FLAME-inars
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06th May 2021 – Talk 9:

Ceramic Multilayer Devices From Antiferroelectrics: Current Materials and Concepts

Prof. Klaus Reichmann Institute of Chemistry and Technology of Materials, Graz University of Technology

Abstract

The need for efficient converters for wind and solar power stations as well as for hybrid drives in cars has triggered the development of buffer capacitors with increased charge density at high electric fields. The technical progress is again driven by miniaturization and energy efficiency. Components for new power electronic systems must be able to handle higher current densities, higher power densities and higher operating temperatures. Especially high-voltage power capacitors have to meet new challenges. In modern power electronics, the capacitors must fit with fast-switching semiconductors based on SiC and GaN that operate at high switching frequencies. These requirements raised interest for antiferroelectric materials for multilayer ceramic capacitors.

In commercial devices, lead-lanthanum-zirconate-titanate (PLZT) is currently the working horse, which is able to fulfill above mentioned requirements. On the basis of this material, a ceramic capacitor technology called CeraLinkTM has been developed for ripple suppression in high-voltage DC-links of inverters and converters. These components offer high current handling capabilities, a very low self-inductance and a high isolation resistance at compact size for high operating voltages up to high temperatures.

This presentation highlights the concepts for tailoring PLZT for commercial components concerning switching field and polarization. It refers to issues concerning iso- and heterovalent doping elements with a glimpse to the concept of Goldschmidt´s tolerance factor.

Klaus Reichmann finished his studies in “Technical Chemistry” at Graz University of Technology in 1990. The Ph.D. thesis was completed in 1993 at the Institute of Chemistry and Technology of Inorganic Materials under the supervision of Professor Gerhard Herzog.

From 1999 to 2000, he worked as a research fellow (Erwin Schrödinger Scholarship) at the Ceramics Department of Josef Stefan Institute with Prof. Marija Kosec and at the Institut für Werkstoffe der Elektrotechnik of RWTH Aachen with Prof. Rainer Waser.

Klaus Reichmann currently holds a position as Associated Professor at the Institute of Chemistry and Technology of Materials at Graz University of Technology. His research area is solid-state chemistry with a focus on functional ceramics. The scientific work on electroceramic materials began with the investigation of ceramic NTCR-materials (Negative Temperature Coefficient Resistor), which were subject of diploma and doctoral thesis. Subsequently, ferroelectric, antiferroelectric, semiconducting and highly conductive oxides extended the list of materials.

In 2001, he joined EPCOS Corporate Development Tasks until 2006, where he was responsible for materials development and the coordination of external cooperation partners of EPCOS Ceramic Components.

From 2008 to 2015, Klaus Reichmann, together with Jürgen Fleig from Vienna University of Technology, directed the Christian Doppler Laboratory for Advanced Ferroic Oxides, which installed research groups at Graz University of Technology, Vienna University of Technology and Sheffield Hallam University. Industrial partner of this laboratory was the TDK-EPC Corporation, the legacy company of TDK Electronics. Since 2018 Klaus Reichmann is member of the senate of the Christian Doppler Society.

About the FLAME-inars

The FLAME-inars are organized by the collaborative project FLAME at TU Darmstadt, in which electronic-structure-property relationships are being developed and exploited to realize novel lead-free antiferroelectric compounds. The seminars will gather experts in processing, characterization and theory to discuss materials and applications, bulk and thin films, fundamental properties, electronic structure & defects, and related aspects.

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