Antiferroelectric Materials and the FLAME Project
Prof. Dr. Andreas Klein Technical University of Darmstadt, Department of Electronic Structure of Materials
As an introduction to the FLAME-inar series, this talk will give an introduction on antiferroelectric materials, properties and applications and the concept and first results of the FLAME (Fermi Level Engineering of Antiferroelectric Materials for Energy Storage and Insulation Systems) project.
Antiferroelectrics are a fascinating class of materials, which exhibit a characteristic double hysteresis loop, in analogy to antiferromagnetic materials. Together with the high permittivity of antiferroelectrics and the low inductance of multilayer ceramic capacitors, the double hysteresis loop offers a higher energy storage capacity than conventional high-permittivity dielectrics in combination with a high operation frequency, which enables more efficient conversion and transmission of electrical energy from renewable sources and in electromobility. In contrast to ferroelectrics, only few antiferroelectric materials are known. Promising properties for applications are only observed with donor-doped, Zr-rich Pb(Zr,Ti)O3. For environmental and health reasons, the substitution of Pb is highly desirable. In the case of piezoelectric materials, where the market is also dominated by Pb-based ferroelectric compositions, considerable advances in the identification of Pb-free materials have been achieved in the last decade, with (K,Na)NbO3 and (Na1/2Bi1/2)TiO3 being prominent examples. The prototype Pb-free material with an antipolar lattice distortion is NaNbO3. However, it does not exhibit the characteristic double hysteresis loop of antiferroelectric materials. AgNbO3 shows nice hysteresis loops but is hardly suitable for large scale applications due to materials cost and processing issues.
The project FLAME, which is funded by the LOEWE programme of the State of Hesse, Germany, is aiming at developing novel Pb-free antiferroelectric materials. Twelve research groups from materials science, chemistry and electrical engineering are collaborating to optimize antiferroelectric properties by adjusting the composition. In contrast to the widely used structure-property relationship for the design of new materials, FLAME is using the electronic structure as the guiding principle. This approach includes to develop the understanding between the electronic structure and antiferroelectric properties.
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.