UCLA

Ferroelectric materials like BaTiO3 and PZT are known for their ability to strongly couple electrical and mechanical energy, which makes them widely used as transducers, sensors, or actuators. There is an ongoing search for better performing materials to optimize device performance. Single crystal relaxor ferroelectrics like PMN-PT and PIN-PMN-PT near the morphotropic phase boundary (MPB) have garnered attention for their large electromechanical properties relative to PZT. A better understanding of the underlying physics will help in the search for next generation materials and optimizing device design. This dissertation focuses on modeling: 1) phase transformations in ferroelectrics materials and 2) novel piezoelectric synthetic jet actuators (SJAs). Ferroelectric material models are known to significantly overpredict the coercive field. This is attributed to a combination of domain wall motion and the presence of metastable wells in the Landau-Devonshire energy function. These metastable wells also prevent current models from capturing important phase transition behavior. An improved energy function for rhombohedral PIN-PMN-PT near the MPB with better thermodynamic stability was developed and used to investigate the effect energy fluctuations have on phase transformations. Results showed that accounting for fluctuations produced closer predictions to experimental observations, including the lower coercive field for switching and the forward and reverse phase transformations during loading and unloading. Two methods to implement these fluctuations in phase field models were assessed. Static local fields were preferred over time-varying noise due to convergence and reproducibility concerns with the latter. For SJAs, current models are unable to efficiently and accurately model novel SJAs that deviate significantly from an ideal Helmholtz resonator. A hybrid finite-element and lumped-element modeling approach was developed to provide more flexibility to explore novel material and geometric designs. This hybrid model reduced reliance on fitting parameters through FEM and a formula to estimate the loss coefficient was proposed. Predicted performance of thin cavity SJAs using the hybrid approach was shown to be in much better agreement with experiments than the prior models. This work provides a deeper understanding of modeling ferroelectric materials and SJAs, and the developed models can be used to help guide material and device design.