Bull. Mater. Sci., Vol. 22, No. 2, April 1999, pp. 103-108. © Indian Academy of Sciences.
X-ray studies on microstructural characterization of tantalum substituted tungsten mixed molybdenum diselenide; W0.6sMo35_xTaxSe2 (0 _< x <_ 0-35)
DEBASHIS PALIT*, S K SRIVASTAVA* and B K SAMANTAY RAY* Department of Chemistry, ~ Department of Physics, Indian Institute of Technology, Kharagpur 721 302, India * Present address: Department of Chemistry, University of Chitlagong, Bangladesh
MS received 2 November 1998; revised 19 January 1999
Abstract. The wide angle X-ray diffraction on W0~sMos_xTaxSe2 (0 Keywords. Tungsten diselenide; tantalum diselenide; microstructure parameters. 1. Introduction their intercalation compounds are useful as high tempe- rature and high pressure lubricants, electrode materials During the past few years there has been a great deal and in secondary batteries, solar energy conversion pur- of research in the study of the properties of materials poses and in the field of catalysis etc. In this regard, having layered type of structure. Probably the greatest MoSe2, WSe 2 and TaSe 2 constitutes structurally and attention has been focussed on transition metal dichalco- chemically well defined family of compounds which find genides (TX2: T = group IV, V and VI transition metals, various applications for modern purposes (Srivastava and X = S, Se, Te) because of their unique properties and Avasthi 1981, 1985). Their crystal structure results from which covered a wide range of spectrum e.g. semi- the hexagonaily packed atoms in the sequence X-T-X, conducting, insulators, metallic and superconducting X-T-X. Within each X-T-X layer the T is either in (Wilson and Yoffe 1969; Subba Rao and Schafer 1979; trigonal prismatic coordination or in octahedral coordi- Srivastava and Avasthi 1981, 1985, 1993; Srivastava nation. The typical layer type structure of MoSe 2 and 1989; Young and Frindt 1996; Srivastava et aI 1997). WSe2 and identical radii of Mo and W suggested the The distinctive feature of these two dimensional materials formation of isomorphous MoxWt_,Se 2 (0 103 104 Debashis Palit, S K Srivastava and B K Samantay Ray ranging from 0-90 to 0.99. Further studies by Palit et al where (1997) have shown that W.65Moo.3sSe2 and W0.65Ta03sSe2 For radial distribution analysis (RDF) and differential strain ((e2)~n), dislocation density p, crystallite size aniso- radial analysis (DRDF) the intensities as observed for tropy (P~/P~o3) and-stacking fault probability (ct) for each of the samples were corrected for respective back- Wo.65Mo0.3s_xTa#Se2 (0 Table 1. Lattice parameters and other crystallographic data for W0.6sMOo.35_~TaxSe2 (0 ~ x ~ 0-35). W~r~M%3s_ ~TaxSe2 a (A) c (A) c/a v (A)3 x = 0-00 3.269 + 0-001 12.959 + 0.002 3.959 119,85 x=O.05 3.279+0.001 12-904+0-003 3.934 120.19 x = 0- ! 5 3-294 + 0.002 12.843 + 0.001 3.899 120.68 x=0-25 3.305+0.003 12.832+0.002 3.882 121.39 x = (~35 3-345 + 0.002 12.802 + 0.001 3.827 124.05 Table 2. Microstructural and layer disorder parameters of W0.65Moo.35_xTaxSe2 (0 _ By /'~ ((e2)),/2 p (1015) Wo.65Moo.3s_~Ta.,Se~ (A) (10-3) lines m -2 g ~, p~,2/P~oa a x = 0.00 280 295 2.69 0.96 0.04 0-001 2.10 0.02 x = 0.05 260 280 3.27 1.40 0.05 0-003 3.11 0.04 x = 0.15 220 250 4.80 2.20 0.10 0.004 4.44 0.08 x = 0.25 275 295 3.09 1- I 1 0.05 0-002 4-83 0.07 x = 0.35 280 310 5.83 1.95 0.02 0-007 I 1.0 0.18 X-ray studies of Wo.65Mo35_xTaxSe 2 107 fiB) ~) I:T I I I I I I 2 3 /-, S 6 7 8 9 2 3 /. 5 6 7 O rCA) ,.(~) Figure 2. (A) Radial distribution function (RDF) and (B) diflerential radial distribution function (DRDF) curves for Wo.65Moo.35_xTa,Se2; (a) x=0, (b) x=0.05. (c) x=0.15, (d) x=0.25 and (e) x=0.35. Table 3. Coupling constant and mean square displacement data of Wo.65Moo.35_xTaxSe2 (0 _ c.c. peak ~2 (/~) peak Wo.65Moo.35_xTa Se2 I 2 3 4 5 1 2 3 4 5 x=0-00 0-21 0-32 0-35 0-58 1.00 1.73 2.76 1.08 1.08 1.38 x=0.05 0.20 0.38 0.54 0.60 1.00 1-08 1-55 3.00 3.24 5.54 x=0.15 0.25 0.36 0.56 0.56 1.00 !.08 1.55 2.43 2.43 4.32 x=0.25 0.25 0.56 0.56 0.61 1-00 1.08 2.43 2.43 2.65 4.32 x=0.35 0.20 0-43 0.52 0-62 1:00 1-38 3.00 3.63 4.32 6.93 confirmed that the M-Se bond corresponding to this References interatomic distance according to White and Lucovsky (1972) is strong and covalent. The coupling constant Agarwal M K and Wani P A 1979 Mater. Res. Bull. 14 825 Agarwal M K, Patel P D, Patel J V and Kshatriya J D 1984 values are relatively much greater corresponding to M-Se Bull Mater. Sci. 6 549 and Se-Se bonds for the second and third peaks in RDF Bissessur D C, DeGroot J L, Schindler and Kannewurf C R curves suggesting thereby a weak interlayer bonding. 1993 J. Chem. Soc. Commun. 687 These studies also further supported the suggestion of Brixner L H 1963 J. Electrochem. Soc. U0 289 White and Lucovsky (1972) that there exists a Se-Se Brixner L H and Teufer G 1963 Inorg. Chem. 2 992 interlayer bonding. Cromer D T and Weber J T 1971 Acta Crystallogr. 18 73 108 Debashis Palit, S K Srivastava and B K Samantay Ray Gamble F R 1974 J. Solid State Chem. 9 358 Srivastava S K 1989 Mater. Res. Bull. 10 211 Hazdu F 1956 Acta Crystallogr. A2rl 73 Srivastava $ K and Avasthi B N 1993 J. Mater. Sci. 28 5032 Hofmann W K 1986 J. Crystal Growth 79 93 Srivastava S K, Mandal T K and Samanta Ray B K 1997 Synth. Kaplow R, Rose A and Averbach B L 1968 Phys. Rev. 168 Metals 90 135 106 Subba Rao G V and Schafer M W 1979 Intercalated layered Krough-Moe J 1956 J. Acta Crystallogr. 9 951 mater/als (ed.) F Levy (Dordrecht: Reidel) p. 99 Kruh R F 1967 Handbook of X-rays (ed.) F E Kaelble (New Young D and Frindt R F 1996 J. Appl. Phys. 79 2366 York: McGraw Hill) Ch. 22, p. ! 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