Differences In Crystallization Behavior Research Articles

Transformation kinetics for low temperature post-deposition crystallization of TiO 2 thin films prepared via atomic layer deposition (ALD) from tetrakis(dimethylamino)titanium(IV) (TDMAT) and water

Background: We report on the fundamental crystallization kinetics of atomic layer deposited (ALD) TiO2 thin films undergoing a post-deposition anneal (PDA) at low temperatures to probe differences in the as-deposited film microstructure. Methods: The system of study is ALD TiO2 thin films prepared from tetrakis(dimethylamino)titanium(IV) (TDMAT) and water at 120 °C, 140 °C and 160 °C followed by ex situ low temperature annealing at temperatures ranging from 140 °C to 220 °C. All as-deposited TiO2 thin films are amorphous by X-ray diffraction (XRD). Post-deposition annealing (PDA) produces large grain anatase crystals, confirmed by XRD and top-view scanning electron microscopy (SEM). A detailed SEM study is performed to quantify the nucleation and growth kinetics by fitting microstructural data to the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Finally, a time-temperature-transformation (TTT) diagram is constructed to summarize the differences in crystallization behavior at different ALD deposition temperatures. Results and conclusions: Fitting microstructural data to the JMAK equation reveals an Avrami exponent close to 3 with continuous nucleation, suggesting two-dimensional, plate-like crystal growth. Applying an Arrhenius relationship to the phase transformation data, the combined activation energy for nucleation and growth is found to be 1.40–1.58 eV atom-1. Nucleation rates are determined, and an Arrhenius relationship is used to calculate the critical Gibbs free energy for nucleation (~1.3–1.4 eV atom-1). As such, nucleation is the rate-limiting step for the amorphous to anatase phase transformation. ALD growth temperature is found to dictate film microstructure with lower deposition temperatures reducing the nucleation rate and leading to larger grain sizes irrespective of PDA conditions. The nucleation rate pre-exponential frequency factor increases with increasing deposition temperature, thereby increasing the likelihood for nucleation. Interestingly, it is this difference in the vibrational modes of the amorphous structure, as indicated by the variation in the nucleation rate pre-exponential frequency factor, that alters the phase transformation rates and not a change in the activation energies for the transformation.

Enantiopurification of Mandelic Acid by Crystallization-Induced Diastereomer Transformation: An Experimental and Computational Study

Chiral purification is crucial in the pharmaceutical industry due to the dramatic differences in biological activity of the two enantiomers of most chiral drugs. In this work, we demonstrate a new enantiopurification route for an important drug precursor, mandelic acid, by forming a diastereomeric amide with enantiopure 1-phenylethylamine. We show that in the presence of a strong base, the resulting diastereomeric system not only undergoes a reversible epimerization reaction but also exhibits a surprising difference in crystallization behavior, i.e., at room temperature, one epimer forms a metastable gel phase, only converting to a more stable crystal over several days, while the other forms a stable crystalline phase. Exploiting these properties, a facile purification technique via crystallization-induced diastereomer transformation (CIDT) was achieved enabling good product yield (>70%) and excellent optical purity (>92%). Enantiopure mandelic acid (∼91% e.e.) can then be recovered via acid hydrolysis. This work highlights that for compounds that are neither conveniently racemizable nor conglomerate-forming such as mandelic acid, CIDT is a powerful alternative to the deracemization technique, capable of yields greater than the 50% in contrast to traditional resolution techniques.

Eminent differences in cryogenic toughness of ultra‐high molecular weight polyethylene with different entanglement densities

AbstractIt is generally believed that the ultra‐high molecular weight polyethylene (UHMWPE) performances are closely related to its molecular weight. However, when we sintered two brands of UHMWPE powders with similar molecular weights, GUR 4012 and GUR 400 Fine, we found they demonstrate eminent differences in cryogenic properties. Particularly, the cryogenic impact strength of GUR 4012 is 236% higher than that of GUR 400 Fine. To explain such an amazing phenomenon, we characterized UHMWPE microstructures and investigated the structure–property relations through scanning electron microscopy, x‐ray scattering diffraction, differential scanning calorimeter, and dynamic mechanical analysis. We observed only a slight difference in crystallization behaviors between them, but the entanglement density of GUR 4012 is much higher than that of GUR 400 Fine. Accordingly, we put forward a potential mechanism to analyze the eminent differences in cryogenic impact strengths. This work may promote our comprehension of the relation between the structure and performances of UHMWPE, which is conducive to promoting UHMWPE performance and broadening its industrial applications.

