RAMAN STUDY OF THE CHEMICAL REACTIONS DURING THE MELTING OF A 15 Na2CO3-10 BaCO3-75 SiO2 BATCH

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RAMAN STUDY OF THE CHEMICAL REACTIONS DURING THE MELTING OF A 15 Na2CO3-10

BaCO3-75 SiO2 BATCH

D. Krol, R. Janssen

To cite this version:

D. Krol, R. Janssen. RAMAN STUDY OF THE CHEMICAL REACTIONS DURING THE MELT-

ING OF A 15 Na2CO3-10 BaCO3-75 SiO2 BATCH. Journal de Physique Colloques, 1982, 43 (C9),

pp.C9-347-C9-350. �10.1051/jphyscol:1982966�. �jpa-00222495�

RAMAN STUDY OF THE CHEMICAL REACTIONS DURING THE MELTING OF A 15 N a

C 0

- i o B a C 0

- 7 5 S i 0

BATCH

D.M. Krol and R.K. Jatissen

Philips Research Laboratories, Eindhoven, The Netherlands

Résume. - Les reactions chimiques qui se produisent pendant la fusion des mélanges vitrifiables de composition 15Na_C0,- 10BaCO 3 -75SiO 2 ont été étudiées par spectroscopie Raman. Au- dessous de 1000 C les produits de reaction sont pour la plu- part cristallins. La teneur en silicate des produits de reac- tion s'accroît avec l'augmentation de la température. Au-dessus de 1000 C une phase vitreuse est formée, dans laquelle des grains de SiO„ sont dispersés.

Abstract. - The chemical reactions that take place during the melting process of 15 Na ² CO ³ -10 BaC0 ³ -75 Si0 ² batches have been

investigated with Raman spectroscopy. The results show that at temperatures below 1000 C the reaction products are mainly crys- talline. The silicate content of the crystalline compounds in- creases with increasing temperature. Above 1000 C the batch con- sists of a melt in which undissolved crystalline SiO ? is dis- persed.

1. Introduction. - Because of the large quantities of glass used in the production of television screens and the severe quality re- quirements it is important to improve the efficiency of the melting of these glasses. This requires, among other things, a better understanding of the chemical reactions that take place in the batch during the melting process.

Recent investigations of the system x K' C0 3 (l-x) SiO, have shown that Raman spectroscopy is very well suited to studying these reactions, especially because it is a technique that can identify both crystalline and vitreous phases L13• Other investi- gations that have been done, such as DTA and TGA, have been mainly concerned with the soda-lime-silica system C2,33 and little is known about television glass batches. The composition of this glass, which contains more than ten different components, can be approximated by 15 Na-COo-lO BaC0 3 ~75 SiO,.

We have started an investigation of the melting processes in these batches, with and without the addition of NaN0 3 and NaSbCU.

In this paper we describe the results of a Raman study of the chemical reactions that take place in undoped 15 Na ? CO 3 ~10 BaC0 3 ~ 75 SiO ? batches as a function of temperature and time.

2. Experimental - Samples were prepared by mixing Na-CCU, BaC0 3 (both Merck p.a.) and ot-quartz (ground rock crystal, Silicon Smelters

(PTY) Ltd.). The grain size of the powders was 1 to 10 urn for BaC0 3

and 100 to 300 urn for Na,C0 3 and cx.-quartz. The batches (20 g) were fired for a certain"period varying between 5 minutes and 16 hours at temperatures between 700 and 1400°C in a Pt/Rh or Al^O..

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1982966

C9-348 JOURNAL DE PHYSIQUE

c r u c i b l e . The samples were t h e n quenched t o room t e m p e r a t u r e . To a v o i d r e a c t i o n w i t h w a t e r from t h e atmosphere t h e samples were quenched u n d e r e v a c u a t i o n and a l l f u r t h e r sample h a n d l i n g was c a r - r i e d o u t i n a d r y n i t r o g e n - f i l l e d glove-box.

The c r y s t a l l i n e s i l i c a t e s were p r e p a r e d e i t h e r by s o l i d s t a t e r e a c t i o n s o f Na2C03, BaCO and S i 0 2 m i x t u r e s o r by c r y s t a l l i z a t i o n of g l a s s e s , according t o d a t a from t h e l i t e r a t u r e [4].

