Radiation hardening of alkali halides and magnesium oxide

Scripta M E T A L L U R G I C A

Vol. 5, pp. 289-294, 1971 Printed in the U n i t e d States

RADIATION OF ALKALI

HALIDES

Pergamon

Press,

HARDENING

AND MAGNESIUM

OXIDE

B. R e p p i c h Institut

for W e r k s t o f f w i s s e n s c h a f t e n

Universit~t

Erlangen-NOrnberg,

(Received

In a series kali

fluorides,

oxide

chlorides,

(4) has been

be d e s c r i b e d elastic field cal

of p r o m i n e n t

by a m o d e l

interaction

of defects

resolved

stress

1971)

the radiation

bromides

It was

of F l e i s c h e r

between

27,

studies

~dides,

(5,6),

that

which

results

is based

In this m o d e l

T o is given

fect

is the CSSR of the u n i r r a d i a t e d material, oo c o n c e n t r a t i o n c=O. The c o n s t a n t K contains the

relationships extending

and a factor w h i c h

between

defect

the F l e i s c h e r

T O as in e q u a t i o n is g e n e r a l l y

the

(i) is obtained.

fulfilled

is derived

and dislocation.

model,

except

strain

the criti-

(i)

T

the t e t r a g o n a l i t y ,

can

on the

by

T O = Too + K-c I/2

where

of al-

and m a g n e s i u m

the

and the t e t r a g o n a l

by irradiation. (CRSS)

hardenin~

(1,2,3)

shown

dislocations

introduced

shear

January

investigated.

I

Germany

i.e.

for a de-

shear modulus,

from g e o m e t r i c a l

In Frank's

same c o n c e n t r a t i o n

model

(7),

dependence relation

of

It was

shown

that

in the m o s t

cases

at low c o n c e n t r a -

(i)

tions.

Recently, solid

solution

busch's uution

Labusch

(8) has g e n e r a l i z e d

hardening

(9).

In c o n t r a s t

s t a t i s t i c a 1 of i n t e r a c t i o n

obstacles

acting

along

forces

theory

the F l e i s c h e r to F l e i s c h e r ' s

takes

and of d i s t a n c e s

the d i s l o c a t i o n

289

while

into account between

model theory

of La-

a distri-

neighbouring

Fleischer's

derivation

Inc

290

RADIATION

starts del

HARDENING

from average

is that

OF ALKALI

values.

HALIDES

A significant

the same m a t h e m a t i c a l

problem

of B l o c h w a l l

pinning

in type II s u p e r c o n d u c t o r s

we apply CRSS

Labusch's

pinning

model

AND M A G N E S I U M

advantage

formalism

(magnetic

(electrical of

Vol.

5, No.

of L a b u s c h ' s

can be applied

hardening)

to the p r o b l e m

OXIDE

to the

and of flux

hardening)

mo-

line

(iO).

If

irradiati~hardening

the

is given by T

The p u r p o s e

= T

o

of this

paper

of i r r a d i a t i o n

experiments

(4) c o n c e r n i n g

the d e f e c t

cide w h i c h m o d e l low d e f e c t

describes

In figures

(left,

according plotting

+ K'-c 2/3

(2)

is to r e e v a l u a t e

on alkali

halides

concentration

published

results

(i) and m a g n e s i u m

dependence

the real

situation

increase

in CRSS

in order

better,

oxide

to de-

especially

for

concentrations.

1 to 5 the

ted as a function plot

oo

of the defect

according

to equ. ~

to equ.

(2)).

versus

(i)),

Reasonably

c I/2- as well

AT = TO-TOO

concentration and

c, both

in the L a b u s c h

straight

lines

is r e p r e s e n -

in the F l e i s c h e r plot

(right,

are o b t a i n e d

as c 2/3.- The F l e i s c h e r

plot

by

AT vs.c I/2"

Q9 Li

O8

~

a6

°2 /

~F

a

~F

0.I

00

a3 °'

0.I

1

FIG.

2

la

0

0

I

FIG.

2

ib

i 3

4

Vo].

5, No.

4

RADIATION

HARDENING

OF A L K A L I

HALIDES

AND

t

l

MAGNESIUM

OXIDE

291

f.O 09

0.91

°t

0.8

Q81

0.7

0.7

0.6

0.6 0.5

04

0.4

03

03

KCl

~

Q2

02

0.1

03

,.l l-',~,,'"IrT -

0

1

I

I

2

I

3

FIG.

4

1

5

t

0

6

0

;

J

2

~

3

FIG.

2a

;0

1.01

09

o9F

08

as~

4

KCI

5

6

7

8

9

~0

2b

07

~

0.6 oSl

/ / , j /

0.4

KBr

03

°, I

02

a2t

O;

0.I]

0 ~ 0

I

2

FIG. FIG.

KBr

o.4t

I

I

I

I

I

3

4

5

6

?

ol

0

3a

;

2

FIG.

3

z,

5

6

?