Liquid-liquid transition and inherited signatures in Zr-Cu-Ni-Al metallic glasses

Up to now, the research of liquid-liquid transition (LLT) has significantly improved the understanding of its liquid structure and evolution, which is crucial to addressing the longstanding problem with glass formation. However, it remains unclear how LLT affects the vitrification and structures of glasses, due to the challenge in experimentally exploring LLT in high-temperature melt well above the liquidus temperature. In the present study, an experiment is conducted to observe LLT in three Zr-Cu-Ni-Al melts at around 1450 K from both dynamic and thermodynamic perspectives. It is discovered that superheated fragility is closely associated with glass-forming ability. By controlling the melt temperature, two types of metallic glasses are obtained, showing difference in crystallization behaviors, which is attributed to the competition between crystal-like clusters and icosahedral-like clusters. Prior to the LLT, the formation of crystal-like clusters is dominant. Afterwards, the LLT promoted formation of icosahedral-like clusters becomes dominant. Due to the inherited signatures in glass, LLT is manifested by the changes in both medium-range order structure and short-range order structure. This study further reveals the pattern of microstructural evolution accompanied by LLT in high-temperature multi-component melts, which is conducive to the control on structure and properties of glasses from liquids.

Intrinsic properties of anodic TiO2 nanotube layers: In-situ XRD annealing of TiO2 nanotube layers

In this work, in-situ annealing of TiO2 nanotube (TNT) layers in an XRD chamber was carried out to investigate the crystallization process of the TNT layers in details. TNT layers of different thicknesses, i.e. 1, 5 and 20 μm, and of different morphology, i.e. double wall vs. single wall, were annealed in the temperature range from room temperature to 500 °C with two distinctly different annealing rates. Additionally, three different annealing atmospheres were explored, namely air as an oxidative, N2 as an inert, and 5%H2/95%N2 as a reductive atmosphere. XRD patterns were measured every 15 °C of the heating ramp and the crystallite sizes of anatase phase were calculated from the anatase peak using Scherer equation at each data point. The differences in crystallization behavior for the different TNT layers as well as the effect of the annealing atmosphere for 5 μm thick TNT layers are described and discussed.

Transformation kinetics for low temperature post-deposition crystallization of TiO2 thin films prepared via atomic layer deposition from TDMAT and water

Background: We report on the fundamental crystallization kinetics of atomic layer deposited (ALD) TiO2 thin films undergoing a post-deposition anneal (PDA) at low temperatures to probe differences in the as-deposited film microstructure. Methods: The system of study is ALD TiO2 thin films prepared from tetrakis(dimethylamino)titanium(IV) (TDMAT) and water at 120 °C, 140 °C and 160 °C followed by ex situ low temperature annealing at temperatures ranging from 140 °C to 220 °C. All as-deposited TiO2 thin films are amorphous by X-ray diffraction (XRD). Post-deposition annealing (PDA) produces large grain anatase crystals, confirmed by XRD and top-view scanning electron microscopy (SEM). A detailed SEM study is performed to quantify the nucleation and growth kinetics by fitting microstructural data to the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Finally, a time-temperature-transformation (TTT) diagram is constructed to summarize the differences in crystallization behavior at different ALD deposition temperatures. Results and Conclusions: Fitting microstructural data to the JMAK equation reveals an Avrami exponent close to 3 with continuous nucleation, suggesting two-dimensional, plate-like crystal growth. Applying an Arrhenius relationship to the phase transformation data, the combined activation energy for nucleation and growth is found to be 1.40–1.58 eV atom-1. Nucleation rates are determined, and an Arrhenius relationship is used to calculate the critical Gibbs free energy for nucleation (~1.3-1.4 eV atom-1). As such, nucleation is the rate-limiting step for the amorphous to anatase phase transformation. ALD growth temperature is found to dictate film microstructure with lower deposition temperatures reducing the nucleation rate and leading to larger grain sizes irrespective of PDA conditions. The nucleation rate pre-exponential frequency factor increases with increasing deposition temperature, thereby increasing the likelihood for nucleation. Interestingly, it is this difference in the vibrational modes of the amorphous structure, as indicated by the variation in the nucleation rate pre-exponential frequency factor, that alters the phase transformation rates and not a change in the activation energies for the transformation.

