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ESR STUDIES OF RADIATION-INDUCED TIN CENTERS IN OXIDE GLASSES
H. Kawazoe, J . Nishii, H. Hosono, T. Kanazawa, H. Imagawa
To cite this version:
H. Kawazoe, J . Nishii, H. Hosono, T. Kanazawa, H. Imagawa. ESR STUDIES OF RADIATION- INDUCED TIN CENTERS IN OXIDE GLASSES. Journal de Physique Colloques, 1982, 43 (C9), pp.C9-155-C9-158. �10.1051/jphyscol:1982929�. �jpa-00222458�
ESR STUDIES OF RADIATION-INDUCED TIN CENTERS I N O X I D E GLASSES
* * * H . Kawazoe*, J . N i s h i i * , H . ~ o s o n o * * , T . ~anazawa~and H . Imagawa
"Department of I n d u s t r i a l Chemistry, Faculty o f Technology, Tokyo Metropolitan University,Fukasawa, Setagaya-ku, Tokyo 158, Japan
**Deparfment o f Inorganic Materials, Nagoya I n s t i t u t e of Technology, Gokiso, Showa-ku, Nagoya 466, Japan
* X I
Toshiba Research and Development Center, Toshiba Corporation, Komukai-Toshiba-cho, Kawasaki 210, Japan
B6sum$+- Les s t r u c t u r e s g l e c t r o n i q u e s e t g6orn6tricfues a u t o u r de Sn e t s n 4 + dans un v e r r e 25Na20.75Si02 o n t g t 6 d 6 t e n n i n 6 e s l ' a i d e d e s d g f a u t s i n d u i t s p a r d e s p h o t o n s c e n t r g s s u r l ' a t o m e d ' g t a i n u t i l i s 6 comrne sonde RPE. Un c e n t r e G l e c t r o n i q u e pi696
( s n 2 + ) - e t un t r o u ~ i S g 6 ( s n 4 + ) - o n t & t 6 d & t e c t g s dans l e s v e r r e s p r e g a r 6 s r e s p e c t i v e m e n t dans l e s c o n d i t i o n s r g d u c t r i c e s ou oxv- d a n t e s . L ' i o n p r 6 c u r s e u r s n 2 + e s t en c o o r d i n a t i o n t 6 t r a g o n a l e p y r a m i d a l e , l a p a i r e i s o l 6 e s u r ~ n 2 + occupant une o r b i t a l e h y b r i - de Spn. On a suppos6 que s n 4 + e s t dans une c o o r d i n a t i o n 2 sym6- t r i e s p h e r i a u e .
A b s t r a c t . - E l e c t r o n i c and g e o m e t r i c a l s t r u c t u r e s around ~ n 2 + and Sn4+ d i s s o l v e d i n 25Na20-75Si02 g l a s s were determined by u s e of t h e photon-induced d e f e c t s c e n t e r e d on a t i n atom a s an ESR probe.
A t r a p p e d e l e c t r o n c e n t e r ( ~ n 2 + ) - and t r a p p e d h o l e c e n t e r ( ~ n 4 + ) - were d e t e c t e d i n t h e g l a s s e s p r e p a r e d under r e d u c i n g o r o x i d i z i n g
c o n d i t i o n , r e s p e c t i v e l y . The p r e c u r s o r i o n ~ n 2 + was found t o b e i n t e t r a g o n a l l y pyramidal c o o r d i n a t i o n , t h e l o n e p a i r on ~ n 2 - f occupying spn t y p e h y b r i d . s n 4 + was c o n s i d e r e d t o b e i n an i o n i c c o o r d i n a t i o n o f s p h e r i c a l symmetry.
