POLARIZED RAMAN SCATTERING STUDIES OF FLUOROZIRCONATE AND FLUOROHAFNATE GLASSES

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POLARIZED RAMAN SCATTERING STUDIES OF FLUOROZIRCONATE AND FLUOROHAFNATE

GLASSES

P. Banerjee, B. Bendow, M. Drexhage, J. Goltman, Subhabrata Mitra, C.

Moynihan

To cite this version:

P. Banerjee, B. Bendow, M. Drexhage, J. Goltman, Subhabrata Mitra, et al.. POLARIZED RAMAN SCATTERING STUDIES OF FLUOROZIRCONATE AND FLUOROHAFNATE GLASSES. Journal de Physique Colloques, 1981, 42 (C6), pp.C6-75-C6-77. �10.1051/jphyscol:1981623�. �jpa-00221314�

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JOURNAL DE PHYSIQUE

Colloque C6, suppl6ment a u n012, Tome 42, de'cembre 1981 page C6-75

POLARIZED RAMAN SCATTERING STUDIES OF FLUOROZIRCONATE AND FLUOROHAFNATE GLASSES

P.K. J3anerjee(11, B.

endow'^),

^M.G. Drexhage, J.T. ~ o l t r n a n * ' ~ ) , S.S. M i t r a * ( 3 )

and C.T. ~ o y n i h a n * * ( ~ )

S o l i d S t a t e S c i e n c e s Z v . , Rome A i r Development Center, Hanscom AFB, Massachu- s e t t s 01731, U.S.A.

" ~ n i v e r s i t ~ o f Rhode I s l a n d , Kingston, Rhode I s l a n d 02881, U.S.A.

** C a t h o l i c U n i v e r s i t y o f America, Washington, D. C. 20064, U.S.A.

Abstract

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We r e p o r t p o l a r i z e d Raman spectra f o r a s e t o f heavy-metal m u l t i - component f l u o r i d e glasses, c o n t a i n i n g t h e f l u o r i d e s o f hafnium, zirconium, barium, lanthanum and thorium. A l l t h e glasses have a dominant peak i n t h e i r V V spectrum i n t h e v i c i n i t y o f 580 cm-l w i t h a corresponding deep minimum i n t h e i r d e p o l a r i z a t i on spectrum. The spectra a r e r e l a t i v e l y depolarized from near 200 cm-1 t o 400 cm-1.

1. I n t r o d u c t i o n

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Many r e p o r t s have appeared r e c e n t l y d e a l i n g w i t h p r e p a r a t i o n and c h a r a c t e r i z a t i o n o f multicomponent heavy-metal f l u o r i d e glasses1, s p e c i f i c a l l y f l u o r o h a f n a t e s and f l u o r o z i r c o n a t e s , i n which HfF4 o r ZrFq i s t h e primary c o n s t i - t u e n t , t h e secondary component i s BaF2, and t h e o t h e r components a r e t h e f l u o r i d e s o f rare-earths, group 111 elements o r a l k a l i s ( e i t h e r s i n g l y o r i n combination).

One important p r o s p e c t i v e a t t r i b u t e o f these glasses i s continuous h i g h t r a n s p a r - ency over an unusually wide range o f frequencies spanning t h e mid-IR t o t h e near UV. I n p a r t i c u l a r , t h e i n f r a r e d c h a r a c t e r i s t i c s are o f i n t e r e s t f o r a wide var- i e t y o f a p p l i c a t i o n s r a n g i n g from l a s e r windows t o i n f r a r e d f i b e r optics. Here we r e p o r t s e l e c t e d r e s u l t s o f p o l a r i z e d Raman s t u d i e s aimed a t o b t a i n i n g i n f o r - mation about t h e fundamental v i b r a t i o n a l c h a r a c t e r i s t i c s o f t h i s r e l a t i v e l y new f a m i l y o f glasses.

