ON THE PROPERTIES OF OXIDIZED AND REDUCED COPPER SAMPLES USED FOR ELECTRON IRRADIATION EXPERIMENTS IN THE kHz-RANGE

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ON THE PROPERTIES OF OXIDIZED AND REDUCED COPPER SAMPLES USED FOR

ELECTRON IRRADIATION EXPERIMENTS IN THE kHz-RANGE

U. Gratzel, K. Lücke, G. Sokolowski, B. Wantzen

To cite this version:

U. Gratzel, K. Lücke, G. Sokolowski, B. Wantzen. ON THE PROPERTIES OF OXIDIZED AND REDUCED COPPER SAMPLES USED FOR ELECTRON IRRADIATION EXPERI- MENTS IN THE kHz-RANGE. Journal de Physique Colloques, 1983, 44 (C9), pp.C9-533-C9-537.

�10.1051/jphyscol:1983978�. �jpa-00223428�

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ON THE PROPERTIES OF OXIDIZED AND REDUCED COPPER SAMPLES USED FOR ELECTRON IRRADIATION EXPERIMENTS IN THE kHz-RANGE

U. Gratzel, K. Liicke, G. Sokolowski and B. Wantzen

Institut far AZZgemeine MetaZZkunde und MetaZZphysik der RWTH Aachen, F.R.G.

Abstract

-

Undeformed oxidized and reduced samples are compared with respect to their pinning behaviour after electron-irradiation, to the existence of Bordoni peaks and to the amplitude dependence of internal friction.

I

-

INTRODUCTION

For copper it has been reported that the internal friction behaviour after cold-work depends strongly on the atmosphere used for the re- crystallization anneal / I / . The oxidized and reduced state of copper had been obtained after anneals at 1173 K in corresponding atmospheres.

For the investigation of internal friction in the Hz-range after electron-irradiation at 130 K such samples have been deformed and before irradiation the deformation-induced point defects and the Hasiguti peaks caused by them have been annealed at 400 K. Thus the irradiation effects could be increased /2/. However, for irradiations at 4.2 K a deformation-induced Bordoni-peak, which does not recover at 400 K , would make the quantitative evaluation of pinning experiments by the Granato- Lucke theory impossible. Therefore, first irradiation experiments with undeformed oxidized and reduced copper samples annealed at 1173 K will be reported here.

I1

-

EXPERIMENTAL PROCEDURE

For the preparation of the samples in the first place rods of 99.999%

ASARCO-copper with 9 mm diameter were rolled to a thickness of 3 mm.

Then blocks of 2 1 x 6 ~ 3 mm were cut and 7 mm of the blocks were milled down to give a section 7 mrn long, 2 mm broad and 0.15 mm thick. This milled section was the active part of the sample, a vibrating canti-

lever beam oscillating flexurally, the remaining thick portion was merely used as a clamping block. This preparation technique corresponds to that used by Sosin et al. / 3 / . The as-machined samples were annealed for 2 h at 1173 K and 1023 K in 0.13 Pa air (0-samples) or 1x105 Pa CO

(R-samples). Before and after the anneals the samples were etched electrolytically in 50% H3P04. Then the thick portion of the sample, possessing two holes, was bolted to a sample holder, the temperature of which could be varied between 4.2 and 323 K. Opposite to the free end of the sample was an insulated electrode to detect the vibrations of the sample by frequency-modulation of a.120 MHz-oscillator. This was at 78 K to reduce the noise. To excite the vibrations of about 2 kHz an alternating voltage of the sample frequency and a polarizing voltage of 10 V were used. The alternating voltaqe was controlled automatically in a closed loop to maintain the amplitude of oscillation constant, thus representing a relative measure of decrement. The maximum strain amplitude was varied between 3x1

o - ~

and 5x1 0-7. The polarizing voltage of 10 V caused a static strain amplitude of 3x10-~. With 300 V the

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1983978

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C9-534 JOURNAL DE PHYSIQUE

static strain amplitude could be increased to 3 x 1 0 - ~ (used only for sample R1173). 3 MeV-electrons were used for the irradiations. A dose of 5x1

o1

electrons/cm2 produced a Frenkel defect concentration of 3x1

o - ~ .

After a dose of 5x1 017 electrons/cm2 the dislocations are pinned so strongly that they no longer contribute to internal friction

(background dose)

.

