Thakurta, Guha S R

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940 Letters to the Editormeasured by Mangal et al, to be 2.8% as compared to 366 KeV gamma-ray. There­fore, the relative intensity of 222 KeV gamma-ray relative to 366 gamma-ray cornea out to be 0.28^0.03. The error includes the summing effect of the K-x ray which is in coincidence with all the gamma-ray transmitions because of the elec­tron capture decay of Ba^ *®.R E F E R E N C E SOasemann, B., Pengra, J, G. and Lindstonn, 1. E., 1957, P h y a . R e v . , 108, 1500. Fagg, L. W., 1958, P h y a . R e v . , 109. 100.Gupta, R. K., tlha, S., Joshi, M. C. and Madan, B. K., 1958, N u o v o  C im e n to , 8, 48. Ramaswarny, M. K., Skool, W. L. and Jastram, P. S*, 1960, N u c l .  P h y a . , 16. 619. Kantole, J. and Fink, R. W., 1961, N u c l .  I n a t . a n d  M e th o d s . , 18, 141.Kantole, 1962, N u c l .  I n a tr .  a n d  M e th o d s , 17, 33.Mann, K. C. and Chaturvedi, R. P., 1963, G a d . J .  P h y a . , 41, 932.Mangal, P. C., Sud, S. P. and Trehan, P. N., I n d ia n  J .  P u r e  A p p l .  P h y a ., (San for pub­lication).Stewart, M. G. and Lu, D. C., 1960, P h y a . R e v . , 117, 1044.Thun, J. E., e t a l . ,  1966, N u c l .  P h y a . , 88, 289.37THERMOELECTRIC POWER OF TUNGSTENITE (WS,) SINGLE CRYSTALSS. R. GUHA THAKURTAD X F A ltT M E N T  0 7  M A O IT E T IS II,  IN V IA K  A S S O C IA T IO N  F O B  T H B  ( !C I.T IV A T IO N  O F S C IB N O B ,Cai.ctjtta-32, I ndia (Received January 25, 1968)Thermoelectric power of naturally occuring single crystals (hexagonal) of tungstenite (WS,) have been measured against copper along both the crystallo­graphic directions and over the temperature range 300°K to 820°K. The results of preliminary measurements are shown in table 1 and in figures 1 and 2.It is observed from the table I, that at the vicinity of room temperature the thermo­electric powers of crystals 1 and 3 are positive in both the crystallographic direc­tions while that of crystal 2 is negative in these directions. The magnitude of thermoelectric power at room temperature which varies from sample to sample (evidently due to differences in the impurity contents which however has not been analysed) has been found to be slightly different in different crystallographic direo-Letters to the Mditor 94lTable IT'hermoelectric power in WS2 crystals along both the crystallographic directions at an ambient temperature 312®K (temperature gradientwithin 2°C toActivation onergy alqng the C-axis Activation energy j_r to 6'-axisCrystal the c-axis in /tv/°C within tho range300°~400°K.within 01© range400°~820fK.L.O.p. J,' LUc^axis in / i v r cwithin tho range300”-400^K.within tho range 400°-820^I51. f  4.0 0.6 ov 0 .5 +  16.0 0. .6 ev^ 0.47 ©V2, -3 6 ,6 0.19 ev 0 .3 3  eir --33.5 0.28 ev 0.32 ©V3. +  4.7 0.34 ev 0.47 <|V +  5.0 0.37 ov 0.46 ov4. +  3.4 0. S9 ev 0.44 0!ir — — —tions. At higher temperatures (fig. 1 and fig. 2) the t.e.p. of crystals having posi­tive sign a t room temperature remains always positive throughout the range of temperature studied. But in case of crystals with negative thermoelectric2010Q0.31Ph1S<D2 -2I- 4 09 0 0100 ^00 Ambient Temperature in ' >Fig. 1. Variation of thermoeleotrio power (along o-aads) with temperature.The number on the curve indicates the serial number of the crystal.942 Letters to Mitorpower at room temperature, the sign changes from negative to positive ivith the rise of temperature, and retains this positive sign at higher temperaures. Pre­liminary measurements of Hall effect with single crystals of WS2 also appear to corroborate the above findings.900too 500Ambient Temperature in ®K -►Fig. 2. Variation of thennoeleotrio power ( i r  to o-axie) with temperature. The number on the curve indicates the serial number of the crystal.It may be mentioned here that Lagrenaudie (1954) from Hall effect measure­ments (within the temperature range 77°K—293°K) with powered (artificial) WS2 (activation energy 0.04 ev, 0.11 ev, 0.18 ev), observed that it was a p-t3rpe semicon­ductor, while Jean Deorue (1956) from electrical conductivity measurements in different atomspheres showed that powered (artificial) WS2 (activitation energy 0.17 ev) was a »-type semiconductor, within the temperature range 297®K—373°K.The Author conveys his best thanks to Shri A. K. Dutta for suggestion and guidance and to Prof. A. Bose for his kind interest in the work.B E F E B E 1 7 0 E SDecme, J., 1066. Heh). O hm , A eta., 89, 619, 812. Lagrenaudie, J., 1954. J . Phy«, Bad., 15, 299.

Thermoelectric Power of Tungstenite (WS2) Single Crystals

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Thermoelectric Power of Tungstenite (WS2) Single Crystals

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