S. Bordas

Phase diagram of the ternary system Ge-Sb-Te: II. The subternary Ge-GeTe-Sb2Te3-Sb

Abstract The phase diagram of the ternary subsystem Ge-GeTe-Sb 2 Te 3 -Sb was investigated using differential thermal analysis, differential scanning calorimetry, thermogravimetry powder X-ray diffraction and metallographic techniques. Five isoplethal sections were constructed. Seven transition reactions (U type) and a melting point minimum of the liquidus surface were characterized. Eight isothermal sections have been constructed in order to follow the reaction path for any composition of the subsystem.

Phase diagram of the ternary system GeSbTe. I. The subternary GeTeSb2Te3Te

Abstract The GeTeSb 2 Te 3 Te phase diagram was investigated using differential thermal analysis, differential scanning calorimetry, thermogravimetry, powder X-ray diffraction and metallographic techniques. Isopleths of four composition sections were constructed. Five transitory reactions (U type) were characterized with compositions in the range 8.5–15 at.% Ge and about 84.5 at.% Te and temperatures very close one of the other. There are also indications of a eutectoid reaction at about 45 at.% Ge and 52 at.% Te. Seven isothermal sections are presented.

Glass-forming ability in the GeSbTeSe quaternary system

Abstract The glass—forming regions in the quaternary system GeSbTeSe have been obtained for quenching in air and for a constant cooling rate of 5°C min−1. The boundaries of the glass-forming regions and the thermal behaviour of the samples have been deduced from differential thermal analysis and X-ray diffraction. The results may be compared with some limited determinations of glass-forming ability in TeSe, GeTe, GeTeSe and GeSbSe systems, allowing for the fact that in the present work the experimental parameters for preparing and quenching the melts are identical for all the compositions studied. The formation and stability of glasses is discussed in terms of the obtained glass-forming regions and the observed thermal behaviour in differential thermal analysis measurements. Potential-device quality memory and switching compositions are suggested.

Phase diagram of the ternary system GeSbSe

Abstract The ternary system GeSbSe was investigated by differential thermal analysis, differential scanning calorimetry, thermogravimetry, X-ray diffraction at fixed and varying temperatures and metallographic microscopy. The quasi-binary system Sb2Se3GeSe2, and various isoplethal and isothermal sections were determinated. In the quadrilateral GeGeSe2Sb2Se3Sb system there is a large liquid-liquid miscibility gap and a solid ternary solution. Seven reactions were observed corresponding to a monotectic, three peritectics, a eutectic, peritectoid and a eutectoid. The triangle GeSe2Sb2 Sc3Se is of the eutectic type.

Phase diagram of the ternary system GeTeSe

Abstract The ternary system GeTeSe was investigated by differential thermal analysis, thermogravimetry, X-ray diffraction and scanning electron microscopy. The quasi-binary systems, various isoplethal sections and the liquidus surface of the system were constructed. The liquid—liquid miscibility gaps have been obtained. The principal results are summarized as follows. 1. No ternary compound appears in the system. 2. The GeSe 2 Te and GeTeGeSe 2 junctions form true quasi-binary systems. 3. The reactions at the main invariant points are 4. Three liquid—liquid miscibility gaps exist: the first is situated entirely in the ternary system giving the monotectic reaction in the GeSe 2 Te quasi-binary system. The other liquid—liquid miscibility gaps are based on those occurring in the GeSe 2 Ge system.

Characterization of Ge-Se-Te glasses by emanation thermal analysis and DTA

Abstract The systematic study of the Ge-Se-Te system was carried out by emanation thermal analysis and DTA. The quenched samples were classified according to the thermal behaviour during heating and cooling. The glass transition, recrystallization and melting of the samples have been investigated. By means of the ETA supplementary information on these processes has been obtained. The differences in thermal behaviour of bulk and powdered samples have been characterized by ETA.

