Novel lead-free materials have displayed unipolar strains larger than that of current lead-containing materials, which is very promising for actuator applications such as nano-positioning and diesel fuel injection systems. The origin of this exceptional behavior has been found to be an electric field-induced transformation from a macroscopic nonpolar (ergodic relaxor) to a macroscopic polar (ferroelectric) order. Due to the instability of the transformation, a reverse polar-nonpolar transformation is found with the removal of the electric field. This allows, essentially, for the poling strain to be re-harnessed with each electric field cycle. Seeds of ferroelectric material can be included in the nonpolar matrix to reduce the nucleation energy required to generate this transition. Numerous applications, however, push ferroelectric materials to more extreme loading conditions, which include the simultaneous application of electric field, stress, and temperature. The primary aim of this proposal is to understand the high temperature nonlinear constitutive behavior of lead- free nonpolar↔polar transforming materials through the measurement of large field electrical properties as a function of applied stress and temperature.
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