Ferroelectric-Ferroelectric Phase Transitions: Insights from a New Model for Pb-free BZT-BCT
Assoc Prof Catherine M. Bishop
Department of Mechanical Engineering, University of Canterbury
Time & Place
Fri, 17 May 2019 13:00:00 NZST in E14 (Lecture Theatre), Engineering CORE
All are welcome
Ferroelectric (FE) ceramics are ubiquitous in the devices and systems that enable modern life, e.g. sensors, actuators and capacitors in electronic devices, manufacturing facilities and communication systems. Lead toxicity has motivated the search for Pb-free FE materials to replace PZT, whose optimal properties near its interferroelectric transition are associated with a reduction of the crystallographic anisotropy of the free energy.
In this field, computational studies employ multi-physics, phase-field models. Current models can reproduce many microstructural features and macroscopic response in single-phase FEs. However, near interferroelectric transitions, existing modelling methodologies artificially couple the free energies of the bulk FE phases with different symmetries. Thus, the interferroelectric transition and structural states in ceramics near this region of phase space are not able to be examined.
Here, a novel phase-field approach is proposed to describe FE materials with a single temperatureinduced interferroelectric transition. The formulation allows the properties of the two FE phases to vary independently. The model is applied to one- and two-dimensional BZT-40BCT ceramic. Our predictions for BZT-40BCT are consistent with experimental observations of a coexistence region between rhombohedral (R) and tetragonal (T) FE phases and a maximum temperature for coexistence.