1. I n t r o d u c t i o n . - Heavy m e t a l l i c c a t i o n s which b e l o n g t o one o f Ib-Wb groups i n t h e p e r i o d i c t a b l e a r e known t o p l a y an i m p o r t a n t r o l e i n o p t i c a l , d i e l e c t r i c and chemical p r o p e r t i e s o f o x i d e g l a s s e s . TWO
t y p e s o f e q u i l i b r i u m must b e c o n s i d e r e d a s a dominant f a c t o r a f f e c t i n g t h e p r o p e r t i e s ; one i s t h e redox e q u i l i b r i u m between t h e c a t i o n o f lower v a l e n c e s t a t e w i t h n s 2 e l e c t r o n i c c o n f i g u r a t i o n and t h a t o f h i g h e r o x i d a t i o n s t a t e w i t h ( n - l ) d 1 ° c o n f i g u r a t i o n , and t h e o t h e r i s t h e c o o r d i n a t i o n e q u i l i b r i u m f o r t h e c a t i o n s i n a lower v a l e n c e s t a t e , b e i n g i n a h i g h e r o r lower c o o r d i n a t i o n n u m b e r [ l ] .
We planned a s y s t e m a t i c work t o s t u d y comprehensively t h e chemi- c a l s t a t e of t h e r e s p e c t i v e c a t i o n s d i s s o l v e d i n o x i d e g l a s s e s by u s e of ESR f o r photon-induced d e f e c t s c e n t e r e d on one of t h e c a t i o n s and f i n i s h e d s e v e r a l works on ~ 1 + [2-41 , ~ b 2 + [5,61 , cd2+[71 and A S ~ + I 5+ [ 8 1 .
I n a p r e s e n t a r t i c l e w e r e p o r t t h e p r e l i m i n a r y r e s u l t s f o r Sn a s s o c i - a t e d c e n t e r s d e t e c t e d i n a l k a l i s i l i c a t e g l a s s e s .
2. Experimental.- Sodium s i l i c a t e g l a s s e s (25Na20-75Si02) c o n t a i n i n g 1 mole%of t i n oxide(Sn02 and SnO) were p r e p a r e d from r e a g e n t g r a d e c h e m i c a l s , S i 0 2 , Na2C03(orNa2C204) and SnO(or SnC204). The o x a l a t e s were u s e d when r e d u c i n g c o n d i t i o n was p r e f e r r e d . The m e l t was oxygen- bubbled i n p r e p a r i n g ~ n 4 + - r i c h g l a s s e s .
The g l a s s e s were-y-irradiated from ~ O C O s o u r c e a t 77K(O.5Mrad/hr x 2 h r ) . ESR s p e c t r a were measured a t 173K on a JEOL PE-3X X-band s p e c t r o m e t e r .
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1982929
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3. R e s u l t s and D i s c u s s i o n . -
F i g u r e 1 shows t h e ESR s p e c t r a o b s e r v e d f o r t h e g l a s s e s p r e - p a r e d u n d e r an o x i d i z i n g o r r e - d u c i n g c o n d i t i o n . Two g r o u p s of s i g n a l s were s e e n i n t h e v i c i n - i t y o f 3300G(group A) and 5000G
( g r o u p B) .
Assignments.- The A s i g n a l was a s s i g n e d t o t h e a b s o r p t i o n due t o Sn3+ h a v i n g i s o t o p e s w i t h z e r o n u c l e a r s p i n ( I = O , 8 3 . 5 % ) and B t o t h e component l i n e o f h y p e r f i n e ( h f ) s t r u c t u r e pro- duced by an i s o t o p e w i t h non- z e r o n u c l e a r s p i n i n ~ n 3 + [ 1 1 7 s n (1=1/2, 7.57%) o r 1 1 9 ~ n ( 1 = 1 / 2 , 8 . 5 8 % ) 1 . Two t y p e s o f Sn3+ w e r e d e t e c t e d ; one i s a t r p p e d h o l e on a p r e c u r s o r Sn2+ d e n o t e d b y
( ~ n 2 + ) +, and t h e o t h e r i s a t r a p p e d e l e c t r o n on Sn4+ a b b r e - v i a t e d a s ( s n 4 + ) - . The a s s i g n - ments a r e b a s e d on t h e f o l l o w -
T a b l e 1. ESR p a r a m e t e r s o f (Sn4+)- and ( s n 2 + ) +
s - c h a r a c t e r (%!I 58.3 34.5 p - c h a r a c t e r ( % )
-
54.0-
1) The f o l l o w i n g v a l u e s w e r e u s e d a s t h e hf cou l i n g e n e r g i e s f o r 117~11 and f19Sn:
~ f g g ~ = 1 . 4 0 0 3 ( ~ ~ ~ ~ n ) and 1.4650 cm ( ' l g s n ) ;
f r e e
Aaniso=O. 0234 ( l 1 7 s n ) and 0.0244 c m ( l 1 9 s n ) .
