American Mineralogist, Volume 79, pages 1159-l 166, 1994

Lead and chalcogenide systems

Hurr.lNc Lru, Luxn L. Y. CH,c.Nc Department of Geology, University of Maryland, College Park, Maryland2O742,U-5.4.

Ansrnlcr Phaserelations in the systemsof and bismuth chalcogenideswere examined in the temperature range of 500-900 "C. In the system PbS-PbSe-BirSr-BirSer,a complete series of solid solutions exists between PbnBioS,,(heyrovskyite) and PbnBioSe,r,whereas along the join from Pb.BiuS,,(lillanite) to PbrBiuSe,,there are two terminal solid solutions. The join PbBirSo-PbBirSeois characterizedby an extensivesolid solution basedon weibullite. Six extensive ranges of solid solution exist in the system PbSe-PbTe-BirSer-BirTer,and their compositionsfall along the joins in Pb(Se,Te):Bir(Se,Te),ratios of l:0, 2.7:1, 2:I, l:1, l:2, and0: I . New phasesand solid solutions in the systemsof lead and bismuth sulfide and and selenide and telluride are all structurally related, and their structures are based on stacked layers of PbTe (two layers) and BirTe, (five layers). The total number of layers (N) in the unit cell of a phase, mPbTe'nBirTer, is expressedby the equation N : Z(2m * 5n), where Z is the number of formula units in the unit cell and can only be derived from experimental data. For the four phasesalong the galena-tetradymitejoin in the PbS- PbTe-BirSr-BirTe, system, PbrBirSrTer, PbrBioSrTeo,PbBirSrTer, -and PbBinS'Teohave N, Z, a, and c-respectively:9, l, q.2l x, and ft.j1 A;32,2,4.23 A, and 60.00A;21,3, 4.8 A. and 39.83A; and 12,1,4.24 A, and 23.12A-

Ixrnouugrron a small range of solid solution, representedby PbrBirSe' at 500 lrad and bismuth chalcogenidesare ofinterest because "C. Phaserelations along the join PbTe-BirTe, have been of the large number of reported in the group. the subject of several studies. Elagina and Abrikosov The atomic structures of Pb and Bi differ by a single 6p (1959) and Golovanova and Zlomanov (1983) reported electron,and their crystallochemicalbehaviors show many a single intermediate phase, PbBioTe', stable along the similarities, which are well illustrated in their sulfides. join. Hirai et al. (1967)also reporteda singleintermedi- The BiSu polyhedron has bond lengths and bond angles phase,but with a compositionof Pb.BioTer.Zhukova very similar to those of the PbSu octahedron. Conse- ate Zaslavskli(1976) and Skoropanovet al. (1985) ob- quently, various galenalike structural units can be formed and the formation of PbrBirTer, PbBirTeo, and Pb- by combining Pb and Bi polyhedra(Makovicky, l98l). served Bi.Te,. Chami et al. (1983)and Dumas et al. (1985)pro- However, no significant solid solutions were found be- poseda join containing two intermediatephases, PbBirTen tween their respectivechalcogenides. The purpose ofthis and PbBi"Te,. study is to examine the distinctions and similarities in the Pb- and Bi-containing systems sulfide and selenide, selenideand telluride, and sulfide and telluride. ExpnnnvrnxrAr, PRoCEDURES Phase relations among lead sulfbismuthinides were Reagent-gradePb, Bi, S, Se, and Te, all with 99.990/o studiedby Van Hook (1960)and Craig (1967).There are purity, were used in the preparation of starting compo- four lead sulfbismuthinides stable along the join PbS- sitions. Heat treatment was performed in electric furnaces BirS.: PbnBios,r,PbsBi6S,7, PbBizSo, and PbBinSr.The in which the temperaturewas controlled to within +2"C, first three phaseshave been shown to be analogous to and the conventional technique of sealed,evacuated sil- heyrovskyite, lillianite, and galenobismutite, respective- ica glasscapsules (Kullerud and Yoder, 1959)was used. ly. PbBioS, is a high-temperature phase stable between Generally, the duration of the treatment ranged from 60 680 and 725 "C. d at 500 "C to I d at 900 "C. At the end of the heat Along the join PbSe-Bi,-Se.,Elagina (1961) reported treatment, the sampleswere quenched to room temper- three intermediate phases, PbrBioSen, PbBirSeo, and ature by compressedair to preserve phase assemblages PbBioSer,and a wide range of PbSe-typesolid solution synthesizedat high temperatures.Test experimentsdem- extendingto 20 molo/oBirSe, at 720'C. Godovikov et al. onstratedthat the quenchingprocedure is capableoflow- .C (1967)reported two phases,PbBirSeo and PbBioSer,and ering the temperature from the 500-900 range to 100 0003-o04x/94llI l2-1 159$02.00 I 159 I 160 LIU AND CHANG: LEAD AND BISMUTH CHALCOGENIDES

