scholarly journals Phase transitions in germanium telluride nanoparticle phase-change materials studied by temperature-resolved x-ray diffraction

2021 ◽  
Vol 129 (9) ◽  
pp. 095102
Author(s):  
Ann-Katrin U. Michel ◽  
Felix Donat ◽  
Aurelia Siegfried ◽  
Olesya Yarema ◽  
Hanbing Fang ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Phase Change ◽  
Phase Change Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Germanium Telluride

Phase transitions in Ge–Te phase change materials studied by time-resolved x-ray diffraction

2009 ◽  
Vol 95 (14) ◽  
pp. 143118 ◽  
Author(s):  
Simone Raoux ◽  
Becky Muñoz ◽  
Huai-Yu Cheng ◽  
Jean L. Jordan-Sweet
Keyword(s):  
Phase Transitions ◽  
Phase Change ◽  
Phase Change Materials ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray

Crystallization Characteristics of Ge-Sb Phase Change Materials

2009 ◽  
Vol 1160 ◽  
Author(s):  
Simone Raoux ◽  
Cyril Cabral ◽  
Lia Krusin-Elbaum ◽  
Jean L. Jordan-Sweet ◽  
Martin Salinga ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
Mass Density ◽  
Large Change ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Time Resolved ◽  
X Ray ◽  
Diffraction Peaks ◽  
Low X

AbstractThe crystallization behavior of Ge-Sb phase change materials with variable Ge:Sb ratio X between 0.079 and 4.3 was studied using time-resolved x-ray diffraction, differential scanning calorimetry, x-ray reflectivity, optical reflectivity and resistivity vs. temperature measurements. It was found that the crystallization temperature increases with Ge content from about 130 °C for X = 0.079 to about 450 °C for X = 4.3. For low X, Sb x-ray diffraction peaks occurred during a heating ramp at lower temperature than Ge diffraction peaks. For X = 1.44 and higher, Sb and Ge peaks occurred at the same temperature. Mass density change upon crystallization and optical and electrical contrast between the phases show a maximum for the eutectic alloy with X = 0.17. The large change in materials properties with composition allows tailoring of the crystallization properties for specific application requirements.

Thermal and elastic properties of Ge-Sb-Te based phase-change materials

2011 ◽  
Vol 1338 ◽  
Author(s):  
P. Zalden ◽  
C. Bichara ◽  
J. v. Eijk ◽  
R. P. Hermann ◽  
I. Sergueev ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Phase Change ◽  
Data Storage ◽  
Crystalline Phase ◽  
Phase Change Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Storage Devices ◽  
Atomic Displacements ◽  
Optical Modes

ABSTRACTPhase-change materials undergo a change in bonding mechanism upon crystallization, which leads to pronounced modifications of the optical properties and is accompanied by an increase in average bond lengths as seen by extended x-ray absorption fine structure (EXAFS), neutron and x-ray diffraction. The reversible transition between a crystalline and an amorphous phase and its related property contrast are already employed in non-volatile data storage devices, such as rewritable optical discs and electronic memories. The crystalline phase of the prototypical material GeSb2Te4 is characterized by resonant bonding and pronounced disorder, which help to understand their optical and electrical properties, respectively. A change in bonding, however, should also affect the thermal properties, which will be addressed in this study. Based on EXAFS data analyses it will be shown that the thermal and static atomic displacements are larger in the meta-stable crystalline state. This indicates that the bonds become softer in the crystalline phase. At the same time, the bulk modulus increases upon crystallization. These observations are confirmed by the measured densities of phonon states (DPS), which reveal a vibrational softening of the optical modes upon crystallization. This demonstrates that the change of bonding upon crystallization in phase-change materials also has a profound impact on the lattice dynamics and the resulting thermal properties.

Pump-probe X-ray Diffraction Technique for Irreversible Phase Change Materials

2010 ◽  
Author(s):  
Yoshimitsu Fukuyama ◽  
Nobuhiro Yasuda ◽  
Shigeru Kimura ◽  
Yoshihito Tanaka ◽  
Hitoshi Osawa ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Materials ◽  
X Ray Diffraction ◽  
Pump Probe ◽  
X Ray

Epitaxy of Single Crystal Phase Change Materials on Si(111)

2011 ◽  
Vol 1338 ◽  
Author(s):  
P. Rodenbach ◽  
K. Perumal ◽  
F. Katmis ◽  
W. Braun ◽  
R. Calarco ◽  
...  
Keyword(s):  
Phase Change ◽  
Molecular Beam ◽  
Phase Change Materials ◽  
Lattice Mismatch ◽  
X Ray Diffraction ◽  
Quadrupole Mass ◽  
Cubic Symmetry ◽  
X Ray ◽  
Si Substrates

ABSTRACTPhase change materials along the GeTe-Sb2Te3 pseudobinary line (GST) are grown by molecular beam epitaxy (MBE) on Si(111). The growth on (111) oriented substrates leads to greatly increased crystal quality compared to (001) oriented substrates, even for a high lattice mismatch. This holds true even for Si substrates which have a lattice mismatch of around 10% with respect to GST. The growth is controlled in situ via line of sight quadrupole mass spectrometer (QMS). Structural characterization is performed in situ by X-ray diffraction (XRD), which reveals a clear cubic symmetry of the film and a lattice slightly rhombohedrally distorted along the [111] direction.

