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RAMAN SCATTERING FROM AMORPHOUS
STATE OF FERROELECTRIC PbTiO3 AND ITS
CHANGE IN THE CRYSTALLIZATION PROCESS
T. Nakamura, M. Takashige, Y. Aikawa
To cite this version:
JOURNAL DE PHYSIQUE
CoZZoque C6, suppZe'ment au n o 12, Tome 42, d6cernbre 1981 page C6-421
RAMAN SCATTERING FROM AMORPHOUS STATE OF FERROELECTRIC PbTiOj AND I T S CHANGE I N THE C R Y S T A L L I Z A T I O N PROCESS
T. Nakamura, M. Takashige and Y. Aikawa
I.S.S.P., Uniu. of Tokyo, Japan.
A b s t r a c t
-
Amorphous s t a t e o f PbTi03 h a s been p r e p a r e d . DTA, o p t i c a l and e l e c t r o n - n i c r o s c o p i c i n v e s t i g a t i o n s h a s c l a r i f i e d t h e c r y s t a l l i z a t i o n t e m p e r a t u r e and t h e d e v i t r i f i c a t i o n phenome- non. I n Raman s p e c t r a , low-lying r e s p o n s e i s found i n - t h e amorphous s t a t e , and t h e f e r r o e l e c t r i c s o f t mode i s found when it i s c r y s t a l l i z e d .Tsuya e t a l l ) f i r s t p r e p a r e d amorphous f l a k e s o f f e r r o e l e c t r i c PbTi03 by a r o l l e r quenching method. C o n f i r m a t i o n o f t h e i r b e i n g r e a l l y amorphous and n e i t h e r c r y s t a l l i t e s n o r c e r a m i c s , h a s been made
2 )
by Uno u s i n g X-ray d i f f r a c t i o n method.
G l a s s and Nassau i n d e p e n d e n t l y p r e p a r e d amorphous f l a k e s o f c r y s t a l s such a s LiNb03, LiTa03, and r e p o r t e d unexpected h i g h v a l u e s
5
10 of d i e l e c t r i c c o n s t a n t i n t h e v i c i n i t y o f c r y s t a l l i z a t i o n temper- a t u r e ? ) L i n e s p u b l i s h e d a t h e o r y , s t a t i n g t h a t t h e amorphous s t a t e of f e r r o e l e c t r i c s having h i g h symmetry s t r u c t u r e such a s p e r o v s k i t e may
adding " g l a s s formers". Confirm- 0
a t i o n of b e i n g r e a l l y i n t h e amor- phous s t a t e i s made by x-ray
4 have f e r r o e l e c t r i c i t y . We p r e p a r e d amorphous f l a k e s o f p u r e ( 9 9 . 9 % ) PbTi03 by t h e twin r o l l e r quenching method, w i t h o u t (S) c r y s t a l l i n e d i f f r a c t i o n s . EXSAFS s t u d y i s i n p r o g r e s s by T e r a u c h i e t a l . a Amorphous f l a k e s o b t a i n e d On h e a t i n g t h e as-quenched
1
I I II
m a t e r i a l , DTA does n o t f i n d 400 450 500 550 600 anomaly a t t h e f e r r o e l e c t r i c TEMPERATURE ( O C) ( A ) as-quenched a r e a b o u t 20 p t h i c k , t r a n s p a r e n t ,2
and o p t i c a l l y i s o t r o p i c , w i t h y e l l o w i s h c o l o r . C u r i e p o i n t (490°C) b u t d o e s f i n d F i g u r e 1-
-
-dJv-
C6-422 JOURNAL DE PHYSIQUE
a s h a r p exothermic peak a t t h e c r y s t a l l i z a t i o n temperature T c r y s
=
5 4 0 ° C ( F i g . l ) .The d e v i t r i f i c a t i o n phenomenon i s observed, when as-quenched 5
f l a k e i s heated up t o about 950°C.
The Raman s c a t t e r i n g experiments were made on t h e p e l l e t s a s d e s c r i b e d above6 ' 7 )
Fig.Z(A) shows Raman spectrum from as-quenched m a t e r i a l . S o f t mode does n o t e x i s t , background i s h i g h , and s e v e r a l b r o a d p e a k s e x i s t .
Fig. 2 (B)
,
( C ) and (D) show e f f e c t of h e a t t r e a t m e n t on Raman s p e c t r a . A f t e r h e a t t r e a t m e n t a t a temperature above Tc r y s
'
s o £ tmode appears. The frequency of t h e damping of t h e s o f t mode i s a f u n c t i o n of annealing temperature(T
max) ' With i n c r e a s i n g t h e anneal-
i n g temperature, t h e s o f t mode becomes s h a r p and h a r d , o t h e r modes than t h e s o f t mode become s h a r p , and t h e background d e c r e a s e s . I f t h e annealing temperature i s
-
T c r y s spectrum i s same a s t h a t from t h e s t a r t i n g m a t e r i a l .
as-quenched
2
FREQUENCY SHIFT (cm-l) FREQUENCY SHIFT (cmW1)
High r e s o l u t i o n , low wave-number s p e c t r a ( u s i n g J o b i n YvonRamanor HG-2s) show low-lying r e s p o n s e . F i g . 3 shows t h e low wave-number s p e c t r a from samples which had been a n n e a l e d a t v a r i o u s t e m p e r a t u r e s . When samples had been a n n e a l e d a t t e m p e r a t u r e s lower t h a n Tcrys,broad
low-lying peak was o b s e r v e d . T h i s peak i s d i f i n i t e l y d i s t i n c t from t h e f e r r o e l e c t r i c s o f t mode, which i s o b s e r v e d when a sample i s
a n n e a l e d above T T h e o r e t i c a l i n v e s t i g a t i o n s on t h i s low f r e q u e n c y c r y s '
a t o m i c v i b r a t i o n s i n t h e amorphous s t a t e a t r a c t much i n t e r e s t . R e f e r e n c e s
1 ) N . Tsuya and K. I. A r a i : J p n . J. Appl. Phys.
18
461 (1979) 2)H. Ozawa and R. Uno : Proc. JSSF-2, Kyoto 1980, J . Phys. SOC.J p n .
49
supp1.B 144 (1980)3)A. PI. G l a s s , M. E. L i n e s , K. Nassau and J. W. S h i e v e r : AP<I. Phys. L e t t e r s
31
249 (1977)4)M. E. L i n e s : Phys. Rev.
B15
388 (1977)5) PI. T a k a s h i g e , T. P l i t s u i , T. Nakamura, Y . Aikawa and 91. S. Jang: J p n . J . Appl. Phys. L159 (1981)
6 ) T . Nakamura and M. Takashige: Proc. JSSF-2, Kyoto 1980, J. Phys. Soc. J p n .