Visiting Researcher Grant - Multiscale modelling of ferroelectric materials for actuator design
Lead Research Organisation:
University of Manchester
Department Name: Materials
Abstract
Piezoelectric ceramics are becoming used increasingly as the basis for electromechanical sensors and actuators for control, medical, electronic and microelectronic machine (MEMS) applications.
Electromechanical actuators take benefit from the strain resulting from the application of an electric field in ferroelectric materials. Many sources of internal stress can arise in actuation devices. First the manufacturing process can introduce residual stresses. The boundary conditions related to the actuator packaging is another source of operating stress. At a finer scale still, due to the heterogeneity of ferroelectric materials (polycrystalline structure), the piezoelectric strain is usually not compatible, resulting in internal stresses when an electric field is applied. Despite its significant role, the dependence of the internal stress on the piezoelectric strain is rarely accounted for in the design of actuators, mainly because it is difficult to quantify or predict. The development of micro-macro models of ferroelectric behaviour provides a pathway to establish fully coupled electro-mechanical constitutive laws for ferroelectric materials. Such constitutive laws will improve the quantitative description of electric field induced strains, and allow the optimisation of piezoelectric actuator design.
Consequently, through the development of multiscale tools the objective of this project is to describe in a quantitative way the effect of applied and internal stress on ferroelectric behaviour. This will provide the tools to design high performance ferroelectric actuators.
Electromechanical actuators take benefit from the strain resulting from the application of an electric field in ferroelectric materials. Many sources of internal stress can arise in actuation devices. First the manufacturing process can introduce residual stresses. The boundary conditions related to the actuator packaging is another source of operating stress. At a finer scale still, due to the heterogeneity of ferroelectric materials (polycrystalline structure), the piezoelectric strain is usually not compatible, resulting in internal stresses when an electric field is applied. Despite its significant role, the dependence of the internal stress on the piezoelectric strain is rarely accounted for in the design of actuators, mainly because it is difficult to quantify or predict. The development of micro-macro models of ferroelectric behaviour provides a pathway to establish fully coupled electro-mechanical constitutive laws for ferroelectric materials. Such constitutive laws will improve the quantitative description of electric field induced strains, and allow the optimisation of piezoelectric actuator design.
Consequently, through the development of multiscale tools the objective of this project is to describe in a quantitative way the effect of applied and internal stress on ferroelectric behaviour. This will provide the tools to design high performance ferroelectric actuators.
Planned Impact
Piezoelectric actuators are at an important stage of development into a large component market. Market pull is generated by large demand for:
- ultra-small scale precision motion devices used in manufacturing and inspection equipment,
- high volume, low cost auto-focus assemblies required in phone cameras,
- high volume, moderate cost ink printing heads used in industrial printers;
- demand for micro actuator medical tools used in minimally invasive surgery and micro-grippers required in manufacturing micro-sized objects such as stents;
- dynamically-driven high temperature actuators for diesel injector valves in automobiles.
Piezo-based technologies are key to the nano- and micro-positioning world. Piezo actuation is increasingly suitable for applications formerly addressable only by magnetic motors, and the technology offers significant benefits in terms of size, speed, reliability, vacuum compatibility, resolution and dynamics. These benefits, in turn, enable significant advances in existing and new applications.
A major report estimated the global market for piezoelectric operated actuators and motors to reach $12.3 billion by 2014, showing an average annual growth rate of 13.2% per year. The current project will help to provide design tools for new actuators. In particular this will benefit our industrial partner to whom we will make available our multi-scale models. They will be fully involved in the project and we will present our findings to them via a sign off meeting at the end of the project. This will also allow us to explore further academic and industrial exploitation of the work.
Knowledge
Without better design tools the development of improved actuators requires a great deal of experimental trial and error both with respect to composition and as-process microstructure. Our tools will directly address this need; furthermore our models can be run on fairly modest computing resources making the techniques available to academics and industrialists.
People
Dr Laurent Daniel has very extensive knowledge of magneto-elastic interactions. The Manchester team have developed synchrotron X-ray methods to probe the state of stress and poling of piezoelectric materials, but currently do not have the tools to interpret the results from a models drive perspective. Bringing Dr Daniel to Manchester will significantly add value to the experimental work already undertaken shedding more light on the piezoelectric couplings.
Equally, importantly it will also establish a longer lasting collaboration between the School of materials in Manchester and Laboratoire de Génie Electrique de Paris, CNRS Univ Paris-Sud 11 on both magnetoelastic and ferroelectric materials. This will give rise to an experimental/modelling partnership involving the exchange of PhD students and will increase the value of both the experimental programme and the modelling studies.