F o r t h e Raman measurements t h e samples were powdered. The Raman equipment h a s been d e s c r i b e d e l s e w h e r e [ 5 ] .

R e s u l t s and D i s c u s s i o n - Some Raman s p e c t r a of p a r t l y r e a c t e d -

15 Na2C0 -10 BaC03-75 SiO b a t c h e s a r e p r e s e n t e d i n f i g s . l a and l b . ~ ~ a from t h e l i n e s g h a t can be a s c r i b e d t o t h e s t a r t i n g r s m a t e r i a l s Na2C03, BaCO and SiO , t h e s e s p e c t r a show some a d d i t i o - n a l s h a r p peaks a s wel? a s b r o a 8 bands. The s h a r p peaks a r e due t o c r y s t a l l i n e compounds which a r e formed upon f i r i n g and t h e broad bands a r e c h a r a c t e r i s t i c of v i t r e o u s p h a s e s C6Ji.e. m o l t e n p h a s e s a t t h e f i r i n g t e m p e r a t u r e .

I n o r d e r t o i d e n t i f y t h e r e a c t i o n p r o d u c t s i n t h e b a t c h t h e

Raman s p e c t r a of t h e s e b a t c h e s have t o be compared w i t h t h o s e o f

t h e c r y s t a l l i n e compounds and v i t r e o u s p h a s e s i n t h e Na O-BaO-

S i 0 2 phase diagram, i n which some 20 c r y s t a l l i n e compounds a r e 2

known [4,9]. A p a r t from Na SiO 2 and Na2Si O5 C61 no Raman d a t a a r e

a v a i l a b l e f o r t h e s e compounds. 3 ~ e have, t g e r e f o r e , measured t h e

Raman s p e c t r a of most c r y s t a l l i n e compounds. T a b l e I l i s t s t h e

c r y s t a l l i n e compounds t h a t e x i s t i n t h e Na 0-BaO-Si02 t o g e t h e r

w i t h t h e i r Raman l i n e s . Some compounds c o u l d n o t be p r e p a r e d w i t h

s u f f i c i e n t p u r i t y t o d e t e r m i n e t h e p o s i t i o n of t h e i r Raman l i n e s .

Because o f t h e p r e s e n c e of argon plasma l i n e s i n t h e low-energy

p a r t o f l t h e s p e c t r u m , Raman l i n e s w i t h wavenumbers l e s s t h a n

250 cm a r e n o t shown e x c e p t f o r t h e s t a r t i n g m a t e r i a l s .

n e s s o f t h e bands i t i s o n l y p o s s i b l e t o d e t e r m i n e t h e t y p e of network i . e . meta-, d i o r t r i s i l i c a t e l i k e .

The a n a l y s i s of t h e Raman s p e c t r a of t h e p a r t l y r e a c t e d b a t c h e s , p r e s e n t e d i n t a b l e 11, shows t h a t below 1 0 0 0 ~ ~ t h e r e a c - t i o n p r o d u c t s a r e mainly c r y s t a l l i n e . Above 1 0 0 0 ~ ~ t h e b a t c h con- s i s t s o f a molten phase c o n t a i n i n g some u n d i s s o l v e d c r y s t a l l i n e SiOZ. The composition of t h e c r y s t a l l i n e compounds t h a t a r e formed d u r l n g f i r i n g i n c r e a s e s i n s i l i c a t e c o n t e n t w i t h i n c r e a s i n g tempe- r a t u r e . T h i s i s i n c o n t r a s t t o t h e r e s u l t s found f o r 30 K CO -70 SiO, b a t c h e g where o n l y c r y s t a l l i n e d i s i l i c a t e was found 2b] ! ^{A t}

700 and 800 C t h e compounds a r e mainly of t h e o r t h o - and pyro- s i l i c a t e t y p e s , w h i l e a t 850 and 9 0 0 ~ ~ t h e y a r e mainly meta- and d i s i l i c a t e s . I t a p p e a r s t h a t no sodium s i l i c a t e s a r e formed a t most t e m p e r a t u r e s . T h i s may have s e v e r a l c a u s e s . I n t h e f i r s t p l a c e t h e g r a i n s i z e of BaC03 ( 1 t o was much s m a l l e r t h a n t h a t o f NaZC03 (100 t o 300 . Thisl:d%!s t h a t BaC03 w i l l r e a c t f a s t e r a s a p p e a r s a l s o frorf:l!e r e l a t i v e i n t e n s i t i e s o f t h e BaCOg and Na CO peaks i g t h e p a r t l y r e a c t e d b a t c h e s a t low tempera- t u r e s f70d and 800 C),lIn t h e s e s p e c t r a t h e i n t e n s i t y of t h e BaC03 peak a t 1060 cm i s l e s s i n t e n s e t h a n t h a t of Na C 3 a t 1080 cm-l, w h i l e t h i s i s t h e r e v e r s e i n t h e u n r e a c t e d b g t c g [ 5 ] .

