New Ceramics for Electronics and Energy Conversion

By Birgit Baustädter

Jurij Koruza and his team are working on electroceramics that are used in electronic devices. The team is part of a new and highly endowed collaborative research centre led by TU Darmstadt.

Electroceramics are at the core of many electronic components. A mobile phone, for example, contains about 500 capacitors consisting of several layers of ceramic and metal. "In ceramics, we can very easily and specifically adjust material’s properties required for the respective application," explains TU Graz materials scientist Jurij Koruza, Institute for Chemistry and Technology of Materials at TU Graz. "And they can also operate under severe conditions, such as high temperatures."

When we talk about "ceramics" at TU Graz, we are not talking about ceramics in the conventional sense - i.e. as a material for plates, cups and other tableware. Instead, we are talking about so-called functional ceramics that are designed to fulfil certain tasks - some are highly conductive, for example, or can catalyse reactions. In Jurij Koruza’s team, the researchers are particularly concerned with dielectrics and piezoceramics, which can store electrical charge or convert mechanical energy into electrical energy. For example, modern ultrasonic transducers enable high-resolution imaging in medicine or environmentally-friendly industrial cleaning. In the future, however, these electroceramics could also be used as a power source for sensors that are placed in inaccessible locations, but receive continuous mechanical energy from vibrations of the environment and transform this into electrical charge - for example, under a road or in a tunnel wall.

Collaborative Research Centre "FLAIR"

Together with four German research institutions and 13 research teams led by TU Darmstadt, the Graz researchers launched a new project in mid-May to conduct research on ceramic materials. The Collaborative Research Centre SFB 1548 (,,FLAIR" - Fermi Level Engineering Applied to Oxide Electroceramics) is being funded by the DFG and the FWF with a total amount of 10 million euros for a period of four years - with the option of extension up to a total project period of 12 years. The aim of the large-scale project is to develop an accurate method for designing certain functional ceramics and, above all, for the targeted prediction of material’s properties. It borrows from the so-called Fermi-level engineering, which is already used in today’s semiconductor industry for the production of high-performance silicon chips. The research consortium now intends to apply this principle to ceramics. "In the first four years of the project, we will lay the foundation for the new design approach, examine model material systems, test dopants and build a database, which will later enable us the development of completely new compositions with targeted properties, also with the help of computers." Koruza explains. In possible further project phases, the team would then want to focus on the applications.

Specialist field in Graz

The focus in Graz lies on dielectrics and piezoceramics. Ceramic samples are produced by means of solid-state synthesis and modified with different elements, to adjust the Fermi level and defect states. The powder is subsequently milled and formed into the desired shape by pressing or 3D printing. After a thermal treatment above 1,000 degrees Celsius, the electroceramics obtain the desired crystal structure, microstructure, and defect concentration, which together define their electrical properties.

Lead-free materials

In addition to the new collaborative research centre, the research team is involved in the topic of environmentally-friendly materials for electronics. Many electroceramic materials and components today contain lead - a toxic heavy metal. But also a metal that is very cheap and universally applicable. While lead-containing ceramics are not dangerous for users or the environment during their use, the problem is their final disposal. Most of our electronic components are not properly disposed of or recycled. They are much more likely to end up in unsecured landfills where they slowly decompose with time, releasing the lead. That is why research is striving to find a viable substitute for lead. In a recent paper published in Nature Communications ,,Tailoring high-energy storage NaNbO3-based materials from antiferroelectric to relaxor states" , Jurij Koruza and his team present just such a material. So, there are promising material compositions, says the researcher, but: "Lead is universally applicable. The replacement materials that are being developed are not. They have to be specifically designed for the respective application. So, of course, production is much more costly because companies suddenly have to deal with many materials instead of one."

Centrepiece

But the researchers continue to work on the problem. Because: "In numerous new applications, it’s not the technology that’s the centrepiece, it’s the material. The material namely enables the functionality - as in solar cells, fuel cells or batteries."