Reddy, Y R

Sirdeshmukh, Lalitha

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Letters to the EditorDielectric properties and effective ionic charge of calcium sulphideL a lt t h a  S ir d b s h m u k h  a n d  Y R . R e d d yPhijs'KA J')f‘piirhaeut, Kakaliya University, A P{Itvct'/rmd 9 Awjunl 1977, •rcvi'^ ed 9 February 197H)Indian J. Pftya. 52A, 564-GC7 (1978)The constant of calcium suliiludc was moasurod by Shanna & Gupta(1963) who obtained a value 6-()9 at 7-2 MHz More recently a value of 8-10 | was n^ported b^ ’^ T)j'ofenik & Azman (1972) It can be seen that thoie is considor- ablo difference m the two values From their value of dielectric constant Drofeiiik & Azman (1972) obtained a value of 0 52 for the effective ionic chaige. The valuer dilTers Irom tlnr value 0-43 obtained by Droleiiik et al (1971) from theoretical calculations lii view ol‘ theSe differiiuces, it v as considcjed worth- whili‘ to measuTc tlu> tJiidectric constant and to calculate the effective ionic cliarge of Ca8A ]mtc sani])lc ol CaS, supplied by Roidel dc Hahn was powdered and sieved to j^ et particle size ol ;=r;45/i. Dicr-pressed cylindrical pellets of 2-5 cm in diameter and ^ 5  mm thick wirre iJicpaied The samples weic dried for seveial hours at lOO'X' before taking measurements The dielectric measurements were done at room temperature on a Marconi Circuit Magnification meter TF 1245 m cou- juiiction with a spcruial Marconi Test Jig 155 0/1 in the frequency range 50 KHz to 50 MHzSeveral iirocediires are available tor obtaining diolectiic constant e ot the solid from the mea'^ured dielectric constant ep for the powder samiiles Wo have us(id the following relation suggested by Dube ef al (1971)I (1)where A is a constant with a value 0*5 and $ is the packing fraction.Tn ordm’ to test the aeciiiacy of the procedute adopted, the-dielectric constant of the die-prcssed poAvderod samples of NaCl and KOI (j3artiele size ?:s45/i) of A^ arious packing fractions Avere investigated at 1 MHz, TJic A'^ ariation of f Avith d are given in Table 1. The average value of e for NaCl and KCl arc also shouui along AAith the literature values. The values obtained are ui fair agreement within ± 3 %564Dielectric properties of oalriurn sulphide 565Thin agrt>oinent indicates llial tJie equation iiKod for cletormmiug < from Gp is valid ovor tho rango ot packing fradion 0-7 to O i) lu the proseut investiga­tion measurements were done for samples with paclting fractions ^0*7. A typical frequency vs dielectric constant (c) riirvi^  foi the sainjile witJi packing fraction 0-7 is shown m figure I Tl'.e Irequency de]iendenee, oi tan li is also shown m figuie I Ovei tho range of frequencies eovi'vod m this investigation, tho diolectric oonslant should bc‘ frequency mdependeiit (Lowmh^ s & MariniK'g 1. Variation of dioloctnc constant r and loss (tan «S) o£ CaS with frequenry.1969) Tho vaiiation observod at low froqueiicies is due to factors like unknown impurities and othei- nnperfeciions. The variation ceases at about 2 5 MHz Tho frequency iudopondont value is taken as tho static dielectric constant Hueh,566 Lalitha Sirdeshmukh and Y. R. ReddyaijumaloiLs ul dioloctnu oojiHtaiit and tan 6' havo boonobKervod by C'Uaudliury & Rao (1969) jn the oa.so of s^ ojuo oxide«J^’al)l(^  1. l)iol(!L‘trjo constant of (ndk ooinjmted i'rojii powder sainplo (partielo M7-(^  Jiieasurod at J MHz.l 'I’v-ital SAuthoj s Avoiaf?c Lileraliiic valueNaCl 0 GO fi-760 74 n 79 5 80 0-890 80 5-82 (AndoL'ji t'. ri 1970)0 90 5 88KCl 0 72 1 720 80 4-70 1 73 4 810 90 4-70 (Andoen C. et a? 1970)0-90 4-73Tb(y frocpioJKiy imlepondmit vaJuo of dieloctno eonKtaut t i4 u.stid to erftnuato tlio olfeetivc  ^ iome ehaige (/* from the Szigoli (1950) equation( )^where oj^  ls Hu? rostrtd\len frequGllc■.