ToC "C in 2-3 s. Visual examination of reaction betweensam- ple and capsuleglass was made, and any experiment with r 100 evidence of reaction was discarded. As a test of equilib- rium, some samples were heated to complete melting, quenched,ground under ,and annealedat the de- for length 1000 sired temperatures the same of time as their counterparts. If the final assemblagesshowed no difer- encescaused by changingthe procedure,equilibrium was assumedto have been attained. 900 X-ray powder diffraction, reflected-light microscopy, and electron microprobe analysis were used for phase characteization. No high-temperature X-ray diffraction 800 was performed to examine phase assemblagesat experi- mental temperatures.Cell dimensions were computed us- ing a least-squaresrefinement program (Benoit, 1987). 700 For the determination of melting, the quenched samples were made into polished sections and examined micro- scopically for the presence of liquid textures. Phase 600 boundaries in the subsolidus region were constructed by both parametric and phase-disappearancemethods.

500 ExpBnrurr.rrAl. REsuLTs The binary joins Phaserelations along the join PbSe-BirSe,established 400 in the present study are shown in Figure la. Three inter- mediate phaseswere found: PbrBioSe,, (phase U), 40 60 80 D ! . ^ PbrBiuSe,,(phase V), and a PbBirSeo-basedsolid solution PbSe t'12583 mol% 6hasi w). trtr first two are Se analoguesto heyrovskyite and lillianite, respectively.The PbBirSeo-basedsolid so- ToC lution (weibullite) has a range of 47-57 molo/oBirSe. at 500 "C and 47-53 molo/oBi,Se. at 400 "C. All lead bis- muth selenidesmelted congruently,and the melting points oC 1000 determinedare 560 + 3 "C for PbrBioSe,s,575 + 3 for PbrBiuSe,r,and 655 + 3 "C for PbBirSeo.Among the reported phases, only PbBirSe4was confirmed in this study. 900 Along the join PbTe-BirTer, results obtained in the present study are shown in Figure lb. There are two lead bismuth tellurides: PbBi,Te, (phase A) and PbBioTe, 800 (phaseM). PbBi.Teomelted incongruently at 585 + 3 'C, and PbBioTe, melted congruently at 570 + 3 "C.

700 The lead and bismuth chalcogenides Phaserelations in the system PbS-PbSe-BirSr-BirSe,at 500 "C are shown in Figure 2a. Heyrovskyite and the 600 seleniananalogue of heyrovskyite form a complete series of solid solution, whereas,between lillianite and the se- c o Qoo ]o a o lenian analogueof lillianite, two terminal solid solutions exist. Cell dimensions determined are listed in Table l. o o o o o o s00 I io o The cell dimensions of hevrovskvite obtained are com-

400 (- Fig. l. Phase relations along the joins (a) PbSe-BirSe,and 40 60 80 (b) PbTe-BirTer. Open circles, solid circles,and half-solid circles PbTe Bi2Te3 representliquid, solid, and two-phaseassemblages, respectively. mol% Irtters denote single phases. LIU AND CHANG: LEAD AND BISMUTH CHALCOGENIDES 1l6l

r60

t4.o

54.4 .3 ro.o a o< I .E cg 80 -cl

/ ./. ./D /+-.++-.H-+-{4

o to 40 50 60 70 too 40 60 Bi2s3 Bi2Se3 PbBi2s4 DolU PbBi2Se4 PbBl2Se4 molo/" Fig.3. Variationof celldimensions with compositionfor the (b) PbBi,(S,Se)"(phase W) solidsolution synthesized at 500'C. PbSe PbTe

