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ULTRASONIC RELAXATION PEAKS IN ELECTRON
IRRADIATED Al-700 ppm Si
E. Johnson, A. Granato
To cite this version:
JOURNAL DE PHYSIQUE
Colloque C10, suppldment
au
11-12, Tome 46, ddcembre 1985 page C10-63ULTRASONIC RELAXATION PEAKS IN ELECTRON IRRADIATED A1-700 ppm ~ i *
E.C. JOHNSON AND A.V. GRANATO
Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign. Urbana, Illinois 61801, U.S.A
A b s t r a c t
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a n d ~ z
A1-700 ppm peaks were
U l t r a s o n i c a t t e n u a t i o n and v e l o c i t y measurements were made a t 10 simultaneously, between 1.5 K and 240 K, on a s i n g l e c r y s t a l o f Si a f t e r i r r a d i a t i o n below 70 K w i t h 2.5 MeV electrons. Two detected. A t 31 Mhz t h e peak i n t h e Cqq mode i s a t 112 K, and t h e second peak i s a t 22.3 K i n t h e
C'
mode. Both peaks anneal o u t near 115 K. What i s seen i n t h i s system bears a remarkable resemblance t o t h a t r e p o r t e d e a r l i e r f o r A1 -Ag.I
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INTRODUCTIONE l e c t r o n i r r a d i a t i o n o f d i l u t e m e t a l l i c a l l o y s o f t e n r e s u l t s i n t h e p r o d u c t i o n o f dip01 a r d e f e c t s which cause d i a e l a s t i c and parael a s t i c responses t o a p p l i e d s t r a i n f i e l d s 111. The d i a e l a s t i c response corresponds t o a p o l a r i z a t i o n o f t h e d i p o l e s r e s u l t i n g i n a temperature and frequency independent ( i n t h i s range o f measurement) s o f t e n i n g o f t h e e l a s t i c constants. The p a r a e l a s t i c response corresponds t o r e o r i e n t a t i o n o f t h e d i p o l e s t o e n e r g e t i c a l l y f a v o r a b l e d i r e c t i o n s . The e f f e c t i s again t o reduce t h e e l a s t i c constants, and i n a d d i t i o n g i v e s r i s e t o an a t t e n u a t i o n .
I n p r e v i o u s work 121, systematic t r e n d s and r e l a t i o n s h i p s were expected i n u l t r a s o n i c s t u d i e s o f a number o f aluminum a l l o y s (Al-Fe, Al-Zn, A1-Ag, Al-Zn-Fe, A1-Mg). Instead, i t was found t h a t each system had i t s own c h a r a c t e r i s t i c p a t t e r n of r e l a x a t i o n peaks bearing l i t t l e resemblance t o o t h e r s studied. I n t h e present study, t h e r a d i a t i o n induced r e l a x a t i o n peaks i n A1-Si are found t o be v e r y s i m i l a r i n n a t u r e t o those p r e v i o u s l y i n v e s t i g a t e d i n A1-Ag.
I 1
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EXPERIMENTA sample approximately 1 cm2 was cut, using an a c i d saw, from a s i n g l e c r y s t a l boule grown by Monocrystals (Columbus, Ohio). Atomic Absorption Spectroscopy i n d i c a t e d a Si c o n c e n t r a t i o n o f 673
'
67 ppm. Mass Spectroscopy r e s u l t s showed t h e c o n c e n t r a t i o n o f other t r a c e i m p u r i t i e s t o be approximately 2 orders o f magnitude l e s s than t h i s . The sample was o r i e n t e d w i t h i n .5' o f <110>, using t h e Laue double exposure scheme developed by Ochs /3/. Two sets o f [ I 1 0 1 faces wereC10-64 J O U R N A L DE PHYSIQUE
e l e c t r o p o l i s h e d f l a t and p a r a l l e l t o almost o p t i c a l tolerances. A .25", 10 MHz, AC-cut, quartz transducer was bonded t o one sample face using Nonaq stopcock grease, and aligned t o produce a <001> p o l a r i z e d (C4 ) shear wave. The sample was i r r a d i a t e d w i t h 2.5 MeV e l e c t r o n s spread u n i f o r m l y ? w i t h i n 10%) over t h e face o f t h e c r y s t a l opposite t h e transducer. A t y p i c a l i r r a d i a t i o n f l u x was 1.5 ~1A/(cm2), and t h e sample was h e l d below 70 K. Measurements o f t h e a t t e n u a t i o n and v e l o c i t y (resonant frequency) as a f u n c t i o n o f temperature were made a t two frequencies before and a f t e r i r r a d i a t i o n , and a f t e r various isochronal anneals. The isochronal anneal time was 10 min. The C4 shear mode was r u n t w i c e because o f d i f f i c u l t i e s experienced i n t h e f i r s t run. ?he <110> p o l a r i z e d (C') shear mode was s i m i l a r l y examined. The sample was allowed t o reach room temperature between runs. The damage (Frenkel p a i r (F.P .) c o n c e n t r a t i o n assuming .0004 uohm-cmlppm F. P.) /4/ was monitored using a t h i n r e s i s t i v i t y sample c u t from t h e same p o r t i o n o f the boule, and placed d i r e c t l y i n f r o n t o f the sample d u r i n g i r r a d i a t i o n .