Critical analysis of zeolite 4A synthesis through one-pot fusion hydrothermal treatment approach for class F fly ash

In this study, ‘‘One-pot fusion assisted hydrothermal synthesis’’ approach was employed to understand the nucleation and crystallization behaviour of the fusion product of Class F fly ash for zeolite 4A synthesis. Two sets of experiments were conducted by tailoring the control parameter of H 2 O/Na 2 O molar ratio (L/S) to investigate the nucleation and crystallization behaviour of zeolite 4A. The molar ratios of SiO 2 /Al 2 O 3 and Na 2 O/SiO 2 were tuned before alkali fusion by adding different amounts of Al(OH) 3 to the fly ash along with the alkali agent, Na 2 CO 3 . Under the conditions of 12h aging at 47 °C and 7h crystallization at 90 °C, the sample with high L/S ratio (3.1 Na 2 O: 2.2 SiO 2 : 1.0 Al 2 O 3 : 79.2 H 2 O) yielded pure phase of Zeolite 4A with 94% relative crystallinity, while the sample with low L/S ratio (3.1 Na 2 O: 2.2 SiO 2 : 1.0 Al 2 O 3 : 42.2 H 2 O) resulted in the highest sodalite impurity. In general, the alkalinity level was observed to be the most dominant factor among all synthesis parameters. Nevertheless, low L/S ratio led to rapid crystallization in just 2.5h at 75 °C. Because of the dependency on the alkalinity level, the dissolution of low-carnegieite (LC) was determined as the decisive factor in the formation of zeolite 4A from the fusion product. The total time of hydrothermal treatment and aging temperature were the other main factors. The crystal growth of zeolite 4A was more sensitive to changes induced by crystallization time and temperature at high L/S ratio. Relative crystallinity of zeolite 4A varied in an expanded range in terms of crystallization time (36%–86%) and temperature (25%–73%) at high L/S ratio. • The control parameter L/S ratio led to sharp differences in crystallization behaviour. • Dissolution of low-carnegieite was decisive on the %crystallinity of zeolite 4A. • Alkalinity level strongly influenced dissolution of low carnegieite. • Alkalinity level was the major factor on the nucleation and crystallization. • Faster dissolution of low-carnegieite resulted in formation of sodalite.

Raman imaging as a useful tool to describe crystallization of aluminum/iron-containing polyphosphate glasses

Polyphosphate glasses are materials of a wide spectrum of applications in many fields. The subject of the work is polyphosphate glasses containing aluminum and iron. Three compositions of the glasses were obtained and the materials have been characterized in terms of their crystallization. The differences in crystallization behavior between powder and bulk materials were compared. The crystallized materials were analyzed by Raman scattering spectroscopy and X-ray diffraction method. It was evidenced that depending on the glass composition the main crystalline phases were Al(PO3)3, AlPO4, FePO4, Fe3(P2O7), Fe4(P2O7)3, FePO4. The glass crystallization leads to enrichment of the residual glassy phase in P2O5 and increases its polymerization. Thus, it was observed the glass inhomogeneities are being increased due to crystallization. The two dimensions spectral maps of the bulk crystallized samples were executed to describe the mechanism and type of crystallization. The depth profiling proves the differences between surface and interior phase composition.

Effect of enzymatic versus titanium dioxide/silicon dioxide catalyst on crystal structure of ‘green’ poly[(butylene succinate)‐co‐(dilinoleic succinate)] copolymers

AbstractFocusing on an eco‐friendly approach, biodegradable poly[(butylene succinate)‐co‐(dilinoleic succinate)] (PBS‐DLS) copolymers with 70:30 (wt%) ratio of hard to soft segments were successfully synthesized via various processes and catalytic systems. In this approach, biobased succinate was polymerized with renewable 1,4‐butanediol and dimer linoleic diol to obtain ‘green’ copolyesters as sustainable alternatives to petroleum‐based materials. In the first procedure, a two‐step synthesis in diphenyl ether was performed using Candida antarctica lipase B (CAL‐B) as a biocatalyst. A second material was produced via two‐step melt polycondensation in the presence of heterogeneous titanium dioxide/silicone dioxide (C‐94) catalyst. The obtained PBS‐DLS copolyesters were further characterized in regard to their number‐average molecular weight (Mn), chemical structure, thermal transition temperatures and crystallization behavior. Here, digital holographic microscopy was used to study the crystallization behavior of synthesized segmented copolyesters for the first time. Using this technique, it was possible to reveal the twisting of crystalline regions in formed spherulites and observe the differences in crystallization behavior of copolyesters depending on the type of catalyst used in their synthesis. Structural characterization indicated random and blocky structure of copolymers depending on the type of catalyst. Mn was noticeably higher in the case of PBS‐DLS 70:30 copolymer catalyzed using C‐94 than PBS‐DLS 70:30 synthesized with the use of CAL‐B. However, the degree of crystallinity was lower for polymer catalyzed with the heterogeneous catalyst. Furthermore, differential scanning calorimetric thermal analysis revealed that synthesized copolyesters exhibit low glass transition temperature as well as high melting point which are typical for thermoplastic elastomers. © 2020 Society of Chemical Industry

