Фазовая диаграмма системы Cu-Tb

К оглавлению: Другие диаграммы (Others phase diargams)

Cu-Tb (Copper-Terbium) P.R. Subramanian and D.E. Laughlin Because of the limited amount of experimental data, the assessed Cu-Tb phase diagram has been calculated from available thermodynamic data and systematics of Cu-lanthanide systems. Melting and eutectic temperatures in the Cu- lanthanide systems show a systematic variation across the lanthanide series. Thus, the invariant temperatures of known Cu-Tb intermediate phases were derived by interpolation of corresponding data for those Cu-lanthanide systems for which experimental phase diagrams are already reported in the literature. The interpolated invariant temperatures were then combined with thermodynamic modeling and systematics of Cu-lanthanide systems to derive the Cu-Tb phase diagram. The Cu-rich and Tb-rich liquidus were calculated from thermodynamic data, whereas the liquidus between 9.5 and 70 at.% Tb was estimated from systematics of Cu-lanthanide systems. The equilibrium phases of the Cu-Tb system are (1) the liquid, L, without any miscibility gaps; (2) the fcc terminal solid solution, (Cu), with negligible solid solubility of Tb in (Cu); (3) the Tb-rich bcc terminal solid solution, ( bTb), based on the equilibrium phase of pure Tb between 1289 and 1356 C; (4) the Tb-rich cph terminal solid solution, (aTb), stable between -53 and 1289 C; (5) the Tb-rich orthorhombic terminal solid solution, (a›Tb), stable below - 53 C; (6) the hexagonal intermediate phase Cu7Tb, stable only at elevated temperatures; (7) the fcc phase, aCu5Tb, stable up to the allotropic transformation temperature of 895 C and the peritectic melting temperature of ~940 C; (9) the orthorhombic phase, Cu2Tb, stable up to the congruent melting temperature of 870 C; and (10) the most Tb-rich intermediate phase, CuTb, with a cubic structure and stable up to the congruent melting temperature of 900 C. In concurrence with the behavior observed for the other Cu-lanthanide systems, mutual solid solubilities are expected to be negligible, except possibly in ( bTb). The existence of Cu9Tb2 and Cu7Tb2 is proposed solely on the basis of the presence of similar phases in the Cu-Gd, Cu-Dy, and Cu-Er systems. [71Bus] reported the high-temperature formation of Cu7Tb, with its subsequent decomposition to Cu5Tb and elemental Cu on annealing at temperatures near 700 C. [70Bus] observed the formation of Cu6Tb with an orthorhombic structure in splat-cooled thin foil samples of Cu5Tb after vacuum annealing at 700 C for 4 days. However, they ruled out the existence of Cu6Tb as a stable phase, because of their inability to obtain it as a single phase through normal melting and annealing techniques. As such, this phase is not shown in the assessed phase diagram. [79Mcg] prepared amorphous thin films with the composition Cu0.507Tb0.497 by sputtering from arc-melted specimens, and by thermal evaporation from Cu and Tb targets, followed by deposition on liquid nitrogen-cooled sapphire substrates. 60Has: S.E. Haszko, Trans. AIME, 218, 763 (1960). 63Sto: A.R. Storm and K.E. Benson, Acta Crystallogr., 16, 701-702 (1963). 64Cab: J.W. Cable, W.C. Koehler, and E.O. Wollan, Phys. Rev. A, 136(1), 240- 242 (1964). 64Cha: C.C. Chao, H.L. Luo, and P. Duwez, J. Appl. Phys., 35, 257-258 (1964). 65Dwi: A.E. Dwight, R.A. Conner, Jr., and J.W. Downey, Rare Earth Res. Conf., Aug 30-Sept 1, Ames, IA, 5, 35-44 (1965). 65Ian: A. Iandelli and A. Palenzona, J. Less-Common Met., 9, 1-6 (1965). 67Pie: J. Pierre, C.R. Hebd. S‚ances Acad. Sci., B, 265, 1169-1172 (1967) in French. 69Bus: K.H.J. Buschow, A.S. van der Goot, and J. Birkhan, J. Less-Common Met., 19, 433-436 (1969). 70Bus: K.H.J. Buschow and A.S. van der Goot, J. Less-Common Met., 20, 309-313 ( 1970). 71Bus: K.H.J. Buschow and A.S. van der Goot, Acta Crystallogr. B, 27(6), 1085- 1088 (1971). 77Bas: A.F. Basha, V.I. Chechernikov, L.G. Sinanyan, and A. Tavansi, Zh. Eksp. Teor. Fiz., 72, 1540-1542 (1977) in Russian; TR: Sov. Phys. JETP, 45(4), 808- 809 (1977). 79Mcg: T.R. McGuire and R.J. Gambino, J. Appl. Phys., 50(11), 7653-7655 (1979). 84Tsv: A.V. Tsvyashchenko, J. Less-Common Met., 99, L9-L11 (1984). Published in Bull. Alloy Phase Diagrams, 9(3a), Aug 1988. Complete evaluation contains 1 figure, 6 tables, and 22 references. Special Points of the Cu-Tb System