parable with those reported by Klominsky et al. (1971), although the naturally occurring heyrovskyite from its type locality contains Ag. The most distinct feature in the systemis the extensive region of solid solution based on weibullite [Pb,*,Bir*"(S,Se)o*.,*,sr], which rangesfrom PbBirSeoto 90 molo/oPbBirSo at n and y : 0. Along the PbS-BirSe, join, the seriesextends to the compositions that include the Pb-Bi ratio of wittite (Johansson,1924). Powder X-ray diffraction data of synthetic weibullite match those from the weibullite obtained by Mumme (1980), and varia- tions of cell dimensions with compositions along the PbBir(S,Se)"join are shown in Figure 3. The changesre- flect the size differencebetween S and Se.The miscibility 20 40 60 join as- Bi2se3 gap along the BirSr-BirSe, forms a three-phase mol"/" semblagewith the weibullite solid solution. Phase relations in the PbSe-PbTe-BirSer-BirTe, syst€m (c) at 500 oC are shown in Figure 2b. Becauseofthe binary Pbs PbTe phasesalong the PbTe-BirTe, join, phaseA and phaseM form two extensive ranges of solid solutions by substitu- tion of Se for Te. Phase A extends from PbBirTeo to PbBir(SeorrTeorr)oand phase M from PbBioTe' to Pb- Bio(SeorrTeor)r.A 2:l type solid solution is slable in the system between PbrBir(Seo*Teo.ro),irnd PbrBir(SeorrTeo rr)r. Despite the small range of solid solution of Se analogueof lillianite and the absenceofa 8:3 phase(heyrovskyite{ype)

(- Fig.2. Phaserelations at 500 .C in the systems(a) PbS-PbSe- Bi,S,-BirSer, (b) PbSe-PbTe-Bi,Ser-Bi,Ter,and (c) PbS-PbTe- BirSr-BirTer. Solid circles, half-solid circles, and triangles rep- resentone-, two-, and three-phaseassemblages. L€tters denote a 40 60 Bi253 Bi2Te3 single phase. Shaded area in a representsweibullite solid solu- molo/o tion. tt62 LIU AND CHANG: LEAD AND BISMUTH CHALCOGENIDES

TABLE1. cell dimensionsof the phasessynthesized in the system pbs-pbse-Birs.-Birse.

Chemicalcomposition (molo/o) Celldimension (A) PbS Birs3 BirSe3 Heyrovskyite 82 018 0 13.6q1) 32.57(21 4.23(1) Heyrovskyitesolid solution 55 27 18 0 13.90(1) 32.75(1) 4.2341) Heyrovskyitesolid solution 40 42 18 0 13.96(1) 32.9q1) 4.2q1) Lillianite 73 027 0 13.51(1) 20.5q1) 4.1q1) Lillianitesolid solution 73 022 J 13.62(1) 20.67(',tl 4.11(1) Lillianitesolid solution 73 010 17 13.74(11 20.85(1) 4.15(1) Lillianitesolid solution 73 00 27 13.8q1) 21.0q1) 4.17(1) Galenobismutite JU 050 0 11.81(1) 14.590) 4.08(1) Weibullite 60 00 40 s4.39(1) 4.2O\1) 1s.7q1) Weibullite 45 00 55 54.2',t(11 4.19(1) 15.73(1) Weibullite c 450 50 54.92(1) 4.24(11 15.77(8) Weibullite 20 300 50 54.78(21 4.23(1) 15.71(4) Wdbullite 35 150 50 54.70(3) 4.22(1) 15.6s(5) Weibullite 50 05 45 54.42(1) 4.2q1) 1s.6q1) Weibullite 50 0 15 35 54.18(1 ) 4.18(1 ) 1s.54(1) Weibullite 50 025 25 53.96(3) 4.15(1) 15.51(4) Weibullite 50 035 15 s3.69(1) 4.12(21 1s.46(1 ) /Vote:standard deviations are in parentheses.All phases listed are orthorhombic.

along the PbTe-BirTe.join, a seriesof solid solutions with PbBio(Te.noSrou)and PbBio(TerurSr.r),phase E with compositions PbrBiu(Se,Te),, is stablein the systemfrom compositionsbetween PbBir(Te, rSrr) and PbBir(TerSr), PbrBiu(SeoruTeo 74)17 to PbrBiu(SeorrTeo ro),r. Variations of phase F with compositionsbetween PbrBio(SrTeo) and cell dimensions with composition in the system are shown PbrBio(S.oTe, u), and phaseJ with compositionsbetween in Figure 4. PbrBir(SrrTe, ,) and PbrBir(SrTe). Powder X-ray diffrac- Phaserelations in the systemPbS-PbTe-BirSr-BirTe. tion data and determined and calculatedcell dimensions at 500 "C are shown in Figure 2c. Both phaseA and phase are listed in Tables 2 and 3, respectively. M of the binary join PbTe-BirTe. have ranges of solid solution by S substitution. The A series extends from DrscussroN PbBirTeo to PbBir(TerurSorr)and the M series from The structure ofheyrovskyite is consideredto contain PbBioTe,to PbBio(TeuorrSo rrr). In addition to slabs ofPbS units connectedby a twin operation on one along the BirSr-BirTe,join, five lead bismuth sulfidetel- set of the (l l3)pbsplanes, and its ideal chemicalformula luride phasesare stable in the system.They are designat- should be PbuBirSn(Otto and Strunz, 1968).The sample ed as phaseK with compositionsbetween PbrBir(Teo rSo r) with such a composition gave a two-phaseassemblage in and PbrBir(TeorSo r), phaseD with compositions between this experimental study, whereasthe synthetic composi-

