Local structure of lead-free relaxor piezoelectrics (LOCPIEZO)

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The LOCPIEZO projects takes advantage of the combination of pair distribution function (PDF) analysis and fist principle calculation by density function theory (DFT) to determine the microscopic origin of lead-free relaxor piezoelectric materials. Relaxor materials offer superior piezoelectric and electromechanical coupling, imperative to electronic applications in control systems, sensors and transducers. Today's state-of-the-art materials are perovskite oxides based on toxic lead oxide. From a health, e nvironmental and legal point of view it is therefore highly desirable to find lead-free alternative relaxor materials. Solid solutions based on the perovskite oxides K0.5Na0.5NbO3, Bi0.5Na0.5TiO3 and Bi0.5K0.5TiO3 are promising candidates to replace lead- containing relaxors. Exploration of lead-free relaxors is still in its beginning, and would benefit greatly from a deeper fundamental understanding of the microscopic chemical and structural origins of relaxor behaviour. Disorder at the atomic scale is a common feature of relaxors, which complicates both the structural characterization by diffraction and the theoretical understanding. Pair distribution function analysis of relaxors can reveal both the local atomic structure as well as the intermediate ran ge order up to several tens of Ångstrøm, which is imperative to understand the structure, stability and dynamics of polar nanoregions, which are believed to be central to the properties of relaxors. Density functional theory calculations can help to expla in the electronic structure and chemical bonding origins of relaxor behaviour. Advanced characterization methods and computational materials science is of mutual benefit to elucidate the relationships between atomic structure and material properties. This insight is imperative to the continuing development of lead-free relaxors, and can enable rational materials design based on fundamental knowledge.