HAL Id: jpa-00224935
https://hal.archives-ouvertes.fr/jpa-00224935
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.
RAPID ASSESSMENT OF STABILITY IN
AMORPHOUS RIBBONS : A NOVEL TECHNIQUE
P. Rougier, R. Krishnan
To cite this version:
P. Rougier, R. Krishnan. RAPID ASSESSMENT OF STABILITY IN AMORPHOUS RIB- BONS : A NOVEL TECHNIQUE. Journal de Physique Colloques, 1985, 46 (C6), pp.C6-417-C6-420.
�10.1051/jphyscol:1985679�. �jpa-00224935�
RAPID ASSESSMENT OF S T A B I L I T Y I N AMORPHOUS RIBBONS: A WOVEL TECHNIQUE P. Rougier and R. Krishnan
Laboratoire de Magne'tisrne, C.N.R.S., 92195 Meudon cedex, France
R6sume - Nous proposons une n o u v e l l e technique basee s u r des mesures de r e s i s - t i v i t e f a i t e s sous d e n s i t e importante de courant. Nous montrons que c e t t e methode permet de cerner l e s q u a l i t e s de s t a b i l i t e des rubans m e t a l l i q u e s amorphes. Deux paramgtres o n t 6 t 6 d e f i n i s e t c a l c u l e s experimentalement. D i f f e - r e n t e s compositions d ' a l l i a g e s o n t Cite etudiees. Cette technique p o u r r a i t Gtre u t i l i s a b l e comme t e s t de c o n t r d l e au niveau de l a production.
A b s t r a c t - A novel technique c o n s i s t i n g o f t h e r e s i s t i v i t y measurements using h i g h r e n t d e n s i t i e s i s described and shown t h a t i t enables one t o assess
t h e q u a l i t y o f t h e amorphous ribbons. Two parameters, namely, t h e energy c o e f f i c i e n t o f r e s i s t i v i t y and energy c o e f f i c i e n t o f s t a b i l i t y have been d e f i n e d and c a l c u l a t e d e x p e r i m e n t a l l y . Several types o f a l l o y s have been examined. It i s proposed t h a t t h i s technique which i s simple and r a p i d can be used as a p r o d u c t i o n t e s t .
I - INTRODUCTION
We describe here a new method t o assess t h e thermal s t a b i l i t y o f amorphous r i b b o n s based on r e s i s t i v i t y measurements. This method c h a r a c t e r i z e s i t s e l f by i t s s i m p l i c i t y and r a p i d i t y . This method o f measuring t h e r e s i s t i v i t y t h a t we have developped u s i n g r e l a t i v e l y h i g h c u r r e n t d e n s i t i e s , c o n t r a r y t o t h e usual w e l l known f o u r p o i n t one, enables us t o study n o t o n l y t h e s t a b i l i t y b u t a l s o t o d e f i n e an energy c o e f f i c i e n t o f s t a b i l i t y f o r amorphous ribbons. The essence o f t h i s method i s t h e r a p i d evalua- t i o n o f r i b b o n s q u a l i t y .
The a c t u a l technique i s as f o l l o w s . Current o f i n c r e a s i n g c o n t r o l l e d i n t e n s i t y i s passed through t h e r i b b o n sample h e l d between two clamps and t h e c u r r e n t serves a l s o t o h e a t t h e sample even t o i t s m e l t i n g p o i n t i f necessary by t h e j o u l e e f f e c t thus dispenses w i t h any furnace f o r t h i s purpose. The r e s i s t a n c e i s c a l c u l a t e d from t h e r a t i o o f t h e v o l t a g e across t h e sample t o t h e c u r r e n t t h a t i s f l o w i n g through i t . The main p a r t i c u l a r i t y here i s t h a t t h e r e s i s t a n c e i s n o t measured (purposely) as a f u n c t i o n o f temperature b u t o f the e l e c t r i c a l power d i s s i p a t e d . Once c r y s t a l l i z e d t h e r e s i s t i v i t i e s i n t h e amorphous and c r i s t a l l i z e d s t a t e s can a l s o be compared.
Changes i n s t r u c t u r e a r e a l s o seen c l e a r l y , and p a r t i c u l a r l y i n t h e r e g i o n of c r y s - t a l l i z a t i o n . We have s t u d i e d using t h i s technique several types o f m e t a l l i c glasses both our own preparations and t h e ones a v a i l a b l e commercially. Ribbons prepared under d i f f e r e n t c o n d i t i o n s have a l s o been analyzed.
