Electromechanical Properties of Some Pb(Mg _1/3 Nb _2/3 )O ₃ ‐PbTiO ₃ ‐(Ba,Sr)TiO ₃ Ceramics: Part Two

Abstract

Compositional change within the Pb(Mg 1/3 Nb 2/3 )O 3 ‐PbTiO 3 ‐(Ba,Sr)TiO 3 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%≤ PT%≤ 14.1%, 1.25%≤ BT,ST%≤ 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 max 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 max 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 max and the lower use temperature invalidates the method for PT > 12 mol%.