Elastic properties of As-Sb-Se glasses

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Aug 23, 1983 - The results of measurement of glass transition temperature (TJ, electrical conductivity and density (d) on glasses of the As-Sb-Se system were ...
Elastic properties of As-Sb-Se glasses A GIRIDHAR, SUDHA MAHADEVAN and A K SINGH Materials Seieoce Division, National Aeronautical laboratory, Bangalore 560017, India

MS received 27 June 1983; revised 23 August 1983 Abtmet. Results of measurement of elastic moddii on As-SbSc &SXS are reported and 1heirmmpositiandcpcndenccd-ssed.TheYaung'saod tbesheacmoduliilieiuthe rangeof 17&2IO and 6S80 kb mpcctivcly. These values are t y p h l of chabgcnidc glasses. For (As, Sb),Sc,, glasses, the modvlii increase monot0nid.y with increasing Sb& content. The observedcompositiondcpendenceofthemoduliifor t h e A s S b , , S e . , . , ~ i s e r a m i n e d i n terms of the chemically ordered structural units in the glassis.

Keywords. As-Sb-Se glarses ekstic properties; CONM model.

1. Introduction The results of measurement of glass transition temperature (TJ,electrical conductivity and density (d) on glasses of the As-Sb-Se system were reported earlier (Giridhar and Sudha Mahadevan 1982). The study covered two groups of glasses: (i) those whose composition could be represented by (As, Sh),,Se,, and (ii) those whose composition could be represented by As,Sb,,Se,,_,. The (As, Sb),,Se,, glasses fall along the (As&,) (Sb,Se,) pseudobinary section and represent the so-called 'stoichiometric' compositions of the As-Sb-Se system. The T,, electrical conductivity and d of these glasses showed a monotonic increase with increasing Sb,Se, content. In the As,Sb,,Se,,+,glasses, with thestoichiometricAs,,Sb,,Se,,compositionasreference, glasses with more than 60 at. %of Se were referred to as Se-rich glasses and those with less than 60 at.% of Se as As-rich glasses of this family. The As,Se,,,-, and Ge,Sh, $e,, glasses show an extremum in T, and d at the respective stoichiometric compositions (Myers and Felty 1967; Mohan et al 1981; Narasimham et al 1981; Giridhar et al1981). The composition dependence of T, and d of the As, Sb,, Sea,-, glasses exhibit an interesting feature, namely, that the T, and d of the As-rich glasses of this famil yare higher than thoseoftheAs,,Sh,,Se,,composition (Giridhar and Sudha Mahadevan 1982). The results of measurements of elastic properties on eight glass compositions are reported in this paper. Four ofthesecompositionscan be represented by (As, Sb),,Se,,, while the other four belong to the As,Sb,,Se,,+, family. ~j

2.

Experimental

The cylindrical samples (about 12 mm in diameter and 6 mm in length) suitable for ultrasonic sound velocity measurements were obtained by the following procedure. 1001

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A Giridhar, Sudha Mahadeuan and A K Singh

The elemental components (SN purity, from Koch Light Co.) in appropriate proportions were sealed in a quartz ampoule (12 mm in diameter) under a vacuum of LO-'torr.Shecontentsoftheampoule were meltedinarotaryfurnaceatabout9M"C for 24 hr. The melt was then cooled to 8W°C and quenched in water at 90°C.Care was taken to see- that the ampoule stayed in a vertical position during the quenching operation. Quenching in hot water rather than in cold Water was found essential to prevent any cracking or shattering of the cylindrical sample during further processing. The ampoule was then introduced into a tubular furnace where the glass was annealed at a temperature of about 5" higher than T, for I hr and then brought to room temperature by slow cooling lust before breaking open, the ampoule was chilled in an ice bath for 15 min to facilitate retrieval ofthe s e m e n from the ampoule. She f a n s of the cylindrical samples thus obtained were rendered Rat and parallel (the wedge angle being better than 0.2 sec) using a lapping-polishingjig specially designed and fabricated for this purpose. Using Salol (phenyl salicilate) as the bonding matsrial the longitudinal and transverse velocities in the samples were measured (at 2YC) by using 10 MHz X s u t and Ycut transducers, by McSkimin's pulse superposition'technique (McSkimin 1961; McSkimin and Andreatch 1962). As already indicated (Sudha Mahadevan er of 1983). an ultrasonic pulse echo interferometer (supplied by Systems Dimensions, Bangalore, model sou1-003) in conjunction with a SO MHz Philips oscilloscope and frequencyltime interval counter (accuracy of one nsec) was used for this purpose. The accuracy of velocity measurements limited mainly by thickness measurenlents (for which a Mitutoyo height mster transfer stand combination was used), was 0.03 %;A spread of about 1.5% was observed in the velocities in different specimens of the same composition. The typical quality of the echo pattern obtained in our set up is shown in figures 1-3. A train of 1&12 echoes could be obtained in most cases (figure 1); this is because of the high parallelism of the faces. The measurement of the delay time was facilitated by the good resolution obtained in the amplitude of the expanded echoes (figures:2 and 3).

