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Title: Structured diffuse scattering and polar nano-regions in the Ba(Ti{sub 1-} {sub x} Sn {sub x} )O{sub 3} relaxor ferroelectric system

Abstract

The observation via electron diffraction of relatively sharp G{+-}{l_brace}001{r_brace}* sheets of diffuse intensity arising from the large amplitude excitation of inherently polar, transverse optical modes of distortion in Ba(Ti{sub 1-} {sub x} Sn {sub x} )O{sub 3} (BTS), 0.1{<=}x{<=}0.5, samples, both at room temperature as well as liquid nitrogen temperature, shows that the polar nano-regions (PNRs) in these relaxor ferroelectric materials correspond to the same highly anisotropic <001> chain dipoles as are characteristic of the normal ferroelectric end member BaTiO{sub 3} itself. The correlation length along the chain of these 1-d PNRs can, in principle, be determined from the width of the observed {l_brace}001{r_brace}* diffuse sheets in reciprocal space and is estimated to be at least 5 nm even for the higher x samples. The distribution of the substitutional Sn ions thus appears to have only a minor effect upon the correlation length along the <001> chain dipole directions. It is suggested that the role of the dopant Sn ions is not to directly induce PNRs but rather to set up random local strain fields preventing the condensation of long wavelength homogeneous strain distortions of the unit cell thereby suppressing transverse correlations of the <001> chain dipoles and the developmentmore » of long-range ordered ferroelectric state/s. - Graphical abstract: The characteristic G{+-}{l_brace}001{r_brace}* sheets of diffuse intensity characteristic of the relaxor ferroelectric Ba(Ti{sub 1-} {sub x} Sn {sub x} )O{sub 3} (BTS), 0.1{<=}x{<=}0.5, system along with the inherently polar, transverse optical modes of distortion responsible.« less

Authors:
 [1];  [2];  [3];  [4]
  1. Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia)
  2. Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia), E-mail: withers@rsc.anu.edu.au
  3. Electronic Materials Research Laboratory (EMRL), Xi'an Jiaotong University, Xi'an (China)
  4. Research School of Earth Sciences, Australian National University, Canberra, ACT 0200 (Australia)
Publication Date:
OSTI Identifier:
21015722
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 180; Journal Issue: 3; Other Information: DOI: 10.1016/j.jssc.2006.12.013; PII: S0022-4596(06)00646-3; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ANISOTROPY; BARIUM COMPOUNDS; CORRELATIONS; DIFFUSE SCATTERING; ELECTRON DIFFRACTION; FERROELECTRIC MATERIALS; OPTICAL MODES; OXIDES; SHEETS; STRAINS; TEMPERATURE RANGE 0273-0400 K; TIN COMPOUNDS; TIN IONS; TITANATES

