Ferroelectric Distortion in Bi4Ti3O12 Studied by Neutron Powder Diffraction

2007 ◽  
Vol 350 ◽  
pp. 65-68 ◽  
Author(s):  
Yuji Noguchi ◽  
Masaru Miyayama
Keyword(s):  
High Temperature ◽  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
Minor Role ◽  
Tio6 Octahedra ◽  
A Minor ◽  
Plane Displacement ◽  
A Site ◽  
Oxide Ions ◽  
Bond Valence Analysis

Crystal structures of Bi4Ti3O12 ferroelectrics have been investigated by high-temperature neutron powder diffraction study. The ferroelectricity in Bi4Ti3O12 is shown to originate from the in-plane displacement of TiO6 octahedra with respect to heavy Bi ions, and that the off-center Ti displacement in the octahedra plays a minor role. Bond valence analysis shows that the underbonding of Bi with the adjacent oxide ions at the perovskite A site in high-temperature paraelectric state plays an essential role in the ferroelectric phase transition in the Bi4Ti3O12 system.

Mn-Mg disordering in cummingtonite: a high-temperature neutron powder diffraction study

2000 ◽  
Vol 64 (2) ◽  
pp. 255-266 ◽  
Author(s):  
J. J. Reece ◽  
S. A. T. Redfern ◽  
M. D. Welch ◽  
C. M. B. Henderson
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
New York ◽  
High Temperature ◽  
Powder Diffraction ◽  
Elevated Temperatures ◽  
Neutron Powder Diffraction ◽  
Site Preference ◽  
A Site

AbstractThe crystal structure of a manganoan cummingtonite, composition [M4](Na0.13Ca0.41Mg0.46Mn1.00) [M1,2,3](Mg4.87Mn0.13)(Si8O22)(OH)2, (Z = 2), a = 9.5539(2) Å, b = 18.0293(3) Å, c = 5.2999(1) Å, β = 102.614(2)° from Talcville, New York, has been refined at high temperature using in situ neutron powder diffraction. The P21/m to C2/m phase transition, observed as spontaneous strains +ε1 = −ε2, occurs at ˜107°C. Long-range disordering between Mg2+ and Mn2+ on the M(4) and M(2) sites occurs above 550°C. Mn2+ occupies the M(4) and M(2) sites preferring M(4) with a site-preference energy of 24.6±1.5 kJ mol−1. Disordering induces an increase in XMnM2 and decrease in XMnM4 at elevated temperatures. Upon cooling, the ordered states of cation occupancy are ‘frozen in’ and strains in lattice parameters are maintained, suggesting that re-equilibration during cooling has not taken place.

NEUTRON POWDER DIFFRACTION AND OXIDE SUPERCONDUCTORS

1993 ◽  
Vol 07 (16n17) ◽  
pp. 3077-3093 ◽  
Author(s):  
A.W. HEWAT
Keyword(s):  
Heavy Metals ◽  
High Temperature ◽  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
Oxide Superconductors ◽  
X Rays ◽  
New Materials ◽  
Oxidation Reduction ◽  
High Temperature Oxide ◽  
Temperature Oxide

Neutron powder diffraction has been essential for understanding the structures of the new high temperature oxide superconductors because of the difficulty in locating oxygen with X-rays in the presence of heavy metals, especially when single crystals are usually not available. This understanding lead to the discovery of new materials. In this paper we will show how it also sheds light on the crystal chemistry of oxide superconductors—the effects of oxidation/reduction, phase separation, pressure etc.

High-Temperature Study of Octahedral Cation Exchange in Olivine by Neutron Powder Diffraction

Science ◽  
1996 ◽  
Vol 271 (5256) ◽  
pp. 1713-1715 ◽  
Author(s):  
C. M. B. Henderson ◽  
K. S. Knight ◽  
S. A. T. Redfern ◽  
B. J. Wood
Keyword(s):  
High Temperature ◽  
Cation Exchange ◽  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
Temperature Study ◽  
Octahedral Cation ◽  
High Temperature Study

Structure of the high-temperature superconductor Ba2YCu3O7 by X-ray and neutron powder diffraction

1987 ◽  
Vol 63 (12) ◽  
pp. 1149-1153 ◽  
Author(s):  
M. François ◽  
E. Walker ◽  
J.-L. Jorda ◽  
K. Yvon ◽  
P. Fischer
Keyword(s):  
High Temperature ◽  
Powder Diffraction ◽  
High Temperature Superconductor ◽  
Neutron Powder Diffraction ◽  
X Ray

Measurement of Atomic Elastic Constants by Pulsed Neutron Powder Diffraction

1992 ◽  
Vol 36 ◽  
pp. 577-583
Author(s):  
A. C. Lawson ◽  
G. H. Kwei ◽  
J. A. Goldstone ◽  
B. Cort ◽  
R. I. Sheldon ◽  
...  
Keyword(s):  
High Temperature ◽  
Neutron Diffraction ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Elastic Constants ◽  
Diffraction Data ◽  
High Temperature Superconductors ◽  
Neutron Powder Diffraction ◽  
Neutron Diffraction Data ◽  
Pulsed Neutron

AbstractWe have developed a technique for determining the atomic elastic constants from measurements of the Debye-Waller factors. The Debye-Waller factors are obtained by Rietveld refinement of time-of-flight neutron diffraction data and interpreted in terms of an atomic Debye-Waller temperature. The method is applicable to powders and to materials that must be encapsulated for safety or environmental reasons. We will illustrate our technique with applications to actinide metals, to metallic hydrides and to high-temperature superconductors.

High-temperature structural evolution of hexagonal multiferroic YMnO3and YbMnO3

2007 ◽  
Vol 40 (4) ◽  
pp. 730-734 ◽  
Author(s):  
Il-Kyoung Jeong ◽  
N. Hur ◽  
Th. Proffen
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Powder Diffraction ◽  
Structural Parameters ◽  
Structural Evolution ◽  
Neutron Powder Diffraction ◽  
Temperature Behaviour ◽  
Rietveld Refinements ◽  
Polar Structure ◽  
Diffraction Patterns

Neutron powder diffraction studies on the structural evolution of hexagonal multiferroic YMnO3and YbMnO3from 1000 K to 1400 K, and from 1000 K to 1350 K, respectively, are presented. The temperature evolution of diffraction patterns suggests that YMnO3undergoes a phase transition to a non-polar structure above 1200 K, while YbMnO3remains ferroelectric up to 1350 K. Detailed structural parameters were obtained as a function of temperature from Rietveld refinements. Based on this result, the distinct differences in temperature behaviour between YMnO3and YbMnO3, and the origin of the ferroelectricity in these hexagonal multiferroics are discussed.

Sign in / Sign up

Export Citation Format

Share Document