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.

scholarly journals Copper microsphere hybrid mesoporous carbon as matrix for preparation of shape-stabilized phase change materials with improved thermal properties

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yi Liu ◽  
Yan Chen ◽  
Junwei Zhang ◽  
Junkai Gao ◽  
Zhi Han
Keyword(s):  
Thermal Properties ◽  
Phase Change ◽  
Photoelectron Spectroscopy ◽  
Mesoporous Carbon ◽  
Phase Change Materials ◽  
Copper Ions ◽  
Thermal Constant ◽  
Step Method ◽  
Scanning Calorimetry ◽  
X Ray

Abstract Copper microsphere hybrid mesoporous carbon (MPC-Cu) was synthesized by the pyrolysis of polydopamine microspheres doped with copper ions that were prepared using a novel, facile and simple one-step method of dopamine biomimetic polymerization and copper ion adsorption. The resulting MPC-Cu was then used as a supporter for polyethylene glycol (PEG) to synthesize shape-stabilized phase change materials (PEG/MPC-Cu) with enhanced thermal properties. PEG/MPC-Cu was studied by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, differential scanning calorimetry and thermal constant analysis. The results demonstrated that the thermal conductivity of PEG/MPC-Cu was 0.502 W/(m K), which increased by 100% compared to pure PEG [0.251 W/(m K)]. The melting enthalpy of PEG/MPC-Cu was 95.98 J/g, indicating that PEG/MPC-Cu is a promising candidate for future thermal energy storage applications. In addition, the characterization results suggested that PEG-MPC-Cu possessed high thermal stability. Therefore, the method developed in this paper for preparing shape-stabilized phase change materials with improved thermal properties has substantial engineering application prospects.

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.

Properties and crystallization of Li2O–CaO–Al2O3–SiO2–TiO2glasses

1993 ◽  
Vol 8 (4) ◽  
pp. 890-898 ◽  
Author(s):  
Moo-Chin Wang ◽  
Min-Hsiung Hon
Keyword(s):  
Thermal Expansion ◽  
Thermal Properties ◽  
Diffraction Analysis ◽  
Crystalline Phase ◽  
Glass Ceramics ◽  
Weight Percent ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

The addition of CaO to Li2O–Al2O3–SiO2–TiO2(LAST), forming the Li2O–CaO–Al2O3–SiO2–TiO2(LCAST) system, is used in the preparation of low themal expansion coefficient glass-ceramics. By a progressive weight percent substitution of CaO for SiO2, at constant ratios of concentration of Li2O, Al2O3, and TiO2, a number of properties of these glasses have been studied. The results indicated that these thermal properties increased progressively with increasing CaO concentration. X-ray diffraction analysis was utilized to identify the crystalline phase in glass-ceramics of the Li2O–CaO–Al2O3–SiO2-TiO2system. Thed-spacings of the major crystallites were precisely measured and fitted with those of β-spodumene. The minor crystalline phase of titanite, CaO · TiO2· SiO2, was also present. The average thermal expansion coefficients from 25 to 700 °C were 3.50 × 10−6/°C, 3.81 × 10−6/°C, and 3.91 × 10−6/°C for samples A, B, and C, respectively.

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

Preparation and Characterization of Octadecylated Poly(vinyl Alcohol) Polymers

2012 ◽  
Vol 482-484 ◽  
pp. 1921-1924 ◽  
Author(s):  
Li Juan Li ◽  
Hai Feng Shi ◽  
Xing Xiang Zhang
Keyword(s):  
Fourier Transform ◽  
Thermal Properties ◽  
Vinyl Alcohol ◽  
Phase Change Materials ◽  
Solid Phase ◽  
Poly Vinyl Alcohol ◽  
X Ray Diffraction ◽  
X Ray ◽  
Storage Properties

Octadecylated poly (vinyl alcohol) (PVA-C18) comb-like polymer was prepared through the reaction between PVA and 1-bromooctadecane via O-alkylation method. The structure, thermal properties and packing mode of PVA-C18 comb-like polymer were detailed investigated with Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), and X-ray diffraction (XRD). The results show that octadecyl side chains had been successfully grafted onto PVA backbones, and PVA-C18 comb-like polymer exhibit the better thermal storage properties with enthalpy of 29.3kJ/mol , indicated that it is one kind of solid-solid phase change materials.

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

Amorphization of Crystalline Phase Change Material by Ion Implantation

2010 ◽  
Vol 1251 ◽  
Author(s):  
Simone Raoux ◽  
Guy Cohen ◽  
Robert M. Shelby ◽  
Huai-Yu Cheng ◽  
Jean L Jordan-Sweet
Keyword(s):  
Ion Implantation ◽  
Phase Change ◽  
Phase Change Material ◽  
Crystalline Phase ◽  
High Dose ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Change Material ◽  
Ion Implanted

AbstractGermanium ion implantation at an energy of 30 keV was used as a different method to re-amorphize thin films of crystalline phase change material Ge2Sb2Te5 (GST). It was found that rather low doses of 5×1013 cm-2 were sufficient to re-amorphize GST. Amorphization was determined by X-ray diffraction (XRD) as well as reflectivity measurements. Re-crystallization characteristics of ion-implantation-amorphized samples was studied using time-resolved XRD. It showed that samples re-crystallize at an increased crystallization temperature with increasing dose compared to as-deposited material. A static laser tester was applied to measure the crystallization times of material that was (1) as–deposited amorphous; (2) crystallized by annealing and re-amorphized by melt-quenching using a laser pulse; and (3) crystallized by annealing and re-amorphized by ion implantation. It was found that as-deposited amorphous and high-dose ion implanted samples had longer crystallization times while melt-quenched amorphous and low-dose ion implanted samples had shorter crystallization times.

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.

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