P-Pt The P-Pt (Phosphorus-Platinum) System By H. Okarnoto ASM International Equilibrium Diagram The assessed P-Pt diagram (Fig. 1) is based primarily on the thermal, metallographic, and X-ray investiga- tions of [35Bil]. The equilibrium phases of the P-Pt sys- tem are: (1) the liquid, L, encompassing a miscibility gap; (2) the terminal phase, (P); (3) cubic pyrite-type P2Pt; (4) monoclirdc P2Pts; and (5) the fcc terminal phase, (Pt). (P) Terminal Solid Solution aP (white) is the most common form of P. The melting point and boiling point of aP are 44.14 [Melt] and 277 "C [Massalski], respectively. Miscibility Gap The L1 "-" L2 + P2Pt monotectic temperature is 683 ~ [35Bil]. The compositions of the two liquids at the this temperature are 48 and 74 at.% Pt [35Bil]. No informa- tion is available regarding the shape of the miscibility gap. P2Pt The existence of PsPt was reported by [29Tho] and con- funned by [35Bill. The sublimation temperature of P2Pt at 1 bar is about 1400 ~ [35Bil]. The melting point (under >1 bar pressure) is higher than 1500 ~ [35Bil]. The "PTPt20" (74.1 at.% Pt) originally speculated by [35Bil] is actually P2Pt5 (71.4 at.% Pt), according to a crystal structure investigation [67Dah]. The L + P2Pt ,-, P2Pt5 peritectic formation temperature is 590 "C [35Bii]. (Pt) Terminal Phase The melting point of Pt is 1769.0 "C [Melt]. The solubil- ity of P in (Pt) is 0.03 at.%, according to metallographic observations [35Jed]. The eutectic temperature be- tween (Pt) and P2Pt5 is 588 "C, according to thermal analysis [35Bil] and high-temperature microscopy [57Rei]. The liquidus trends indicate that the eutectic composition is about 80 at.% Pt (Fig. 1). Other Phases [35Bfl] could not confirm the existence of the '~PsPt3," "PPt," and "PPts" reported in [15Gruel. Crystal Structures and Lattice Parameters P-Pt crystal structure and lattice parameter data are summarized in Tables i and 2, respectively. Table I P-Pt Crystal Structure Data Composition, Pearson Space Strukturberieht Phase at.% Pt symbol group designation Prototype Reference (P)(white) ......... 0 c** .._ . . . . . . [Pearson2] P2Pt .................. 33.3 cPl2 Pa3 C2 FeS2 (pyrite) [29Tho] P2Pt 5 ................ 71.4 mC28 C2/c . . . . . . [67Dah] (Pt) ................... 100 cY4 Yrn3m A1 Cu [Kingl] Table 2 P-Pt Lattice Parameter Data Composition, Lattice parameters, nm pha,u~ at.% Pt a b e Comment Reference P (white) .......... 0 0.718 . . . . . . . . . [Pearson2] P2Pt .................. 33.3 0.5694 . . . . . . . . . [29Tho,60Run] 0.56956 . . . . . . . . . [601~je, 65Fur, 69Dah] 0.56955 . . . . . . [74Bag] P2Pt5 ................ 71.4 1.07642 0.53854 0.74378 13 = 9"91170 ~ [67Dab] Pt ...................... 100 0.39236 . . . . . . . . . [Massalski] Bulletin of Alloy Phase Diagrams Vol. 11 No. 5 1990 511 P-Pt Ci ted References 15Gme: Gmelin.Kraut Handbook, Vol. 5, part 3,329 (1915) in German. (Equi Diagram; Compilation) 29Tho: L. Thomaseen, "Crystal Structures of Some Binary Compounds of Platinum Metal II," Z. Phys. Chem. B, 4, 281-283 (1929) in German. ~B ih W. Biltz, F. Weibke, E. May, and K Meisel, "Alloyability of Platinum and Phosphorus," Z. Anorg. Chem., 223, 129- 143 (1935) in German. 35Jed: k. Jedele, "Influence of Phosphorus and Sulfur on the Mechanical and Technological Properties of Platium and Palladium," Z. Metallkd., 27(12), 271-275 (1935) in Ger- marl. F ig . 1 Assessed P -P t Phase D iagram 0 ~030 40 50 60 70 1800 _ ~ 1 , ~ ,ooot 1400 r~ 1200 1000 800- 800- Weight Percent P la t inum 80 90 >1500~ ; \ ,, , ,, , I' \ i Li i t l \ i i i 48 t \ L i + L 2 883~ 590~ L2 i i i i i i t i i i i t ! 74 80 588~ 100 ;~ 1"~69.ooc 400 -~ 0 P 30 20 30 40 50 60 70 Atomic Percent P la t inum ALomic Percent P ia t inum 40 50 60 80 90 70 80 90 100 100 Pfl r o g E 1600 1400 1200. I000 800- E, 600- >1500~ \ ' \ L1 \ ,, L i + L 2 %) 683~ 85.3 590~ 400 i , . . . . . . . . . , 70 80 90 Weight Percent P la t inum Lz l % i t t t i t ,~ _ i 98 I00 Pt H. Okamoto, 1990. 