I 1 - EXPERIMENTAL
The experimental s e t up i s s c h e m a t i c a l l y shown i n F i g . 1. The r e s i s t a n c e R o f t h e sample i s obtained by an analogic c a l c u l a t o r which measures t h e r a t i o o f t h e v o l t a g e V appearing across t h e sample t o t h e c u r r e n t I f l o w i n g through i t and which i n t u r n i s obtained by measuring t h e v o l t a g e v across a shunt o f O.l,ohm. This c a l c u l a t o r a l s o gives d i r e c t l y t h e e l e c t r i c a l power involved. F i n a l l y t h e v a r i a t i o n o f t h e
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1985679
C6-4 18 JOURNAL DE PHYSIQUE
r e s i s t a n c e R i s d i r e c t l y t r a c e d on a X-Y r e c o r d e r . D i f f e r e n t r a t e s o f h e a t i n g were t r i e d (by using d i f f e r e n t r a t e s o f c u r r e n t s d l ) t o o p t i m i z e t h e c o n d i t i o n s o f measu-
rement. X
I 1 1 - RESULTS AND DISCUSSIONS
L e t us f i r s t l o o k a t some t y p i c a l r e s u l t s which i l l u s t r a t e t h e type o f i n f o r m a t i o n obtained by t h i s technique. F i g . 2 shows t h e v a r i a t i o n o f t h e r e s i s t a n c e R(Q) as a f u n c t i o n o f power (P w a t t s ) i n a NiBSi amorphous ribbon, f o r d i f f e r e n t r a t e s o f heating. I t i s seen t h a t the r e s i s t a n c e increases as t h e power i s increased (and hence as a f u n c t i o n o f temperature) and a t a c r i t i c a l power PC i t drops suddenly The value o f PC i s h i g h e r the h i g h e r t h e h e a t i n g r a t e ( d I / d t ) . For i n s t a n c e
d t
P = 8.7 W and 11 W f o r - = 0.82 and 20.4 mA/s r e s p e c t i v e l y . I t i s a l s o seen t h a t
c dT
decrease i n R shows s t r u c t u r e f o r lower d I / d t values b u t i t g r a d u a l l y disappears when t h i s i s increased. The two stage decrease i n R corresponds t o two stages o f c r y s t a l l i z a t i o n which was v e r i f i e d i n s i m i l a r a l l o y s by DTA measurements ( I ) . Considering t h i s p o i n t we have standardized o u r measurements f o r d I / d t = 2.5 mA/sec.
F i n a l l y when t h e programme i s reversed, and power decreased t o zero, t h e r e s i s t a n c e decreases and reaches a \)a1-le which i s w e l l below the i n i t i a l one i n d i c a t i n g t h a t t h i s l o w e r i n g i s due t o c r i s t a l l i z a t i o n . F i g . 3 shows r e s u l t s obtained f o r
d I / d t = 2.5 m~.s-1. Two remarks c o u l d be made. J u s t before t h e c r y s t a l l i z a t i o n s t a r t s ( p o i n t b) t h e r e i s a d e f i n i t e increase i n t h e r e s i s t a n c e i n d i c a t i n g a change i n t h e temperature dependence o f r e s i s t i v i t y dR . Then a f t e r two steps again t h e r e s i s t a n c e increases ( p o i n t c ) . A t p o i n t d t h e c r y s t a l l i z a t i o n process i s over and i t i s seen aT
t h a t dR i n t h e c r y s t a l 1 iz e d sample i s much h i g h e r . F i g . 4 shows t h e r e s u l t s f o r N i 7 0 F e ~ O B 1 2 ~ i 8 r i b b o n s . dT It i s i n t e r e s t i n g t o note t h a t i n t h i s case t h e c r y s t a l l i z e d sample has a h i g h e r r e s i s t a n c e . This could be a t t r i b u t e d t o a d d i t i o n a l phases pre- sent due t o t h e a d d i t i o n o f Fe. F i n a l l y Fig. 5 shows t h e r e s u l t s f o r amorphous MgT0Zn ribbons. As t h e power i s increased R shows a small b u t a d e f i n i t e decrease i n d l c a ? l n g a n e g a t i v e temperature c o e f f i c i e n t o f r e s i s t i v i t y , u n l i ke i n t h e prece- ding cases. This r e s u l t agrees w i t h t h a t obtained by M o o i j e t a1 ( 2 ) u s i n g t h e c l a s s i c a l f o u r p o i n t method. This f u r t h e r strengthens o u r confidence i n o u r new technique o f measurement.
From these measurements i t i s p o s s i b l e t o d e f i n e two q u a n t i t a t i v e parameters which c o u l d serve t o c h a r a c t e r i z e t h e m e t a l l i c glasses. L e t us consider f i r s t t h e parameter which we s h a l l designate as energy c o e f f i c i e n t o f r e s i s t i v i t y d e f i n e d as y = 1. 6R where p i s t h e r e s i s t i v i t y o f t h e m a t e r i a l ( c a l c u l a t e d from t h e r e s i s - tance, as measured and knowing t h e s e c t i o n and l e n g t h o f t h e r i b b o n ) and 6 R i n d i - cates t h e increase i n t h e r e s i s t a n c e over t h e i n i t i a l value observed j u s t b e f o r e t h e c r y s t a l l i z a t i o n s e t s i n . PC i s t h e c r i t i c a l power a t which t h e d i s c o n t i n u i t y i n R beqi,ns t o appear under our experimental c o n d i t i o n s and described i n e a r l i e r sections. The second parameter which we s h a l l designate as energy c o e f f i c i e n t o f s t a b i l i t y i s d e f i n e d as A = Pc/weight o f t h e sample expressed i n u n i t s o f ~ a t t s . g - I . These two parameters y and A enable us t o assess t h e thermal s t a b i 1 i ty o f t h e amorphous a l l o y s .
