a specific temperature regime based on the concept of a lower and upper use temperature is presented. This works well for low levels of PT, but decoupling between T,,, and the lower use temperature invalidates the method for PT > 12 mol%.

Electrostrictive ceramics in the (l-x)[( l-y)Pb(Mgl/3Nb~3)03-yPbTiO3]-xMeTiO3 system, where Me is Sr or Ba, have discriminating properties for a variety of electromechanical applications. Electrostrictors fill niches that depend on a large mechanical energy density (24 kJ/m3), large (>lo00 ppm) field-induced strain, high (>600 pC/N) effective d33, and low electromechanical hysteresis (~2 % ) . As relaxor ceramics, the weak-field material behavior is dependent on both temperature and frequency. Two groups of materials with differing microstructures were examined to assess the relaxor nature of the high-field electromechanical properties. Both weak and high-field measurements were used to clarify the transition behavior and assess the engineering utility of the two material types. Although these two groups of materials were synthesized from identical starting materials, major differences were obtained in terms of grain size, relative permittivity, dielectric aging, and strain and average hysteresis.