Structural studies of α-Bi2O3by neutron powder diffraction

2001 ◽  
Vol 16 (4) ◽  
pp. 227-230 ◽  
Author(s):  
S. A. Ivanov ◽  
R. Tellgren ◽  
H. Rundlo¨f ◽  
V. G. Orlov
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
High Temperature ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Structural Phase ◽  
Magnetic Behavior ◽  
Neutron Powder Diffraction ◽  
Structural Studies ◽  
Electron Subsystem

A detailed neutron powder diffraction study of the atomic structure of α-Bi2O3at high temperatures using the Rietveld method was performed to clarify the nature of the unusual magnetic behavior and the origin of the high temperature dielectric anomalies of α-Bi2O3in the temperature interval 300–700 K. Analysis of obtained experimental data shows that there are no evidence of a structural phase transition in α-Bi2O3between 295 and 660 K. The observed high temperature dielectric anomalies in α-Bi2O3are evidently governed by changes in the electron subsystem of the bismuth oxide.

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.

High Resolution Neutron Powder Diffraction Studies of the Ferroelastic Phase Transition in LaNbO4

1989 ◽  
Vol 166 ◽  
Author(s):  
W I F David
Keyword(s):  
Phase Transition ◽  
High Resolution ◽  
Powder Diffraction ◽  
Structural Phase ◽  
Strain Tensor ◽  
Neutron Powder Diffraction ◽  
Line Broadening ◽  
Neutron Powder Diffraction Data ◽  
Ferroelastic Phase Transition ◽  
Principal Axes

ABSTRACTAnalysis of high resolution neutron powder diffraction data of ferroelastic LaNbO4 indicates a monoclinic to tetragonal structural phase transition that is accompanied by anomalous line broadening. The origins of this line broadening have been investigated using a novel modification of the Rietveld technique. The results show that strain broadening is associated with the ferroelastic phase transition both above and below the transition temperature. This anomalous ‘microstrain’ is well-described by a second rank strain tensor, the principal axes of which are collinear with the spontaneous lattice strain. This phenomenon may be a general feature of proper ferroelastic phase transitions.

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.

Structural Phase Transition of Orthorhombic LaCrO3 Studied by Neutron Powder Diffraction

2000 ◽  
Vol 154 (2) ◽  
pp. 524-529 ◽  
Author(s):  
K. Oikawa ◽  
T. Kamiyama ◽  
T. Hashimoto ◽  
Y. Shimojyo ◽  
Y. Morii
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Powder Diffraction ◽  
Structural Phase ◽  
Neutron Powder Diffraction
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