HAL Id: jpa-00225357
https://hal.archives-ouvertes.fr/jpa-00225357
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.
ACOUSTIC EMISSION DURING CDW TRANSITION
IN 1T-TaS2 AND (TaSe4)2 I
K. Ohtake, E. Sato, Y. Suzuki, R. Yamamoto, M. Doyama, K. Endo, S.
Wakayama, T. Kishi
To cite this version:
JOURNAL DE PHYSIQUE
C o l l o q u e C 1 0 ,
supplement
au
n o
1 2 , Tome 46,decembre 1985
p a g e C10-681ACOUSTIC EMISSION DURING
CDWTRANSITION IN IT-TaS, AND (TaSe,),I
K. OHTAKE, E. SATO, Y. SUZUKI, R. YAMAMOTO, M. DOYAMA,
K.
ENDO*
,
S
.
WAKAYAMA+
+AND T. KISHI+
+Department of Metallurgy and Materials Science, Faculty of
Engineering, The University of Tokyo,
7 - 3 - 1Hongo, Bunkyo-ku,
Tokyo
113,
Japan
'Electrotechnical Laboratory,
1-1-4
Umezono, Sakura-mura,
Niihari-gun, Ibaragi 305, Japan
"Interdisciplinary Research, Faculty
of
Engineering, The
University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153, Japan
A b s t r a c t
-
A c o u s t i c e m i s s i o n s t u d i e s o n low-dimensional c o n d u c t o r s 1T-TaS2 and-1 have b e e n performed t o i n v e s t i g a t e t h e p o s s i b i l i t y of d e t e c t i n g CDW (Charge D e n s i t y Wave) t r a n s i t i o n s . The a c o u s t i c e m i s s i o n due t o t h e CDW t r a n - s i t i o n was o b s e r v e d j u s t o n l y a t t h e t r a n s i t i o n t e m p e r a t u r e i n 1T-TaS2, b u t i t was d e t e c t e d above t h e t r a n s i t i o n t e m p e r a t u r e i n ( T a S e + ) z I . The e x i s t e n c e of
t h e CDW domains was a l s o d i s c u s s e d . [ I ] INTRODUCTION A c o u s t i c e m i s s i o n may b e d e f i n e d a s t h e t r a n s i e n t e l a s t i c waves g e n e r a t e d i n a m a t e r i a l by r a p i d , u s u a l l y l o c a l i z e d , s t r e s s ( o r s t r a i n ) r e l a x a t i o n s accompanying, f o r example, t h e p r o p a g a t i o n of d i s l o c a t i o n s o r t h e growth of c r a c k s
111.
T h i s method h a s been s u c c e s s f u l l y a p p l i e d t o s t u d y t h e m e c h a n i c a l p r o p e r t i e s o f t h e m a t e r i a l s121.
I t h a s improved o u r u n d e r s t a n d i n g o f t h e l a t t i c e d e f o r m a t i o n and t h e f r a c t u r e . Although t h e r e h a s b e e n some a t t e m p t s t o s t u d y t h e p h a s e t r a n s i t i o n s i n s t r u c t u r a l m a t e r i a l s , f o r example, m a r t e n s i t i c t r a n s i t i o n i n i r o n b a s e d a l l o y s131,
o n l y a few s t u d i e s have b e e n performed f o r t h e phas'e t r a n s i t i o n s i n f u n c t i o n a l m a t e r i a l s . I n t h i s r e s e a r c h , we t r i d t o a p p l y t h e a c o u s t i c e m i s s i o n t e c h n i q u e t o t h e s t u d y o f t h e CDW (Charge D e n s i t y Wave) t r a n s i t i o n i n t h e low-dimensional
c o n d u c t o r s . R e c e n t l y t h e r e h a s b e e n a l o t o f i n t e r e s t i n low-dimensional c o n d u c t o r s which undergo s t r u c t u r a l p h a s e t r a n s i t i o n s w i t h t h e f o r m a t i o n o f c h a r g e d e n s i t y waves, CDW t r a n s i t i o n s
141.
The CDW t r a n s i t i o n s produce s m a l l p e r i o d i c l a t t i c e d i s t o r t i o n s and s t a t i c p e r i o d i c m o d u l a t i o n s i n t h e c o n d u c t i o n e l e c t r o n d e n s i t y . Many i n t e r e s t i n g phenomena have b e e n o b s e r v e d i n t h e s e s y s t e m s due t o t h e CDW t r a n s i t i o n . E s p e c i a l l y , a n o n l i n e a r t r a n s p o r t p r o p e r t y a s s o c i a t e d w i t h t h e d e p i n n i n g of CDW's i s one of t h e most r e m a r k a b l e phenomena. Although t h ec o f i s i d e r a b l e amount o f work f o r t h e e l e c t r o n i c p r o p e r t i e s have b e e n made, o n l y a few s t u d i e s f o r t h e a c o u s t i c p r o p e r t i e s h a v e b e e n performed.