512 Bulletin of Alloy Phase Diagrams Vol. 11 No. 5 1990 P-Pt SI-Zr 57Rei: G. Reinacher, "Determination of the Minimum Fusion Joints of Platinum Systems with a High-Temperature Microscope," Rev. Met., 54, 321-336 (1957) in French 60Kje: A. I~ekshns, "p, edetermined Lattice Constants of PtP2, PtAs2, PtSb2, and a-PtBi2,'Acta Chem. Scand., 14(6), 1450-1451 (1960) 60Run: S. Rundqvist, "Phosphides of the Platinum Metals," Nature, 185, 31-32 (1960) 65Fur:. S. Furuseth, K. Selte, and A. Kjekshns, "Redeter- mined Crystal Structures of PdAs2, PdSb2, PtP2, PtAs2, PtSb2, ct-PtBi2, and AuSb2," Acta Chem Scand., 19(3), 735- 741 (1965). (Crys Structure; Experimental) 67Dab: E. Dahl, "The Crystal Structure of PtsP2,'Acta Chem. Scand., 21(5), 1131.1137(1967) 69Dah: E. Dahl, "Refined Crystal Structures of PtP2 and FePs,'Acta Chem. Scand., 23(8), 2677-2684 (1969) 74Bag: A. Baghdadi, A. Finley, P. Russo, R.J. Arnott, and A. Wold, "Crystal Growth and Characterization of PtP2," J. Leas.Common eL, 34(1), 31-38 (1974) * Indicates keypaper. # Indicates presence of a phase diagram. P-Pt evaluation contributed by H. Ob=moto, ASM International, Materials Park, OH 44073. This work was supported by ASM Internation- al. Literature searched through 1987. Dr. Okamoto is the ASM/NIST Data Program Category Editor for miscellaneous binary alloys. The Si-Zr (Silicon-Zirconium) System By H. Okamoto ASM INTERNATIONAL Equilibrium Diagram The equilibrium phases in the assessed Si-Zr phase diagram (Fig. I) are: (Si); Si2Zr; ~- and aSiZr; f~- and aSi4Zrs; Si2Zr3; Si3Zr5; SiZr2; SiZr3; (~Zr); and (aZr). Special points of Fig. 1 are summarized in Table 1. Many investigations concur that there are several in- termetallic phases in the Si-Zr system, but unanimity as to the appropriate stoichiometries is lacking. One of the reasons for disagreement is that a small amount of impurity stabilizes Si3Zr5 and makes other phases relatively unstable. The assessed diagram is based pri- marily on [76Koc]. This system was reviewed by [10Bar] and more recently by [68Bru] and [76Alc], as well as [Hansen], [Elliott], and [Shunk]. Llquidus The data of [76Koc] are accepted as the experimental basis for the liquidus in Fig. 1. The liquidus tempera- tures between 10 and 60 at.% Zr are significantly higher than those given in previous diagrams [I-Iansen, 76Aic] (the latter was also used in [Massalski]), which were based primarily on [53Lun] and [54Kie] (see data points in Fig. 1). The liquidus data of [76Koc] obtained by thermal analysis are preferred to those of [54Kie] obtained by using an optical method. [68Bru] (same phase diagram in [69Rud]) showed the liquidus bound- aries at even higher temperatures, because alloys with compositions near Si2Zr3 collapsed on heating at 2325 ffi 25 ~ Because the melting points of pure Si and Zr as- sumed by [68Bin] were about 20 ~ higher (1340 and 1876 ~ respectively) than the currently accepted values, there may be systematic deviation in the data of[68Bru]. The Si-rich eutectic reaction occurs at slightly below 10 at.% Zr [51Job], 10 at.% Zr and 1355 ⢠15 "C [53Lun], 9.3 at.% Zr and 1360 "C [54Kie], 10.0 ffi 0.5 at.% Zr and 1353 ⢠5 "C [68Bru], or 10 at.% Zr and 1375 "C [76Kec]. The liquidus trend on each side of the eutectic is ac- cepted from [76Koc]. However, because the melting point of Si assumed by [76Koc] was 6"C higher than the currently accepted value of 1414 "C [Melt], the eutectic temperature is shown at 1370 ~ in Fig. 1. The composition of the Zr-rich eutectic reaction, 91.2 at.% Zr, is accepted from [53Lun]. In good agreement, [49She], [50And], [54Kie], [68Bru], [74Koc], and [76Koc] observed it in the range between 90 and 91.3 at.% Zr. The eutectic temperature is 1570 [76Koc], 1575 ⢠5 [68Bru], or 1610 ~ [53Lun]. The value of [76Koc] appears to be defined better (see data points in Fig. 1). (Si) Terminal Solid Solution No solubility of Zr in (Si) was detected [51Joh]. The solubility is considerably less than 5 wt.% (1.6 at.%) Zr [53Lun]. Si2Zr The existence of Si2Zr was detected by [06Hon] and [lOWed]. The assessed peritectic formation tempera- ture is 1620 ~ [76Koc]. [53Lun] showed the peritectic temperature at 1520 ⢠15 ~ based on two data points shown in Fig. 1. Incipient melting data of [68Bru] indi- cated that the peritectic decomposition temperature is 1584 ffi 5 ~ According to [62Erm], the melting point of Si2Zr is 1680 ~ which [Shunk] considered to cor- respond to the liquidus temperature, based on the dia- gram shown in [Hansen]. It actually may have been a Bulletin of Alloy Phase Diagr~mA Vol. 11 No. 5 1990 513