Stable and metastable phase equilibria in the GeSe sub(2)-Se system

Stable and metastable phase equilibria in the binary system GeSe sub(2)-Se have been investigated by means of optical and electron microscopy, electron probe microanalysis (EPMA), x-ray diffraction (XRD), thermal analysis, and adiabatic calorimetry. A revised equilibrium phase diagram is presented....

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Bibliographic Details
Published in:Journal of phase equilibria 1999-02, Vol.20 (1), p.17-28
Main Authors: Stolen, S, Johnsen, H B, Boe, C S, Grande, T, Karlsen, O B
Format: Article
Language:English
Subjects:
Crystal structure
Electron microscopy
Phase diagrams
Phase equilibria
Phase transitions
Semiconducting germanium compounds
Solid solutions
X ray diffraction analysis
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Summary:Stable and metastable phase equilibria in the binary system GeSe sub(2)-Se have been investigated by means of optical and electron microscopy, electron probe microanalysis (EPMA), x-ray diffraction (XRD), thermal analysis, and adiabatic calorimetry. A revised equilibrium phase diagram is presented. A not previously observed gamma -type phase transition was observed near approximately 420 K (147 degree C) for GeSe sub(2). The intermediate phase, phi , which earlier had been considered as metastable, is shown to be stable through extensive annealing experiments and by adiabatic calorimetry. The phi phase, with composition near Ge sub(3)Se sub(7), melts incongruently at 658 plus or minus 5 K (385 plus or minus 5 degree C) to GeSe sub(2) and a liquid with 85 plus or minus 2 at.% Se. The liquidus of GeSe sub(2) and phi was determined by EPMA of annealed-and-quenched samples. Both a stable ( phi -Se-liquid) and a metastable (GeSi sub(2)-Se-liquid) eutectic point were observed. The stable one was observed at 480 plus or minus 2 K (207 plus or minus 2 degree C) and 92.5 plus or minus 1.0 at.% Se, whereas the temperature of the metastable eutectic (GeSe sub(2)-Se-liquid) was observed to be approximately 10 K lower. Metastable phase equilibria, obtained on thermal evolution of glasses with different compositions, are described and discussed.
ISSN:1054-9714