Microstructural engineering of piezoelectric composites
Lead Research Organisation:
University of Bath
Department Name: Mechanical Engineering
Abstract
This project will create novel fabrication approaches, using the freeze-casting method combined with slip- and tape-casting, to produce piezoelectric composites with microstructures tailored to yield piezoelectric properties that exceed the performance of off-the-shelf materials, whilst providing advantages over traditional manufacturing methods. The global market for piezoelectric ceramics was valued at $19.6 billion in 2019 and is expected to grow in the areas of energy harvesting, IoT-related sensors and piezoelectric composites in the next decade. Piezoelectric composites are critical to the UK's defence (SONAR), and public health (medical ultrasound) sectors, as well as being used widely in the transport and energy industries. Developing new methods for producing high performance piezoelectric composites represents a significant benefit in terms of materials cost and manufacture, as well as device performance, by enabling low-cost fabrication of bespoke piezoelectric materials with properties tuned depending on the desired application.
Freeze casting is an effective method for controlling the microstructures of porous materials, whereby pores are templated on solvent crystals whose growth and morphology depends on temperature gradients and freezing behaviour during processing. These porous microstructures, e.g. porous piezoelectric ceramics, can then be infiltrated with polymer second phases to improve mechanical and electrical properties. The properties of piezoelectric composites depend strongly on local interactions between electric- and mechanical fields and the material structure over a range of length scales, from ferroelectric domains (sub-micron) through to macro-structure (on the order of millimetres) of the composites. In this project, the aim is to increase the understanding of these electromechanical field/material interactions in piezoelectric composites and design microstructures to exploit beneficial effects accordingly. This will be underpinned by developing advanced numerical models to both aid with microstructural/fabrication process design, and provide insight into experimental observations of the properties of materials fabricated during the project.
The methods that will be investigated offer several advantages over current techniques used to produce commerically available piezoelectric composites. Firstly, the materials can be produced at near-net shape, reducing post-machining processes or manual fibre lay up common for macro-fibre composites fabricated by dice-/arrange-and-fill processes. Secondly, the level of control that is theoretically possible, although not yet realised, by utilising freezing processes to template microstructures, provides the potential to fabricate materials with bespoke properties tuned to specific applications, yielding an optimised combination of piezoelectric, dielectric and mechanical properties to promote enhanced electromechanical coupling between the active piezoelectric and the wider device. Thirdly, the reduced length scale of microstructural features introduced using freeze casting, compared to dice-and-fill composites for example, may provide a route to engineering the inherent properties of the piezoelectric ceramic matrix. Using water as a freezing agent means these processes have a low environmental impact, and near-net shape, optimised composite microstructures with comparable performance to dense piezoceramics will reduce the volume of raw material required in the first place.
Freeze casting is an effective method for controlling the microstructures of porous materials, whereby pores are templated on solvent crystals whose growth and morphology depends on temperature gradients and freezing behaviour during processing. These porous microstructures, e.g. porous piezoelectric ceramics, can then be infiltrated with polymer second phases to improve mechanical and electrical properties. The properties of piezoelectric composites depend strongly on local interactions between electric- and mechanical fields and the material structure over a range of length scales, from ferroelectric domains (sub-micron) through to macro-structure (on the order of millimetres) of the composites. In this project, the aim is to increase the understanding of these electromechanical field/material interactions in piezoelectric composites and design microstructures to exploit beneficial effects accordingly. This will be underpinned by developing advanced numerical models to both aid with microstructural/fabrication process design, and provide insight into experimental observations of the properties of materials fabricated during the project.
The methods that will be investigated offer several advantages over current techniques used to produce commerically available piezoelectric composites. Firstly, the materials can be produced at near-net shape, reducing post-machining processes or manual fibre lay up common for macro-fibre composites fabricated by dice-/arrange-and-fill processes. Secondly, the level of control that is theoretically possible, although not yet realised, by utilising freezing processes to template microstructures, provides the potential to fabricate materials with bespoke properties tuned to specific applications, yielding an optimised combination of piezoelectric, dielectric and mechanical properties to promote enhanced electromechanical coupling between the active piezoelectric and the wider device. Thirdly, the reduced length scale of microstructural features introduced using freeze casting, compared to dice-and-fill composites for example, may provide a route to engineering the inherent properties of the piezoelectric ceramic matrix. Using water as a freezing agent means these processes have a low environmental impact, and near-net shape, optimised composite microstructures with comparable performance to dense piezoceramics will reduce the volume of raw material required in the first place.
Publications
Kurt P
(2023)
Improving piezoelectric energy harvesting performance through mechanical stiffness matching
in Mechanics of Advanced Materials and Structures
Li Z
(2023)
A comprehensive energy flow model for piezoelectric energy harvesters: Understanding the relationships between material properties and power output
in Materials Today Energy
Li Z
(2024)
Energy Harvesting from Water Flow by Using Piezoelectric Materials
in Advanced Energy and Sustainability Research
Nakagawa K
(2023)
The unusual case of plastic deformation and high dislocation densities with the cold sintering of the piezoelectric ceramic K0.5Na0.5NbO3
in Journal of the European Ceramic Society
Nakagawa N
(2023)
The unusual case of plastic deformation and high dislocation densities with the cold sintering of the piezoelectric ceramic K0.5Na0.5NbO3
in Journal of the European Ceramic Society
Description | The ongoing work in this project has highlighted the importance of considering mechanical properties and conditions at the interface between piezoelectric ceramics and the environment they are operating within. These effects occur at the the microscale in composites derived from piezoelectric ceramics, with local structure having a significant effect on the final piezoelectric and dielectric properties, and at the macroscale where we have started to demonstrate through modelling and experimental work the importance of matching the mechanical properties of the composites to their working environment. In the second case, this enables efficient mechanical energy transfer into the piezoelectric materials and can thereby increase the output electrical energy. This work is of interest for piezoelectric sensors and energy harvesters. Three papers on these topics are currently under preparation or review. |
Exploitation Route | I am currently writing a follow up EPSRC proposal to transfer the initial findings into a more application focussed research project to develop low cost acoustic transducers for underwater sensing, non-destructive inspection and medical ultrasound devices. This is being strongly supported by several industrial partners; if not successful, we will explore alternative routes to transfer the promising findings into commercial and societal impact |
Sectors | Aerospace, Defence and Marine,Electronics,Healthcare,Manufacturing, including Industrial Biotechology |
Description | Ionix |
Organisation | Ionix Advanced Technologies |
Country | United Kingdom |
Sector | Private |
PI Contribution | We are currently planning to fabricate piezoelectric ceramics and composites as the active elements in ultrasound devices, e.g. for non-destructive testing, using the freeze-casting process. To date we have discussed the industrial partner requirements and are in the process of designing the moulds for casting. We have planned for a joint experimental study that will lead to a publication. |
Collaborator Contribution | Ionix have provided us with approx 1 kg of their material to enable us to create prototype sensors. |
Impact | No outcomes to date. |
Start Year | 2021 |
Description | School visit (SGS College Filton) |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | For the past 3 years I have given a talk about materials science and engineering focussed around my research on piezoelectrics and the processing of ceramics, including challenges and perspectives for future research. The talks are for A-Level students at a college in North Bristol and mature/access students studying GCSEs and A-Levels. Some students have now gone on to study Materials Science subjects at University |
Year(s) Of Engagement Activity | 2021,2022,2023 |