Projects / Programmes
Multifunctional materials for actuator and cooling devices
| Code |
Science |
Field |
Subfield |
| 2.09.01 |
Engineering sciences and technologies |
Electronic components and technologies |
Materials for electronic components |
| Code |
Science |
Field |
| T153 |
Technological sciences |
Ceramic materials and powders |
| Code |
Science |
Field |
| 2.05 |
Engineering and Technology |
Materials engineering |
Electrocalorics, piezoelectrics, electrostrictors, actuators, cooling devices
Researchers (17)
Organisations (2)
Abstract
Society is becoming increasingly demanding in terms of electrical energy, functional heating and cooling in everyday life. Energy storage, conversion, supply and consumption have thus become of a global priority. Severe regulations are expected in the near future in EU and world-wide, resulting in a strong pressure on basic and applied research in the field of functional materials.
Multifunctional materials, so-called multiferroics, have established an important, but still growing role in electronic and microelectronic components. These materials are piezoelectric, meaning that they can convert electrical energy into mechanical energy and viceversa. It is this property that is largely exploited in a number of applications in sensing, actuation and ultrasound transducer devices, covering important areas, such as energetics, automotive, aerospace and medical industry.
Over 50 years, the market of piezoelectric materials has been dominated by Pb(Zr,Ti)O3 (PZT). Interestingly, in terms of piezoelectricity, relaxor ferroelectrics have been proven to be even more efficient than PZT. A representative member of the relaxor ferroelectric family is (1-x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (100(1-x)PMN-100xPT) solid solution. The morphotropic phase boundary (MPB) composition, 65PMN-35PT, exhibits outstanding piezoelectric response with longitudinal piezoelectric coefficient as high as 700 pC/N in bulk ceramics (J. Kelly et al., J. Am. Ceram. Soc. 80, 957–964, 1997). On the other hand, PMN is a prototypic relaxor, exhibiting a high electrostrictive response (G. Trefalt et al., J. Am. Ceram. Soc. 94, 2846–2856, 2011).
In addition to the electro-mechanical (EM) coupling, ferroelectric relaxor materials have been recently considered due to another electro-thermal property coupling, which is the electrocaloric (EC) effect. EC effect is related to a reversible temperature change in the material at adiabatic conditions induced by the application of an electric field. Complex perovskite materials have demonstrated to exhibit the largest EC temperature changes with, e.g., PMN-PT exhibiting almost 3 K at 90 kV/cm (B. Rožič et al., J. Appl. Phys. 110, 064118, 2011). This is one of the highest values ever measured in any bulk ceramic material.
PMN-PT of selected compositions thus exhibits both piezoelectric and/or electrostrictive potential as well as large EC response. Interestingly, the use of both these functional properties simultaneously has not yet been reported. The aim of this project is to prepare actuator elements based on PMN-PT, in which both EM and EC effects can be exploited.
In the first part of the project we will prepare PMN-PT in a wide range of compositions and grain sizes. This will allow us to screen the whole range from relaxor to ferrolectric behaviors and states in between. Particular emphasis will be given to the relationship between local (atomic, nano) and macroscopic properties. This will lead to: (i) the understanding of basic phenomena at a local scale that are crucial for macroscopic EM and EC responses, such as electrical conductivity, point defects and domain-wall dynamics, and (ii) the selection of the best performing PMN-PT material(s) for the second stage of the project.
The aim of the second part of the project is to prove the concept of multifunctionality and create a potential platform for “all-in-one” actuator/cooling devices. Selected PMN-PT compositions will be used to prepare simple structures (e.g., cantilevers), which would exploit both EM and EC effects. The design of the elements will be supported by numerical, finite-element modelling.
In summary, based on microscopic and macroscopic measurements we will develop a detailed understanding of the coupling between the EM and the EC properties in PMN-PT materials and incorporate this understanding in the design of multifunctional elements, whose intent is to prove the project’s concept of multifunctionality.
Significance for science
The electrocaloric effect (ECE), i.e., a change of temperature in a material that is induced by application of typically large electric field, has recently attracted a particular attention due to its strong potential of replacing the present cooling technologies, such as the gas-compression based techniques. To date, however, the EC temperature changes do not reach levels that are required for practical applications (typically )2 K). There is thus an urgent need with strong competition between research institutions world-wide to find and develop materials with large EC effect and reliable operation under elevated electric fields. As the development of materials from their structural and microstructural perspectives is undergoing, the understanding of microscopic mechanisms, e.g., of electrical conductivity, which is of a great importance for the EC effect due to the Joule heating, or details of the domain structure and internal, atomic structure of domain walls in ferroelectrics, which may affect the EC effect, are not understood, even in most promising materials for EC applications, such as PMN-PT. The present project will address some of these aspects both in relation to EC and electromechanical (piezoelectric/electrostrictive) functionality of the complex project material compositions. Investigations will be performed with highly sophisticated tools, such as atomic-scale TEM, and will thus reveal new data in the field.
With our research we aim not only to pave the way to a better tailoring of materials for high-performance EC applications, but also to gain insight into fundamental aspects of the structure-property relationships in these materials with the support of up-to-date and innovative characterization methods. This part of the study will represent an original contribution to the field.
Significance for the country
In the last ten years, the increased interest in the electrocaloric (EC) effect has boosted, on one side, a strong research on EC materials, and, on the other side, engineering studies on design, development and optimization of cooling devices that would exploit the EC effect. The market of EC devices is still to be created, making pressure not only on basic research, but also on applicative/engineering development of EC devices. Research and development projects, such as the one herein proposed, are timely and essential for the future economy related to new markets and business opportunities, both in Slovenia and Europe.
The objective of the project is to fabricate and demonstrate the potential applicability of multifunctional elements in cooling devices in which both electromechanical and electrocaloric effects will be exploited; the project’s results may be thus of a highly practical interest. EC cooling may find a broad range of applications, from compact cooling devices to active cooling in microelectronics.
For Slovenia it is now very important to build up knowledge for potential high value-added products and technologies, and to be thus prepared for future investments in the field of EC. Both topics, cooling technologies based on EC effect and research of piezoelectric materials for, e.g., pressure sensors, have been included in the initiatives of Smart Specialization Strategy, together with industrial partners, including the house-appliances company Gorenje, and Hidria, producer of automotive components.
Most important scientific results
Interim report,
final report
Most important socioeconomically and culturally relevant results
Interim report,
final report