- ultra-small scale precision motion devices used in manufacturing and inspection equipment,
- high volume, low cost auto-focus assemblies required in phone cameras,
- high volume, moderate cost ink printing heads used in industrial printers;
- demand for micro actuator medical tools used in minimally invasive surgery and micro-grippers required in manufacturing micro-sized objects such as stents;
- dynamically-driven high temperature actuators for diesel injector valves in automobiles.
Piezo-based technologies are key to the nano- and micro-positioning world. Piezo actuation is increasingly suitable for applications formerly addressable only by magnetic motors, and the technology offers significant benefits in terms of size, speed, reliability, vacuum compatibility, resolution and dynamics. These benefits, in turn, enable significant advances in existing and new applications.
A major report estimated the global market for piezoelectric operated actuators and motors to reach $12.3 billion by 2014, showing an average annual growth rate of 13.2% per year. The current project will help to provide design tools for new actuators. In particular this will benefit our industrial partner to whom we will make available our multi-scale models. They will be fully involved in the project and we will present our findings to them via a sign off meeting at the end of the project. This will also allow us to explore further academic and industrial exploitation of the work.
Knowledge
Without better design tools the development of improved actuators requires a great deal of experimental trial and error both with respect to composition and as-process microstructure. Our tools will directly address this need; furthermore our models can be run on fairly modest computing resources making the techniques available to academics and industrialists.
People
Dr Laurent Daniel has very extensive knowledge of magneto-elastic interactions. The Manchester team have developed synchrotron X-ray methods to probe the state of stress and poling of piezoelectric materials, but currently do not have the tools to interpret the results from a models drive perspective. Bringing Dr Daniel to Manchester will significantly add value to the experimental work already undertaken shedding more light on the piezoelectric couplings.
Equally, importantly it will also establish a longer lasting collaboration between the School of materials in Manchester and Laboratoire de Génie Electrique de Paris, CNRS Univ Paris-Sud 11 on both magnetoelastic and ferroelectric materials. This will give rise to an experimental/modelling partnership involving the exchange of PhD students and will increase the value of both the experimental programme and the modelling studies.
Publications
Daniel L
(2015)
Revisiting the blocking force test on ferroelectric ceramics using high energy x-ray diffraction
in Journal of Applied Physics
Daniel L
(2014)
A multiscale modelling analysis of the contribution of crystalline elastic anisotropy to intergranular stresses in ferroelectric materials
in Journal of Physics D: Applied Physics
Daniel L
(2014)
A multiscale model for reversible ferroelectric behaviour of polycrystalline ceramics
in Mechanics of Materials
Daniel L
(2014)
Identification of crystalline elastic anisotropy in PZT ceramics from in-situ blocking stress measurements
in Journal of Applied Physics
Walton LA
(2015)
Morphological Characterisation of Unstained and Intact Tissue Micro-architecture by X-ray Computed Micro- and Nano-Tomography.
in Scientific reports
| Description | A multiscale model for reversible ferroelectric behaviour of polycrystalline ceramics has been proposed, encompassing the range from the single crystal level to the multi-domain level and finally to the polycrystal. Most notably, it has enabled an estimation of the evolution of internal stresses in piezoelectric ceramics during electromechanical loading. By this means, it has been shown that although domain switching is the main contributor to internal stresses in polycrystalline ferroelectrics, the role of local elastic anisotropy is also significant. From the experimental point of view, in-situ neutron diffraction experiments have been carried out at ISIS and at the SNS (Spallation Neutron Source) at ORNL (Oak Ridge National Laboratory) in Tennessee. These experiments provided a practical means of monitoring the domain switching processes and internal stresses in polycrystalline piezoelectric ceramic samples subjected to coupled electric and mechanical loading. |
| Exploitation Route | A potential application of this work is the use of micromechanical approaches as a tool for the optimisation of material composition and microstructure (material processing industry) or for the design of piezoelectric devices (actuators or sensors manufacturers). The results of the experiments provide an insight into the microscopic mechanisms responsible for the macroscopic strain and polarisation switching processes in ferroelectric ceramics under electromechanical loading. They will be particularly useful to carry a critical assessment of micromechanical models for ferroelectric behaviour. The modelling tools developed during the project give an estimate of internal stresses in ferroelectric materials and provide a link between the domain switching mechanisms and the macroscopic behaviour. Furthermore, they can be used to explore the optimum operating conditions for piezoelectric devices and to evaluate the mechanisms responsible for fatigue and failure. The next step would be the implementation of micromechanical models into structural analysis software. |
| Sectors | Electronics,Energy |