Key findings
- Scientists have developed a new way to make piezoelectric ceramic materials that can better withstand extreme heat and continue performing reliably in sensors and actuators.
- Using heat to organise lead-free bismuth ferrite-barium titanate ceramic from within, they created tiny regions with slightly different chemical compositions throughout the ceramic.
- Together these regions formed an internal network that changes how the material reacts to electrical and mechanical forces.
- By creating these "bulk ferroelectric heterostructures", the researchers have demonstrated for the first time a way to reproduce interface-driven effects inside a bulk solid .
- This research could be translated to improving high-temperature piezoelectric sensors, ultrasonic transducers and electromechanical actuators - particularly when conventional materials struggle in extreme heat.
Scientists have developed a new way to engineer ferroelectric materials by creating nanoscale heterostructures throughout the interior of a ceramic, offering a potential route to more robust sensors, actuators and transducers for demanding operating environments.
The international team have created what they describe as "bulk ferroelectric heterostructures" within a lead-free bismuth ferrite-barium titanate ceramic. Rather than relying on interfaces engineered layer by layer in thin films, the researchers used a carefully controlled heat treatment to generate nanoscale regions with different chemical compositions throughout a bulk material. These regions form interconnected networks that function as built-in heterointerfaces.
The study published in Science Advances addresses a longstanding challenge in materials science. Many of the unusual electrical and electromechanical behaviours that emerge at interfaces can be achieved in thin-film devices, but translating these effects into solid materials suitable for practical applications has proved difficult. The new study demonstrates a way to reproduce these interface-driven effects inside a scalable ceramic architecture.
Potential application areas identified by the researchers include high-temperature piezoelectric sensors, ultrasonic transducers and electromechanical actuators, particularly in situations where conventional materials face limitations due to temperature, electrical loading or long-term stability requirements.
Dr David Hall , Reader in Ceramics in the Department of Materials and the Henry Royce Institute at The University of Manchester, explains: "Many of the most interesting behaviours in ferroelectric materials have historically been confined to thin films, where interfaces can be carefully engineered. What we have shown is that similar interfacial effects can be generated throughout a solid ceramic. This creates new opportunities to control the electrical and mechanical behaviour of these materials."
Using atomic-resolution microscopy, spectroscopy and computational modelling, the researchers found that the heat treatment drives nanoscale elemental partitioning, creating Bi-rich and Ba-rich regions within a coherent crystal lattice. These compositionally distinct regions generate local electric fields, elastic strain fields and charged domain walls that influence how the material behaves under electrical and mechanical loading.
One of the most striking findings was the impact on thermal performance. The researchers report a Curie temperature of 824°C in the engineered material, more than 350°C higher than the starting material. The ceramic also maintained strong piezoelectric performance at temperatures relevant to industrial sensing and monitoring applications.
The team also demonstrated a method for creating programmable ferroelectric behaviour. By combining electrical or mechanical conditioning with thermal ageing, they were able to imprint preferred domain configurations into the material. These configurations remain recoverable after the application of strong electrical fields, enabling reversible electromechanical responses that are often difficult to achieve in conventional bulk ferroelectrics.
In one configuration, the researchers achieved large reversible shear strains, a characteristic that could be useful in actuator technologies. The study also reports internal bias fields exceeding 8 MV m⁻¹, substantially higher than those typically observed in traditional bulk ferroelectric materials.
The work builds on around a decade of research into lead-free piezoelectric ceramics at The University of Manchester and has already led to intellectual property protection for the underlying materials and manufacturing approach. The research team behind this study is supporting the translation of the research towards potential industrial applications.
The study involved researchers from The University of Manchester, the Henry Royce Institute, ShanghaiTech University, the Chinese Academy of Sciences, Diamond Light Source, the University of Leeds and Sheffield Hallam University.
Dr Hall added: "The broader significance of this work is that it introduces a new design framework. Instead of focusing solely on changing composition, we can use controlled nanoscale self-organisation to build new functionality directly into a material. We believe this concept could be applied across a much wider range of ferroic materials in future."
Journal: Science Advances
Full title: Bulk Ferroelectric Heterostructures
DOI: 10.1126/sciadv.aef9861
URL: https://www.science.org/doi/10.1126/sciadv.aef9861