Comparative Study on the Different Interaction Pathways between Amorphous Aluminosilicate Species and Organic Structure-Directing Agents Yielding Different Zeolite Phases

Zeolites possessing novel structures and compositions have been produced using guest organic species, which are called organic structure-directing agents (OSDAs). However, the specific roles of OSDAs have not been clarified yet. In this work, *BEA- and CHA-type zeolites are synthesized from the same starting inorganic materials but with different OSDAs, and the crystallization pathways are observed using various analytical techniques. During the synthesis of *BEA-type zeolite, the gradual evolution of the aluminosilicate structure leads to the transformation from an amorphous structure to a crystalline one. On the other hand, during the synthesis of CHA-type zeolite, a few CHA nuclei are formed in “partially-ordered amorphous species” and grow through the consumption of “buffer amorphous species” on the surfaces of CHA-type zeolite crystals. This clear difference in crystallization behaviors of the two zeolites under the same synthetic conditions is attributed to the differences in the structure-directing...

A study of ADMET polyethylene with 21‐carbon branches on every 15th compared to every 19th carbon: What a difference four extra backbone methylenes make

ABSTRACTPrecision polyethylenes with 21‐carbon alkyl branches precisely spaced on every either 15th or 19th carbon along the polymer backbone lead to the formation of two kinds of lamellae, yielding different thicknesses during the crystallization process. Thinner lamellae originate from side‐chain crystallization, whereas thicker lamellae are formed by cocrystallization of the branch and the main chain. Side‐chain crystallization (separate from main chain crystallization) is favored when the branch is placed on every 15th carbon. Cocrystallization (side chain with main chain) is favored with the branch on every 19th carbon. Both form stable hexagonal crystal units. A branch spacing separation of just four carbons along the main chain makes a remarkable difference in crystallization behavior. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3090–3096

Unique isodimorphism and isomorphism behaviors of even-odd poly(hexamethylene dicarboxylate) aliphatic copolyesters

Three series of even-odd aliphatic copolyesters, poly(hexamethylene gluarate-co-hexamethylene pimelate) (PHGP), poly(hexamethylene pimelate-co-hexamethylene azelate) (PHPA), and poly(hexamethylene gluarate-co-hexamethylene azelate) (PHGA), were firstly synthesized derived from even diol of 1,6-hexanediol with odd diacids of glutaric acid, pimelic acid or azelaic acid, respectively. Then, their cocrystallization behaviors were systematically investigated by DSC, WAXD, and POM techniques. It is found that both PHGP and PHPA showed isodimorphism with a characteristic eutectic behavior observed from the plot of melting point versus composition, however, PHGA exhibited strict isomorphism in the whole composition range without a eutectic point. WAXD studies also confirmed the unique isodimorphism and isomorphism behaviors for even-odd copolyesters. The only slight change of the methylene number in alkyl unit of comonomers could generate so large difference in crystallization behavior, which exhibits unique physicochemical properties and structure–properties correlations in such even-odd copolyesters. Furthermore, the difference in cocrystallization miscibility effect of comonomers was analyzed by thermodynamics based on the defect Gibbs energy calculated from Wendling-Suter model. For PHGP and PHPA, the comonomer units have better miscibility in the case of the incorporation of shorter unit into the longer unit crystal than the opposite case. By contrast, in the case of PHGA, the HG and HA units are perfectly miscible in a same crystal lattice with only a little difference in crystal cell dimensions due to the identity of chain conformation of HG and HA units during packing into the crystal lattice. Finally, a model of crystal lattice structure of copolyesters was proposed to better understand the difference in cocrystallization miscibility effect of comonomers between isodimorphism and isomorphism.

