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  4. Lead-Oxygen Bond Length Distributions of the Relaxor Ferroelectric 0.67PbMg(1/3)Nb(2/3)O(3)-0.33PbTiO(3) from Pb-207 Nuclear Magnetic Resonance
 
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research article

Lead-Oxygen Bond Length Distributions of the Relaxor Ferroelectric 0.67PbMg(1/3)Nb(2/3)O(3)-0.33PbTiO(3) from Pb-207 Nuclear Magnetic Resonance

Avalos, Claudia E.  
•
Walder, Brennan J.  
•
Emsley, Lyndon  
June 27, 2019
Journal Of Physical Chemistry C

We investigate changes in the local environment of Pb-207 sites in the relaxor ferroelectric 0.67PbMg(1/3)Nb(2/3)O(3)-0.33PbTiO(3) using variable temperature magic angle spinning nuclear magnetic resonance. We observe a Gaussian distribution of Pb-207 chemical shifts with a mean chemical shift of -1469 +/- 8 ppm and a standard deviation of 229 +/- 8 ppm at 306 K and a mean chemical shift of -1410 +/- 1 ppm and a standard deviation of 275 +/- 1 ppm at 117 K. This corresponds to a decrease in the mean Pb-O bond length and a concurrent decrease in the effective coordination number from 6 to 5.8. An observed change in the asymmetry parameter from 0.4 to 0.8 for deshielded sites as well as a change in the shielding anisotropy of 300 ppm compared to 180 ppm for the more shielded resonances, indicating that the lead sites experience a more asymmetric environment at low temperature. Our observations support the unique direction model for Pb2+ ion displacements, in line with similar relaxor ferroelectric systems near room temperature. Multifield T-1 relaxation behavior observed between 9.4 and 21.1 T is indicative of a slowing down of dynamics around 200 K, and appears to be determined by spin-rotation fluctuations at high temperatures and a magnetic-field-dependent relaxation pathway at low temperatures.

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Type
research article
DOI
10.1021/acs.jpcc.9b04001
Web of Science ID

WOS:000473251300042

Author(s)
Avalos, Claudia E.  
•
Walder, Brennan J.  
•
Emsley, Lyndon  
Date Issued

2019-06-27

Publisher

AMER CHEMICAL SOC

Published in
Journal Of Physical Chemistry C
Volume

123

Issue

25

Start page

15744

End page

15750

Subjects

Chemistry, Physical

•

Nanoscience & Nanotechnology

•

Materials Science, Multidisciplinary

•

Chemistry

•

Science & Technology - Other Topics

•

Materials Science

•

solid-state

•

chemical-shifts

•

nmr

•

relaxation

Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LRM  
ISIC-GE  
Available on Infoscience
July 14, 2019
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/159106
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