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Author Andreev, O. V. ♦ Kharitontsev, V. B. ♦ Polkovnikov, A. A. ♦ Elyshev, A. V. ♦ Andreev, P. O.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY ♦ ANIONS ♦ ELECTRIC CONDUCTIVITY ♦ EUTECTICS ♦ FUSION HEAT ♦ HARDENING ♦ LATTICE PARAMETERS ♦ MELTING ♦ MELTING POINTS ♦ MICROHARDNESS ♦ PHASE DIAGRAMS ♦ PHASE TRANSFORMATIONS ♦ SAMARIUM ♦ SELENIUM ♦ SOLID SOLUTIONS ♦ TEMPERATURE DEPENDENCE ♦ THERMAL ANALYSIS ♦ VACANCIES ♦ VALENCE ♦ YTTRIUM SELENIDES
Abstract A phase diagram for the Y–Y{sub 2}Se{sub 3} system has been constructed in which the YSe and Y{sub 2}Se{sub 3} phases melt congruently. The daltonide type YSe phase (ST Y{sub 0,75}Se, a=1.1393 nm, melting point=2380 K, H=2200 MPa) forms a double-sided solid solution from 49–50–53 at% Se. In the 50–53 at% Se range, the unit cell parameter increases to 1.1500 nm, the microhardness increases to 4100 MPa and electrical resistivity increases from 0.018 to 0.114 Ω m. These changes are caused by the dominating influx of newly formed structural cationic vacancies arising from the selenium anions that are surplus for the 1:1 Y:Se stoichiometry. The full-valence Y{sub 2}Se{sub 3} composition exists as a low-temperature modification of ε-Y{sub 2}Se{sub 3} (ST Sc{sub 2}S{sub 3}, a=1.145 nm, b=0.818 nm, c=2.438 nm, melting point=1780 K, ∆fusion enthalpy=4±0.4 J/g) and transforms into a modification of ξ-Y{sub 2}Se{sub 3} that does not undergo fixing by thermo-hardening. The eutectic melting point between the YSe and Y{sub 2}Se{sub 3} phases is 1625±5 K, with a eutectic composition that is assumed to be 57.5 at% Se and have an enthalpy of fusion of 43±4.3 J/g. The eutectic for the Y and YSe phases appears at a temperature of 1600 K and 5 at% Se. - Highlights: • Phase equilibria in the Y–Y{sub 2}Se{sub 3} system from 1000 K to melt were studies. • High-temperature polymorphic transition for Y{sub 2}Se{sub 3} were observed. • Singular points in solid solutions areas for YSe and Y{sub 2}Se{sub 3} were found.
ISSN 00224596
Educational Use Research
Learning Resource Type Article
Publisher Date 2015-10-15
Publisher Place United States
Journal Journal of Solid State Chemistry
Volume Number 230


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