The search for ecologically friendly ferroelectric systems that have the potential to replace the exemplary PbZr_1-xTi_xO₃ as an industrial material, requires a deep understanding of the composition-induced changes in the structure on a multiscale level. The lead-free _(1-x)Na_0.5Bi_0.5TiO_3-xBaTiO₃ (NBT-xBT) solid solution (perovskite structure type) has been identified as an attractive “green” ferroelectric, but the effect of Ba on its nanoscale structure across the morphotropic phase boundary still remains an enigma, in spite of extensive research over the past decade. One way to elucidate the relationship between the chemistry, local polar distortions, and net polarization is to study the structural transformations under external stimuli (temperature, pressure or electric field) by complementary X-ray diffraction and Raman-spectroscopic analyses, as these methods probe the structure at different length and time scales. Pressure in particular is a powerful thermodynamic variable that can oppose to the internal chemical pressure generated by substitutent cations and thus reveal the local elastic strains associated with compositional variations. In this lunch seminar, I will be first recalling some basic concepts of ferroelectric solid solutions and how to perform high pressure experiments using the diamond-anvil-cell technique, and then I will be presenting our recent results on the high-pressure behavior of NBT-xBT single crystals with compositions across the MPB [1-3].

[1] Rösche et al. Phys. Rev. B., 108, 094110 (2023)
[2] Rösche et al. Sci. Rep., 14, 18799 (2024)
[3] Rösche et al. Phys. Rev. B., 112, 184102 (2025)