Crystallization kinetic studies: A means to evaluate time-temperature-transformation curves. Application to metallic glasses

It is shown that the study of the kinetics of crystallization of an amorphous alloy may be used to obtain the correct form of the low temperature part of the time-temperature-transformation (T-T-T) curves. A unified review of the current kinetics of crystallization studies is presented and the general kinetic equation which gives the reaction rate as a function of temperature and crystalline fraction is shown to contain information related to theT-T-T-curves. Finally examples of application to two metallic glasses, Nd3Fe77B20 and Fe67.5Co15Nb1.5B16, obtained by rapid solidification techniques are presented. The comparison between theory and experiment is satisfactory.ZusammenfassungEs wird gezeigt, daß die Untersuchung der Kristallisationskinetik von amorphen Legierungen genutzt werden kann, die korrekte Form des Niedertemperaturbereiches der Zeit-Temperatur-Transformation (T-T-T) Kurven zu erhalten. Es wird ein einheitlicher Überblick über die jüngsten Untersuchungen von Kristallisationskinetiken gegeben und an der allgemeinen Gleichung der Reaktionsgeschwindigkeit als eine Funktion von Temperatur und Kristallanteil wird gezeigt, daß sie Informationen bezüglich der T-T-T-Kurven beinhaltet. Letztlich wird eine Anwendung an zwei, durch schnelles Erstarren gewonnenen metallischen Gläsern Nd3Fe77B20 und Fe67.5Co15Nb1.5B16 dargelegt. Zwischen Theorie und Praxis konnte eine ausreichende Übereinstimmung festgestellt werden.

Interacti on of buprenorphine with phosphatidylcholine

Abstract The interaction between phosphatidylcholine and buprenorphine have been studied by means of differential scanning calorimetry of liposome, compression isotherms and penetration kinetics of monolayers. The results show that the interactions are highly dependent on the ionized state of the buprenorphine molecules, being higher in buffered solutions.

Residual entropy of glasses and their relation with the crystallization behaviour

For the alloy of eutectic composition in the quasibinary GeSe2-Sb2Se3 system the heat capacities of the glass, undercooled and stable liquid and crystalline phases have been measured using differential scanning calorimetry. Enthalpy, entropy and Gibbs free energy differences of vitreous and crystalline forms have been deduced for this alloy. The kinetic parameters of crystallization for glasses of nearby composition have been obtained by continuous heating experiments. The effective activation energy obtained has a value that accounts for the activation energy for nucleation calculated using simple nucleation theory formulae.ZusammenfassungDie Wärmekapazitäten von Glas, unterkühlter und stabiler Flüssigkeit und kristallinen Phasen von Mischungen der eutektischen Zusammensetzung des quasibinären Systems GeSe2-Sb2Se3 werden mittels DSC gemessen. Aus den Ergebnissen werden Enthalpie, Entropie und freie Enthalpie der glasartigen und kristallinen Formen dieser Mischung abgeleitet. Die kinetischen Parameter der Kristallisation von Gläsern benachbarter Zusammensetzungen wurden durch temperaturprogrammierte Untersuchungen ermittelt. Die erhaltenen effektiven Aktivierungsenergien entsprechen dem für die Keimbildung nach einfachen theoretischen Formeln berechneten Wert.РезюмеМетодом дифференциа льной сканирующей калориметрии опреде лены теплоемкости стеклообразной фазы, переохлажденной и ус тойчивой жидкости, а также крис таллических фаз для сплава эвтектиче ского состава в квази бинарной системе GeSe2-Sb2Se3. Для стекл образной и кристаллической фор м этого сплава опреде лены изменения энтальпии, энтропии и свободной энергии Гиббса. Путем непрерывного нагрев а получены кинетические параме тры кристаллизации стекол близкого сост ава. Полученная эффек тивная энергия активации им ела значение принятое для энергии активации образован ия центров кристаллизации, вычи сленной из простой теоретической форму лы теории образовани я центров кристаллизации.

Possibilities of emanation thermal analysis for the characterization of semiconducting glasses

Abstract The evolution of structure and structural transformations taking place in representative specimens of semiconducting glasses in the system Ge-Sb-Se-Te during their thermal treatment were investigated by emanation thermal analysis.