Interactions between substitutional and orientational orders. The phase transitions in enantiomeric and racemic crystals of TMHP. II. X-ray structural investigations of the two phase transitions in the racemic solid solution of TMHP

1991 ◽  
Vol 1 (4) ◽  
pp. 559-572
Author(s):  
J. Lajzerowicz-Bonneteau ◽  
B. Suchod
Keyword(s):  
Solid Solution ◽  
Phase Transitions ◽  
Two Phase ◽  
Structural Investigations ◽  
X Ray ◽  
Racemic Crystals

Structural and phase equilibria studies in the system Pt-Fe-Cu and the occurrence of tulameenite (Pt2FeCu)

1985 ◽  
Vol 49 (353) ◽  
pp. 547-554 ◽  
Author(s):  
M. Shahmiri ◽  
S. Murphy ◽  
D. J. Vaughan
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Critical Temperature ◽  
Grain Boundary ◽  
Phase Region ◽  
X Ray Diffraction ◽  
Two Phase ◽  
Slow Cooling ◽  
X Ray ◽  
Diffraction Patterns

AbstractThe crystal structure and compositional limits of the ternary compound Pt2FeCu (tulameenite), formed either by quenching from above the critical temperature of 1178°C or by slow cooling, have been investigated using X-ray diffraction, transmission electron microscopy, differential thermal analysis and electron probe microanalysis.The crystal structure of Pt2FeCu, established using electron density maps constructed from the measured and calculated intensities of X-ray diffraction patterns of powdered specimens, has the (000) and (½½0) lattice sites occupied by Pt atoms and the (½0½) and (0½½) sites occupied by either Cu or Fe atoms in a random manner. The resulting face-centred tetragonal structure undergoes a disordering transformation at the critical temperature to a postulated non-quenchable face-centred cubic structure. Stresses on quenching, arising from the ordering reaction, are relieved by twinning along {101} planes or by recrystallization along with deformation twinning; always involving grain boundary fracturing.Phase relations in the system Pt-Fe-Cu have been investigated through the construction of isothermal sections at 1000 and 600°C. At 1000°C there is an extensive single phase region of solid solution around Pt2FeCu and extending to the binary composition PtFe. At 600°C the composition Pt2FeCu lies just outside this now reduced area of solid solution in a two-phase field. Comparison of the experimental results with data for tulameenite suggests that some observed compositions may be metastably preserved. The occurrence of fine veinlets of silicate or other gangue minerals in tulameenite is suggested to result from grain boundary fracturing on cooling below the critical temperature of 1178°C and to be evidence of a magmatic origin.

scholarly journals Thermal evolution of the crystal structure and phase transitions of KNbO 3

2018 ◽  
Vol 5 (6) ◽  
pp. 180368 ◽  
Author(s):  
S. L. Skjærvø ◽  
K. Høydalsvik ◽  
A. B. Blichfeld ◽  
M.-A. Einarsrud ◽  
T. Grande
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Thermal Evolution ◽  
Dynamical Instability ◽  
X Ray Diffraction ◽  
Two Phase ◽  
X Ray ◽  
Cell Parameters ◽  
First Order ◽  
Heating And Cooling

The thermal evolution of the crystal structure and phase transitions of KNbO 3 were investigated by high-temperature powder X-ray diffraction and Rietveld refinement of the diffraction data. Two phase transitions from orthorhombic ( Amm 2) to tetragonal ( P 4 mm ) and from tetragonal to cubic ( P m 3 ¯ m ) were confirmed, both on heating and cooling. Both phase transitions are first order based on the observed hysteresis. The mixed displacive and order–disorder nature of the tetragonal to cubic transition is argued based on symmetry and apparent divergence of the atomic positions from pseudo-cubic values. The transition between the orthorhombic and tetragonal phase shows no temperature-dependence for atomic positions and only thermal expansion of the unit cell parameters and is thus discussed in relation to a lattice dynamical instability.

Carbonates of the magnesite–siderite series from four carbonatite complexes

1990 ◽  
Vol 54 (376) ◽  
pp. 413-418 ◽  
Author(s):  
H. A. Buckley ◽  
A. R. Woolley
Keyword(s):  
Solid Solution ◽  
Partial Melting ◽  
Solid Solution Series ◽  
Two Phase ◽  
X Ray ◽  
Liquidus Phase ◽  
Solution Series ◽  
The Past ◽  
Complete Solid Solution ◽  
Textural Evidence

AbstractCarbonates of the magnesite-siderite series have been found and analysed in carbonatites from the Lueshe, Newania, Kangankunde, and Chipman Lake complexes. This series has been represented until now only by a few X-ray identifications of magnesite and three published analyses of siderite and breunnerite (magnesian siderite). Most of the siderite identified in carbonatites in the past has proved to be ankerite, but the new data define the complete solid-solution series from magnesite to siderite. They occur together with dolomite and ankerite and in one rock with calcite. The magnesites, ferroan magnesites and some magnesian siderites may be metasomatic/hydrothermal in origin but magnesian siderite from Chipman Lake appears to have crystallized in the two-phase calcite + siderite field in the subsolidus CaCO3-MgCO3-FeCO3 system. Textural evidence in Newania carbonatites indicates that ferroan magnesite, which co-exists with ankerite, is a primary liquidus phase and it is proposed that the Newania carbonatite evolved directly from a Ca-poor, Mg-rich carbonatitic liquid generated by partial melting of phlogopite-carbonate peridotite in the mantle at pressures >32 kbar.

