Lattice relaxation in high-temperature pure crystalline materials and substitutionally disordered alloys. I. Multiple-scattering formalism for displaced atoms

1985 ◽  
Vol 32 (12) ◽  
pp. 7713-7719 ◽  
Author(s):  
A. Gonis ◽  
A. J. Freeman ◽  
P. Weinberger
Keyword(s):  
High Temperature ◽  
Multiple Scattering ◽  
Lattice Relaxation ◽  
Crystalline Materials ◽  
Disordered Alloys

scholarly journals Dopants Modulate Crystal Growth in Molten Salts Enabled by Surface Energy Tuning

2021 ◽  
Author(s):  
Xiaoqiao Li ◽  
Linming Zhou ◽  
Han Wang ◽  
Dechao Meng ◽  
Guannan Qian ◽  
...  
Keyword(s):  
Crystal Growth ◽  
High Temperature ◽  
Surface Energy ◽  
Molten Salts ◽  
Rational Approach ◽  
Temperature Synthesis ◽  
Crystalline Materials ◽  
Size Dependent ◽  
High Temperature Synthesis ◽  
Energy Tuning

Crystalline materials are routinely produced via high-temperature synthesis and show size-dependent properties; however, a rational approach to regulating their crystal growth has not been established. Here we show that dopants...

Phase transitions in solid cycloheptene

1990 ◽  
Vol 68 (4) ◽  
pp. 604-611 ◽  
Author(s):  
Julian Haines ◽  
D. F. R. Gilson
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Low Temperature ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Scanning Calorimetry ◽  
Spin Lattice ◽  
Low Temperature Phase

The phase transition behaviour of cycloheptene has been investigated by differential scanning calorimetry, proton spin-lattice relaxation, and vibrational spectroscopy (infrared and Raman). Two solid–solid phase transitions were observed, at 154 and 210 K, with transition enthalpies and entropies of 5.28 and 0.71 kJ mol−1 and 34.3 and 3.4 JK−1, respectively. Cycloheptene melted at 217 K with an entropy of melting of 4.5 JK−1 mol−1. The bands in the vibrational spectra of the two high temperature phases were broad and featureless, characteristic of highly disordered phases. The presence of other conformers, in addition to the chair form, was indicated from bands in the spectra. The ring inversion mode was highly phase dependent and exhibited soft mode type behaviour prior to the transition from the low temperature phase. The low frequency Raman spectra (external modes) of these phases indicated that the molecules are undergoing isotropic reorientation. In the low temperature phase, the vibrational bands were narrow; the splitting of the fundamentals into two components and the presence of nine external modes are consistent with unit cell symmetry of either C2 or Cs with two molecules per primitive unit cell. A glassy state can be produced from the intermediate phase and the vibrational spectra were very similar to those of the high temperature phases, indicating that static disorder was present. The barriers to reorientation, as obtained from proton spin-lattice relaxation measurements, are 9.0 kJ mol−1 in both the high temperature phases, and 15.4 kJ mol−1 in the low temperature, ordered phase. Keywords: cycloheptene, phase transition, differential scanning calorimetry, NMR, vibrational spectroscopy.

LPE Growth of Doped Sige Layers Using Multicomponent Phase Diagrams Calculations

1991 ◽  
Vol 234 ◽  
Author(s):  
J.-P. Fleurial ◽  
A. Borshchevsky ◽  
D. Irvine
Keyword(s):  
Thin Films ◽  
High Temperature ◽  
Melting Point ◽  
Phase Diagrams ◽  
Available Phosphorus ◽  
Crystalline Materials ◽  
Quaternary Phase ◽  
Limited Solid Solubility ◽  
Heavy Doping ◽  
Good Agreement