g r o u p A
-47-
g r o u p B3280 3300 4600 5000 5400
MAGNETIC FIELD [Gauss]
1 h o l e , " . 1 ::
F i g . 3 Models f o r t h e I I I I I I
c e n t e r s ( ~ n 4 + ) - 3100 3300 3500
and (Sn2+) +. MAGNETIC FIELD [Gauss]
F i g . 1 ESR s p e c t r a of y - i r r a d i a t e d 2 5 N a 2 0 ~ 7 5 S i 0 2 g l a s s e s c o n t a i n i n g 1 mol% o f SnO o r Sn02.
( a ) : p r e p a r e d u n d e r o x i d i z i n g c o n d i t i o n , (b) and ( c ) : u n d e r r e d u c i n g c o n d i t i o n .
SnS04 [ 9 , 1 0 ] . 2) The i n t e n s i t y r a t i o between t h e s i g n a l A and B a r e a p p r o x i m a t e l y e q u i v a l e n t t o t h e abundance r a t i o between t h e i s o t o p e s w i t h z e r o and nonzero n u c l e a r s p i n . 3) ~ n 3 + having t h e f o r m a l e l e c t r o - n i c c o n f i g u r a t i o n of 5 s l i s e x p e c t e d t o b e c h a r a c t e r i z e d by a l a r g e hf c o u p l i n g i n t e r a c t i o n and t o y i e l d t h e hf component l i n e a t a b o u t 5000G[7]. 4) The o t h e r component o f t h e hf s t r u c t u r e c o u l d n o t b e d e t e c t e d . The f a c t i s r e a s o n a b l y e x p l a i n e d by t h e e x t r a o r d i n a r i l y broad d i s t r i b u t i o n o f t h e e x p e c t e d f i e l d s a r i s i n g from s i t e t o s i t e s t r u c t u r a l d i s t r i b u t i o n of t h e c e n t e r [ 7 ] . 5) The s i g n a l s l a b e l l e d by a a r e e x c l u s i v e l y d e t e c t e d f o r t h e o x i d i z e d g l a s s , whereas t h o s e r e - p r e s e n t e d by B and y a r e pronounced f o r t h e reduced g l a s s . 6 ) HC1 c e n t e r ( t h e h o l e t r a s e e d on a n o n b r i d g i n g oxygen i n 5i-0-R'), which i s c o m p e t i t i n g w i t h Sn i n t r a p p i n g a h o l e , was n o t d e t e c t e d f o r t h e reduced g l a s s , w h i l e it was c l e a r l y v i s i b l e i n t h e o x i d i z e d g l a s s . A n a l y s i s o f hf a b s o r p t i o n . - The hf l i n e o f ~ n 3 + can b e a n a l y z e d by s p i n Hamiltonian
Z = ~ H . ? . $ + s . K . x , (1)
where symbols have t h e i r u s u a l s i g n i f i c a n c e . The l i n e shape o f t h e a a b s o r p t i o n , t h e t a i l i n g t o lower magnetic f i e l d ( F i g . l ( a ) ) , , i s chasac- t e r i s t i c o f n s l c e n t e r s i n g l a s s y m a t e r i a l s w i t h isotropic % a n d A t e n s o r s 151. T h e r e f o r e , B r e i t - R a b i s o l u t i o n [ l l ] can b e used i n d e r i v - i n g ESR p a r a m e t e r s . The shape o f 6 i s c h a r a c t e r i z e d by a n i s o t r o p i c 5
a n d z t e n s o r s and by t h e l a r g e hf i n t e r a c t i o n . The newly developed s o l u t i o n must be used f o r a n a l y z i n g t h e a b s o r p t i o n [ l 2 , 1 3 ] . The singu- l a r f i e l d s w e r e l e s s pronounced i n 8 , s o t h e ESR p a r a m e t e r s were e v a l u a t e d by computer s i m u l a t i o n [ 3 , 1 3 ] . An example i s given i n Fig.2.
