Phase diagram of the Y–Y{sub 2}Se{sub 3} system, enthalpies of phase transformations

Journal Article · Thu Oct 15 00:00:00 EDT 2015 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2015.06.042· OSTI ID:22486806

Andreev, O. V.; Kharitontsev, V. B. ^[1]; Elyshev, A. V. ^[1]; Andreev, P. O. ^[2]

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1. Tyumen State University (Russian Federation)
2. Tyumen State Oil and Gas University (Russian Federation)

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.

• OSTI ID: 22486806
• Journal Information: Journal of Solid State Chemistry, Vol. 230; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 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