Furthermore t h e m e l t i n g t e m p e r a t u r e of Na2Si O5 2 i s 8 7 4 O ~ C63 ,

which i n d i c a t e s t h a t t h e molten phase a t 900 C w i l l c o n s i s t mainly of sodium d i s i l i c a t e . I t i s n o t p o s s i b l e a t t h e moment t o g i v e any q u a n t i t a t i v e i n f o r m a t i o n a b o u t t h e amounts of t h e d i f - f e r e n t compounds. T h i s r e q u i r e s t h e Raman s p e c t r a o f s t a n d a r d mix- t u r e s . Both t h e q u a n t i f i c a t i o n of t h e d a t a and t h e e f f e c t of d i f - f e r e n t g r a i n s i z e s a r e p r e s e n t l y under i n v e s t i g a t i o n .

Table I. Raman

of

compound

I ^Na2C03

~tartlng BaC03

materlals

ortho- { ^Na4SlO4

s ~ l ~ c a t e Ba2SlOq pyro- { ^Nags1207

slllcate Na2Ba2S1207

meta- Na2S103

I

s111cate Bas103

Na2BaS1206

Ba2Sl308 BagSlg021

Ba3Si5013 oc-Na2S1205 slllcate ( 3 - ~ a s 1 ~ 0 ~

"-

{ Na2BaqS110025

NagS1~01g

Na2Sx307 Gate

w - c r l s t o b a - l l t e

VS

I > 90% , lntenslty

startlng materlals and

compounds

the Na20-BaO-S102 System.

posltlon and lntenslty of Raman

188W 7 0 0 W 1432* 1770*

139M 154M 2 2 4 W 691W 1423* 1508*

1770*

128M 206W 2 6 4 W 356VW 395* 402*

698* 795* 807* 1067* 1083* 1162"

no Raman spectrum measured

370VW 4981 522VW 860W 888VW 914W

5 3 5 W 5978 8 8 1 W 919M 1028M 300VW 320W 3638 376W 5 0 7 W 6 1 4 W 883VW 912M 946VW 993VW 1080W

400W 5868 - ^971VS 1 0 2 0 W

312m 396W 407W 535VW 5 4 8 W 600s 928VW 965VS 1062W

-

266VW 290W 3 6 6 W 391W 479VW 520VW 5 5 4 W

631s 891VW 897W lOOOM 1056W

no Raman spectrum measured

288W 312W 502W 5361 550N 614W 926W l067VS

no Raman spectrum measured

312VW 391W 5221 968VW 1016W 1061M 269VW 2 9 2 W 316W 333W 476VW 5351 2738 2981 321W 3481 463W 508N 573m 1081VS

-

3571 413W 540M 7 9 2 W 10611 1130W not formed above 665'C, no Raman spectrum measured

*- [TO]

1s

more than 90% of the intensity of the strongest

S = 70%

I

90%. M = 30% c I 4 70%. W

10%

I C 30%, W

5% < I

10%. *

I

5%.

C9-350 JOURNAL DE PHYSIQUE

T a b l e

A n a l y s i s o f t h e Raman s p e c t r a o f p a r t l y r e a c t e d 15 Na2C03-10 BaC03-75 S i 0 2 b a t c h e s .

4 . ~ n c l u s i o n s - On t h e b a s i s of o u r Raman measurements t h e m e l t i n g

b e h a v i o u r o f 15Na C03-10BaC03-75Si02 b a t c h e s can b e d e s c r i b e d . Below 1 0 0 0 ~ ~ mainly crystalline r e a c t i o n p r o d u c t s a r e formed. The s i l i c a t e c o n t e n t of t h e s e c r y s t a l l i n e compounds i n c r e a s e s w i t h i n c r e a s i n g t e m p e r a t u r e . Above 1 0 0 0 ~ ~ t h e b a t c h c o n s i s t s of a m e l t i n which u n d i s s o l v e d S i 0 2 i s d i s p e r s e d .