I n t h i s s t u d y , t h e a c o u s t i c e m i s s i o n s d u r i n g t h e CDW t r a n s i t i o n s have b e e n s t u d i e d i n two-dimensional CDW system 1T-TaS2 and one-dimensional CDW s y s t e m (TaSe4)21 t o i n v e s t i g a t e t h e p o s s i b i l i t y o f d e t e c t i n g CDW t r a n s i t i o n . IT-TaSz undergoes two CDW t r a n s i t i o n s which o c c u r a t
350K
and a b o u t200
K w i t h h y s t e r e s i s of20
K1 5 1 ,
w h i l e t h e CDW t r a n s i t i o n o c c u r s i n (TaSe4)zI o n l y a t260 K 161.
Both o f them a r e t y p i c a l low-dimensional CDW s y s t e m s .JOURNAL
DE PHYSIQUE
[ 2 ] EXPERIMENTAL
The specimens u s e d i n t h i s e x p e r i m e n t were p r e p a r e d by t h e c h e m i c a l v a p o r t r a n s p o r t t e c h n i q u e . A s f o r IT-TaS2, t h e e v a c u a t e d q u a r t z t u b e w i t h IT-TaS2 powder, e x c e s s s u l p h u r o f 0 . 1 mg/cm3to t h e ampoule volume, and i o d i n e of 0.5 mg/cm3was s e t w i t h t h e t e m p e r a t u r e r e g i o n from 1073 K t o 1 1 7 3 K ; c r y s t a l s were grown a t 1123 K.
( T a S e G ) z I was p r e p a r e d by d i r e c t r e a c t i o n of s t o i c h i o m e t r i c m i x t u r e s o f c o n s t i t u e n t s i n a n e v a c u a t e d q u a r t z t u b e a t a b o u t 773 K i n a t e m p e r a t u r e g r a d i e n t o f 923 K
/
663 K f o r a week. The s i z e of t h e s i n g l e c r y s t a l s was a b o u t 6 x 5 x 0.2 mm3and 0.5 x 0.5 x 1 0 mm: r e s p e c t i v e l y f o r IT-TaS2 and (TaSek) 2 1 . The e x p e r i m e n t a l s e t u p i ss c h e m a t i c a l l y shown i n F i g u r e 1. The sample was sandwiched between two t r a n s d u c e r s by two s p r i n g w i r e s . To d i s t i n g u i s h AE s i g n a l s from e n v i r o n m e n t a l n o i s e s , 2 c h c o i n c i d e n c e method ( r e s o l v i n g time 2 v s e c ) was a p p l i e d . The PZT p i e z o e l e c t r i c t r a n s d u c e r s r e s o n a n t a t 140 kHz a n d 500 kHz were used. E l a s t i c waves from t h e sample a r e t r a n s f o r m e d a s t h e e l e c t r i c a l s i g n a l s , t h e n i t was p u t i n t o a
d i s c r i m i n a t o r t h r o u g h a p r e - a m p l i f i e r , a band-pass f i l t e r and main a m p l i f i e r . The g a i n of a p r e - a m p l i f i e r was 40 dB and a main a m p l i f i e r 30 dB. The t h r e s h o l d v o l t a g e of a d i s c r i m i n a t o r was 50 mV. The c o u n t e r measured t h e t o t a l c o u n t s o f t h e a c o u s t i c e m i s s i o n
(AE)
e v e n t . The measurement o f t h e c o u n t s was made a s a f u n c t i o n oft e m p e r a t u r e from 167 K t o 242 K f o r 1T-TaSz, and from 250 K t o 293 K f o r (TaSer)nI. The t e m p e r a t u r e was changed a t t h e r a t e o f a b o u t 3 K/min
.
DIGI.
VOL.
[pb-I
V.
F1
LTER
.MAIN AMP.