TABLE2. X-ray powder diffraction data for phases D, E, F, and J in the system PbS-PbTe-Bi"S"-Bi"Te"

Phase D Phase E Phase F

du" de d* de dd d* 16 4.6134 4.6242 005 17 4.4210 4.4235 009 53 4.6115 4.6156 0.0.13 16 5.5760 5.5711 (X)3 12 3.6273 3.6299 101 18 3.6027 3.6044 102 36 3.s280 3.5296 0.0.17 13 4.1720 4.1783 004 21 3.2981 3.3030 007 6 3.4361 3.4392 104 83 3.3689 3.3674 107 22 3.5783 3.5795 101 100 3.10163.1016 104 26 3.3230 3.3176 0.0.12 100 3.0385 3.0403 r.0.11 25 3.3420 3.3427 005 10 3.6567 2.6597 106 100 3.0796 3.0807 107 74 2.3225 2.3207 1.0.20 100 3.0585 3.0615 103 6 2.5655 2.5690 009 4 2.9491 2.9511 108 u 2.1890 2.1873 1.0.22 u 2.2162 2.2176 106 4 2.4541 2.4568 107 13 2.6945 2.6963 1.0.10 35 21410 2.1429 0.0.28 23 2.1161 2.1157 110 6 2.3088 2.3121 0.0.10 I 2.5630 2.6541 0.0.15 74 2.1159 2.1141 110 18 2.0899 2.0892 008 39 2.2781 2.2719 108 10 2.5744 2.5752 1.0.11 49 2.1003 2.1024 113 35 2.0020 2.0005 107 44 2.1211 2.1221 110 6 2.3483 2.3500 1.0.13 45 2.03i!3 2.03/'8 118 35 1.8151 1.8149 108 23 1.9544 1.9571 1.0.10 51 2.2464 2.2467 1.0.14 78 1.9699 1.9712 1.1 .1 1 19 1.7911 1.7898 202 16 1.92821.9286 115 I 2.2112 2.2117 0.0.18 69 1.8179 1.81fft 0.0.St 20 1.7413 1.7405 103 I 1.8268 1.8246 1.0.11 49 2.1160 2.1160 110 51 1.7909 1.7905 207 12 1.7847 1.7854 117 I 2.0585 't.7514 2.0586 1.0.16 52 1.7291 1.7282 1.1.20 25 1.7519 204 28 1.9733 1.97U 1.0.17 10 1.9093 1.9088 119 10 1.8956 1.8958 0.0.21 11 1.8195 1.8190 1.0.19 16 ',t.7849 1.78l'0 1.1.12 30 1.7447 1.7442 207

/Voteidiffraction conditions: Kc, I : 1.5418 A, Ni filter, peak height intensities,W metat (99.99997o)as internatstandard, with (110) at 40.2e, cutoff lV 20. LIU AND CHANG: LEAD AND BISMUTH CHALCOGENIDES I 163

(a) (b)

4 r76

444 tz5 4.42 4.40 t7.4 438 436 t73 434 o< 4.32 2o< 4.3? t7.2 ag (J .g 4.3o 'g 62.O (J .g 428 l7.l 6r I 426 424 t7.o 422 4.24 420 t69 oto 20 50 40 50 60 70 80 90 too o t0 20 30 40 50 60 70 80 90 loo PbBB16sel Eolf pbBBi6TelT PbrBlUTe' 7 Pb2B12Se5 nolZ PbrBirTe, PbZBaZTe5

(c) (d)

4t8 442 4.2

t6 440 438 ?4.O t4 436 4 4t? 434 4 ?3.8 43? 434 4 r,o 43? 430 23.6 € o< 408 c).! 4"4 (J 4.28 406 426 23.4 426 4?4 404 4?2 4A? ?32

