Structural phase sequence and modulated phases of (C3H7NH3)2CuBr4

1998 ◽  
Vol 205 (1) ◽  
pp. 119-132
Author(s):  
I. R. Jahn ◽  
H. Ritter ◽  
K. Schwab ◽  
K. Knorr
Keyword(s):  
Structural Phase ◽  
Modulated Phases ◽  
Phase Sequence

Incommensurate modulated phases of the NbxTa1-xTe4 charge density wave system

1992 ◽  
Vol 50 (1) ◽  
pp. 58-59
Author(s):  
S. Ritchie ◽  
J. C. Bennett ◽  
A. Prodan ◽  
F.W. Boswell ◽  
J.M. Corbett
Keyword(s):  
Charge Density ◽  
Charge Density Wave ◽  
Direct Evidence ◽  
Density Wave ◽  
Wave System ◽  
Modulated Phases ◽  
Metal Atoms ◽  
Incommensurate Modulation ◽  
End Members ◽  
Modulation Wave Vector

A continuous sequence of compounds having composition NbxTa1-xTe4; 0 ≤ x ≤ 1 have been studied by electron diffraction and microscopy. Previous studies have shown that the end members of the series, TaTε4 and NbTε4 possess a quasi-one-dimensional character and exhibit charge density wave (CDW) distortions. In these compounds, the subcell structure is tetragonal with axes (a × a × c) and consists of the metal atoms (Nb or Ta) centered within an extended antiprismatic cage of Te atoms. At room temperature, TaTε4 has a commensurate modulation structure with a 2a × 2a × 3c unit cell. In NbTε4, an incommensurate modulation with × ∼ 16c axes is observed. Preliminary studies of the mixed compounds NbxTα1-xTε4 showed a discontinuous jump of the modulation wave vector commensurate to incommensurate when the Nb dopant concentration x, exceeded x ≃ 0.3, In this paper, the nature of the compositional dependence of is studied in greater detail and evidence is presented for a stepwise variation of . This constitutes the first direct evidence for a Devil's staircase in CDW materials.

The excavation of a medieval ring-ditch enclosure at Hayknowes Farm, Annan, Dumfries and Galloway

2001 ◽  
Vol 23 (2) ◽  
pp. 119-139
Author(s):  
R. A. GREGORY ◽  
D. W. HALL ◽  
D. W. SHIMWELL
Keyword(s):  
Radiocarbon Dating ◽  
Structural Phase ◽  
Morphological Characteristics ◽  
Internal Structures

Excavation at a crop-mark site found close to Annan, Dumfries and Galloway, revealed evidence of a ring-ditch containing a number of intriguing internal structures. Initially this was presumed to be a prehistoric monument, but pottery and radiocarbon dating, unexpectedly, indicated that the main structural phase of the site falls between the 11th-13th centuries AD. This suggests that a degree of caution is required when interpreting crop-mark sites on morphological characteristics alone. Moreover this excavation makes clear that morphological interpretation can have a constraining influence on excavation strategy, so caution is required when designing fieldwork programmes.

Exploring the Influence of Substitution on the Structure and Transport Properties in the Sodium Superionic Conductor Na11+xSn2+x(Sb1−yPy)1−xS12

2020 ◽  
Author(s):  
Marvin Kraft ◽  
Lara Gronych ◽  
Theodosios Famprikis ◽  
Saneyuki Ohno ◽  
Wolfgang Zeier
Keyword(s):  
Electrochemical Impedance ◽  
Structural Phase ◽  
Ionic Transport ◽  
Sodium Ion ◽  
Ionic Conductors ◽  
Temperature Dependent ◽  
Activation Barriers ◽  
Rietveld Refinements ◽  
High Performing ◽  
The Given

<p>Sulfidic sodium ion conductors are currently investigated for the possible use in all-solid-state sodium ion batteries. The design of high performing electrolytes in terms of temperature-dependent ionic transport is based upon the fundamental understanding of structure – transport relationships within the given structural phase boundaries inherent to the investigated materials class. In this work, the Na<sup>+</sup> superionic structural family of Na<sub>11</sub>Sn<sub>2</sub>PS<sub>12</sub> is explored by using the systematic antimony substitution with phosphorous in Na<sub>11+<i>x</i></sub>Sn<sub>2+<i>x</i></sub>(Sb<sub>1-<i>y</i></sub>P<i><sub>y</sub></i>)<sub>1-<i>x</i></sub>S<sub>12</sub>. A combination of Rietveld refinements against X-ray synchrotron diffraction data with electrochemical impedance spectroscopy is used to monitor the changes in the anionic framework, the Na<sup>+</sup> substructure and the ionic transport. A new simplified descriptor for the average Na<sup>+</sup> diffusion pathways, the average Na<sup>+</sup> polyhedral volume is introduced, which is used to correlate the contraction of the overall lattice and the found activation barriers in the system. This study exemplifies how substitution affects diffusion pathways in ionic conductors and widens the knowledge about the related structural motifs and their influence on the ionic transport in this novel class of ionic conductors.</p>

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