EXAFS STUDIES OF THE FERROELECTRIC PHASE TRANSITIONS INDUCED BY OFF-CENTER IONS IN PbSxTe1−x and ZnxCd1−xTe ALLOYS

1992 ◽  
Vol 06 (23) ◽  
pp. 1413-1425
Author(s):  
ZHIHAI WANG ◽  
BRUCE A. BUNKER ◽  
ROBERT A. MAYANOVIC ◽  
URSULA DEBSKA ◽  
JACEK K. FURDYNA ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Local Structure ◽  
Ferroelectric Phase ◽  
Temperature Phase ◽  
Zinc Ions ◽  
Anion Sublattice ◽  
X Ray ◽  
Ferroelectric Phase Transitions ◽  
X Ray Absorption ◽  
Low Temperature Phase

Using the Extended X-ray Absorption Fine Structure (EXAFS) technique, we have investigated the local structure of disordered PbSxTe1−x and ZnxCd1−xTe alloys at temperatures below and above the reported ferroelectric transition temperatures. For the PbSxTe1−x alloys (x=0.10, 0.18, and 0.30), the sulphur ions are found to be off-center in both the high and the low temperature phase and Pb sublattice and Te sublattice shift relative to one another below the transition temperature. For ZnxCd1−xTe alloys (x=0.10 and 0.20), the zinc ions are found in a slightly asymmetric site in the cages formed by four NN Te ions and no relative shift between the cation and anion sublattice is observed. We discuss our results concerning the ferroelectric phase transitions (FPT) induced by off-center ions in these two systems.

X-ray study of the low-temperature phase transitions in LiKSO4

1983 ◽  
Vol 4 (1) ◽  
pp. 37-45 ◽  
Author(s):  
P. E. Tomaszewski ◽  
K. Łukaszewicz
Keyword(s):  
Phase Transitions ◽  
Low Temperature ◽  
Temperature Phase ◽  
X Ray ◽  
Low Temperature Phase

Single-Crystal X-Ray Scattering Study of Superstructures and Phase Transitions in Graphite-Hno3 and Graphite-Br2 Intercalation Compounds

1982 ◽  
Vol 20 ◽  
Author(s):  
R. Moret ◽  
R. Comes ◽  
G. Furdin ◽  
H. Fuzellier ◽  
F. Rousseaux
Keyword(s):  
Phase Transitions ◽  
Low Temperature ◽  
Room Temperature ◽  
Temperature Phase ◽  
Temperature Structure ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Temperature Liquid ◽  
Low Temperature Phase

ABSTRACTIn α-C5n-HNO3 the condensation of the room-temperature liquid-like diffuse ring associated with the disorder-order transition around 250 K is studied and the low-temperature. superstructure is examined.It is found that β-C8n-HNO3 exhibits an in-plane incommensurate order at room temperature.Two types of graphite-Br2 are found. Low-temperature phase transitions in C8Br are observed at T1 ≍ 277 K and T2 ≍ 297 K. The room-temperature structure of C14Br is reexamined. Special attention is given to diffuse scattering and incommensurability.

Reversiblechair↔skewconformational interconversion of 1,3,2-dioxaphosphorinane ring in the solid state

2016 ◽  
Vol 72 (1) ◽  
pp. 117-125 ◽  
Author(s):  
Katarzyna Anna Ślepokura
Keyword(s):  
Phase Transitions ◽  
Single Crystal ◽  
Dihydroxyacetone Phosphate ◽  
Temperature Phase ◽  
Coordination Geometry ◽  
Phosphate Anion ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cyclic Phosphate ◽  
Low Temperature Phase

β-NH4[(MeO)2cDHAP] (where cDHAP is cyclic dihydroxyacetone phosphate) has been investigated by X-ray crystallography in the temperature range 350–100 K. Three reversible single-crystal-to-single-crystal phase transitions have been examined and four phases (high-, room-, medium- and low-temperature phase, HTP, RTP, MTP and LTP, respectively) have been structurally determined: HTP (at 350 K,P21/a,Z= 24), RTP (290 K, P \overline{1},Z= 12), MTP (205 K,P21/a,Z= 4) and LTP (100 K, P \overline{1},Z= 24). Various puckering modes of the 1,3,2-dioxaphosphorinane ring of the organic cyclic phosphate anion have been revealed in the crystal:chairandskew. Thechair↔skewring flipping, which has been shown to take place during the phase transitions, results in various populations ofskewandchairconformers in different phases. The flexibility in the coordination geometry of ammonium cations is considered to assist in the conformational flexibility of the dioxaphosphorinane ring.

An X-ray scattering study of the low-temperature phase transitions of LiKSO4

1995 ◽  
Vol 7 (44) ◽  
pp. 8445-8452 ◽  
Author(s):  
A Desert ◽  
A Gibaud ◽  
A Righi ◽  
U A Leitao ◽  
R L Moreira
Keyword(s):  
Phase Transitions ◽  
Low Temperature ◽  
Temperature Phase ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Low Temperature Phase ◽  
Ray Scattering

scholarly journals Structural Study of Ferroelectric Phase Transition of Sn-doped SrTiO3

2014 ◽  
Vol 70 (a1) ◽  
pp. C61-C61 ◽  
Author(s):  
Hirofumi Kasatani ◽  
Shoichiro Suzuki ◽  
Akira Ando ◽  
Eisuke Magome ◽  
Chikako Moriyoshi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Local Structure ◽  
Ferroelectric Phase Transition ◽  
Nearest Neighbor ◽  
Ferroelectric Phase ◽  
Rietveld Analysis ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray

Recently, ferroelectricity was discovered in Sn-doped SrTiO3 (abbreviated by SSTO), in which Sr-atom was substituted by a few percent Sn-atom[1]. The ferroelctricity of SSTO was confirmed by means of the appearance of the dielectric anomaly, that reached several thousands and the clear D-E hysteresis loop in low temperature phase. In order to clarify the mechanism of ferroelectric phase transition of SSTO from the viewpoint of the crystal structure, we investigated the average crystal structure and the local structure around the substitutional Sn-atom of SSTO10 (10% Sn concentration, ferroelectric phase transition temperature 180K) by means of synchrotron-radiation powder X-ray diffraction and transmission XAFS spectrum of Sn:K-edge, respectively. From the results of MEM/Rietveld analysis of powder X-ray diffraction data, it was obtained that crystal structure of paraelectric phase of SSTO10 was cubic perovskite structure with the disorder state of Sn-atom. In ferroelectric phase, the crystal system was tetragonal, which was similar in structure to tetragonal ferroelectric structure of BaTiO3, and Sn-atom was order state. XAFS study revealed that the valence of Sn-ion was +2 charge and the local structure of Sn-atom was seemed as being the self-insistent state of SnO crystal structure. However, strangely, the coordination number of the nearest neighbor atom, that is O-atom, was 2 instead of 4. This is a mystery result and we have been analyzing. We have considered that the ferroelectricity of SSTO is induced by the distortion around the subsitituional Sn-atom. At the meeting, we are planning to discuss the precise crystal structure and the mechanism of the ferroelectric phase transition of SSTO.

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