^  ^ it the refraedive mdex, m tJie reduced ]iias,s. Zc ili(i foiinal charge and v the volume jier ion pair Tim v^ alue of cup is Lalusii Iroin Drofenik & Azmaii (1972), n. is taken lioin ''Hand Book of Physics and Ohomistry’ (Clumiical Rubber Oo 1973-1974). /; is eStiiualod from r the nearestneig]d ‘^>i»’ distance taken from Guiitert Faessler (1956). The values of ( and (j* arii given in table 2 along with those given by earlu^ i workersTabki 2. Uielocti'ie constant and JSzigeti charge of CaS.PresentworkDrolenikandAzman(1972)DojTonik Shanmi Koltei'anrl andGupta Azman(19C3) (1971)7 11 0*418 10 0-52'J’h.e data given in table 2 shows that the present \'alue of c is closer to the value ohtaiiied by Sharma Gupta (1963) than that obtained by Drofenik & Azman (1972) Oui value of q* is ddfereut from tlic value obtained by Drofenik & Azman (1972). How'ever it agiees wmll Avith theoretical value obtained by Drofenik c/ ul (1971).C o m p lex  p erm ittiv ity  and con d u ctiv ity 567Oui- tlianka arc due to Prof D !B. Sirdeslumikli for Ixclpful cli^ iouswioiiH One ol ua (\ .R R ,) tli,aaiks tlut t\S J R. tor tlio awaid of a ftllmvshipR e f e r e n c e sAndeou C., FoiUanoUa .1 & Schuolo D 1970 Phys Rev. B2, 500S ChoudhuryA K. efe llao K  V Piiys. ,Slat Sol 32,Drofenik JVl., Kcjitoj- d. & \zman A 1971 Z , NcUumJh 269, 325.Drofemk M. & zVzmaii A. 1972 7. Phys Chvm. SoUds 33, 761Dubo D. C., Yodav K S. & Tavahad R 1971 Iv d . J  Pure. A pp l. P hys 9, 719Guuiort O J. & RaoHhk'v A. 1956 Z  K rist. 107, 357L owiuIrs R. J'. & Martin 11. IT. 1969 Proc R oy Soc {Land.) 308A, 473Sharma H N & Gujaa H. ,S. 1963 Im l J  Phys. 37, 33.Szigoti B. 1950 P/oc, Roy. Sot {London) 204A, 50In d ia n  J .  Phys. 52, 567-572 (1978)Microwave measurement of complex permittivity and conductivity of silicon by a simple techniqueR N a t a r a j a n , D  0 D u b e  a n d  V  K  T b ip a t h iDcpurlnmil of Physioi, Indian Inshl'uie of Teohiohu/y,Delhif New J0029{Received 4 (kioher 1977, revised 23 March 1978)TJxo [H'oportiea of aciniconductois at luicruwavo frotiuoiioie.s atuduid oarliui' CBeiicdiet A; Slioekloy 1953, 'RomidKst 1953, Goldlov &. Brown 1955) fall jnto two eat-e.^ ories Tn tho first, the soinkionduot.or parameters wtue obtaijied from the propagation rharaotiai,sties of the i/ianhinitteid signal The otlier ielates tt> the changes intioduced hy the sample msidci a cavity in tlie resonant trequeiicy and quality factor Moiitgoineiy (1947) Prom devices’ point of view, the con­ductivity is one of tho most important paianieters which at microwave fioqueiioios htxeomes complex. zVs the time peiiod ol tlvo wave is coinparablo with the mean floe time of carriers, the i‘(,al and imaginary parts of conductivity are of the same order i.c , the relaxation effects are important The earlier wtirkeis employed (Ic mothods to investigate the conductivity behaviour of semieonductors But these methods aulfer ft cm the limitations of using low eurients to avoid heating of samples and having ohmic and surface contacts. HoAvovor, miorowavo methods automatically overcome those difficultiesIn the present paper nioasuroments made on silicon wafers, of different resistivities, for tho determination of the complex permittivity and the micro­wave conductivity variation with toniperaturo are reported using a different technique.9

Dielectric Properties and Effective Ionic Charge of Calcium Sulphide

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Dielectric Properties and Effective Ionic Charge of Calcium Sulphide

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