R e f e r e n c e s

1. VERWEIJ H . , van den BOOM H . and BREEMER R.E., J . A m e r . C e r . Soc. 61 (1978) 118.

2. CABLE M . , G l a s t e k n i s k T i d s k r i f t 24 (1969) 147.

3 . KROGER C . and MARWAN F . , G l a s t e c h n . Ber. 30 (1957) 222.

4. GUNAWARDANE R.P. and GLASSER F . P . , J . ~ m e c C e r . Soc. 57

( 1 9 7 4 ) 201.

5. KROL D . M . , R i v i s t a d e l l a S t a z . S p e r . V e t r o , i n p r e s s . 6 . BRAWER S.A. and WHITE W . B . , J . Chem. Phys. 63 (1971) 2421.

7. TOROPOV N.A., BARZAKOVSKII V.P., LAPIN V.V. and KURTSEVA N . N . , Handbook o f phase diagrams o f s i l i c a t e s y s t e m s , Vol. 1 . B i n a r y Systems, I s r a g 1 Program f o r S c i e n t . T r a n s . , J e r u s a l e m ( 1 9 7 2 ) . 8 . BATES J . B . , J . Chem. Phys. 57 (1972) 4042.

1 ) The

- q u a r t z

t h e b a t c h E l r e d f o r 16 h r s a t 1 0 0 0 ~ ~

t h e

~n

t h e b a t c h f ~ r e d f o r 1 h r a t l l O o O c .

21 The v i t r e o u s s l l l c a t e h a s t h e d r - o r t r l s l l l c a t e c o m p o s ~ t r o n .

The p o s i t i o n and i n t e n s i t y o E t h e b r o a d bands I n t h e s p e c t r a o f b a t c h e s f i r e d a t t e m p e r a t u r e s above 1 0 0 0 ~ ~ i n d i c a t e s t h a t t h e molten phase i s of t h e d i - o r t r i s i l i c a t e t y p e . Because o f t h e s u b t l e d i f f e r e n c e s between t h e Raman s p e c t r a of d i - and t r i s i l i c a t e g l a s s e s i t i s n o t p o s s i b l e t o d i s t i n g u i s h between them.

The i n t e n s i t y r a t i o o f t h e cx-quartz peak a t 465-ym-l ( t o g e - t h e r w i t h t h e s m a l l peak o f o c - c r i s t o b a l i t e a t 420 cm ) and t h e i n t e g r a t e d intensity of t h e b r o a d bands g i v e s some information a b o u t t h e amount of r e s i d u a l c r y s t a l l i n e S i 0 2 i n t h e m o l t e n b a t c h . A s a p p e a r s from t a b l e 11, a h i g h e r t e m p e r a t u r e i n c r e a s e s t h e d i s - s o l u t i o n r a t e o f SiO c o n s i d e r a b l y . The q u a n t i f i c a t i o n of t h e d a t a , mentioned above, w i l ? a l s o b e used t o g i v e a more q u a n t i t a t i v e d e s c r i p t i o n o f t h e d i s s o l u t i o n r a t e o f S i 0 2 i n t h e m e l t .

T

1°C) t i h r s l o r t h o - Na4S104 s.l,cate { ^Ba2Sxo4

P Y ~ O - { ^Na6s12+

s l l l c a t e Na2Ba2Sr20, meta-

Ba2S1308 Ba5Si802 1 Ba3SL5013 K-Na2Sl2o5 s ~ l l c a t e (j -BaSr205

"'-

{ N a 2 B a 4 S ~ l o 0 2 5 Na6S18019

tri-

Na2S1 0

3 7

5 1 1 1 c a t e

K - q u a r t z m - c r ~ s t o b a l l t e v l t r e o u s s l l i c a t e 2 '

1400 1/6 1/4

X

x

1000 1/4 1 16

X X

X X

x

x x

(XI

X x

850

x x x

X X X

X I

x x

X X

x x x

900

16

x x

X

700

1 16

( x ) x

i x )

x

1100 1/4 1 16

x x l . x x l )

x

x x

800 1 16

x x

X X

X X X

x x

x x

1200 1/4

x X X X