Investigation of Phase Transitions in Stacked GeTe/SnTe and Ge2Se3/SnTe Chalcogenide Films

2011 ◽  
Vol 687 ◽  
pp. 677-683 ◽  
Author(s):  
Fei Ming Bai ◽  
Huai Wu Zhang ◽  
Surendra Gupta ◽  
Santosh Kurinec
Keyword(s):  
Phase Transition ◽  
Solid Solution ◽  
Phase Transitions ◽  
Phase Change Memory ◽  
Thin Layers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Area Detector ◽  
Memory Applications ◽  
Change Memory

Phase transitions in stacked GeTe/SnTe and Ge2Se3/SnTe thin layers for potential phase-change memory applications have been investigated by X-ray diffraction using an area detector system and by scanning electron microscopy. The as-deposited underlying GeTe or Ge2Se3 layer is amorphous, whereas the top SnTe layer is crystalline. In GeTe/SnTe stack, the crystallization of GeTe phase occurs near 170°C, and upon further heating, GeTe phase disappears, followed by the formation of rocksalt-structured GexSn1-xTe solid solution. In Ge2Se3/SnTe stack, the phase transition starts with the separation of SnSe phase due to the migration of Sn ions into the Ge2Se3 layer. The migration of Sn ions and the formation of SnSe are believed to facilitate the crystallization of Ge2Se3 solid solution at ~360°C, which is much lower than the crystallization temperature of Ge2Se3, therefore consuming less power during the phase transition.

Low-temperature crystal structure of RS-thiocamphor

2004 ◽  
Vol 219 (9) ◽  
Author(s):  
E. Louise R. Robins ◽  
Michela Brunelli ◽  
Asiloé J. Mora ◽  
Andrew N. Fitch
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Low Temperature ◽  
Room Temperature ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Two Phase ◽  
X Ray ◽  
Low Temperature Crystal Structure

AbstractDSC and high-resolution powder X-ray diffraction measurements in the range 295 K–100 K show that RS-thiocamphor undergoes two phase transitions. The first, at around 260 K on cooling, is from the room-temperature body-centred-cubic phase to a short-lived intermediate. At 258 K the low-temperature form starts to appear. The crystal structure of the latter is orthorhombic, space group

Thermodynamic Rationalization of the Microstructures of CrFeNi & CuCrFeNi Alloys

2012 ◽  
Vol 585 ◽  
pp. 3-7 ◽  
Author(s):  
Anil Kumar Singh ◽  
Anandh Subramaniam
Keyword(s):  
Solid Solution ◽  
Regular Solution Model ◽  
Phase Segregation ◽  
Free Energy Calculations ◽  
Induction Melting ◽  
X Ray Diffraction ◽  
Equimolar Ratio ◽  
Two Phase ◽  
X Ray ◽  
High Entropy

In high entropy alloys (HEA) a disordered solid solution is entropically stabilized, in competition with possible intermediate compounds or phase segregation. It has been reported that disordered solid solutions are stabilized by the presence of five or more elements in the alloys; typically in an equimolar ratio. In the current investigation, the effect of Cu addition on the microstructure of CrFeNi alloy is rationalized by Gibbs free energy calculations. Two phase (both are FCC) solid solution are seen to form in CuCrFeNi alloy. The alloys are prepared by induction melting and are characterized by x-ray diffraction and scanning electron microscopy (in as-cast and annealed state). Enthalpies of mixing were calculated using Miedema's model and the regular solution model. Entropy of mixing is determined by using the Boltzmann's hypothesis.

Phase relationships in the Ce–Nd–B system at 773 K

2020 ◽  
Vol 111 (6) ◽  
pp. 526-532
Author(s):  
Xuehong Cui ◽  
Jinming Zhu ◽  
Ketong Luo ◽  
Jianlie Liang
Keyword(s):  
Solid Solution ◽  
Ternary System ◽  
Continuous Solid Solution ◽  
Solution Phase ◽  
Solid Solution Phase ◽  
X Ray Diffraction ◽  
Two Phase ◽  
X Ray ◽  
Three Phase ◽  
Phase Relationships

Abstract Phase relationships in the Ce-Nd-B ternary system at 773 K were investigated by means of X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy techniques. Six borides, i. e. CeB4, CeB6, NdB4, NdB6, NdB66 and Nd2B5 are confirmed in this work. No ternary compound was observed. CeB4 and NdB4 were discovered to form the continuous solid solution phase (Ce,Nd)B4, CeB6 and NdB6 also form the solid solution phase (Ce,Nd)B6. The maximum solid solubility of Ce in (Ce,Nd)2B5 phase is 46.5 at.%. The isothermal section of the Ce-Nd-B ternary system at 773 K consists of 3 three-phase regions, 7 two-phase regions and 7 single- phase regions.

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