HAL Id: jpa-00225212
https://hal.archives-ouvertes.fr/jpa-00225212
Submitted on 1 Jan 1985
HAL is a multi-disciplinary open access
archive for the deposit and dissemination of
sci-entific research documents, whether they are
pub-lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d’enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.
LOW-FREQUENCY RAMAN SCATTERING IN A
NUCLEATED CORDIERITE GLASS
A. Boukenter, Bernard Champagnon, E. Duval, A. Wright
To cite this version:
JOURNAL DE PHYSIQUE
Colloque C8, supplément au n°12, Tome 46, décembre 1985 page C8-443
LOW-FREQUENCY RAMAN SCATTERING IN A NUCLEATED CORDIERITE GLASS
A. B o u k e n t e r , B. Champagnon, E. Duval and A . F . W r i g h t *
Spectroscopie des Solides, U.A, 442 au CNRS, Université Lyon I, 69622 Villeurbanne Cedex, France
*I.L.L., 156 X, 38042 Grenoble Cedex, France
Résumé - Les spectres Raman des verres de cordierite soumis à différents traitements thermiques de nucléation montrent l'existence d'une bande à fréquence beaucoup plus basse que la "bande des bosons" observée habituelle-ment dans les verres. Elle est attribuée aux germes présents dans le verre.
On montre expérimentalement que sa position dépend de la taille des germes. Un modèle est proposé permettant de calculer cette taille â partir de la position du maximum de la bande très basse fréquence.
Abstract - Raman spectra of cordierite glass after a heat-treatment leeding to nucleation show a band at a much lower frequency than the usual low-frequency "bosons peak" observed in glasses. It is attributed to the nuclei in the glass. Experiments show that its position is a function of the size of these nuclei . A model allowing to calculate these sizes from the position of the maximum of the very low frequency band is proposed.
I - INTRODUCTION
Low frequency Raman scattering in glasses refers to the inelastic scattering of light at frequencies lower that ~ 100 cm~l / l / . The low frequency Raman spectrum in glasses differs from that observed in crystals as it is a first order vibrationnal spectrum,all owed by the breakdown of wave-vector selection rules due to the disorder of the amorphous material.
In this paper the low frequency Raman scattering is studied in correlation with the nucleation of the glass. Nucleation in our glasses is controlled by thermal treat-ments below the crystallization temperature which allows formation and growth of clusters, the size of which is known from S.A.N.S. (Small Angle Neutron Scattering) or Electron Microscopy / 2 / , their characterization was achieved from E.S.R. (Electron Spin Resonance) and laser spectroscopy / 3 / .
In the following study, a shift of the low-frequency Raman band and very low fre-quency bands in the region 5 - 2 0 cm are observed. They are correlated with parti-cles sizes and nature of microcrystallites. An interpretation of these new features is proposed.
II - EXPERIMENTS AND RESULTS
The glass used is a cordierite like composition glass (52 Si02» 34.7 AI2O3, 12.5 MgO) containing 0.8 CrgOo. The chromium ion is the nucleating agent and heat treatment between 825°C and 1050°C leeds firstly to the formation of clusters and then to the formation of Mg(>204 spinel microcrystallites /2,3/.
The kinetics of growth of microcrystallites during the heat-treatment is obtained by S.A.N.S. and Electron microscopy and is summarized in table (1).
JOURNAL
DE
PHYSIQUE Table 1 Sample A B CRaman s p e c t r a were recorded,in a 90" geometry w i t h an Argon Coherent R a d i a t i o n l a s e r . The 4880 A and 5145 A l i n e s were used.A Jobin-Yvon double monochromator
'U IOU" was f o l l o w e d by a photon counting system. A mu1 t i c h a n n e l analyzer recorded t h e s i g n a l and monitored t h e wavelength o f monochromator a l l o w i n g accumulation o f spectra i n o r d e r t o improve t h e s i g n a l / n o i s e r a t i o . Stokes and anti-Stokes spectra and t h e d i f f e ' r e n t s l a s e r l i n e s were used t o a v o i d spurious e f f e c t s .
Low frequenty Raman s c a t t e r i n g a t room temperature has been observed between 3 cm-I and 100 cm-
.
Low frequency.peaks observed can be c l a s s i f i e d i n two types....
...
...
....
:" NO T REATMENT (A)....