Table I summarizes t h e r e s u l t s on Ni 0 Fe B S i r i b b o n s ( 3 ) . There i s a c l e a r increase i n t h e r e s i s t i v i t y w i t h t h e addiflo: o f $$, Ehereas t h e c o e f f i c i e n t y i s n o t so c l e a r l y c o r r e l a t e d . (Nevertheless t h e h i g h e r t h e y t h e h i g h e r w i l l be t h e s t a b i l i t y o f t h e amorphous s t a t e ) . Table I 1 shows r e s u l t s on ribbons commercialised by Vacuumschmelze, Hanau. Our values o f p a r e i n good agreement w i t h those given by t h e manufacturer. We consider t h e Co based a l l o y as t h e most s t a b l e c o n s i d e r i n g t h e h i g h e s t value f o r A , namely 182 As regards y i t shows t h e same t r e n d a s a g i v e n by t h e manufacturers and i n d e e d y can be a s s i m i l a t e d t o t h e p a r a m e t e r a .
The f a c t t h a t A i s c o r r e l a t L d t o t h e thermal s t a b i l i t y i s a g a i n i l l u s t r a t e d by o u r study o f amorphous Mg70Zn30 ribbons. We o b t a i n a value o f A = 52 w . ~ - I which i s p a r t i c u l a r l y low compared t o o t h e r m e t a l l i c glasses s t u d i e d here. These samples have
Analogic Calculator
Fig.1 E l e c t r i c c i r c u i t diagram
F i g . 3 Resistance v a r i a t i o n f o r d i / d t
= 2,5 ~ A . s - ' i n NiS0B12Si8.
F i g . 2 Resistance v a r i a t i o n w i t h power f o r d i f f e r e n t d i / d t i n NiSiB
Fig. 4 Resistance v a r i a t i o n w i t h power i n Ni70Fe10Si12B8
Fig. 5 Resistance v a r i a t i o n w i t h power in Mg70Zn30
C6-420 JOURNAL DE PHYSIQUE
been s t u d i e d i n d e t a i l by u s ( 4 ) . We found t h e s e r i b b o n s c r y s t a l l i z e d when s t o r e d f o r a b o u t s i x months.
These r e s u l t s g i v e u s c o n f i d e n c e i n t h e u t i l i t y of t h i s s i m p l e and r a p i d t e c h - n i q u e o f a s s e s s i n g t h e amorphous a l l o y s . We f e e l t h a t t h i s t e c h n i q u e c o u l d be o f u s e a s a p r o d u c t i o n t e s t and p a r t i c u l a r l y t o o b t a i n a r e l a t i v e e v a l u a t i o n of t h e samples produced.
T a b l e I - Some e x p e r i m e n t a l r e s u l t s on Ni80-,FexB12Si8 r i b b o n s
T a b l e I 1 - R e s u l t s on some commercially a v a i l a b l e r i b b o n s from Vacuumschmel z e , Hanau .
x 0 0.1 1 2.4 5.6 8 10.4 128 16
REFERENCES
y lo-3 / w a t t 7.8 9.6 9.2 1.7 7.4 9.1 7.9 5.4 9 . 5
P ~ Q c m
94 9 5 99 107 107 115 126 126 134
( 1 ) R. Krishnan, M. Dancygier, M. L a r i d j a n i , P. Rougier and M. P e r r i n IEEE T r a n s . Mag. MAG-20 (1984) 1370.
A W/g 78 127 11 1 79 9 5 100 90 154 154
M a n u f a c t u r e r s d a t a
Our e x p e r i m e n t a l r e s u l t s
( 2 ) J.H. Mooij
Phys. S t a t . S o l . A 17 (1973) 521.
Ribbons based on :
p (M R cm) a (10-4/deg)
Tc (OC)
p ( P R cm) Y (10-3/W)
A (W/g)
( 3 ) M. Dancygier
T h e s i s U n i v e r s i t 6 d e P a r i s , 1983.
( 4 ) A. Sadoc, R. Krishnan and M. Rougier J . Phys. F -- 15 (1985) 241.
Co 135 1 - 2
500 144 8 . 3 182 Fe
130 2 500 134 8 . 6 118
Fe-Ni 135 2.3 450 137 13.3
9 1