8

9

3b

1-3:

The i n c r e a s e of the c r i t i c a l r e s o l v e d s h e a r s t r e s s AT = T - T after y-irradiation as a f u n c t i o n of d e fect c o n c e n t r a t i o n ~ for ~ I k a l l h a l l d e s i n g l e c r y s t a l s : f l u o r l d e s (fig.l), c h l o r i d e s (fig.2), b r o m i d e s and j o d i d e s (fig.3). D e f o r m a t i o n at r o o m t e m p e r a t u r e , d e f o r m a t i o n r a t e ~ = iO-3s -I. left (fig. la, 2a, 3a) : the o r i g i n a l F l e i s c h e r p l o t of N a d e a u (i) O

right

(fig.

ib,

2b,

.

.

AT vs. c I/2 (equ. (i)). 3b) : The L a b u s c h p l o t of the AT Vs.

c 2/3

(equ. (2)).

same

data

10

292

RADIATION

HARDENING

OF A L K A L I

HALIDES

AND MAGNESIUM

OXIDE

Vol.

5, No.

I0

Mgo • electron irrodiated and ~- icrodioted 0 electron ,)'rodiatedand optical~ bleoched

9 8

/ ///

/

/

/

•

/ 4

4

3

3 2 I

I I

I 2

I 3

I 4

I 5

i 6

0

10

0

20

I z,,O

3O

50

tcc,o -' J" FIG.

4a

FIG.

4b

~0

24

iI

O

!41

• ,e~ma ~,o~,~ or~ ~ - ~ O~ #~dMtd

22

J

/ /

r8I r61 F4

t2

~

,o 8 6

6

4

4 2

2

O~

5

FIG.

FIG.

4 and

I

5:

10

5a

I

15

0

4

I JO0

50

FIG.

I /50

5b

The i n c r e a s e of the c r i t i c a l r e s o l v e d s h e a r s t r e s s AT = T - T as a f u n c t i o n of c o n c e n t r a t i o n of c e n t r e s oo c for h i g h p u r e M g O ~ i n g l e c r y s t a l s a f t e r i r r a d i a t i o n : w i t h h i g h energy electrons (1.8 MeV) and y (Fig. 4), w i t h n e u t r o n s (>i MeV) and y (Fig. 5). (ref. 4) .Deformation in c o m p r e s s i o n t e s t s at r o o m t e m p e r a t u r % d e f o r m a t i o n rate = 10-3 s-l. _1/2 left (fig. 4a, 5a): F l e i s c h e r p l o t AT Vs. u2/3 (equ. (i)). r i g h t (fig. 4b, 5b): L a b u s c h p l o t AT vs. c / (equ. (2)).

4

Vol.

5, No.

4

RADIATION

HARDENING

OF ALKALI

extrapolated

to c=O yields negative

and neutron

irradiated MgO. Moreover,

lation yields

too-Values

&t-values

determined

is limited to dilute

material

(KBr and neutron

(LiF, NaCI).

solid solutions.

that

irra-

This is particu-

On the other hand,

straight

From this comparison alloys

investigated

it may be concluded

sults of the solid solution

hardening

hardening

that,

experimentally.

in analogy to re-

in fcc alloys

(14), the statistical

a better d e s c r i p t i o n

the La-

lines through the origin

over the whole range of concentrations

radiation

KBr

with regard to the fact that the Fleischer model

busch plot &t vs. c 2/3 yields

hexagonal

OXIDE

in these cases the extrapo-

and may be even negative

larly remarkable

for LiF, NaCI,

of CRSS of the unirradiated

are lower than e x p e r i m e n t a l l y diateQ MgO)

HALIDES AND M A G N E S I U M

(11-13)

theory of Labusch

of the defect concentration in alkali halides

and

leads to

dependence

of the

and MgO.

REFERENCES

(I)

J.S. Nadeau,

J. Appl.

Phys. 35,

(2)

J.S.

Nadeau,

J. Appl.

Phys.

(3)

W.A.

Sibley,

E. Sonder,

(4)

W.C. Mc Gowan,

(5)

R.L.

Fleischer,

Acta Met.

I__OO, 835

(1962)

(6)

R.L.

Fleischer,

J. Appl.

Phys. 33,

3504

(7)

W° Frank,

(8)

R. Labusch,

(9)

R.L.

W.A.

Fleischer,

(1964)

33, 3480 34, 2248

(1962) (1963)

J. Appl.

Sibley,

Z. Naturforschg. phys.

1248

stat.

Phys. 34,

Phil. Mag. 19,

22a,

365

sol. 41,

Acta Met. 9,

996

2366 967

(1963) (1969)

(1962)

(1966)

2 (1970) (1961 and ii,

203

(1963)

(IO){R. Labusch, Crystal Lattice Defects i, 1 (1969) P. Haasen, Nachr. G~tt. Akad. Wiss. ~1970) No 6 (ii) P. Jax, P. Kratochvil, P. Haasen, Acta Met. 18, 239 (12) T. Kan,

P. Haasen,

Z. Metallk.

(13) T. Kan,

P. Haasen,

Mater.

(14) h. Scharf,

P. Lucac,

61,

355

Sci. Eng. 5,

M. Bocek,

(1970)

(1970) 176

P. Haasen,

(1970) Z. Metallk.

59, 799 (1968)

293