400 4 r8 4 18 416 23.0 416 598 o1o2030405060708090 r00 o I0 20 an 40 50 60 70 90 roo PbBi4SeT molZ PbBi4TeT PbBi4TeT PbBirSeO uolZ PbBirTeO PbllirTeO

Fig.4. Variations of cell dimensions with composition for (a) PbrBiu(Te,Se),,solid solution, (b) PbrBi,(Te,Se)' solid solution, (c) PbBi,(Te,Se)osolid solution, and (d) PbBio(Te,Se),solid solution, synthesizedat 500 "C.

tion of PbroBi2oseindicates a structural formula of formula of Pb3*-,Bi2,rr,Su (or Pb3'8Bir,rS.), has a mono- (Pb54Bio4)BirSn,in which 0.6Pb atoms are replacedby clinic symmetry and is not a dimorph of lillianite. No 0.4Bi, relative to nine S atoms. The natural heyrovskyite stability field of xilingolite was found in this system.The has compositionsranging from [PbonrBio,.o(Ag,Cu)o or]BirSn above results show that in these slab-twinning structures to [PbrrrBio.o(Ag,Cu)o ,8]Bi2Se, in which the coupledsub- of lead and bismuth sulfosaltsa certain amount of Bi is stitution of Bi + (Ag,Cu) + 2Pb is used to satisfy the required to fill in the Pb sites to stabilize the structures. structural requirement. The with the ideal hey- With the substitution of S and Se, weibullite has an rovskyite formula (PbuBirsr) and monoclinic symmetry, extensiverange ofsolid solution in the systemPbS-PbSe- which was named aschamalmite(Mumme et al., 1983), BirSr-BirSer.The extent and limit of the solid solution is not a stablephase in the systemat 500 "C. For lillianite, may be structurally controlled. The of the ideal formula is PbrBirSu(Otto and Strunz, 1968), weibullite comprises two elongated blocks (Mumme, which produced a two-phaseassemblage in the systemat 1980).One block has an octahedralgalenalike structure, 500 "C. The syntheticcomposition of Pb282Bi, ,rS. shows and the other block contains Pb and Bi atoms in irregular a substitution of 0. l2Bi for 0. I 8Pb in terms of the struc- coordinations. Both blocks elongate along (001) and are ture formula. Xilingolite (Hong et al., 1982), with the in alternating sequence.The octahedral block has the tt64 LIU AND CHANG: LEAD AND BISMUTH CHALCOGENIDES

Trsle 3. Experimentallydetermined and calculatedcell dimensionsof the phases in the tead and bismuth chalcogenidesystems

Cell climension(A) PbX-BirXs Layers in Phase Composition ratio unit cell lAal PbS-PbTe-Bi2Sr-Bi,Te. K Pb2Bir(feo el So @)5 1:1 9 4.44\1) 17.s4(1) 4.47 17.61 0.03 0.07 J PbrBi,(s3Ter) 2:1 I 4.2541) 16.71(1) 4.21 16.71 o.o2 0.00 D PbBil(fe453) 1:2 12 4.24(1) 23.12(1) 4.21 23.14 0.03 0.02 M PbBiiTe?' 1:2 12 4.42(11 24.1q21 4.47 24.06 0.05 0.04 'l:2 M PbBil0eosSo6D 12 4.42(1) 24.O7(11 E PbBi"(S.Ter) 1:1 21 4.23(11 3s.8q1) 4.21 39.85 0.02 0.02 A PbBi"Teo* 1:1 21 4.44(1) 41.7q21 4.47 41.67 0.03 0.03 A PbBi20eo s5Soo5)1 1:1 21 4.42(1) 41.54(21 A PbBi2Oeo e6So o7s)1 1:'l 21 4.40(1) 41.32(5) F Pb3Bi.(SsTe1) 3:2 32 4.2311) 60.00(2) 4.2'l 59.99 0.02 0.01 PbSe-PbTe-Birses-Bi2Tes K PbrBirOeo sSeo 6)s 2:1 9 4.4s(1) 17.s9(1) 4.46 17.57 0.01 0.o2 K PbrBi2(Seo 73Teor7)5 2:1 a 4.27(11 16.93(1) 4.26 16.96 0.01 0.03 PboBi6(Seo6rTeo3s)17 8:3 31 4.33(1) 62.2(1) 4.3!l 58.5 0.0 3.7 PboBi6Oeo sSeo s)r7 8:3 31 4.38(1) 62.8(0) 4.4 59.4 0.o2 3.4 /Vote.'standard deviations are in parentheses. 'Confirmed by structural determination(lmamov and Semiletov,1970; petrov and lmamov, 1969).

