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

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

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Author(s)

  • Bi-Xia Wang
  • Hong Zheng
  • Matthew Krogstad
  • J. F. Mitchell
  • Daniel Phelan

Detail(s)

Original languageEnglish
Pages (from-to)7249-7256
Journal / PublicationCrystal Growth and Design
Volume19
Issue number12
Online published25 Oct 2019
Publication statusPublished - 4 Dec 2019
Externally publishedYes

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 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. We suggest that as-grown single crystals are oxygen deficient and that the oxygen vacancies can be eliminated by an oxygen annealing treatment.

Citation Format(s)

Single Crystal Growth of Relaxor Ferroelectric Ba2PrFeNb4O15 by the Optical Floating Zone Method. / Wang, Bi-Xia; Zheng, Hong; Ren, Yang et al.
In: Crystal Growth and Design, Vol. 19, No. 12, 04.12.2019, p. 7249-7256.

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review