2. Experiment and Results

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The glasses u t i l i z e d i n t h e present study were syn- t h e s i z e d a t RADC and C a t h o l i c Univ. from h i g h p u r i t y oxide o r f l u o r i d e s t a r t i n g m a t e r i a l s u t i l i z i n g procedures described i n d e t a i 1 e l sewherel. Samples several cm i n diameter and 2-4 mm t h i c k were prepared o f compositions s e l e c t e d from t h e c e n t e r o f t h e glass formation regions. These compositions, denoted as ZBT, HBT, ZBL and HBL a r e i n d i c a t e d i n Table 1.

Table 1. F l u o r i d e Glass Compositions

ZrF4 BaF2 ThF4 HfF4 LaF3

HBL

--

^33.75

--

^57.5 ^8.75

HBT

--

^33.75 ^8.75 ^57.5

--

ZBL 57.5 33.75

-- --

^8.75

ZBT 57.5 33.75 8.75

-- --

P o l a r i z e d Raman spectra were taken i n t h e 90" s c a t t e r i n g geometry u t i l i z i n g a Spex 1400 Spectrometer i n c o n j u n c t i o n w i t h an argon-ion l a s e r and a cooled FW130 p h o t o m u l t i p l i e r ; t h e s p e c t r a l s l i t w i d t h was

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⁵^cm-l. The p o l a r i z e d VV spectra Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1981623

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C6-76 JOURNAL DE PHYSIQUE

a r e shown i n Fig. 1. A summary o f t h e Raman data on these glasses i s presented i n Table 11. The corresponding d e p o l a r i z a t i o n r a t i o , p (which i s t h e r a t i o o f MI t o VV i n t e n s i t i e s ) i s shown i n Fig. 2.

Fig. 1. P o l a r i z e d VV Raman spec- POLARIZED RAMAN SPECTRUM t r u m vs. frequency s h i f t f o r f o u r

f l u o r i d e glasses.

;r

FREQUENCY SHIFT (10~ctll-')

Fig. 2. D e p o l a r i z a t i o n r a t i o vs. f r e - quency s h i f t f o r f o u r f l u o r i d e glasses.

Table 2. Summary o f Raman Data (cml) on f l u o r o z i rconate and fl uorohafnate Glasses

r

t%T

n

^ZB

vv ^MI vv HV vv HV vv HV

577v,p 578v,p 577v,p 578v, p

480w 49& 4 8 h 480111,

400w 400111 400w 400111 390m 380111

250111 260111 250m,sh 250m 235w,sh 230w,sh

200w 200m 200w 200m 200m 200m,sh

1 6 h 1 6 h 160111

loom loom

Symbols: v=very strong, p=polarized, m=medium, w=weak, sh=shoulder 3. Discussion

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A l l o f t h e VV spectra a r e dominated by an i n t e n s e peak near 580 cm-1 which i s associated w i t h a corresponding deep minimum i n t h e d e p o l o r i z a t i o n

r a t i o . The p o s i t i o n o f t h i s peak, and t h e major featuers o f a l l o f t h e spectra a r e s i m i l a r f o r b o t h hafnium as w e l l as zirconium f l u o r i d e based glasses. This un- expected r e s u l t may i n d i c a t e a weakening o f t h e f o r c e constants i n ZrFq as opposed t o HfF4 glasses. The e f f e c t on t h e spectrum of changing t h e t h i r d component (LaF3 o r ThF4) i s r e l a t i v e l y small, as i s t h e case f o r IR r e f l e c t i v i t y 2 .

The d e p o l a r i z a t i o n spectrum o f any i s o t r o p i c disordered m a t e r i a l i n c l u d i n g glasses, l i q u i d s and gases should be c h a r a c t e r i z e d by 0 < ^p< 3/4, which i s indeed t h e case w i t h t h e glasses s t u d i e d here. The sharp pronounced minimum i n p ( ~ ) near

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590 cm-1 corresponds t o t h e peak a t

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580 cm-1 i n t h e VV spectrum. Based on molten s a l t data3, i t may be i d e n t i f i e d w i t h symmetric s t r e t c h i n g modes o f t h e M F , ~ - ~ c o o r d i n a t i o n species (where x

,.

