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Title: Single Crystal Growth of Relaxor Ferroelectric Ba2PrFeNb4O15 by the Optical Floating Zone Method

Abstract

Uniaxial tungsten bronzes have received increasing interest because of their potential application as lead-free ferroelectrics as well as their flexibility-via chemical substitution. Here we demonstrate growth of single crystals of one such material, Ba2PrFeNb4O15, which possesses the tetragonal tungsten bronze structure, by the optical floating zone method. The challenge of this growth is to control the stability of the molten zone which allows the growth to persist for a long enough time to achieve large volume single crystals. Our work reveals that the use of a slight overpressure of air allows the molten zone to be maintained up to 7 h at a traveling speed of 4 mm/h. The obtained crystals were studied using high-resolution single crystal scattering, powder X-ray diffraction, and dielectric measurements. We find that Ba2PrFeNb4O15 possesses a rather complex average structure with a monoclinic symmetry in a P112/m space group and unit cell parameters of a = 12.49188(8) Å, b = 12.49232(8) Å, c = 3.92863(1) Å, and γ = 90.056 °, with an additional incommensurate superstructural modulation superimposed. The temperature dependence of dielectric properties has been investigated by comparing as-grown, O2-annealed, and Ar-annealed samples. A broad relaxation dielectric peak is observed around 150 K for themore » O2-annealed sample, indicating a typical relaxor behavior below 150 K. A larger dielectric permittivity (ε' ≈ 1300) than those of corresponding ceramics (up to ε' ≈ 200) is found in the oxygen annealed crystals. In conclusion, we suggest that as-grown single crystals are oxygen deficient and that the oxygen vacancies can be eliminated by an oxygen annealing treatment.« less

Authors:
ORCiD logo [1];  [1];  [1];  [1];  [1];  [1]
  1. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
OSTI Identifier:
1581151
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Accepted Manuscript
Journal Name:
Crystal Growth and Design
Additional Journal Information:
Journal Volume: 19; Journal Issue: 12; Journal ID: ISSN 1528-7483
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; behavior; phase-transition; SBN; SM; states; Strontium-Barium Niobate

Citation Formats

Wang, Bi -Xia, Zheng, Hong, Ren, Yang, Krogstad, Matthew, Mitchell, J. F., and Phelan, Daniel. Single Crystal Growth of Relaxor Ferroelectric Ba2PrFeNb4O15 by the Optical Floating Zone Method. United States: N. p., 2019. Web. doi:10.1021/acs.cgd.9b01147.
Wang, Bi -Xia, Zheng, Hong, Ren, Yang, Krogstad, Matthew, Mitchell, J. F., & Phelan, Daniel. Single Crystal Growth of Relaxor Ferroelectric Ba2PrFeNb4O15 by the Optical Floating Zone Method. United States. https://doi.org/10.1021/acs.cgd.9b01147
Wang, Bi -Xia, Zheng, Hong, Ren, Yang, Krogstad, Matthew, Mitchell, J. F., and Phelan, Daniel. Fri . "Single Crystal Growth of Relaxor Ferroelectric Ba2PrFeNb4O15 by the Optical Floating Zone Method". United States. https://doi.org/10.1021/acs.cgd.9b01147. https://www.osti.gov/servlets/purl/1581151.
@article{osti_1581151,
title = {Single Crystal Growth of Relaxor Ferroelectric Ba2PrFeNb4O15 by the Optical Floating Zone Method},
author = {Wang, Bi -Xia and Zheng, Hong and Ren, Yang and Krogstad, Matthew and Mitchell, J. F. and Phelan, Daniel},
abstractNote = {Uniaxial tungsten bronzes have received increasing interest because of their potential application as lead-free ferroelectrics as well as their flexibility-via chemical substitution. Here we demonstrate growth of single crystals of one such material, Ba2PrFeNb4O15, which possesses the tetragonal tungsten bronze structure, by the optical floating zone method. The challenge of this growth is to control the stability of the molten zone which allows the growth to persist for a long enough time to achieve large volume single crystals. Our work reveals that the use of a slight overpressure of air allows the molten zone to be maintained up to 7 h at a traveling speed of 4 mm/h. The obtained crystals were studied using high-resolution single crystal scattering, powder X-ray diffraction, and dielectric measurements. We find that Ba2PrFeNb4O15 possesses a rather complex average structure with a monoclinic symmetry in a P112/m space group and unit cell parameters of a = 12.49188(8) Å, b = 12.49232(8) Å, c = 3.92863(1) Å, and γ = 90.056 °, with an additional incommensurate superstructural modulation superimposed. The temperature dependence of dielectric properties has been investigated by comparing as-grown, O2-annealed, and Ar-annealed samples. A broad relaxation dielectric peak is observed around 150 K for the O2-annealed sample, indicating a typical relaxor behavior below 150 K. A larger dielectric permittivity (ε' ≈ 1300) than those of corresponding ceramics (up to ε' ≈ 200) is found in the oxygen annealed crystals. In conclusion, we suggest that as-grown single crystals are oxygen deficient and that the oxygen vacancies can be eliminated by an oxygen annealing treatment.},
doi = {10.1021/acs.cgd.9b01147},
journal = {Crystal Growth and Design},
number = 12,
volume = 19,
place = {United States},
year = {2019},
month = {10}
}

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Figures / Tables:

Figure 1 Figure 1: Crystal structure of tetragonal tungsten bronze viewed along c-axis.

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