overallcomposition (Pb,Bi),.(S,Se)ro, and the other block dimensions. As derived from anionic distribution in has the composition (Pb,Bi),0(S,Se)ro,with 22 of the (S,Se) Bir(Te,Se), (Nakajima, 1963),it can be predicted that Se atoms in common between them. Such an arrangement first fills the inner layersof the unit stacksin Pb-Bi-(Te,Se) allows extensive substitution between S and Se. In gale- solid solutions. nobismutite, on the other hand, the Pb atom is coordi- In the system PbS-PbTe-BirSr-BirTe.,both layer- nated by eight S atoms (Iitaka and Nowacki, 1962), and stacking sequencesand anionic substitution patterns of any substitution of Se for S increasesthe size of the co- the structurescan be derived from experimentally deter- ordinated anions, which is not favored by the eightfold- mined cell dimensions and the schemeof layer stacking coordinatedgalenobismutite structure. describedabove. PhasesK. A. and M contain < l0 molo/o In lead and bismuth tellurides, the subunits of PbTe S ofthe total anion and have nine, seven,and 12 layers (two layers) and BirTe. (five layers) are simply stacked in their unit stacks, respectively, as calculated from the togetherto form the structure of the complex compounds, equation L : 2m * 5n. When one considersthat Pb each subunit keeping its own structural characteristics should be in the regular octahedralposition as in PbX (X (bond length,bond angle,coordination configuration).The : S, Se, Te), and when one also refers to the structures resulting structuresare all hexagonalin symmetry, simi- of PbBirTeo and PbBioTe, determined by Petrov and lar to BirTer. The number of layers in the complex com- Imamov (1969) and Imamov et al. (1970),the Te end- pounds depends on the chemical composition (Imamov members of the phasesK, A, and M are predicted to have and Semiletov, 19701,Imamov et al., 1970).If the for- layer sequencesof TeBiTePbTePbTeBiTe, TeBiTePb- mulas ofthe compoundsare expressedas mPbTe.nBirTer, TeBiTe, and TeBiTePbTeBiTe TeBiTeBiTe in their unit the number of layers (Z) in the unit stack of the structure stacks,respectively. The substitution ofS for Te suggests is (2m + 5n), and the total number of layers (A) in the that S occupiesthe inner 3,2, and 3 anionic layersofthe cell can be expressedby the equationN: Z(2m + 5n), unit stacks in phases K, A, and M, respectively, when where Z is the number of formula units in the unit cell one considersthat the inner positions ofthe stack exhibit and can only be determined experimentally. Cell dimen- bonding more ionic in nature, as suggestedby Nakajima sions of the compounds can be predicted by the equation (1963) for Bi,STe, and BirSeTer,in which S and Se oc- cupy the inner sites. The resulting anionic substitution an*: Yz(a'n* + at2",); cn^: (Z/3)(mai3'h+ n(h.,) pattern for phasesK, A, and M is one in which the inner where a(.. and ci.- are cell dimensions of BirTer, arrd ai anionic layersaccommodate up to 16.7, 17.5, and 17.5 is the cubic cell dimension of PbTe. molo/oS in their structures, respectively.These are rela- Experimental data from this study show that structures tively large amounts when one considersthat PbTe can and cell dimensions of lead and bismuth tellurides and accommodate only l0 molo/oPbS in its structure at 500 of Se-Te solid solutions follow exactly the scheme de- 'C. On the other hand, the random substitution of S in scribed above, although pure lead and bismuth selenides all the anionic layerslimits the substitution to < l0 molo/0. from this study cannot be indexed on the basis of hex- PhaseE has 50-55 molo/oS ofthe total anion and seven agonal symmetry. Table 3 lists four phasesestablished in layers in the unit stack, as calculated.Compared with the the system PbSe-PbTe-BirSer-BirTe,with their compo- structure of PbBirTeoflmamov and Semiletov, 1970)and sition types, number of layers in the unit cell, and cell BirSTe, (Harker, 1934),the atomic arrangementin phase LIU AND CHANG: LEAD AND BISMUTH CHALCOGENIDES I 165

