Phase separation in Fe9S10 crystal

1986 ◽  
Vol 44 ◽  
pp. 462-463
Author(s):  
Thao A. Nguyen ◽  
Linn W. Hobbs
Keyword(s):  
Low Temperature ◽  
Iron Sulfide ◽  
Temperature Phase ◽  
The Past ◽  
Transmission Electron ◽  
In Situ Heating ◽  
Two Phases ◽  
The Stability ◽  
Low Temperature Phase

The low temperature phase relation of iron sulfide compounds Fe1-xS, with composition ranging from FeS to Fe7S8, has been investigated extensively over the past several decades. Despite these efforts conflicting reports on the stability of low temperature phases still exist and major disagreements between proposed phase diagrams remain unresolved. In this paper we report preliminary findings of our effort to determine whether the low temperature iron sulfide compounds form a homologous series Fen-l,Sn n≥ 8 [1] or a solid solution [2]. We have examined the stability of iron sulfide crystal of composition Fe9S10 using in situ heating experiment and image contrast transmission electron microscopy. We have found that Fe9S10 decomposes to two distinct phases. These two phases are labelled as H and K phases.

Low temperature phase separation in CeSi1.86

1990 ◽  
Vol 5 (10) ◽  
pp. 2126-2132 ◽  
Author(s):  
R. Madar ◽  
E. Houssay ◽  
A. Rouault ◽  
J. P. Senateur ◽  
B. Lambert ◽  
...  
Keyword(s):  
Phase Separation ◽  
Low Temperature ◽  
Close Relation ◽  
Structure Type ◽  
Primary Phase ◽  
Second Phase ◽  
Temperature Phase ◽  
Transmission Electron ◽  
Two Phases ◽  
Low Temperature Phase

Samples of CeSi1.86 which exhibit Kondo behavior are shown by neutron powder diffraction and transmission electron microscopy to consist of two closely related tetragonal phases. The primary phase is of the ThSi2 structure type with some vacancies in the silicon sublattice. The second phase presents an ordering of these vacancies. These two phases coexist at low temperature, but the abundance of the second phase increases with decreasing temperature. Neutron diffraction measurements and TEM experiments show that the phase separation occurs reversibly around 260 K, in close relation with an anomaly in the transport properties. The presence of a hysteresis indicates that we are dealing with a first order transition.

In situ S-doped ultrathin gC3N4 nanosheets coupled with mixed-dimensional (3D/1D) nanostructures of silver vanadates for enhanced photocatalytic degradation of organic pollutants

2019 ◽  
Vol 43 (26) ◽  
pp. 10618-10630 ◽  
Author(s):  
Subi Joseph ◽  
Sinoj Abraham ◽  
Ragam N. Priyanka ◽  
Thomas Abraham ◽  
Arya Suresh ◽  
...  
Keyword(s):  
Low Temperature ◽  
Diffusion Processes ◽  
Kirkendall Effect ◽  
Temperature Phase ◽  
Phase Conversion ◽  
1D Nanostructures ◽  
Ultrasonic Assisted ◽  
And Diffusion ◽  
Low Temperature Phase

A novel plasmonic Z-scheme sulphur doped gC3N4/Ag3VO4/β-AgVO3/Ag (SGA-x) hybrid quaternary photocatalyst was successfully fabricated via the ultrasonic assisted Kirkendall effect and diffusion processes followed by low temperature phase conversion.

Polymorphism of CaTeO3 and solid solutions Ca x Sr1 − x TeO3

2009 ◽  
Vol 65 (2) ◽  
pp. 167-181 ◽  
Author(s):  
Berthold Stöger ◽  
Matthias Weil ◽  
Erich Zobetz ◽  
Gerald Giester
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Solid Solutions ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Temperature Modification ◽  
Reversible Phase Transition ◽  
Two Phases ◽  
Layer Groups ◽  
Low Temperature Phase