3. Results and discussion 3.1

(As, Sb),,Se,, glasses

The results for these glasses are summarised in figure 4 and table 1. The shear (C).the Young's (E), the bulk (K)modulii and the Poisso'n's ratio (u)of (As, Sh),,Se,, glasses increase monotonically with increasing Sb,Se, content (figure4). Extrapolation ofG, E, K and a values (figure 4) of these glasses to zero Sb,Se, content, which corresponds to As,%,, gives the values of modulii which agree well with one set of reported values for As& phompson and Bailey 1978). She other values (Hilton and Hayes 1975; Soga and Kunugi 1973) fall slightly away from the extrapolated data Also shown in figure 4 is the variation of the mean atomic volume with composition. For isostructural crystalline compounds, the bulkmodulus increases withdecrease in volume (Anderson and Nafe 1965). However, in our discussion (Sudha Mahadevan er al 1983) of the variation of K with mean atomic volume ofseveral chalcogenide glass systems, namely Ge-Sb-Se, Ge-As-Se, Ge-Sb-S and Ge-Se, it was Seen that the m a n atomic volume is not the only factor determining the bulk modulus of these glasses. Besides volume, other factors such as the nature of the type of bonding could also he effective in

As-Sb-Se glasses

I003

Figures 1-3 1. Typicalexponential sha train for a Ar,,Sb,,Sc,, samplc for longitudinal waves. 2. Erpanddecho wave form for pulw superposition for p = 2. minimum ampllrude. 3. Expanded s h o wave form for puke superposition for p = 2. maximum ampiitude.

1004

A Ciridhar. Sudha Mohadeoan and A K Singh

determining the bulk modulus. In (As. Sb),,Se,, glasses, (figure 4) the bulk modulus increases with increasing Sh,Se, content while the corresponding volume has also increased. Therefore, the type of bonding, rather than the volume has greater influence in determining the bulk modulus 01 these glasses. 0

Thompson and B o i l q , 1978

Sogo and K u n u g ~ .1973 Hilton and H o p s , 1975

G

Ik

bars1

65 -

210

E l k bars) 190 -

170

K k bars1 17.04

130 -

"a Cc/rnolel

032 -

16-84

-

U

028-

-

i - 1 0

20

10

~~

Atomic percent of Sb in ( A s . SbIw Ses0

F i p 4. Varialion of elantic modulii and m a n atomic volume for (As, Sb)&,, show ss B function of Sb content. Data for As,%, are fiom Lteratuce.

Tabk Grnpsition

1. Elastic data for As-Sb-Sc M

dW-1

(As:Sb:%)

35:15:50 3O:lJ:JJ 25:15;60 20:15:65 10:15:75 35: 5:W

Long. "el c, Im/W

s

Trans.

Shear

Young's

Bulk

Poi-n's

"el. c, (mirec.)

mod.

mod. E &bars1

mod.

ratio

C (kbzrs)

