Field-induced inter-ferroelectric phase transformations and domain mechanisms in high-strain piezoelectric materials: insights from phase field modeling and simulation

Large, reversible and anhysteretic strain induced by external field is desired for multifunctional materials used in sensors, actuators and transducers. However, these desired attributes usually compromise each other, leading to trade-offs in materials’ properties and limiting their applicability. This paper focuses on field-induced inter-ferroelectric phase transformations. Some fundamental principles and domain mechanisms are systematized based on insights learned from phase field modeling and simulations, whose synergistic operations are expected to provide unique combination of large, reversible, and anhysteretic strain attributes. These working principles are: (i) Field-induced inter-ferroelectric structural phase transformation to achieve large strain; (ii) Field-induced stable-metastable phase transformation to maximize reversibility; (iii) Heterogeneous nucleation-and-growth process at domain walls to enhance low-field responses; (iv) Deactivation of domain wall motion by applying external fields along nonpolar axes to minimize hysteresis; (v) Domain wall broadening mechanism and domain size effect to exploit nanoscale engineered domain microstructures; and (vi) Bridging domain mechanism and phase coexistence to promote ferroelectric shape memory effects. It is shown that special initial domain microstructures and preferred evolution kinetic pathways can be achieved by crystallographic domain engineering technique, which allow multiple principles to work together without compromising one another. Due to the commonalities and fundamental interrelations among ferroelectric, ferromagnetic and ferroelastic materials, the gained understanding of thermodynamic and kinetic principles has general implications to displacive phase transformations in ferroic materials and is helpful for design of new functional materials with advanced field-induced strain properties.