Single crystals and microcrystalline samples of the calcium tellurate(IV) phases α-, β-, β′- and γ-CaTeO3 as well as of two solid solutions Ca x Sr1 − x TeO3 (x = 0.55 and 0.77) have been synthesized and characterized by X-ray diffraction and thermal analysis. A comparative description of the structures and the relations between the polymorphs is given. The main building units of the hitherto unknown structures are isolated [TeIVO3]2− units and [(Ca,Sr)O x ] (x = 6–8) polyhedra. All structures exhibit channels in which the TeIV electron lone pairs protrude. The low-temperature phase α-CaTeO3 is stable up to 1168 K. It exhibits nearly cylindrical channels (diameter ∼ 4 Å) and differs structurally from the other phases, whereas the metastable high-temperature phases are closely related to each other. They feature oval channels (shortest and longest diameter ∼ 2 and 8 Å). γ-CaTeO3 can be described as an order–disorder (OD) structure of two non-polar layers with layer groups p121/m1 and p1211. The γ-CaTeO3 crystal under investigation consists of two polytypes with a maximum degree of order. The two phases Ca x Sr1 − x TeO3 (x = 0.55 and 0.77) are isostructural to the MDO1 polytype of γ-CaTeO3. β-CaTeO3 shows a distinct reversible phase transition at ∼ 293 K. The low-temperature modification β′-CaTeO3 as well as its high-temperature modification β-CaTeO3 can be considered as threefold superstructures along [100] based on the MDO1 polytype of γ-CaTeO3.

Low-temperature phase separation in GaN nanowires: An in situ x-ray investigation

2008 ◽  
Vol 92 (16) ◽  
pp. 161901 ◽  
Author(s):  
S. Y. Wu ◽  
J.-Y. Ji ◽  
M. H. Chou ◽  
W.-H. Li ◽  
G. C. Chi
Keyword(s):  
Phase Separation ◽  
Low Temperature ◽  
Temperature Phase ◽  
X Ray ◽  
Gan Nanowires ◽  
Low Temperature Phase

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

Role of boundaries in the crystallization of amorphous films

1988 ◽  
Vol 46 ◽  
pp. 626-627
Author(s):  
D. A. Smith
Keyword(s):  
Low Temperature ◽  
Amorphous State ◽  
Nucleation And Growth ◽  
Amorphous Films ◽  
Island Nucleation ◽  
Surface Steps ◽  
Transmission Electron ◽  
Component Systems ◽  
Temperature Deposition

The nucleation and growth processes which lead to the formation of a thin film are particularly amenable to investigation by transmission electron microscopy either in situ or subsequent to deposition. In situ studies have enabled the observation of island nucleation and growth, together with addition of atoms to surface steps. This paper is concerned with post-deposition crystallization of amorphous alloys. It will be argued that the processes occurring during low temperature deposition of one component systems are related but the evidence is mainly indirect. Amorphous films result when the deposition conditions such as low temperature or the presence of impurities (intentional or unintentional) preclude the atomic mobility necessary for crystallization. Representative examples of this behavior are CVD silicon grown below about 670°C, metalloids, such as antimony deposited at room temperature, binary alloys or compounds such as Cu-Ag or Cr O2, respectively. Elemental metals are not stable in the amorphous state.

Influence of ion-milling on the T2 phase in Al-2.5%Li-2.5%Cu alloy

1989 ◽  
Vol 47 ◽  
pp. 288-289
Author(s):  
J. R. Reed ◽  
D. J. Michel ◽  
P. R. Howell
Keyword(s):  
Thin Foil ◽  
Icosahedral Symmetry ◽  
Ion Milling ◽  
Cu Alloy ◽  
Thin Foils ◽  
Heat Treated ◽  
Aluminum Solid Solution ◽  
In Situ Heating ◽  
The Stability

The Al6Li3Cu (T2) phase, which exhibits five-fold or icosahedral symmetry, forms through solid state precipitation in dilute Al-Li-Cu alloys. Recent studies have reported that the T2 phase transforms either during TEM examination of thin foils or following ion-milling of thin foil specimens. Related studies have shown that T2 phase transforms to a microcrystalline array of the TB phase and a dilute aluminum solid solution during in-situ heating in the TEM. The purpose of this paper is to report results from an investigation of the influence of ion-milling on the stability of the T2 phase in dilute Al-Li-Cu alloy.The 3-mm diameter TEM disc specimens were prepared from a specially melted Al-2.5%Li-2.5%Cu alloy produced by conventional procedures. The TEM specimens were solution heat treated 1 h at 550°C and aged 1000 h at 190°C in air to develop the microstructure. The disc specimens were electropolished to achieve electron transparency using a 20:80 (vol. percent) nitric acid: methanol solution at -60°C.

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