I11
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RESULTSA C44 peak was detected near 112 K (Fig. 1). This peak annealed near 115 K. The associated resonant frequency d i s p e r s i o n was n o t determined due t o a combination o f t h e l a r g e background slope a t t h i s temperature and t h e 1/T dependence o f t h e r e l a x a t i o n strength. The d i a e l a s t i c effect i n C44, however, was e a s i l y determined a t low temperatures where the frequency background f l a t t e n s out.
A C 1 peak was detected near 21 K. This peak also annealed near 115 K, b u t a t a s l i g h t l y f a s t e r r a t e . The d i s p e r s i o n accompanying t h i s peak i s shown i n Fig. 2. The d i a e l a s t i c drop can also be seen i n t h i s f i g u r e .
Both t h e C44 and C ' r e s u l t s are summarized i n Table I. Assuming an Arrhenius r e l a t i o n , T = ~ ~ e x p ( Q / k T ) , t h e a c t i v a t i o n energy Q, and t h e jump time . ,T, were
determined from t h e temperature s h i f t o f t h e peak w i t h frequency 151. The experimental h a l f w i d t h HWe, i s compared w i t h the i d e a l s i n g l e re1 a x a t i o n Debye w i d t h HWd. The d i a e l a s t i c drop i n each mode i s given a f t e r i r r a d i a t i o n f d l , a f t e r t h e 120 K anneal fd2, and a f t e r t h e 200
K
anneal fd3.I V
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DISCUSSIONThe annealing behavior associated w i t h these peaks c o r r e l a t e s w i t h a r e s i s t i v i t y substage r e p o r t e d by Ceresara e t . al.,
161
i n A1-Si. A1-Ag also e x h i b i t e d one peak i n each mode. The A1-Ag C44 peak occurred near 113 K (30 Mhz). The A1-Ag C ' peak occurred near 21 K. Both peaks annealed near 120 K w i t h t h e C ' annealing a t a s l i g h t l y f a s t e r r a t e . I n an EXAFS171
study o f Al-Ag, o n l y one d e f e c t s t r u c t u r e was r e p o r t e d t h a t annealed o u t a t t h i s temperature.I t i s n o t evident why A1-Si and A1-Ag should g i v e r i s e t o s i m i l a r r e l a x a t i o n spectra. The valence s t r u c t u r e s o f Ag and Si are s i g n i f i c a n t l y d i f f e r e n t . The t h e o r e t i c a l c a l c u l a t i o n s o f Dederichs e t . a1
.,
/8/ suggest t h a t t h e atomic m i s f i t between s o l u t e and solvent atoms should determine t h e types o f d e f e c t s t r u c t u r e s produced. Ag, however, i s s l i g h t l y oversized i n the aluminum l a t t i c e , whereas Si i s almost 16% undersized 191. Al-Si and A1-Ag are the f i r s t systems encountered which d i s p l a y such a s t r i k i n g s i m i l a r i t y . Further work on these systems i s i n progress.ACKNOWLEDGEMENTS
JOURNAL
DE
PHYSIQUEREFERENCES
/1/ K. L. Hultman, PhD Thesis, U n i v e r s i t y o f I l l i n o i s (1979).
/2/ A. V. Granato, J. Holder, K. L. Hultman, D. L. Johnson, G. G. Setser, P. Wallace, and H. Wong, P o i n t Defects and Defect r n t e r a c t i o n s i n Metals, ed. J. Takamura e t . al., (Japan: U n i v e r s i t y o f Tokyo Press), 360 (1982).
/3/ T. Ochs, Jour. Sci
.
I n s t . (Jour. Phys. E),1
,
1122 (1968). 141 F. R. F i c k e t t , Cryogenics, 11, 349 (1971)./5/ A. S. Nowick and B. S. B e r r y , " A n e l a s t i c Relaxation i n C r y s t a l l i n e Solidsu, Academic Press, N.Y. and London, 61.
/6/ S. Ceresara, T. Federighi, F. P i e r a g o s t i n i , Phy. L e t t .
5,
No. 2, 152 (1963). /7/W.
Weber and H. Peisl, P o i n t Defects and Defect I n t e r a c t i o n s i n Metals, ed. J. Takamura e t . al., (Japan: U n i v e r s i t y o f Tokyo Press), 368 (1982)/8/ P. H. Dederichs, C. Lehmann, H. R. Schober, A. Scholz and R. Z e l l e r , Jour. Nucl. Mat., 69 & 70, 176 (1978).
