Structural transformations in (1x)Na0.5Bi0.5TiO3xBaTiO3 single crystals studied by Raman spectroscopy

G. de la Flor, T. Malcherek, S. Gorfman, and B. Mihailova
Phys. Rev. B 96, 214102 – Published 8 December 2017

Abstract

Hard-mode Raman spectroscopy was applied to analyze the temperature-induced transformation processes in perovskite-type (ABO3) single crystals of (1x)Na0.5Bi0.5TiO3xBaTiO3 (NBT-xBT) in a wide temperature range between 100 and 1010 K and a composition range of x=00.074 across the morphotropic phase boundary (MPB). The results show abundant uncoupled ferroic structural distortions even at 1010 K and coexistence of two types of mesoscopic-scale ferroic order at lower temperatures. Octahedral BO6 tilting is typical of pure NBT, while the incorporation of A-site Ba2+ suppresses the tilting and promotes the off centering of BO6 octahedra. The temperature evolution of the phonon modes clearly reveals the two macroscopically observed critical temperatures Tm and Td as well as, in the case of x0, two characteristic temperatures T and T preceding the Tm and Td, respectively, which are attributed to mesoscopic-scale antiferroelectric and ferroelectric coupling processes within the A-site-cation subsystem. At x<xMPB the two sublattices, off-centered A-site cations and off-centered B-site cations, remain incoherent in the entire temperature range. Only when the amount of Ba reaches xMPB the two subsystems couple dynamically, which can explain the enhancement of properties at the MPB. The overall ferroic distortion, however, has a minimum at the MPB, probably because at xMPB the ferroelectric coupling between B-site Ti4+ cations is reduced to a greater extent than the enhancement of ferroelectric coupling between A-site Bi3+ cations.

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  • Received 11 September 2017
  • Revised 2 November 2017

DOI:https://doi.org/10.1103/PhysRevB.96.214102

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

G. de la Flor1,2,*, T. Malcherek1, S. Gorfman3, and B. Mihailova1

  • 1Department of Earth Science, University of Hamburg, Hamburg 20146, Germany
  • 2Departamento de Física de la Materia Condensada, Universidad del País Vasco UPV/EHU, Bilbao, Spain
  • 3Department of Materials Science and Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel

  • *gemma.delaflor@uni-hamburg.de

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Vol. 96, Iss. 21 — 1 December 2017

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