P a r t i c l e diameter from Raman s c a t t e r i n g 157i
210i
273i
Heat-treatment Non-treated 4h 875°C+
2h 900°C 4h 875°C+
4h 900°C 2h 875°C+
lOmn 1050°CFig: 1
-
Low frequency Raman s c a t t e r i n g o f c o r d i e r i t e glass w i t h d i f f e r e n t annealings. P a r t i c l e diameter D from SANS o r EM 240i
(SANS) 200a
(EM) 280 (SANS) 350 (EM)A peak near 80 cm-' ( i n t h e non t r e a t e d sample), s i m i l a r t o t h a t observed i n SiO which g r a d u a l l y s h i f t s towards t h e Rayleigh l i n e and decreases d u r i n g h e a t - t r e a G e n t The Raman spectra,as recorded, are shown on f i g u r e 1. Sample A i s t h e non-treated sample. Sample B heated from 4 h o r n a t 875°C and 2 hours a t 900°C shows t h e s h i f t o f t h i s bands. I n sample C heated f o r 2 hours at^ 875OC and 10 mn a t 1050°C t h i s band disappears completely. I n previous papers /1,2/ t h e heat-treatment f o r t h i s sample C
During heat-treatment a t 900°C and a t h i g h e r tempratures amther peak r e f e r e d asNvery- low frequency peak" appears between 5 cm-l and 20 cm-1. This peak i s n o t observed i n the non t r e a t e d sample. It increases w i t h time o r temperature o f annealing and s h i f t s simultaneously towardsthe Rayleigh l i n e . F i g u r e 2 shows t h i s peak i n t h e sample C where i t s i n t e n s i t y i s maximum.
E (cm-9
F i g . 2
-
Very-low frequency Raman F i g . 3-
P o s i t i o n o f t h e v e r y low frequency s c a t t e r i n g f o r a c o r d i e r i t e g l a s s Raman peak as f u n c t i o n o f t h e i n v e r s e o f t h e h e a t - t r e a t e d 2h 875°C+
lOmn 1050°C. diameter o f t h e p a r t i c l e s (obtained fromneutron s c a t t e r i n g o r e l e c t r o n microscopy). Energy p o s i t i o n o f these peaks as f u n c t i o n o f t h e i n v e r s e of t h e diameter of c l u s t e r s o r m i c r o c r y s t a l l i t e s measured by SANS o r e l e c t r o n microscopy i s p l o t t e d on f i g u r e 3 f o r glasses w i t h d i f f e r e n t h e a t treatments. A l i n e a r c o r r e l a t i o n i s c l e a r l y observed.
Fig. 4
-
P o l a r i z e d spectra f o r c o r d i e r i t e glass h e a t - t r e a t e d 2h 875°C+
2h 900°C. R e l a t i v e t I n .-*I
J-
z W +z .
n W t-*
< ...
. ' W .v-v
[ I . ... ...;..
...
..;-..;>',-
...;I... . .
' '. ... :...-. .-.-..-..
...:... j .......
' "--. . .-. .- ' .'.-
.....+.. ;--.--.--
:
H
-V
JOURNAL DE PHYSIQUE
I 1 1
-
INTERPRETATIONThe broad band a t frequencies lower than 80 cm-I i s i n t e r p r e t e d by Shuker and Gamman/5/and J S c k l e / l / i n t e r m s o f f i r s t order Raman s c a t t e r i n g due t o breakdown o f t h e momentum s e l e c t i o n r u l e s . I n an amorphous m a t e r i a l w i t h s h o r t range c o r r e l a - t i o n a l l t h e modes o f t h e m a t e r i a l c o n t r i b u t e t o t h e s c a t t e r e d l i g h t . The s c a t t e r e d frequency a t %can be expressed as t h e F o u r i e r transform o f t h e c o r r e l a t i o n func- t i o n o f t h e d i g l e c t r i c s u s c e p t i b i l i t y
Taking i n t o account b o t h mechanical and e l e c t r i c a l d i s o r d e r o f a s e m i - i n f i n i t e medium MARTIN and BRENIG /6/ e x p l a i n t h e low-frequency dependance o f t h e Raman spec- trum o f an amorphous f i l m . This model has been a p p l i e d by NEMANICH t o chalcggenide glasses and a l l o y s t o determine s t r u c t u r a l c o r r e l a t i o n ranges l e s s than 10 A b u t seems i n a p p r o p r i a t e t o our samples as these a r e known t o c o n t a i n l a r g e c l u s t e r s ( t a b l e 1 ) .
