Compositional tuning of Ba-⁠based ferroelectrics and relaxors

Abstract: A-⁠ and B-⁠site substitution of barium titanate with homovalent or heterovalent dopants is at the basis of solid solutions that lately found increasing importance for dielectric, piezoelectric, energy storage and microwave applications. High dielectric permittivity—stable over a large temperature range—and large high-⁠field piezoelectric coefficients are typically sought-⁠for figures of merit. Yet, compositional tuning to attain specific properties has been largely based on macroscopic observations and very little is known about the fine material structure on the short range that is necessary to induce those properties. In relaxors, for instance, it is not yet clear whether their peculiar behaviour originates from random electric fields or simple dipolar interactions. Raman spectroscopy, being sensitive to the material’s short range structure, is a very attractive technique to study structure-⁠property relationships in Ba-⁠based ferroelectrics and relaxors. In this presentation, an overview will be given on this technique and on the information it can convey on these systems. It will be shown that the Raman method is complementary to diffraction and macroscopic property measurements, and can add decisive details to understanding the whole picture, especially if coupled with atomistic simulations. We will focus on both A-⁠ and B-⁠site substituted BaTiO3 (with Bi and Zr, respectively) and also A-⁠ and B-⁠site co-⁠doped systems (with Bi, Yb and Fe).