Instabilities arising from the electronic configuration of ions in a material can lead to distortions in coordination environments, such as second-order Jahn-Teller effects in transition metals with empty d-orbitals (d0 configuration) and stereochemically active lone pairs of main group cations (s2 configuration). Of great interest in the solid state is that these distortions can be local in nature, where they occur in a material but are not correlated with each other, or they can manifest crystallographically when correlated over long ranges producing a polar crystal structure. Many energy and technology-driven applications rely on the polar nature of materials that contain elements with the d0 and/or s2 electronic configuration necessary for these distortions. Of these, lead (Pb)-based materials exhibit the highest performance. However, the known toxicity of Pb and subsequent regulations prompt the investigation of alternative chemistries for technological applications. Herein we will discuss the characterization of materials with alternative chemistries inspired by prototypical polar perovskites BaTiO3 and PbTiO3. Systems of focus in this talk include perovskite and pyrochlore materials that contain cations with d0 (Nb5+, Ti4+) and s2 (Bi3+, Sn2+) electronic configurations. The discussion will focus on the determination of local distortions of coordination environments, and the role of these local distortions on the realization of correlated, polar phases in complex materials.

Structural complexities in solids: Understanding functionality through local distortions in perovskite and pyrochlore materials

2019 Fall National Meeting

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