E may be TeBiSPbSBiTefor 50 molo/oS (PbBirSrTer). RrrpnrNcns cmED For 55 molo/oS (PbBirSrrTe,r), the two Te layersmust accommodate l0 molo/oS, which is consistent with the Benoit, P.H. (1987) Adaption to microcomputer of the Appleman-Evans solid-solution rangeand the resulting anionic substitution program for indexing and least-squares refinement of powder-diffiac- pattern of phaseC (tetradymite,BirSTer-BirS, ,Te, ,). tion data for unit cell dimensions. American Mineralogist, 72, l0l8- PhaseD has 43-48 molo/oS of the total anion and 12 t019. Tedenac, and Maurin, M. (1983) Investigation layers in the unit stack, as calculated. By with Chami, R., Brun, G., J.C., analogy of ternary lead-bismuth-: Study of the section the structure of PbBioTe, (Petrov and Imamov, 1969), (PbTeFbismuth telluride @i,Te,). Revue de Chimie Min6rale, 20, 305- the layer sequenceof the unit stack may be TeBiSPb- 313 (in French). SBiTe TeBiSBiTe, which is actually a seven-layerphase Craig, J.R. (1967) Phaserelations and mineral assemblagesin the Ag-Bi- E (rucklidgeite) unit stack with an additional five-layer Pb-S system.Mineralium Deposita, l,278-306. B., Brun, and Tedenac, (1985) Phasedi- phase Dumas, J.F., Liautard, G., J.C. C (tetradymite) unit stack. If the substitution data agrams of lead-bismuth-tellurium systern. Calorimetrie et Analyse obtained from these structures were used, the four Te Thermique, 16, 335-341 (in French). layers in the phase E and phase C unit stacks could ac- Elagina,E.I. (1961) The systemPbSe-B!Se,. Voprosy Metallogenii Fiziki commodate up to l0 molo/oS, and the amount of S in Poluprovedikov, Akademiya Nauk SSSR,Moscow, 153-158 (in Rus- phase D would be in the range 43-49 sian). of molo/oof the Elagina,E.I., and Abrikosov, N.Kh. (1959) An investigationofthe PbTe- total anion, which is in good agreementwith the experi- Bi.Te, and SnTe-Sb,Te.systems. Russian Journal oflnorganic Chem- mental data obtained. The result also confirms the atomic istry,4,738-740. arrangementproposed for phaseE. Godovikov, A.A., Nenasheva,S.N., and leibson, R.M. (1967) kad se- PhaseF has a PbX-Bi,X, ratio of 3:2, with 56-60 molo/o lenium-bismuth system.Trudy Institut Geologii i Geofiziki, Akademiya Nauk SSSR,Sibirskoe Otdelenie, 5,34-54 (in Russian). S ofthe total anion. Its calculatedunit stackhas I 6 layers. Golovanova, N.S., and Zomanov, V.P. (1983) Reaction of lead telluride The layer sequencemay be arranged as TeBiSPbSPb- with . Izvestia Akademie Nauk, SSSR,Neorganiches- SBiTe TeBiSPbSBiTe,in which the amount of S is 56 kie Materialy, 19, 74O-7 43. molo/oof the total anion. By using the anionic distribution Harker, D. (1934)The crystal structureof the mineral tetradymite. Amer- data of phasesC, D, and E, in which the ican Mineralogist, 19, 6l-70. outer Te layers Hirai, T., Takeda, Y., and Kurata, K. (1967) The pseudo-binaryV'VI]- accommodate up to l0 molo/oS, the resulting amount of IV-VI cornpounds syslems, Bi,Te,-PbTe, BirTe,-SnTe, Sb'Te,-SnTe S (predicted)in phaseF would just be in the rangeof 56- and BirSe.-SnSe.Journal of kss-Common Metals, 13, 352-356. 60 molo/oof the total anion. PhaseJ has a composition Hong, H., Wang, X., Shi, N., and Pene,Z. (1982)Xilingolite, a new sulfide range of 60-64 molo/oS of the total anion. Its calculated oflead and bismuth, Pbr*.Bir-/r-56. Acta PetrologicaMineralogica et Analytica, I, 14-18 (in Chinesewith English abstract). unit stack has nine layers, with a sequence of TeBi- Iitaka, Y., and Nowacki, W. (1962)A redeterminationof the crystal struc- SPbSPbSBiTe,and the outer two Te layers may also ac- ture of galenobismutite, PbBi,S". Acta Crystallogaphica, 14, l29l- commodate0-10 molo/oS. 1292. In summary, the ternary compounds and solid solu- Imamov, R.M, and Semiletov, S.A. (1970) The crystal structure of the phases Bi-Se, Bi-Te, and Sb-Te. Kristallografiya, 15, tions formed in the system