I

/

R 1173

1710 I ~=86r10-'

"=--%.B

1 Dose T,,,

0 0 -

0 5x10" 4 2 K

- .

,

4 I' v 5x10" 323 K

E.

2?b80 B\,e- *

c

a, 'a

'

0

'

¹⁶⁵⁰^1630,

1

^1W Temperature ²⁰⁰

^''..

lK1 ^g\^{3 0}^a\

^j

F i e : Temperature dependence of

-

Fig.2: Amplitude dependence

frequency for sample R.1173: be- of frequency for sample fore irradiation (squares), after R.1173 at 30 and 323 for 5x1 015 electrons/cm2 at 4.2 K polarizing voltages of 10 V

(circles) and after the background (open symbols) and 300 V dose of 5x1

o1

electrons/cm2 (triangles). (full symbols)

.

I11

-

EXPERIMENTAL RESULTS

The reduced sample R.1173 was annealed at 1173 K and during the measurements and irradiations a polarizing voltage of 300 V was used.

Fig.1 depicts the temperature dependence of frequency for this sample:

before irradiation (squares)

,

^{after 5x1}

o1

electrons/cm2 (circles) and after the background dose of 5 x 1 0 ~ ~ electrons/cm2 (triangles). The coincidence of all three curves indicates that there is no irradiation effect. In Fig.2 the amplitude dependence of this sample is given for two temperatures and two polarizing voltages. At 30 K the static strain amplitude of 3x1

o - ~

(300 V) decreases the modulus by 0.85% with respect to the 10 V-curves. For 323 K the effect is smaller because both measurements (10 V and 300 V) were performed at slightly different temperatures. So the temperature dependence of the modulus decreases the effect. The observed modulus decrease due to the bowing-out of the dislocations under the static stress indicates that there is a suffi- cient modulus defect under these conditions. Furthermore, one can con- clude from the weak amplitude dependence, that for the statically small (1 0 V) and large (300 V) bow-outs of the dislocations their mean free loop length is rather small.

The temperature dependence of decrement for the oxidized sample 0.1173/2 (annealed at 1 1 73 K) is depicted in Fig.3 (full symbols).

One recognizes a marked Bordoni-peak at about 90 K. -The reduction of the annealing temperature to 1023 K for sample 0.1023/2 (open

symbols) gives a temperature dependence of decrement without a Bordoni-peak. For both annealing temperatures the oxidized samples show an irradiation effect /4/.

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Temperature LKI

10-~ lo1

Strain Amplitude E

Fig.4: Amplitude dependence of frequency for sample R.1023/2 at different temperatures.

0.11 73/3 (full symbols) and for sample 0.1023/2 (open symbols).

2168i---' 10-

18

1 6 ~

Strain Amplitude E

~ i g . 5 : AmpEit ude dependence of frequency for sample 0.1023/3 at different temperatures.

For the reduced samples annealed at 1023 K dislocation pinning is observed after irradiation at 4.2 K / 4 / . The amplitude dependence of frequency for such a sample is shown for R.1023/2 in Fig.4. It can be seen that for low temperatures (T = 30 K ) the amplitude de- pendence is very weak, but for high r temperatures (T = 323 K ) it starts at amplitudes of about 1x10- rl

.

For the oxidized sample 0.1023/3

(annealed at 1023 K ) the amplitude dependence of frequency is givene8 in Fig.5. One recognizes that for all temperatures below about 6x10 the modulus is amplitude independent.

IV

-

DISCUSSION

The state of the sample R.1173 is characterized by a residual resisti- vity ratio RRR = 564, e.g. a high concentration of homogeneously dispersed single impurity atoms. However, the missing irradiation effect for this sample cannot be explained by a complete pinning of the dislocations by these impurity atoms. For the sample has been irradiated and measured in a statically bowed-out position of the dislocations corresponding to a maximum statical strain amplitude of

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C9-536 JOURNAL DE PHYSIQUE

3x1

o - ~

(300 V )

.