Citation Formats

Liu Yun, Withers, Ray L., Wei Xiaoyong, and Fitz Gerald, John D. Structured diffuse scattering and polar nano-regions in the Ba(Ti{sub 1-} {sub x} Sn {sub x} )O{sub 3} relaxor ferroelectric system. United States: N. p., 2007. Web.
Liu Yun, Withers, Ray L., Wei Xiaoyong, & Fitz Gerald, John D. Structured diffuse scattering and polar nano-regions in the Ba(Ti{sub 1-} {sub x} Sn {sub x} )O{sub 3} relaxor ferroelectric system. United States.
Liu Yun, Withers, Ray L., Wei Xiaoyong, and Fitz Gerald, John D. Thu . "Structured diffuse scattering and polar nano-regions in the Ba(Ti{sub 1-} {sub x} Sn {sub x} )O{sub 3} relaxor ferroelectric system". United States. doi:.
@article{osti_21015722,
title = {Structured diffuse scattering and polar nano-regions in the Ba(Ti{sub 1-} {sub x} Sn {sub x} )O{sub 3} relaxor ferroelectric system},
author = {Liu Yun and Withers, Ray L. and Wei Xiaoyong and Fitz Gerald, John D.},
abstractNote = {The observation via electron diffraction of relatively sharp G{+-}{l_brace}001{r_brace}* sheets of diffuse intensity arising from the large amplitude excitation of inherently polar, transverse optical modes of distortion in Ba(Ti{sub 1-} {sub x} Sn {sub x} )O{sub 3} (BTS), 0.1{<=}x{<=}0.5, samples, both at room temperature as well as liquid nitrogen temperature, shows that the polar nano-regions (PNRs) in these relaxor ferroelectric materials correspond to the same highly anisotropic <001> chain dipoles as are characteristic of the normal ferroelectric end member BaTiO{sub 3} itself. The correlation length along the chain of these 1-d PNRs can, in principle, be determined from the width of the observed {l_brace}001{r_brace}* diffuse sheets in reciprocal space and is estimated to be at least 5 nm even for the higher x samples. The distribution of the substitutional Sn ions thus appears to have only a minor effect upon the correlation length along the <001> chain dipole directions. It is suggested that the role of the dopant Sn ions is not to directly induce PNRs but rather to set up random local strain fields preventing the condensation of long wavelength homogeneous strain distortions of the unit cell thereby suppressing transverse correlations of the <001> chain dipoles and the development of long-range ordered ferroelectric state/s. - Graphical abstract: The characteristic G{+-}{l_brace}001{r_brace}* sheets of diffuse intensity characteristic of the relaxor ferroelectric Ba(Ti{sub 1-} {sub x} Sn {sub x} )O{sub 3} (BTS), 0.1{<=}x{<=}0.5, system along with the inherently polar, transverse optical modes of distortion responsible.},
doi = {},
journal = {Journal of Solid State Chemistry},
number = 3,
volume = 180,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • The observation via electron diffraction of relatively sharp, G{+-}{l_brace}111{r_brace}* sheets of diffuse intensity arising from the large amplitude excitation of inherently polar, transverse optical modes of distortion in [(Pb{sub 1-y}La{sub y}){sub 1-{alpha}}{open_square}{sub {alpha}}][(Zr{sub 1-x}Ti{sub x}){sub 1-{beta}}{open_square}{sub {beta}}]O{sub 3} (PLZT), 7.5/65/35 and 7.0/60/40, samples close to the morphotropic phase boundary in this system shows that the fundamental dipolar units in these materials correspond to highly anisotropic <111> chain dipoles formed from off-centre Pb/La and coupled Ti/Zr displacements. The correlation length along the chain of these 1-d dipoles can, in principle, be determined from the width of the observed {l_brace}111{r_brace}* diffuse sheetsmore » in reciprocal space and is estimated to be at least 2-3 nm. The primary role of the dopant La ions appears to be to set up random local strain fields preventing the condensation of long wavelength homogeneous strain distortions of the unit cell thereby suppressing transverse correlations of the fundamental <111> chain dipoles and the development of macro-, or even nano-scale, ordered ferroelectric domain state/s in the absence of an applied external electric field. - Graphical abstract: Shows a plausible model for the nano-scale polar ordering of the PLZT (7.5/65/35 and 7.0/60/40) transparent ferroelectric samples in a single layer of the average cubic structure normal to a [110] direction. The fundamental dipolar units in these materials correspond to highly anisotropic <111> chain dipoles formed from off-centre Pb and coupled Ti/Zr displacements.« less
