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JPEDAV (2007) 28:582 DOI: 10.1007/s11669-007-9114-x 1547-7037 ÓASM International

Au-Ho (Gold-Holmium) H. Okamoto

The Au-Ho phase diagram in [Massalski2] was redrawn from [1987Gsc]. This phase diagram was derived by thermodynamic modeling by assuming systematic changes Table 1

in thermodynamic parameters of related phases in the goldrare earth systems. Figure 1 shows the Au-Ho phase diagram determined by [2002Sac] by means of X-ray powder diffraction, optical and scanning electron microscopy, electron probe microanalysis and differential thermal analysis. A new phase Au10Ho7 was found in this work. Table 1 shows Au-Ho crystal structure data.

Au-Ho crystal structure data

Phase

Composition, Pearson at.% Ho symbol

(Au) Au6Ho Au4Ho Au51Ho14 Au3Ho Au2Ho Au10Ho7 bAuHo aAuHo AuHo2 (Ho)

0 to 4 14.3 20 21.5 25 33.3 41.1 50 50 66.7 > 99 to 100

cF4 tP56 tI10 hP65 oP8 tI6 tI136 cP2 oC8 oP12 hP2

Space group

Strukturbericht designation Prototype

Fm3m P42/ncm I4/m P6/m Pmmn I4/mmm I41/acd Pm3m Cmcm Pnma P63/mmc

A1 ... D1a ... D0a C11b ... B2 Bf C23 A3

Cu Au6Ho MoNi4 Ag51Gd14 bTiCu3 MoSi2 Au10Gd7 CsCl CrB Co2Si Mg

References 1987Gsc: K.A. Gschneidner, Jr, F.W. Calderwood, H. Okamoto, and T.B. Massalski, The Au-Ho (Gold-Holmium) System, in Phase Diagrams of Binary Gold Alloys, H. Okamoto and T.B. Massalski, Eds., ASM International, Metals Park OH, 1987, p 139-141 2002Sac: A. Saccone, D. Maccio`, S. Delfino, and R. Ferro, Alloying Behavior of the Rare Earth Metals with Gold: The Ho-Au, Er-Au, and Tm-Au Systems, Intermetallics, 2002, 10(9), p 903-913

Weight Percent Holmium 0

10

20

30

40

50

60

70

80

90

100

1800

βAuHo

1700°C 1610°C

1600

L

1474°C

1400

1350°C 40.5 1360°C 28 1230°C

1200

38.5

1285°C

1095°C

17.5 1060°C

1064.43 1000

70 985°C

15 950°C

>99

78

13 840°C

AuHo2

αAuHo

Au10Ho7

Au2Ho

Au6Ho

600

Au51Ho14 Au3Ho

805°C 4 11

800

Au4Ho

Temperature, °C

1250°C

(Ho)

(Au)

400

200 0

Au

10

20

30

40

50

60

70

80

90

Atomic Percent Holmium

Fig. 1 Au-Ho phase diagram

582

Journal of Phase Equilibria and Diffusion Vol. 28 No. 6 2007

100

Ho