Switching Dynamics in Polycrystalline Ferroelectrics

In combination with the knowledge generated through the thin-film ferroelectric switching model, the multitude of grain-grain ferroelectric interactions that occur during poling in bulk ferroelectrics are being detailed in the present project. Here, switching mechanisms such as simple switching (where domains perform electrical work against the applied electric field) and domain pinning of domains are being quantified and experimentally demonstrated to understand the long-term large-field reliability of bulk ferroelectric materials.

As a recent application, the macroscopic hysteretic response associated with the underlying microscopic switching of domains of a polycrystalline ferroelectric was investigated for bipolar, sesquipolar, and unipolar electrical loadings. As a result of the intergranular interactions and physical electromechanical couplings, the statistical contribution from each of the self-stabilized interactions (see left) demonstrate that the asymmetric polarization distribution corresponds to the linear superposition of four Gaussian polarization distributions. Results show that in the sesquipolar regime, tensile stresses are minimized by 33% and compressive stress minimized by 38%. The maximum strain output decreases by only 1%, thus, making it a favorable fatigue-reduced actuation design. In this research a parameter to define asymmetric electric field loads, the electrical load ratio, R_E, was defined. This description parallels the well- known mechanical load ratio, R_σ =σ_min/σ_max, and is written as R_E=E_min/E_max.