  • We have used neutron diffraction to characterize the diffuse scattering in five single crystals of the relaxor ferroelectric (1-x)Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-xPbTiO{sub 3} (PMN-xPT) with x=0, 10, 20, 30, and 40%. The addition of ferroelectric PbTiO{sub 3} modifies the well-known 'butterfly' and 'ellipsoidal' diffuse scattering patterns observed in pure PMN (x=0), which are believed to be associated with the presence of randomly oriented polar nanoregions. In particular, the anisotropy of the diffuse scattering diminishes as the PT content increases. The spatial correlation length {xi} along the [110] direction derived from the width of the diffuse scattering at room temperature increasesmore » from 12.6 A for PMN to 350 A for PMN-20%PT. In addition, the diffuse scattering intensity at q=0 grows and reaches a maximum value around the morphotropic phase boundary (MPB), which suggests that it is proportional to the dielectric susceptibility. Beyond x=30%, a concentration very close to the MPB, no diffuse scattering is observed below T{sub C}, and well-defined critical behavior appears near T{sub C}. By contrast, the diffuse scattering for x{<=}20% persists down to low temperatures, where the system retains an average cubic structure (T{sub C}=0). Finally, the anisotropic soft transverse optic (TO) modes observed in PMN are found to be isotropic for PMN-30%PT, which strongly suggests a connection between the anisotropic diffuse scattering and the TO modes.« less
  • Diffuse scattering and relaxor behavior in Na{sub 0.5}Bi{sub 0.5}TiO{sub 3} (NBT) and NBT-5.6 at. %BaTiO{sub 3} (NBT-5.6%BT) were investigated. X-ray diffraction revealed two types of diffuse scattering in NBT: (i) broad and (ii) asymmetric L-shaped. After modification with 5.6%BT, the broad diffuse scattering patterns became narrow, and the asymmetric L-shaped ones were replaced by symmetric ones. The symmetric diffuse scattering in NBT-5.6%BT disappeared with increasing dc electric field (E) for E ≥ 9.5 kV/cm where the frequency dispersion in the dielectric constant disappeared. These results demonstrate that the relaxor characteristics are directly correlated with the diffuse scattering and the presence polar nano-regions.
  • Diffuse neutron scattering is a valuable tool to obtain information about the size and orientation of the polar nanoregions that are a characteristic feature of relaxor ferroelectrics. In this paper, we present new diffuse scattering results obtained on Pb(Zn1/3Nb2/3)O3 (PZN for short) and (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3(PZN-xPT)single crystals (with x=4.5 and 9%), around various Bragg reflections and along three symmetry directions in the [100]-[011] zone. Diffuse scattering is observed around reflections with mixed indices, (100), (011) and (300), and along transverse and diagonal directions only. No diffuse scattering is found in longitudinal scans. The diffuse scattering peaks can be fitted well with amore » Lorentzian function, from which a correlation length is extracted. The correlation length increases with decreasing temperatures down to the transition at Tc, first following a Curie-Weiss law, then departing from it and becoming flat at very low temperatures. These results are interpreted in terms of three temperature regions: (1) dynamic polarization fluctuations (i.e. with a finite lifetime) at high temperatures, (2) static polarization reorientations (condensation of polar nanoregions) that can still reorient as a unit (relaxor behavior) at intermediate temperatures and (3) orientational freezing of the polar nanoregions with random strain fields in pure PZN or a structural phase transition in PZN-xPT at low temperatures. The addition of PT leads to a broadening of the diffuse scattering along the diagonal ([111]) relative to the transverse ([100]) direction, indicating a change in the orientation of the polar regions. Also, with the addition of PT, the polar nanoregions condense at a higher temperature above Tc.« less
  • Neutron elastic diffuse scattering experiments performed on Pb(Zn{sub 1/3}Nb{sub 2/3})O{sub 3} (PZN) and on its solid solution with PbTiO{sub 3}(PT), known as PZN-xPT, with x=4.5 and 9 % around many reflections show that diffuse scattering is observed around reflections with mixed indices in the transverse and diagonal directions only. From the width of the diffuse scattering peak a correlation length is extracted. In PZN, we have reported that the diffuse scattering is more extended in the transverse than in the diagonal directions [D. La-Orauttapong, J. Toulouse, J. L. Robertson, and Z.-G. Ye, Phys. Rev. B 64, 212101 (2001)]. In themore » present work, the results show that the addition of PT leads to a broadening of the diffuse scattering along the diagonal, relative to the transverse directions, indicating a change in the orientation of the polar regions. Also, with the addition of PT, the polar nanoregions condense at a higher temperature above the transition than in pure PZN (>40K), due to stronger correlations between the polar regions. Neutron inelastic scattering measurements have also been performed on PZN-xPT. The results show the broadening of the transverse acoustic phonon mode at a small momentum transfer q upon cooling. We attribute this broadening to the appearance of the polar nanoregions.« less