I t was assumed i n t h e s i m u l a t i o n t h a t o n l y A i s o ( i s o t r o p i c p a r t of A ) i s t h e d i s t r i b u t e d p a r a m e t e r , t h e d i s t r i b u t i o n f u n c t i o n of Aiso b e i n g shown i n ( d ) .
The ESR p a r a m e t e r s of ( ~ n 4 + ) - and ( ~ n 2 + ) + a r e shown i n T a b l e 1.
Models.- The s- and p - c h a r a c t e r ( T a b 1 e 1) e x p r e s s t h e p a r t i c i p a t i o n of Sn 5 s and 5p atomic o r b i t a l s t o t h e semi-occupied m o l e c u l a r o r b i t a l . The l a r g e s p i n p o p u l a t i o n on 5 s i n ( ~ n 4 + ) - i s t h e m a n i f e s t a t i o n o f t h e u n p a i r e d s p i n b e i n g on t h e a n t i - b o n d i n g a o r b i t a l , which i s c o n s i d e r e d t o b e c o n s t r u c t e d by 5 s of Sn and spn h y b r i d s o f l i g a n d oxygens. The p r e c u r s o r ~ n 4 + i o n i s c o n s i d e r e d t o b e i n a s p h e r i c a l c o o r d i n a t i o n a s observed i n Sn02 c r y s t a l ( F i g . 3 A ) . The atomic o r b i t a l 5p of Sn would b e t h e major component o f t h e r e m a i n i n g 40% o f s p i n d e n s i t y , a l t h o u g h t h e e x t r a - b r o a d e n i n g d i s t u r b e d t h e q u a n t i t a t i v e e s t i m a t i o n o f t h e p - c h a r a c t e r o f ( ~ n 4 + ) - . The s p i n p o p u l a t i o n i n
( s n 2 + ) + s u g g e s t s t h e c o o r d i n a t i o n s t r u c t u r e of t e t r a g o n a l l y pyramidal, w i t h t h e l o n e p a i r e x t r u d i n g i n t o a d i r e c t i o n . The l i g a n d oxygen i s r e p e l l e d by t h e l o n e p a i r l o c a t i n g on t h e apex o f t h e pyramid. The d i s t o r t e d c o o r d i n a t i o n s t r u c t u r e i s s i m i l a r t o t h a t observed i n SnO c r y s t a l . The model s t r u c t u r e s a r e shown i n F i g . 3 . The a s s i g n m e n t of y s i g n a l i s n o t c o n c l u s i v e . The o r i g i n of t h e c e n t e r i s c o n s i d e r e d t o b e s n 2 + o r SnO b e c a u s e t h e s i g n a l was n o t observed i n t h e o x i d i z e d g l a s s . I n a d d i t i o n , t h e i s o l a t e d t i n atom, S n O , must b e u n s t a b l e i n t h e m e l t and t e n d s t o become c o l l o i d a l Sn. Thus, we t e n t a t i v e l y a s s i g n y s i g n a l t o ( s n 2 + ) - c e n t e r ; t h e s i g n a l a t a b o u t 3 3 0 0 G ( F i g . l ( c ) ) was o r i g i n a t e d from t h e t i n n u c l e i w i t h 1=0 and t h e d o u b l e t appeared a t b o t h s i d e s o f t h e s i g n a l ( o b s e r v e d a t 3300G) was due t o t h e n u c l e i w i t h I=1/2.