Controlling silicon crystallization in aluminum-induced crystallization via substrate plasma treatment

The effect of reactive ion etching using chlorine or fluorine-based plasmas on aluminum-induced crystallization (AIC) of silicon on fused silica glass substrates was investigated with the goal of chemically modifying the substrate surface and thereby influencing the crystallization behavior. Chlorine etching of the glass prior to AIC resulted in six times faster silicon crystallization times and smaller grain sizes than films formed on untreated substrates while fluorine etching resulted in crystallization times double than those on untreated surfaces. The differences in crystallization behavior were attributed to changes in surface chemistry and surface energy of the glass as a result of the plasma treatment as supported by X-ray photoelectron spectroscopy and contact angle measurements. The different surface treatments were then combined with optical lithography to control the location of crystallization on the substrate surface to realize the production of patterned polycrystalline silicon films from initially continuous aluminum and silicon.

Influence of plasticizers and cryogenic grinding on the high‐cooling‐rate solidification behavior of PBT/PET blends

ABSTRACTTwo structurally different plasticizers (cyclic and linear) and the effect of cryogenic grinding on the solidification behavior at high cooling rates by a continuous cooling transformation approach of poly(butylene terephthalate)/poly(ethylene terephthalate), PBT/PET, blends are described. The solidification curve (density versus cooling rate) is confirmed as an effective tool to compare the differences in crystallization behavior under conditions mimicking processing. In comparison to the bulky cyclic plasticizer, the linear oligomeric one was found to have a more pronounced influence on the crystallization behavior. A 60/40 by weight PBT/PET blend shows a drop‐off of density at ∼50 K/s. In the plasticized sample, the long‐range crystalline order appears up to a cooling rate of ∼250K/s, making the blend comparable to pure PBT. Grinding the components before blending further improves crystallizability and synergy to the addition of the plasticizer. The results suggest the important role of local chain mobility in the solidification behavior at high cooling rates. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43083.

Effect of Mannitol on Nucleation and Crystal Growth of Amorphous Flavonoids: Implications on the Formation of Nanocrystalline Solid Dispersion

In this work, we studied crystallization kinetics of amorphous hesperetin (HRN) and naringenin (NRN) alone, and in 1:1 proportion with mannitol at Tg + 15 K. Crystallization rate of NRN was found to be significantly higher than HRN. Mannitol accelerated crystallization of HRN as well as NRN. NRN exhibited higher crystallization rate than HRN, in presence of mannitol, as well. Finke-Watzky model was used to deconvolute the crystallization kinetics data into nucleation and crystal growth rate constant. HRN alone had 9.56 × 10(9) times faster nucleation rate and 1.88 times slower crystal growth than NRN alone. Mannitol increased nucleation and crystal growth rate of HRN as well as NRN. In presence of mannitol, HRN possessed 1.34 × 10(10) times faster nucleation rate and 1.70 times slower crystal growth rate than NRN. Differences in crystallization behavior of HRN and NRN were explained by their thermodynamic properties.

Composite biodegradable biopolymer coatings of silk fibroin – Poly(3-hydroxybutyric-acid-co-3-hydroxyvaleric-acid) for biomedical applications

Composite silk fibroin–poly(3-hydroxybutyric-acid-co-3-hydroxyvaleric-acid) (SF–PHBV) biodegradable coatings were grown by Matrix Assisted Pulsed Laser Evaporation on titanium substrates. Their physico-chemical properties and particularly the degradation behavior in simulated body fluid at 37°C were studied as first step of applicability in local controlled release for tissue regeneration applications.SF and PHBV, natural biopolymers with excellent biocompatibility, but different biodegradability and tensile strength properties, were combined in a composite to improve their properties as coatings for biomedical uses.FTIR analyses showed the stoichiometric transfer from targets to coatings by the presence in the spectra of the main absorption maxima characteristic of both polymers. XRD investigations confirmed the FTIR results showing differences in crystallization behavior with respect to the SF and PHBV content. Contact angle values obtained through wettability measurements indicated the MAPLE deposited coatings were highly hydrophilic; surfaces turning hydrophobic with the increase of the PHBV component. Degradation assays proved that higher PHBV contents resulted in enhanced resistance and a slower degradation rate of composite coatings in SBF. Distinct drug-release schemes could be obtained by adjusting the SF:PHBV ratio to controllably tuning the coatings degradation rate, from rapid-release formulas, where SF predominates, to prolonged sustained ones, for larger PHBV content.

