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Controlled tuning of atomic structure in functional materials by acoustic waves and electric fields

Subject Area Experimental Condensed Matter Physics
Synthesis and Properties of Functional Materials
Term from 2019 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 409743569
 
Final Report Year 2023

Final Report Abstract

Significant advances in the understanding of the formation of electric polarization and magnetoelectric phenomena as a result of active research in the field of condensed matter and nanotechnology over the last decades have enabled the design of new classes of functional elements based on the combination of magnetoelectric and piezoelectric coupling. Macroscopic properties such as multiferroism and piezoelectricity are associated with local structural changes that occur under the influence of external disturbances. For a controlled setting of the underlying atomistic shifts, the in-situ characterization of the structural response to the external field parameters provides a key approach. In this project, German and Russian groups of scientists investigated in particular the influence of standing acoustic waves and electric fields on the atomistic crystal structure of selected piezoelectrics with the aim of better understanding the causes of the coupling phenomena and locally structuring the variability of derived material properties and thus also opening them up for new fields of application. For the considered materials LiNbO3/LiTaO3, TeO2, Li2B4O7, ZnO, RbH2PO4, BaTiO3, YMn2O5 and the MFP phase in SrTiO3 a deeper understanding of atomic displacements and symmetry breaking was obtained and versatile material questions were answered. The material-specific insights include in particular the local symmetry reduction and vacuum migration in TeO2, the polarization evolution and defect dynamics in LiMO3, the electronic structure of the homologous series of Ruddlesden-Popper phases in SrTiO3, as well as the origin of ferroelectricity in the commensurably modulated low-temperature phase of YMn2O5. On the one hand, systematic theoretical modelling, prediction and interpretation by means of density functional theory and molecular dynamics and, on the other hand, the accompanying experimental characterization of the crystal structural changes under the externally specified boundary conditions of pressure and electric field, both in the laboratory and with high time resolution >100 kHz in-situ at the synchrotron, were used. In addition, new methodological approaches for reversible transformation control of structural parameters in the functional materials based on resonant X-ray diffraction as well as new experimental sample environments compatible with both conventional X-ray sources and state-of-the-art measuring stations in synchrotron radiation facilities were further developed in the project. In the joint research cooperation, it was shown that macroscopic crystal structuring through external physical fields and the associated symmetry breaking, as well as corresponding defect engineering, can be used as a path towards the development of new piezoelectrics.

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