Preparation and Properties of Polyalcohol Phase Change Material for Insulation

2012 ◽  
Vol 512-515 ◽  
pp. 936-939 ◽  
Author(s):  
Wei Wu ◽  
Yu Feng Chen ◽  
Xing Shi ◽  
Shi Chao Zhang ◽  
Hao Ran Sun
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Phase Change Materials ◽  
Heat Insulation ◽  
X Ray Diffraction ◽  
Test Device ◽  
X Ray ◽  
Composite Phase Change Materials ◽  
Change Material ◽  
Properties Of Composites

In this paper, the composite phase change materials for insulation were prepared by melt-soaking method. Trimethylolethane (PG) was chosen to be the phase change material (PCM) and two kinds of porous materials as the supporting matrices separately. The effects of both matrices to PG were analyzed by X-ray diffraction (XRD), and the heat insulation properties of composites were evaluated by Plat heat insulation test device. At last, microstructures of composites were observed by scanning electron microscope (SEM) and their effects to composites were discussed.

Use of Differential Scanning Calorimetry and X-Ray Diffraction as Experimental Tools to Understand How Nucleating Agent Concentration Affects Supercooling in Microencapsulated Phase Change Materials

2005 ◽  
Author(s):  
Jorge L. Alvarado ◽  
Charles Marsh ◽  
Chang Sohn ◽  
Ty Newell ◽  
Jasmeet Singh Johar
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Change ◽  
Phase Change Materials ◽  
Nucleating Agent ◽  
Experimental Results ◽  
Experimental Techniques ◽  
Heat Of Fusion ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray

In this paper, a description and explanation of the experimental techniques used to understand and quantify supercooling will be presented, including differential scanning calorimetry and x-ray diffraction. Differential scanning calorimetry experimental results indicate that supercooling in microencapsulated n-Tetradecane can be suppressed significantly when 4% to 6% of a homologous material is used as nucleating agent. X-ray diffraction experimental results elucidate how nucleating agent concentration affects the morphology of the phase change material after solidification. Both experimental techniques in unison prove to be valuable experimental tools and provide a better understanding of how inclusion of nucleating agents affects the solidification process. Quantitative characterization of microencapsulated n-Tetradecane thermal properties is also presented including latent heat of fusion and melting point data.

Femtosecond x-ray diffraction reveals a liquid–liquid phase transition in phase-change materials

Science ◽  
2019 ◽  
Vol 364 (6445) ◽  
pp. 1062-1067 ◽  
Author(s):  
Peter Zalden ◽  
Florian Quirin ◽  
Mathias Schumacher ◽  
Jan Siegel ◽  
Shuai Wei ◽  
...  
Keyword(s):  
Phase Transition ◽  
Liquid Phase ◽  
Phase Change ◽  
Phase Change Materials ◽  
Crystallization Process ◽  
Pair Correlation ◽  
Atomic Scale ◽  
X Ray Diffraction ◽  
Liquid Phase Transition ◽  
X Ray

In phase-change memory devices, a material is cycled between glassy and crystalline states. The highly temperature-dependent kinetics of its crystallization process enables application in memory technology, but the transition has not been resolved on an atomic scale. Using femtosecond x-ray diffraction and ab initio computer simulations, we determined the time-dependent pair-correlation function of phase-change materials throughout the melt-quenching and crystallization process. We found a liquid–liquid phase transition in the phase-change materials Ag4In3Sb67Te26 and Ge15Sb85 at 660 and 610 kelvin, respectively. The transition is predominantly caused by the onset of Peierls distortions, the amplitude of which correlates with an increase of the apparent activation energy of diffusivity. This reveals a relationship between atomic structure and kinetics, enabling a systematic optimization of the memory-switching kinetics.

Polyamide as a Matrix for the Creation of Form-Stable Phase Change Materials

2009 ◽  
Vol 610-613 ◽  
pp. 414-418 ◽  
Author(s):  
Jing Guo ◽  
Nan Li
Keyword(s):  
Block Copolymer ◽  
Phase Change ◽  
Phase Change Materials ◽  
Polyamide 6 ◽  
Stable Phase ◽  
X Ray Diffraction ◽  
Thermal Reliability ◽  
Scanning Calorimetry ◽  
X Ray

Phase change materials (PCMs) with storing and releasing energy properties have been widely used in lots of fields such as solar energy storing, smart housing, thermo-regulated fibers, and agricultural greenhouse. Here, PCMs based on polyamide 6 (PA6) blended with Polyethylene glycol (PEG) was studied. In order to improve the compatibility between PA6 and PEG, a PA6-PEG block copolymer was synthesized and added to the blends. The structure and properties of the block copolymer were determined by Fourier Transform Infrared (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and optics microscope (OM). The results of DSC analysis showed that tThe copolymer block is phase separated. DSC results also showed that the phase transition temperature of the blend is different from that of pure PEG, indicating the interaction occurrence between PEG and PA6 by using PA6-PEG block copolymer, the latent heat of PEG/PA6 blend increased with the mass percent of PEG. The results of tThermal cycling tests showed that the blend as a PCM has good long-term thermal reliability.

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