ABSTRACTHeavy doping of n-type Si-Ge alloys is necessary for improving their high temperature thermoelectric properties. Because of the limited solid solubility of the best dopant available, phosphorus, simultaneous additions of gallium were started several years ago. The substantially higher carrier concentration values obtained in such super-saturated, hot-pressed SiGe/GaP materials point to significant changes in dopant solid solubilities. To better understand the behavior of these alloys, investigation of homogeneous single crystalline materials were needed. As a near-thermodynamic equilibrium technique with processing temperatures well below the melting point of these materials, liquid-phase epitaxy (LPE) was particularly suited to the study of the mechanisms of multidoping. Based on successful crystal growth of Si1-xGex thin films using metals such as Ga, In, Sn and Bi for solvents, several experiments were designed to grow multi-doped SiGe layers with III-V dopant combinations. Knowledge of ternary and quaternary phase diagrams is essential to develop the LPE process. Ternary Si-Ge-M systems computations in good agreement with experimental determinations were used to calculate some of the necessary multicomponent phase diagrams and assess the strength of the various III–V interactions.

Development of Multi-Phase Intermetallic Alloy Composed of Ni3X-Type Structures

2007 ◽  
Vol 127 ◽  
pp. 161-166
Author(s):  
Takayuki Takasugi ◽  
Yasuyuki Kaneno
Keyword(s):  
High Temperature ◽  
Creep Test ◽  
Intermetallic Alloy ◽  
High Yield ◽  
Eutectoid Reaction ◽  
Crystalline Materials ◽  
Low Temperature Annealing ◽  
Phase Intermetallic ◽  
New Type ◽  
Multi Phase

Dual multi-phase intermetallic alloy, which is composed of Ni3Al(L12) and Ni solid solution (A1) phases at high temperature annealing and is additionally refined by a eutectoid reaction at low temperature annealing, according to which the Al phase is transformed into the Ni3Al(L12)+Ni3V(D022) phases, was prepared. High-temperature tension and creep test were conducted using single crystalline materials. The alloy with such a novel microstructure showed extremely high yield and tensile stresses with good temperature retention. The creep test conducted at high temperature showed extremely low creep rate and creep rupture time when compared with advanced Ni-based superalloys. The results obtained are promising for the development of a new-type of high-temperature structural materials.

Superconductivity of Y5Rh6Sn18; Coexistence of the high temperature thermal lattice relaxation process and superconductivity

2020 ◽  
Vol 819 ◽  
pp. 152959 ◽  
Author(s):  
A. Ślebarski ◽  
P. Zajdel ◽  
M.M. Maśka ◽  
J. Deniszczyk ◽  
M. Fijałkowski
Keyword(s):  
High Temperature ◽  
Relaxation Process ◽  
Lattice Relaxation

Structural Phase Transitions and Ionic Motions in Pyridinium Hexachlorotellurate(IV),Hexachlorostannate(IV), and Hexabromostannate(IV) Crystals as Studied by 1H NMR

1989 ◽  
Vol 44 (4) ◽  
pp. 300-306 ◽  
Author(s):  
Yutaka Tai ◽  
Tetsuo Asaji ◽  
Ryuichi Ikeda ◽  
Daiyu Nakamura
Keyword(s):  
Phase Transitions ◽  
High Temperature ◽  
Structural Phase ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Scanning Calorimetry ◽  
Spin Lattice ◽  
H Nmr

Abstract The 1H NMR second moment M2 and the spin-lattice relaxation time T1 are determined for pyridinium hexachlorotellurate(IV), hexachlorostannate(IV), and hexabromostannate(IV) at various temperatures above ca. 140 K. The phase transition temperatures already reported from halogen NQR experiments are determined as 272, 331, and 285 K, respectively, by differential thermal analysis (DTA). The DTA as well as differential scanning calorimetry measurements show that the above phase transitions are of second-order. For pyridinium hexachlorotellurate(IV) and hexa-bromostannate(I V), a sharp 1H T1 dip was observed at the transition temperature. This is interpreted in terms of a phenomenon related to the critical fluctuation of an order parameter. From the measurements of 1H M2, 60° two-site jumps (60° flips) around the pseudo C6 axis of the cation are suggested to occur in the high temperature phases of the complexes. Modulation of X...1H (X = CI, Br) magnetic dipolar interactions due to the reorientational motion of the complex anions is considered as a possible relaxation mechanism in the high temperature phases.

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