= 6 t o 8). S p e c i f i c a l l y , t h e l a t t e r suggests t h a t t h e dominant peak be p r i n c i p a l l y assigned t o t o t a l l y symmetric M F ~ " s t r e t c h - i n g modessin general agreement w i t h c r y s t a l l i n e peaks reported$ i n t h e range 570-590 cm-1 f o r b o t h ~ r ~ and H ~ F ~ Z - . ~ 2 - The l a r g e w i d t h o f t h i s l i n e (- 60 cm-1) compared t o t h a t o f c r y s t a l s (10 t o 20 cm-l) i s an expected a t t r i b u t e o f a d i s - ordered system. The d e p o l a r i z a t i o n spectrum suggests t h a t t h e broad Raman bands below 400 cm-l a r e n o t p r i m a r i l y due t o symmetric modes. Thus, c o n t r i b u t i o n s o f Ba-F symmetric modes, which would be expected t o occur i n t h e general v i c i n i t y o f 250 cm-1, a r e n o t evident i n t h e c u r r e n t spectra. The low frequency modes a r e more l i k e l y a t t r i b u t a b l e t o bending v i b r a t i o n s o f Zr o r Hf w i t h F. It i s a l s o i n t e r e s t i n g t o n o t e t h e r e l a t i v e featurelessness o f b o t h t h e Raman and I R spec- t r a o f multicomponent glasses l i k e ZBT, HBT, ZBL and HBL. This c o u l d be a t t r i b u - t e d t o near coincidences o f t h e fundamental mode frequencies o f various components, and/or t h e one-mode behavior c h a r a c t e r i s t i c o f c e r t a i n mixed systems.

F i n a l l y , we note t h a t I R spectra d i s p l a y two broad peaks i n t h e h i g h (400-600 cm-1) and low (150-300 cm-1) frequency regions. The Raman f e a t u r e s i n t h e v i c i n - i t y o f 580 and 250 cm-I f a l l in-between t h e TO and LO modes deduced from r e f l e c - t i v i t y . This behavior i s s i m i l a r t o t h a t manifested i n c r y s t a l l i n e a l k a l i n e e a r t h f l u o r i d e s , where t h e Raman mode a l s o f a l l s in-between t h e corresponding To and LO m d e s o f t h e c r y s t a l .

(1)IPA Appointee a t RADC; permanent address : Rhode I s l a n d J u n i o r Coll , Warwick, RI.

(2) Present Address: The BDM Corporation,l801 Randolph Rd, SE, Albuquerque,NM 87106 (3)Research supported by Rome A i r Development Center (AFSC), under Contracts No.

F19628-77-C-0109 (U.R.I. ) and F19628-77-C-0061 (C.U. ). Present address o f J.

Goltman: Naval Underwater Systems Center, Newport, R I ; Present address o f C.T.

Moyni han : Dept. o f M a t e r i a l s Engineering, RPI, Troy, NY, 12181.

References

1. See, e.g. M.G. Drexhage e t a l , Laser Focus 16, 62(1980); B. Bendow and M.G. Drexhage, O p t i c a l Engineering (1981, i T p r e s s ) ; M.G. Drexhage e t a l , i n

"Physics o f Fiber Optics", B. Bendow and S.S. M i t r a , eds (Amer. Ceramic Soc, Columbus, Ohio, 1981).

2. 6. Bendow e t a1 , Sol i d S t a t e Commun. 37, 485(1981).

3. L.M. Toth e t al,,J. Phys. Chem.

3,

1384(1973).

4. See, e.g., K. Nakamoto, " I R and Raman Spectra o f Inorganic Coord. Compounds"

(Wiley, NY, 1978), pp 132-194.