Development of an ultrasonic shear reflection technique to monitor the crystallization of cocoa butter

The quasi-isothermal crystallization process of cocoa butter was monitored by an ultrasonic shear reflection technique utilizing a custom-built experimental set-up in a temperature controlled environment. To facilitate the interpretation of the measurement results, the propagation of shear waves was first theoretically studied in different configurations of gas, liquid or solid layers with varying thickness for the case of normal incidence, yielding theoretical equations of the shear wave reflection coefficient (swRC) for different layering conditions. The typical experimentally observed pattern of the swRC during quasi-isothermal cocoa butter crystallization was subsequently linked to the theoretical equations. The remarkable oscillatory damped response in the swRC as function of the crystallization time could be explained by constructive and destructive interference of a first reflection at the boundary between a plexiglass delay line and the crystallized cocoa butter and a second reflection occurring at the interface between crystallized and liquid substance. This hypothesis was supported by the excitation frequency dependence of the oscillations. The quality of the fit of the theoretical model to the experimental results was very good and also the reproducibility between different independent measurements was acceptable. Finally, measurements at different temperatures (18°C and 20°C) suggested that the technique was able to detect differences in crystallization behavior, as measurements at 18°C displayed faster oscillations compared to measurements at 20°C. Moreover, this was also confirmed by the theoretical model, as a higher value of the crystallization rate parameter K, exhibited more rapid oscillations.

Organic solvent‐assisted crystallization of inorganic salts from acidic media

AbstractBACKGROUNDSolvent displacement crystallization (SDC) provides an energy‐efficient alternative to evaporative crystallization potentially leading to crystal products of superior quality, both in terms of purity and size, due to better supersaturation control. The present work investigates the SDC process in terms of appropriate organic solvent selection and application to several metal (K+, Na+, Mg2+ Fe2+, Cu2+, Ni2+, Co2+, Zn2+, Fe3+ and Al3+) sulfate and chloride systems of hydrometallurgical interest.RESULTSCriteria for the screening of organic compounds with suitable physical and chemical properties have been established and 2‐propanol was selected as an effective salting out agent to precipitate crystalline metal sulfates of practical interest; differences in crystallization behaviour among the various salts were linked to the hydration energy of the cation. None of the tested metal chlorides could be successfully separated, due to enhanced metal chloride solubility in non‐aqueous solvents relative to water by formation of chloro‐complexes with larger stability constants.CONCLUSIONSThe solvent displacement crystallization process was investigated and selection criteria for the organic solvent were established. 2‐propanol proved to be the most effective salting out agent for metal sulfates resulting in > 90% cation removal. By contrast none of the metal chlorides could be successfully separated due to salting‐in behaviour. © 2014 Society of Chemical Industry

Vacancy-mediated three-center four-electron bonds in GeTe-Sb2Te3phase-change memory alloys

Although GeTe-${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ (GST) alloys are widely used in data storage, many fundamental issues are still under debate. Here, we demonstrate that the presence of vacancies in the crystalline phase has far-reaching consequences, namely, a triad of twofold coordinated Te atoms with lone-pair electrons generated around the vacancy enables the formation of soft three-center four-electron bonds, whose properties provide an explanation for the unusual characteristics of GST, in particular, the increase in local disorder upon crystallization, the co-existence of a very fast switching rate with a large property contrast, the possibility of a solid-solid amorphization process that excludes conventional melting, and the drastic difference in crystallization behavior between GST and the ideal binary GeTe. Anisotropy of the three-center bonds may serve as an additional degree of freedom for information recording and provide a unified explanation for a variety of unique effects observed in lone-pair semiconductors.

Pd40Ni40Si5P15 bulk metallic glass properties variation as a function of sample thickness

This work presents a comparative study of different properties variation of Pd40Ni40Si5P15 bulk metallic glass (BMG), namely: density, hardness, relaxation enthalpy and mechanical properties as a function of the sample thickness. The samples were produced in the form of a long pyramid by conventional Cu-mold casting in an Ar atmosphere. The results illustrate significantly different sensitivity of these properties of the glassy phase to the cooling rate. The difference in crystallization behavior is also discussed.