The e v o l u t i o n o f t h e "boson peak" i n these glass i s significant:when t h e s i z e o f t h e c l u s t e r s increases the boson band g r a d u a l l y s h i f t s towards t h e Rayleigh l i n e and i t s i n t e n s i t y decreases u n t i l i t disappears i n t h e sample C c o n t a i n i n g a l a r g e percentage o f m i c r o c r ~ ~ s t a l l i t e s . This can be i n t e r p r e t e d as a progressive increase o f t h e o r d e r i n glass which tends towards a c r y s t a l : t h e "boson peak" gives i n f o r - mation on the v a r i a t i o n o f t h e s t r u c t u r e i n t h e glass.
The s m a l l e r and narrower very low frequency band, c l o s e t o t h e Rayleigh l i n e obser- ved i n t h e samples B and C i s a new band as no such s t r u c t u r e has been r e p o r t e d u n t i l now. The l i n e a r c o r r e l a t i o n between i t s energy and t h e i n v e r s e o f the diame- t e r o f t h e m i c r o c r y s t a l l i t e s observed i n these glasses /2,3/ leeds us t o a t t r i b u t e t h i s band t o these m i c r o c r y s t a l l i t e s . Using equation ( 1 ) and t a k i n g i n t o account the d e n s i t y o f s t a t e s and t h e boson occupation f a c t o r we suppose a s p h e r i c a l form f o r t h e m i c r o c r y s t a l s and c a l c u l a t e t h e F o u r i e r t r a n s f o r m on t h i s volume. The maximum of t h e s c a t t e r e d l i g h t i s then obtained when t h e diameter o f t h e microcrystals,2a, i s 0.8 times t h e wavelength o f t h e phonons i n t h e g l a s s . From t h e energy o f these phonons ( o = 5.37 cm-I i n t h e sample C) and from t h e v e l o c i t y o f a c o u s t i c waves deduced f r o N B r i l l o u i n measurements /8/ we c a l c u l a t e t h e diameter o f t h e
.
. articlesv 3
2 a = 0.8
-
(with v = 5.52 10 m. s-I). k'e deduce 2 a = 273 f o r t h e sample C . c a mComparison w i t h p a r t i c l e s i z e s obtained from o t h e r techniques g i v e s a r a t h e r good agreement b e a r i n g i n mind t h e s i m p l i c i t y o f t h e model. For example t h e s p h e r i c a l approximation f o r m i c r o c r y s t a l l i t e s i s crude as can be observed by e l e c t r o n micros- copy /9/.Refinements on the model proposed above a r e expected t o g i v e b e t t e r agree- ment w i t h the experimental data.
A complementary nay t o e x p l a i n t h e existence o f these bands i s t o say t h a t wave v e c t o r conservation imposes t h a t l i g h t can o n l y i n t e r a c t w i t h phonon having a zero wave v e c t o r i .e non propagating phonons. The wavelength o f t h e phonons which can be trapped i n the m i c r o c r y s t a l l i t e s have t o f u l f i l l e d a resonance c o n d i t i o n w i t h t h e dimension o f these c r y s t a l l i t e s . The s c a t t e r i n g o f t h e l i g h t w i t h these phonons i s
maximum and can be observed i n t h e Raman spectrum. I V
-
CONCLUSIONREFERENCES
/I/ JACKLE, J., "Low frequency Raman s c a t t e r i n g i n g l a s s e s " , Topics i n c u r r e n t Physics Vol
.
24, (1981) 135-160. S p r i n g e r V e r l a g ( B e r l i n ) ./2/ D U R V I L L E , ~ . , CHAMPAGNON, B., DUVAL, E., BOULON, G., GAUME, F., WRIGHT, A.F. and FITCH, A.N.. Physics and Chem. o f Glasses 25 (1985) 126.
/3/ DURVILLE, F., CHAMPAGNON, B., DUVAL, E . anTBOULON, G.. J. Physics and Chem. o f S o l i d s (1985) t o be p u b l i s h e d .
/4/ HASS, M. S o l i d S t a t e Comm. 7 (1969) 1069-71.
/5/ SHUKER, R. and GAMMON, R.W.-Phys. Rev. L e t t e r s 25 (1970) 222. /6/ MARTIN, A.J. and BRENIG, W. Phys. S t a t . S o l i d i
v)
64
(1974) 163./ 7 / NEMANICH, R.J. Phys. Rev. B16 (1977) 1655. /8/ PELOUS, J. ( t o be p u b l i s h e d 7