r u
c
,--I<
1
I
3Y STEM
1-*SENSOR
I
1-
CRYOSTAT
HEATER
OSCI LLOSCOPE
F i g u r e 1 : Block Diagram o f a c o u s t i c e m i s s i o n measuring system. 131 RESULTS AND DISCUSSIONS
C10-684
JOURNAL
DE
PHYSIQUEs e v e r a l e v e n t s c o u n t s of t h e a c o u s t i c e m i s s i o n o b s e r v e d
i r
t h i s s t u d y s u g g e s t t h e p o s s i b i l i t y of t h e domain s t r u c t u r e of t h e CDW t r a n s i t i o n by t h e a n a l o g y of t h et r a n s f o r m a t i o n band s t r u c t u r e of t h e m a r t e n s i t i c t r a n s i t i o n . While t h e a c o u s t i c e m i s s i o n was d e t e c t e d o n l y a b o u t a t t h e CDW t r a n s i t i o n t e m p e r a t u r e 216 K , d u r i n g h e a t i n g up i n two-dimensional CDW s y s t e m IT-TaSz, i t was o b s e r v e d a t t h e t e m p e r a t u r e r a n g e between t h e t r a n s i t i o n t e m p e r a t u r e , 260 K and 285 K d u r i n g h e a t i n g up and c o o l i n g down i n one-dimensional CDW s y s t e m (TaSe4)zI. There was a l s o d i f f e r e n c e o f t h e c o u n t s between h e a t i n g up and c o o l i n g down f o r ( T a S e s ) z I . The c a u s e o f t h i s h y s t e r e s i s h a s n o t b e e n made c l e a r y e t . From t h e s e r e s u l t s and d i s c u s s i o n s , t h e
f o l l o w i n g c o n c l u s i o n s c a n b e o b t a i n e d ;
(1) The a c o u s t i c e m i s s i o n due t o t h e CDW t r a n s i t i o n was o b s e r v e d a t t h e f i r s t time. The a c o u s t i c s o u r c e of t h e CDW t r a n s i t i o n i s mainly t h e l a t t i c e d i s t o r t i o n i n t h e CDW t r a n s i t i o n . From t h i s s t u d y , i t was confirmed t h a t a c o u s t i c e m i s s i o n c a n b e a p p l i e d t o t h e s t u d y o f t h e CDW t r a n s i t i o n .
( 2 ) As mentioned above, w h i l e t h e a c o u s t i c e m i s s i o n was d e t e c t e d o n l y a t t h e t r a n s i t i o n t e m p e r a t u r e
i n
IT-TaSz, i t was o b s e r v e d a l s o above t h e t r a n s i t i o n t e m p e r a t u r e ( T a S e - ) e I . I t i s c a u s e d by t h e d i f f e r e n c e of t h e f l u c t u a t i o n of t h e CDW's beeween t h e one-dimensional and two-dimensional CDW system. I n t h eone-dimensional s y s t e m ( T a S e s ) z I , t h e f l u c t u a t i o n of t h e CDW's i s much l a r g e r t h a n t h a t i n two-dimensional s y s t e m 1T-TaSz and t h e CDW t r a n s i t i o n o c c u r s l o c a l l y above t h e t r a n s i t i o n t e m p e r a t u r e , t h e n t h e a c o u s t i c e m i s s i o n was d e t e c t e d a l s o above t h e t r a n s i t i o n t e m p e r a t u r e i n (TaSes)nI. T h i s f l u c t u a t i o n of t h e CDW's i n ( T a S e s ) z I was o b s e r v e d a l s o by X-ray d i f f r a c t i o n / 9 / . (3) S e v e r a l e v e n t c o u n t s of t h e a c o u s t i c e m i s s i o n were o b s e r v e d , which s u g g e s t s t h e p o s s i b i l i t y of t h e e x i s t e n c e of t h e CDW domain i n t h e CDW t r a n s i t i o n by t h e a n a l o g y of t h e c a s e of t h e m a r t e n s i t i c t r a n s f o r m a t i o n .
Acknowledgement
--
The a u t h o r s a r e g r a t e f u l t o P r o f s . R. H o r i u c h i and K.K u r i b a y a s h i f o r t h e i r s t i m u l a t i n g d i s c u s s i o n s and t h e i r k i n d n e s s t o o f f e r t h e i r e x p e r i m e n t a l a p p a r a t u s , and t o D r . S. Yoshida f o r k i n d encouragement. T h i s work was p a r t i a l l y s u p p o r t e d by a G r a n t i n Aid f o r S c i e n t i f i c R e s e a r c h from t h e M i n i s t r y
of E d u c a t i o n , S c i e n c e and C u l t u r e of Japan. REFERENCES
/1/ Wadley, H.N.D., Scruby, C.B., and Shrimpton, D., Acta m e t a l l . 29 (1981) 399. / 2 / See f o r example, Lord, A.E., P h y s i c a l A c o u s t i c s ( E d i t e d by Mason, D.P., and T h u r s t o n , R.N.) Vol.11, Ch.6, Academic P r e s s , New York ( 1 9 7 5 ) .
/ 3 / Takashima, K., Higo, Y., and Nunomura, S., P h i l . Mag. A, 49 (1984) 231. / 4 / See f o r example, P r o c . I n t . Sympo. o n N o n l i n e a r T r a n s p o r t and R e l a t e d Phenomena i n I n o r g a n i c Quasi One Dimensional C o n d u c t o r s , Sapporo, J a p a n 1983 / 5 / Wilson, J.A., D i s a l v o , F . J . , and Mahajan, S., Adv-Phys. 24 (1975) 117. / 6 / Wang, Z.Z., Saint-Langer, M.C., Monceau, P., Renard, M . , G r e s s i e r , P . , Meerschaut, P., Guemas, L., and Rouxel, J., S o l i d S t a t e Commun. 46 (1983) 497.
/ 7 / See f o r example, Nishiyama, Z . , M a r t e n s i t i c T r a n s f o r m a t i o n (Academic P r e s s , New York) (1978)
