Фазовая диаграмма системы Ge-Hf
К оглавлению: Другие диаграммы (Others phase diargams)
Ge-Hf (Germanium-Hafnium)
A.B. Gokhale and G.J. Abbaschian
The assessed Hf-Ge phase diagram is based partially on the work of [60Now1]
and in part on investigations not directly related to the phase equilibria but
pertaining to the crystal structures of the intermediate phases. The
temperatures measured by [60Now1] are only approximate. For example, they
indicated the presence of a eutectic between HfGe2 and (Ge) at 945 C, i.e.,
higher than the currently accepted melting temperature for Ge (938.3 C). In
this evaluation, this discrepancy has been corrected, and the eutectic is
indicated to occur at a temperature somewhat lower than 938.3 C.
The experimentally determined equilibria are shown by solid lines in the
assessed diagram, while those indicated by broken lines are speculative, and
are included only to complete the diagram. The broken lines were drawn based
on assumed similarities between the Hf-Si and Hf-Ge systems.
The key features of the Hf-Ge system are: tetragonal Hf3Ge, the richest in Hf;
tetragonal Hf2Ge, which forms peritectically at ~2026 C; hexagonal Hf5Ge3,
which melts congruently at 2200 C; tetragonal Hf3Ge2; the intermediate phases
Hf5Ge4 and HfGe; orthorhombic HfGe2, the richest in Ge, which forms
peritectically at 1744 C; and two eutectics, between (bHf) and Hf3Ge at 1775
C and ~10 at.% Ge, and between HfGe2 and (Ge) at ~930 C and ~98 at.% Ge.
There are no reports on the homogeneity ranges of the intermediate phases.
The maximum terminal solid solubility of Ge in (bHf) appears to be less than 1
at.% [60Now1]. The solid solubility of Hf in Ge has not been determined, but
is likely to be small.
Some ambiguity remains as to the total number of intermediate phases in the
system. The following have been variously reported: Hf3Ge, Hf2Ge, Hf5Ge3,
Hf3Ge2, Hf5Ge4, ~Hf6Ge5, HfGe, and HfGe2. All but Hf5Ge3 may be taken as
established. However, some reservations may be noted regarding Hf5Ge3; the
phase has been reported to be stable only in the presence of C [59Par] and C
and O [60Now2]. Also, similar (D88) phases in the Zr-Si and Hf-Si systems
appear to be ternary or higher order, and not strictly binary. However, Hf5Ge3
has been tentatively included in the assessed diagram following reports by [
60Now1], [68Bon], [77Mar], and [82Zyu].
[65Ros] reported the presence of a phase that corresponded approximately to
the stoichiometric composition Hf6Ge5. The composition is sufficiently close
to that of HfGe, so the data of [65Ros] have been assigned to HfGe. [82Zyu]
indicated the presence of Hf5Ge4, but not the HfGe. [77Mar] noted the
presence of HfGe instead of Hf5Ge4 on the Hf-Ge-B ternary isotherm at 800
C, as did [60Now1] and [60Now2]. At present, there are insufficient data
either to accept or discard the presence of either or both intermediate phases.
However, in the Hf-Si system, [68Bru] noted the presence of Hf5Si4 and HfSi.
Consequently, Hf5Ge4 and HfGe have both been tentatively included in the
assessed diagram.
[60Now1] reported a eutectic between (bHf) and Hf2Ge. However, [64Sch] later
established the presence of Hf3Ge. Consequently, the eutectic reaction is
indicated to occur between (bHf) and Hf3Ge in this evaluation.
57Smi: J.F. Smith and D.M. Bailey, Acta Crystallogr., 10, 341-342 (1957).
59Par: E. Parthe, Acta Crystallogr., 12, 559-560 (1959).
60Now1: H. Nowotny, H. Braun, and F. Benesovsky, Radex Rundsch., 6, 367-372 (
1960) in German.
60Now2: H. Nowotny, F. Benesovsky, Monatsch. Chem., 91, 270-275 (1960) in
German.
64Sch: K. Schubert, H.G. Meissner, and W. Rossteutscher, Naturwissenschaften,
51, 506-507 (1964) in German.
65Ros: W. Rossteutscher and K. Schubert, Z. Metallkd., 56(11), 813-822 (1965)
in German.
68Bon: V.N. Bondarev, V.A. Podergin, and V.P. Perminov, Izv. Akad. Nauk SSSR,
Neorg. Mater., 4, 1689-1693 (1968) in Russian.
68Bru: C.E. Brukl, Tech. Rep. AFML-TR-65-2, Part 1 (13), 72 pp (1968).
77Mar: M.A. Marko and Yu. Bu Kuzma, Izv. Akad. Nauk SSSR, Neorg. Mater., 13(5),
925 (1977) in Russian.
82Zyu: A.I. Zyubrik, R.R. Olenich, I.A. Mizak, and Ya.P. Yarmolyuk, Dopov.
Akad. Nauk Ukr. RSR, Ser. A. Fiz.-Mat. Tekh. Nauki, (5), 78-81 (1982) in
Ukrainian.
Published in Bull. Alloy Phase Diagrams, 11(3), Jun 1990. Complete evaluation
contains 1 figure, 4 tables, and 16 references.
Special Points of the Hf-Ge System
