Abstract
The enthalpy of the La3Se4 and La2Se3 boundary compositions of the La3−xSe4 phase (0 ≤ x ≤ 1/3) at temperatures from 370 to 2260 K is studied calorimetrically. The values obtained are used and the equilibria of the La-Se system are analyzed to establish, for the first time, the temperature-concentration relationships for the thermodynamic properties of La3−xSe4 selenides in the homogeneity region at 298 K ≤ T ≤ 2123 K. The enthalpy function (J/mole) of La3−xSe4 is given by H(T) − (298 K) = (3837 · 103T−1 − 85852 + 266.925 · T − 8.7503 · 10−2 T2 + 3.437 · 10−5 T3) · e−0.2869x. The formation and melting enthalpies of La3Se4 are determined: ΔfH °(298 K) = −1340 ± ± 28 kJ/mole), ΔmH = 147.5 ± 9.6 kJ/mole. It is shown that the high-temperature stability of different La3−xSe4 compositions is strongly dependent on pressure: as pressure decreases and temperature increases, the selenium content is reduced and the composition tends to La3Se4.
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Translated from Poroshkovaya Metallurgiya, Vol. 47, No. 7–8 (462), pp. 112–119, 2008.
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Litvinenko, V.F., Kopan’, A.R. Thermodynamic properties and high-temperature behavior of lanthanum selenides La3Se4-La2Se3 . Powder Metall Met Ceram 47, 466–471 (2008). https://doi.org/10.1007/s11106-008-9044-0
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DOI: https://doi.org/10.1007/s11106-008-9044-0