I n t h i s s t a t e t h e r e e x i s t s a modulus d e f e c t of 0.85%

w i t h r e s p e c t t o a s t a t i c a l bow-out of 3x1 0-* (1 0 V )

,

i n d i c a t i n g t h a t t h e r e i s a s u f f i c i e n t c o n t r i b u t i o n of t h e d i s l o c a t i o n s t o t h e modulus and d i s l o c a t i o n p i n n i n g s h o u l d be d e t e c t a b l e a f t e r i r r a d i a t i o n . How- e v e r , t h e weak a m p l i t u d e dependence of t h i s sample c o r r e s p o n d s t o s h o r t l o o p l e n g t h s o f t h e d i s l o c a t i o n s . To o b t a i n a c e r t a i n mean num- b e r o f p i n n i n g p o i n t s p e r l o o p more p o i n t d e f e c t s a r e n e c e s s a r y t h a n f o r l o n g e r l o o p s . But t h e f a c t t h a t even a t t h e background d o s e no m e a s u r a b l e p i n n i n g e f f e c t c o u l d be o b s e r v e d r e q u i r e s an a d d i t i o n a l assumption: The number o f p o i n t d e f e c t s a r r i v i n g a t t h e d i s l o c a t i o n s i s t o o s m a l l . T h i s reduced sample h a s t h e h i g h e s t c o n c e n t r a t i o n o f i m p u r i t y atoms i n t h e l a t t i c e , which must a c t a s t r a p p i n q c e n t e r s f o r p o i n t d e f e c t s . Thus t h i s t r a p p i n g o f d e f e c t s a n d t h e s h o r t l o o p l e n q t h can a c c o u n t f o r t h e m i s s i n g p i n n i n g e f f e c t . A f t e r an a n n e a l a t 1023 K t h e reduced samples show a v a l u e RRR = 816. Obviously, t h e s m a l l e r c o n c e n t r a t i o n o f t r a p p i n g c e n t e r s and a l o n g e r l o o p l e n g t h o f t h e d i s l o c a t i o n s g i v e s a p i n n i n g e f f e c t . However, t h i s s t a t e o f t h e sample i s c h a r a c t e r i z e d by an am l i t u d e dependence of i n t e r n a l f r i c t i o n s t h a t s t a r t s a t a b o u t I X I O - ~ a t 323 K . T h i s means t h a t an a p p l i c a t i o n o f t h e amplitude-independent Granato-Lucke t h e o r y i s o n l y p o s s i b l e f o r measurements a t v e r y low a m p l i t u d e s .

The o x i d i z e d sample ( F i g . 3 ) shows a Bordoni-peak a f t e r t h e r e - c r y s t a l l i z a t i o n a n n e a l a t 1173 K . The e x i s t e n c e o f t h i s peak i s n o t due t o a c c i d e n t a l d e f o r m a t i o n s d u r i n g t h e h a n d l i n g o f t h e samples, b e c a u s e i t n e v e r a p p e a r s i n t h e reduced samples, which a r e handled i n t h e same way. The Bordoni-peak s h o u l d b e due t o s u r f a c e o x i d a t i o n e f f e c t s d u r i n g t h e a n n e a l s . Oxide i s l a n d s have been ob- s e r v e d on t h e s u r f a c e o f o x i d i z e d samples used f o r i n t e r n a l f r i c t i o n e x p e r i m e n t s / 5 / . There i s a d i f f e r e n c e by a f a c t o r of 18 between t h e c o e f f i c i e n t s of t h e r m a l e x p a n s i o n o f c o p p e r and c u p r o u s o x i d e f o r i n s t a n c e /6/. Such a d i f f e r e n c e c a u s e s s t r e s s e s under t h e o x i d e is- l a n d s wnen t h e sample i s c o o l e d down from 1173 K . P l a s t i c d e f o r m a t i o n w i l l o c c u r t h e r e and c a u s e t h e Bordoni-peak. T h a t n o t o n l y s t r e s s e s a r e r e s p o n s i b l e f o r t h e Bordoni-peak i s e v i d e n t , b e c a u s e a f t e r t h e a n n e a l t h e samples were e t c h e d e l e c t r o l y t i c a l l y and a s u r f a c e l a y e r i n c l u d i n g t h e o x y d e i s l a n d s was removed. For o x i d i z i n g a n n e a l s a t 1023 K t h e s u r f a c e o x i d a t i o n seems t o b e reduced s o f a r , t h a t no Bordoni-peak a p p e a r s ( F i g . 3)

.