4.990 4-93 4.980 4.920

202.05

4.8543

17014 181.24

30:lO:W

4-7Y) 4-8M

22:18:W

SOLO

gkrscs

199.46

202-30 186-05

188.50

211.40

0

K lkbarrl 159.97 159.21 173.26 151-78 129.66 14480

156-07 19014

02895 02912 03054 02957 02813 02914 02987 03147

As-Sb-Se %/awes

3.2 AsSb,,Se,,.,

1005

glasses

The data for As,Sb,,Se,,-, glasses are shown in figure 5 and table 1. With the stoichiometric composition As,lSb,,Se,, as reference, the G and E of As-rich glasses are seen to be essentially constant while those of the Se-rich glasses show a decrease with increasing Se-content.The bulk modulusexhibitsamaximumforthestoichiometrk composition (figure5). Also shown in figure 5 is the variation of the mean atomic volume with composition. Based on the denease of the mean atomic volume With increasing As content in the As-rich glasses, an increase of bulk modulus is expected, while it is seen that the bulk modulii of these glasses have decreased (figure 5). In Ge-Sh-S and Ge-Sb-Se systems (Hayes et al1974; Hilton and Hayes 1975; Sudha Mahadevan er al 1983) the Poisson's ratio (u)increases with increasing chalcogen content. As u denotes the ratio of transverse to longitudinal strains which arise from a single tensile stress, its h e a x with increasing chalcogen content has been attributed to a change in glass structure from an essentially network to a chain-like form (Hilton and Hayes 1975). However, in the As>b, ,Se,, ~I glasses studied presently, u exhibits a maximum for the stoichiometriccomposition and there is a decrease of u for the %-rich glasses in contrast to the expected increase. The chemically-ordered network model (corr~) wherein the maximum number of

80 G ( k bors) 60 -

--.-*--.

200 E - ;h$6 -

\

= .* ...-

180

-

K ( k bars) -

120

-

17 6 "0

/y:

lcc/m&)

- 168

031 -

-.-

U

028

~

I I 60 70 Alomic percent of Se m As,Sb,,Se,,_, I

I

50

80

1006

A Giridhar. Sudho Mahaahan and A K Singh I

I

170

1 L

(Fo " 0.28

heteroplar bonds are formed first and the r d n i n g part of the valence requirement is met with by homopolar bonding at random accounted satisfactorily for the-composition dependence of the density of these glasses (Giridhar and Sudha Mahadevan 1982). For a correlation of the elastic properties with composition, the results were e x a m i n e d u s i n g t h e m ~model. ~ Aclosestudyoftheglasscompsitions inview ofthe results of figure 5 indicates the importance of As,%, content (i.e. As-% bonds) in determining the elastic properties of these glasses, as the observed features in the composition dependence of K and a can be linked to the As,%, content in rhese glasses. I t can be seen (figure 6) that the modulii do show in general an increase with increasing As,%, content in the glasses Though scatter in the p i n t s is seen in the dependence of the modulii on the As,%, content (figure 6), the increase in these quantities is obvious.

4.

Conclusions

Elastic modulii of (As, Sb),,Se,, As, Se, content in the glasses.

glasses decrease monotonically with decreasing

In theAs,Sb,,%,,.,glasses,with theAs,,Sb,,Se,,glassasreference,theshearand Young's modulus of As-rich glasses d o not vary much with the composition, while those of the %-rich glasses decrease with increasing Se content. The bulk modulus and the Poisson's ratio of these glasses exhibit a maximum at the stoichiometnc composition. An examination ofthe results indicates that the elastic properties of these glasses are sensitive to the As,%, content in these glasses.

E i As-Sb-Se glosses

IW7

Referewes *ndaJoo 0 L and Nafc I E 1965 I . Gwphys. R a . 10 3951 Gidhsr A, N a m s k b m P S L a d Sudha Mahadswn 1981 J . Non€ryrr. Solids 43 29 Giridhv A and S u d h Mabadwan 1982 I . NonCryrr. Solids 51 I05 &yes D I. RIshtin M D and Hilton A R 1974 Ulfrawnirr Symp. Proc. p. 502 (d.) Ds Klerk. ln~titutionof E k k A and E l a r o o k Engin-. New York Hilton A Rand Hayes D I 1915 1. NmCrysr. Solids 11 319 McSkimin H J 1961 J. Aca.rI. &.Am 33 12 McSLimin H I and Andrcltsh P 1962 J . Acorn. Soc. Am 34 609 Mohsn R, PsocbapkT S and Rao K J 1981 Bull. Moter. Sci. 3 29 M m M Band Fdr, E J 1961 M o m . Re$. Bull. 2 535 " u i i h a m P S L. Giridhv A and Sndhp Mahadmn I981 I . NonCrysr. Solids 43 365 S o p N and Kunugi M 1913 J. Phys. Chem Solids 34 2141 kdha Mahadsvan, Mridhv A a d Sin& A K 1981 I . Nan-Cryst. sdids 51 423 Thompson I C +d Bailey K E 1918 J. NonCrysl. Solids 21 161