4 . Conclusion.- Three t y p e s o f Sn a s s o c i a t e d c e n t e r s , ( ~ n 4 + ) -, ( s n 2 + ) + and (SnL+)-, were d e t e c t e d i n Sn-doped 25Na20-75Si02 g l a s s e s p r e p a r e d under r e d u c i n g o r o x i d i z i n g c o n d i t i o n . I t was found t h a t ~ n 4 + i s i n a s p h e r i c a l c o o r d i n a t i o n s t a t e and ~ n 2 + i s i n a d i s t o r t e d and t e t r a - g o n a l pyramid, Sn atom b e i n g on t h e apex of t h e t e t r a g o n a l pyramid.
C9-158 JOURNAL DE PHYSIQUE
R e f e r e n c e s
[ I ] Cotton P.A. and Wilkinson G., "Advanced Inorganic Chemistry, 4th Ed.", John Wiley, New York, 1980
[2] Hosono H., Kawazoe H., Nishii J. and Kanazawa T., J. Phys. Chem. E(1982) 161 [31 Hosono H., Xawazoe H. and Kanazawa T., J. Non-Cryst. Solids, t o be published [41 Kawazoe H., Hosono H. and N i s k i i J., J. Non-Cryst. Solids, to be published [51 Hosono H., Nishii J., Kawazoe H., Kanazawa T. and A m e t a n i K., J. Phys. Chem.
84 (1980) 2316
[ 6 ] =sono H. , Kawazce H. and Kanazawa T. , J. Ceram. Soc. Japan, to be published [71 Hosono H., Kawazoe H., Nishii J. and Kanazawa T., J. Non-Cryst. Solids fi
(1981) 149
[81 Imagawa H. , Hosono H. and Kawazoe H. , J. Physique, to be published [91 Booth R. J., S t a r k i e H.C. and Symons M.C.R., J. Phys. Chem. E(1972) 141 [I01 Booth R.J., Starkie H.C., . Symons M.C.R. - and Eachus R.S., J.C.S. Dalton
1973 2233
[ l l ] B r e i t G. and Rabi I.I., Phys. Rev. E ( 1 9 3 1 ) - 2082
[12] Kawazoe H. , Hosono H. and Nishii J. , J. Chan. Phys. E(1982) 3422
1131 Kawazce H., Hosono H., Nishii J. and Kanazawa T., J. Chm. Phys. z(198213429
g, = l . 97 2
Aiso = 0 . 4 8 3 ( 1 1 7 ~ n ) [ c m - l ] (0.505 (119Sni
(mean v a l u e )
4800 5000
H [ G a u s s ]
F i g . 2 E x p e r i m e n t a l ( a ) and c a l c u l a t e d ( b ) s p e c t r a o f the h f a b s o r b t i o n f o r ( ~ n 2 ~ ) + i n y - i r r a d i a t e d 25Na20. 75Si02 g l a s s c o n t a i n i n g 1 m o l % o f SnO. S p i n H a m i l t o n i a n p a r a m e t e r s u s e d i n t h e c a l c u l a - t i o n a r e g i v e n i n ( c ) . The d i s t r i b u t i o n f u n c t i o n s o f A i s o f o r l 1 7 s n a n d 1 1 9 ~ n assumed i n t h e c a l c u l a t i o n a r e shown i n ( d ) . G a u s s i a n d i s t r i b u t i o n ( 0 = 2 . 3 % ) was assumed.