The a m p l i t u d e dependence o f sample 0.1023/3 ( F i g . 5 ) is much l e s s pronounced t h a n t h a t of R.1023/2 ( F i g . 4 ) . T h i s c a n n o t b e due t o d i f f e r e n c e s i n l o o p l e n g t h a l o n e , b e c a u s e f o r t h e reduced sample w i t h t h e lower r e s i d u a l r e s i s t i v i t y r a t i o s h o r t e r l o o p l e n g t h s s h o u l d be e x p e c t e d t h a n f o r t h e o x i d i z e d sample. Thus t h e r a t i o o f l o o p l e n g t h s s h o u l d be j u s t o p p o s i t e t o t h e o b s e r v e d b e h a v i o u r of a m p l i t u d e dependence. T h e r e f o r e it i s assumed, t h a t d i f f e r e n t b i n d i n g e n e r g i e s e x i s t between t h e p i n n i n g p o i n t s and d i s l o c a t i o n s f o r b o t h s t a t e s of t h e samples. I n t h e reduced s t a t e one can e x p e c t a h i g h concen- t r a t i o n o f s i n g l e i m p u r i t y atoms a c c o r d i n g t o t h e low RRR-value.

The p i n n i n g p o i n t s t h a t d e t e r m i n e t h e mean f r e e l o o p l e n g t h i n t h e reduced samples w i l l be such s i n g l e i m p u r i t y atoms. I n a c c o r d a n c e w i t h t h e o b s e r v e d d i f f e r e n c e i n a m p l i t u d e dependence t h e i r b i n d i n g energy s h o u l d b e s m a l l e r t h a n t h a t o f t h e p i n n i n g p o i n t s i n t h e o x i d i z e d s t a t e . I n t h i s s t a t e a l l o x i d i z a b l e i m p u r i t y atoms form i m p u r i t y - o x i d e c l u s t e r s , a s c a n b e s e e n from t h e h i g h e r RRR-value of o x i d i z e d copper. One c a n e x p e c t t h a t i m p u r i t y - o x i d e s o r s m a l l i m p u r i t y - o x i d e - c l u s t e r s w i l l a c t a s p i n n i n g p o i n t s i n t h e s e samples, h a v i n g a h i g h e r b i n d i n g e n e r g y a s t h e p i n n i n g p o i n t s i n t h e reduced samples. Thus f o r t e m p e r a t u r e s up t o 323 K t h e i n t e r n a l f r i c t i o n o f sample 0.1023/3 i s amplitude-independent f o r a m p l i t u d e s 6 6x10-*.

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The i r r a d i a t i o n o f undeformed samples showed t h a t f o r t h e r e d u c e d s t a t e t h e r 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 must b e d e c r e a s e d t o 1023 K i n o r d e r t o o b t a i n p i n n i n g e f f e c t s a f t e r i r r a d i a t i o n . However, t h e n t h e a m p l i t u d e dependence of i n t e r n a l f r i c t i o n b e g i n s a t a b o u t 1 X I

oW8

f o r 323 K. A l s o i n t h e o x i d i z e d s t a t e t h e a n n e a l i n g t e m p e r a t u r e h a s t o b e d e c r e a s e d t o 1023 K t o a v o i d t h e e x i s t e n c e of a Bordoni-peak.

So b o t h t y p e s of s a m p l e s a r e s u i t a b l e f o r i r r a d i a t i o n e x p e r i m e n t s , b u t t h e r e d u c e d t y p e must b e measured a t v e r y low a m p l i t u d e s .

REFERENCES

/ I / E. T r o g e r , K. Liicke,G. S c h r o e d e r and G . Sokolowski; i n " I n t e r - n a l F r i c t i o n a n d U l t r a s o n i c A t t e n u a t i o n i n S o l i d s " , Ed.

C.C. S m i t h , Pergamon P r e s s (1980) p.79

/ 2 / A. S c h n e l l , G. Sokolowski and K . Liicke; C r y s t a l l L a t t i c e D e f e c t s 8 (1980) 201

-

/ 3 / D. K e e f e r , A. S o s i n ; A c t a Met.

11

( 1 9 6 4 ) 1041

/ 4 / B. Wantzen, G . Sokolowski a n d K . Liicke; t h i s c o n f e r e n c e / 5 / H. Miillner; Nuovo Cirnento

33B

(1976) 177

/ 6 / R.F. T y l e c o t e ; J. I n s t . of M e t a l s

78

( 1 9 5 0 / 5 1 ) 7 8