Stabilization of Polar Nanoregions in Pb-free Ferroelectrics

Abstract

The formation of polar nanoregions through solid-solution additions is known to enhance significantly the functional properties of ferroelectric materials. Despite considerable progress in characterizing the microscopic behavior of polar nanoregions (PNR), understanding their real-space atomic structure and dynamics of their formation remains a considerable challenge. Here, using the method of dynamic pair distribution function, we provide direct insights into the role of solid-solution additions towards the stabilization of polar nanoregions in the Pb-free ferroelectric of Ba(Zr,Ti)O_{3}. It is shown that for an optimum level of substitution of Ti by larger Zr ions, the dynamics of atomic displacements for ferroelectric polarization are slowed sufficiently below THz frequencies, which leads to increased local correlation among dipoles within PNRs. The dynamic pair distribution function technique demonstrates a unique capability to obtain insights into locally correlated atomic dynamics in disordered materials, including new Pb-free ferroelectrics, which is necessary to understand and control their functional properties.

Multifunctional barium titanate ceramics via chemical modification tuning phase structure

“…For B‐site substitution, a representative example is Zr 4+ doped BT, which shows typical relaxor behavior. Ba(Ti 0.85 Zr 0.15 )O 3 ceramic exhibits the considerable Δ T of 0.4 K near RT over a wide temperature region 150 . Furthermore, aliovalent ion substitution at B site is also investigated.…”

“…A and B, ε r ‐ T curves and corresponding Δ T ‐ E curves for pure BT, 148 (Ba 1‐ x Sr x )TiO 3 , 149 (Ba 0.94 RE 0.04 )TiO 3 (RE = rare earth ions), 62 Ba(Ti 1‐ x Zr x )O 3 , 150 and Ba(Ti 1‐ x Nb x )O 3 ceramics 151 . Reproduced with permission 148 .…”

“…Copyright 2016, The Royal Society of Chemistry. Reproduced with permission 150 . Copyright 2018, American Physical Society.…”

“…Copyright 2019, The Royal Society of Chemistry. H and I, Electric field dependence of Δ T near room temperature for BT‐, BNT‐, KNN‐ and Pb‐based ceramics 19,62,138‐146,148‐163 …”

Real-Space Description of Dynamics of Liquids

“…I predict in ten years up to 1/3 of the results of inelastic neutron scattering experiments may be presented in real-space, just as that much of neutron powder diffraction results are now presented as the PDF in real space following our advocacy [7]. Indeed, DyPDF was recently used in the study of local dynamics in lead-free relaxor ferroelectrics [49], and more measurements to determine DyPDFs for various complex matters are scheduled. Concomitantly the scattering facilities need to be developed to accommodate this demand.…”