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Title: A new way of phase identification, of AgGaGeS{sub 4}∙nGeS{sub 2} crystals

The phase identification of AgGaGeS{sub 4}·nGeS{sub 2} (n=0–4) crystals grown by vertical Bridgman–Stockbarger technique was carried out to find the boundary value n between a homogeneous solid solution and its mixture with GeS{sub 2}. To obtain reliable results, the conventional methods of X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) were completed by less common vapor pressure measurement in a closed volume and precise density measurements, which are very sensitive to the detection of small amounts of crystalline and glassy GeS{sub 2} and heterogeneous state of the crystals. The boundary value n=1.5 at 1045 K and the coexistence of the solid solution AgGaGeS{sub 4}·1.5GeS{sub 2} with the β-GeS{sub 2} phase for n>1.5 was found. Glassy GeS{sub 2} (∼2 mol%) was revealed by vapor pressure measurement and XRD studies in all the crystals. This is discussed in terms of the supersaturated solid solution decomposition upon temperature decreasing and the microphase separation of overcooled melt near the melting point under non-equilibrium crystallization. For the first time, the p–T dependence for glassy GeS{sub 2} was measured by the vapor pressure measurements. - Graphical abstract: lg p–1/T dependences of as-grown AgGaGeS{sub 4}·nGeS{sub 2} crystals. - Highlights: • Vapor pressure measurement as a powerfulmore » tool of phase identification. • Thermal characteristics of glassy GeS{sub 2}. • The homogeneity range of AgGaGeS{sub 4} from the GeS{sub 2} side.« less
Authors:
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Publication Date:
OSTI Identifier:
22309056
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 203; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CRYSTALLIZATION; CRYSTALS; DECOMPOSITION; DENSITY; DETECTION; GERMANIUM SULFIDES; MELTING POINTS; SOLID SOLUTIONS; X-RAY DIFFRACTION; X-RAY SPECTROSCOPY