Фазовая диаграмма системы Eu-Ge

К оглавлению: Другие диаграммы (Others phase diargams)


Eu-Ge (Europium-Germanium) A.B. Gokhale and G.J. Abbaschian The assessed Eu-Ge phase diagram is based entirely on the work of [80Ere]. These evaluators have changed only the melting temperatures of the pure components to conform with the currently accepted values. There are no other reported investigations of the phase equilibria in this system. The system is characterized by: (1) the intermediate phase Eu3Ge, the richest in Eu, which melts congruently at 1215 C; (2) the tetragonal intermediate phase EuGe, which melts congruently at 1220 C; (3) the intermediate phase Eu2Ge3, which decomposes peritectoidally at 916 с 6 C; (4) the hexagonal intermediate phase Eu3Ge5, which forms peritectically at 1011 с 6 C and decomposes eutectoidally at 755 с 1 C. The phase also exhibits an allotropic transformation at 870 с 3 C; the crystal structure of the high-temperature form is unknown; (5) the hexagonal intermediate phase EuGe2, the richest in Ge, which melts congruently at ~1030 C and exhibits an allotropic transformation at 810 с 8 C; the crystal structure of the high-temperature form is unknown; and (6) four eutectics-between (Eu) and Eu3Ge at 758 с 8 C and 9.1 at.% Ge, between Eu3Ge and EuGe at 1145 с 16 C and 46.5 at.% Ge, between EuGe and Eu3Ge5 at 986 с 4 C and 53.8 at.% Ge, and between EuGe2 and (Ge) at 723 с 4 C and 80.9 at.% Ge. All the intermediate phases are nearly stoichiometric. The mutual terminal solid solubilities of the pure elements appear to be very small. [67Mer] carried out magnetic measurements on EuGe and reported that it obeyed the Curie-Weiss law in the range -180 to 200 C, with a Weiss temperature of 90 C. They also indicated that Eu exists in a divalent state in this compound. [69Shi] reported on the basis of an analysis of M”ssbauer spectra that Eu exists in a divalent state in EuGe2. 64Gla: E.I. Gladyshevskii, Dopov. Akad. Nauk Ukr. RSR, 209-212 (1964) in Ukrainian. 67Mer: F. Merlo and M.L. Fornasini, J. Less-Common Met., 13, 603-610 (1967). 69Shi: I. Shiklovsky and I. Mayer, J. Phys. Chem. Solids, 30, 1207-1213, (1969) . 78Bea: B.J. Beaudry and K.A. Gschneidner, Jr., Handbook on the Physics and Chemistry of Rare Earth Metals, Vol. 1, 215, North Holland Publ., Amsterdam ( 1978). 80Ere: V.N. Eremenko, I.M. Obushenko, Yu.I. Byuanov, and K.A. Meleshevich, Diagr. Sostoyaniya Tugoplavk. Sis., Kiev, 163-171 (1980) in Russian. Submitted to the APD Program. Complete evaluation contains 1 figure, 2 tables, and 12 references. Special Points of the Eu-Ge System