PbS-PbTe-BirS,-Bi,Te, in the systems are 972-978. actually composedof severalbasic structures,such as five- Imamov, R.M., Semiletov, S.A., and Pinsker, Z.G. (1970). The crystal layer (phaseC, tetradymite), seven-layer(phase E, ruck- chemistry of semiconduclorswith octahedraland mixed atomic coor- lidgeite), and nine-layer (phase J), and their combina- dination. Kristallografiya, 15, 287-293. gruva. tions, such as phase D (five and seven layers) and phase Johansson,K. (1924) Ett par selenforandemineral frln Falu Arkiv ftir Kemie Mineralogi och Geologi, 9, l-7. (seven F and nine layers). PhasesK, A, and M may be Klominsky, J., Rieder, M., Kieft, C., and Mraz, L. (1971) Heyrovskyite, considered as binary solid solutions in which small 6(Pbo,uBioor(Ag,Cu)o @)S' Birsr from Hurky, Czechoslovakia,a new amounts of S are randomly distributed in the Te layers. mineral of geneticinterest. Mineralium Deposita, 6, 133-147. Combining experimental resultsestablished in the lead Kullerud, G., and Yoder, H.S. (1959) Pyrite stability relations in the Fe-S 2. and bismuth chalcogenide systems with system.Economic Geology, 54, 533-57 the structural Makovicky, E. (1981) The building principles and classificationof bis- features of the end-members, the composite layer-type muthlead sulfosaltsand related compounds. Fortschritte der Miner- structures should also have the following characteristics: alogie,59, 137-19O. (l) PbX layers form the central parts ofthe unit stacks. Mumme, w.G. (1980) Seleniferouslead-bismulh sulphosaltsfrom Falun, (2) As in PbX compounds, the PbXu polyhedra should Sweden: Weibullite, wittite, and nordstrdmite. American Mineralogist, 65,789-796. be regular, and so the two X layers above and below the Mumme, W.G., Niedermayr, G., Kell, P.R., and Paar, W.H. (1983) As- Pb layer should be the same in composition. (3) On the chamalmite, Pb, ,rBi, *Sr, from Untersulzbach Valley in Salzburg, Aus- basis of the structure of tetradymite, if two or more chal- tria: "Monoclinic heyrovskyite." Neues Jahrbuch fiir Mineralogie cogen elements are present, the smaller one should oc- Monatshefte,433. (1963) of BirTe, Physics cupy the inner layers ofthe unit stacks.(4) The Nakajima, S. The crystal structure ,Se,. Joumal degreeof and Chemistry of Solids, 24, 479-485. substitution among the chalcogenelements in eachX lay- Otto, H.H., and Strunz, H. (1968) Zur Kristallchemie synthetischerBlei er should be similar to that in their end-members. Wismut-Spiessglanz. Neues Jahrbuch liir Mineralogie Abhandlungen, 108,l-19. AcxxowlrocMENTs Petrov, I.I., and Imamov, R.M. (1969) Electron difFaction study of phases in the lead telluride-bismuth telluride system.Kristallografiya, 14,699- The authors are indebted to Peter Bayliss and W.G. Mumme for re- 703 (in Russian). viewing the manuscript and for making valuable comments. Skoropanov, A.S., Valevskii, B.L., Skums, V.F., and Samal, G.I. (1985) I 166 LIU AND CHANG: LEAD AND BISMUTH CHALCOGENIDES

Physicochemicalinvestigation of lead (germanium) telluride-bismuth Zhukova, T.B., and Zaslavskii, A.I. (1976) Characteristicsofpowder pat- () telluride (Pb(Ge)Te-Bi,(Sb,)Te.)system ternary compound terns of compounds in the PbTe-Bi,Te. system. Izvestia Akademie formation. Thermal Analysis, Proceedingsof the 8th International Nauk, SSSR,Neorganicheskie Materialy, 12,539-541 (in Russian). Conferenceon Thermal Analysis (August l9-23, 1985), l, 595-598. Van Hook, H.L. (1960) The ternary system AgrS-BirS,-PbS.Economic MeNuscnrvr RECEIVEDJnr.n-renv ll,1994 Geology, 55, 759-788. MeNuscnrsr AcCEPTEDJvtv 28,1994

ERRATUM

An improved method for algebraic analysis of metamorphic mineral assemblages,by GeorgeW. Fisher (v. 78, p. 1257-1261). Tim Fagan of the University of California, Davis, has pointed out that Equations 19 and 20 are incorrect. They should read as follows: (D.A).(D.B): C (1e) Bb: (D.A)\(D.C). (20)