Neutron diffraction study of the structure of the antifluorite crystal (NH4)2TeCl6

1991 ◽  
Vol 69 (2) ◽  
pp. 137-141 ◽  
Author(s):  
Robin L. Armstrong ◽  
Paul Dufort ◽  
Brian M. Powell
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Structural Phase ◽  
Mean Field ◽  
Neutron Diffraction Study ◽  
Cubic Phase ◽  
Space Group ◽  
Trigonal Structure ◽  
Primary Order ◽  
Reduced Temperature

A neutron diffraction study of the crystal structure of (NH4)2TeCl6 is presented. The data support a previous contention that this crystal undergoes a ferrorotative structural phase transition at 85 K, from a cubic structure with space group Oh5 to a trigonal structure with space group C3i2. The primary-order parameter is the rotation angle, Φ, of the TeCl6 octahedra about a [111] axis of the cubic phase. The data indicate that the temperature dependence of Φ is non-mean-field like over an extended reduced temperature range.

Neutron diffraction study of the structure of the antifluorite crystal (NH4)2PbCl6

1989 ◽  
Vol 67 (11) ◽  
pp. 1040-1043 ◽  
Author(s):  
Robin L. Armstrong ◽  
Bryan Lo ◽  
Brian M. Powell
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Lattice Distortion ◽  
Structural Phase ◽  
Neutron Diffraction Study ◽  
Cubic Phase ◽  
Space Group ◽  
Trigonal Structure ◽  
Small Lattice ◽  
Primary Order

A neutron diffraction study of the crystal structure of (NH4)2PbCl6 is presented. Data taken at 100 and 4.2 K support a previous contention that (NH4)2PbCl6 undergoes a ferrorotative structural phase transition at 80 K, from a cubic structure with space group [Formula: see text] to a trigonal structure with space group [Formula: see text]. The primary-order parameter is the rotation angle [Formula: see text] of the PbCl6 octahedron about a [111] axis of the cubic phase; [Formula: see text] is 3.1° at 4.2 K. A small lattice distortion and an (NH4)+ ion displacement along [111] also occur and represent secondary-order parameters.

Neutron diffraction study of (KxNa1−x)NbO3-based ceramics from low to high temperatures

2016 ◽  
Vol 49 (3) ◽  
pp. 891-901 ◽  
Author(s):  
Henry Mgbemere ◽  
Gerold Schneider ◽  
Markus Hoelzel ◽  
Manuel Hinterstein
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
High Temperatures ◽  
Neutron Diffraction Study ◽  
Cubic Phase ◽  
Temperature Structure ◽  
Two Phase ◽  
Space Group ◽  
Space Groups ◽  
Best Fit

A neutron diffraction study of (KxNa1−x)NbO3-based ceramics has been carried out from 5 K to high temperatures well above the Curie temperature. The diffraction data were analysed using Rietveld refinement. For pure KNN samples, especially at the Na-rich side of the phase diagram, the low-temperature structure of simple rhombohedral symmetry changes to a highly complex monoclinic structure at a higher temperature. Chemical analysis on the samples showed good agreement of the expected and actual compositions. Trigonal, monoclinic, orthorhombic, tetragonal and cubic phase models as well as two-phase mixtures are observed depending on the temperature of measurement. Space groupsR3c,P1m1,P11m,Amm2,P4mm, Pm\overline 3m and their combinations are used to refine the trigonal, monoclinic, orthorhombic, tetragonal, cubic and mixed phases, respectively. For the (K0.48Na0.48Li0.04)(Nb0.86Ta0.1Sb0.04)O3sample at temperatures between 5 and 300 K, the monoclinicP11mspace group gives the best refinement fit. For the (K0.17Na0.83)NbO3sample, a two-phase refinement using the trigonalR3cand monoclinicPmspace groups gave the best fit at 300 K, while at 5–150 K the trigonalR3cspace group gives the best fit. The understanding of the structure of these lead-free ceramics will help in the optimization of their piezoelectric properties.

NEUTRON DIFFRACTION STUDY ON (Bi−Pb)2Sr2Ca2Cu3O10

1990 ◽  
Vol 04 (12) ◽  
pp. 791-794 ◽  
Author(s):  
YANG JI-LIAN ◽  
YE CHUN-TANG ◽  
ZHANG BAI-SHENG ◽  
LI JI-ZHOU ◽  
KANG JIAN ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Neutron Diffraction ◽  
Diffraction Study ◽  
Single Phase ◽  
Polycrystalline Sample ◽  
Neutron Diffraction Study ◽  
Structure Study ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray

The polycrystalline sample of (Bi–Pb)2Sr2Ca2Cu3O10 with Tc=107 K was prepared. The X-ray diffraction proved that the sample is single phase. The crystal structure study on the sample has been carried out by neutron diffraction. The result shows that its structure is tetragonal body-centre structure with space group of I4/mmm, containing a few oxygen atoms at 4e site in Bi–Pb layers.

Neutron-diffraction study of a structural phase transition in the deuterated molecular ferromagnet Fe(dtc) 2 Cl

2002 ◽  
Vol 74 (0) ◽  
pp. s923-s925
Author(s):  
J. Campo ◽  
J. Luz�n ◽  
F. Palacio ◽  
G. DeFotis ◽  
J. Christophel ◽  
...  
Keyword(s):  
Phase Transition ◽  
Neutron Diffraction ◽  
Diffraction Study ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Neutron Diffraction Study

Single-crystal neutron diffraction study of the structural phase transition in Ba0.95Ca0.05TiO3

1998 ◽  
Vol 10 (4) ◽  
pp. 899-899
Author(s):  
P U M Sastry ◽  
A Sequeira ◽  
H Rajagopal ◽  
B A Dasannacharya ◽  
S Balakumar ◽  
...  
Keyword(s):  
Phase Transition ◽  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Study ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Neutron Diffraction Study
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