The effect of the heat treatment on the superconducting properties of fast quenched AlSi

Physica 109 & I IOB (1982) 2067-2069 North-Holland Publishing Company

‘067

THE EFFECT OF THE HEAT TREATMENT PROPERTIES Kuan

OF FAST QUENCHED

WEI-YEN,

Chen

Institute

of Physics,Academia

Cheng

WU and Pierre

Lahoratoirr

de Physique

The effect of prepared by the transitions has superconducting

tivity

Sinica, Beijing,

des Solides,

Wang

ZU-LUN

China

Uniuersite’ Paris XZ, 91405 Orsay, France

heat treatment on the microstructure and superconducting properties of the eutectic alloy Al-l 1.3 at% Si splat quenching technique has been studied. The anomalous magnetoresistivity in superconducting-normal been found and low temperature heat capacity was measured. Our results reveal the existence of two phases in this sample

has been interest

of the enhancement

in the

Yi SUN-SHENG,

GAROCHE

In the past few years there the study

SY-SEN,

ON THE SUPERCONDUCTING

AI-Si

eutectic

in

of superconduc-

Al-Ge

and

AI-Si

parameter 4.042 A.

of the a Al solid solution Selected

area

diffraction

is equal patterns

to of

alloys

[l-4]. The present note reports the effect of heat treatment on the microstructure and superconducting properties of the eutectic alloy AI-Si made by rapid cooling from the liquid state. The purity

alloy

studied

contained

11.3 at%

of the Si was 99.9999%

was 99.99%.

Under

and that of the Al

the vacuum

of 10e5Torr

alloy was prepared by induction tinuous ribbon specimens were these

master

alloys

under

Si. The

melting. prepared

a protective

the Confrom

argon

atmosphere using a splat quenching technique. Two of the samples were heated at 100°C for SO h and at 200°C for 100 h, respectively, evacuated and sealed quartz purified Ar or He gas. The results of the analyses different Rapidly diffraction

states

ampule

in an

filled with

for the samples

of

are as follows.

cooled state. image obtained

We know from the by transmission elec-

tron microscopy that the state consists of two phases (1 and 2 of fig. I). Region 1 is located in region 2 like an island. Selected area diffraction patterns of region 1 show that it is an aAI solid solution with single crystal orientation. X-ray analysis results indicate that the lattice 037X-4363/X2/0000-00(~0/$02.75

0

1982 North-Holland

Fig. 1. Al- I I .3 at% Si. rapidly cooled state. (a) TransmiaGun electron micrographs (JEM- 1000) (the samples were reduced in thickness by Ar ion bombardment) 45000~. (h) Selected area ditfractlon pattern of region I. (c) Selected area diffraction pattern of region 7.

K. Wei-yen

2Oh8

region

et al. I Effect of heat treatment

2 show a few diffusion

rings.

that region 2 is an amorphous minium and silicon atoms. Samples

annealed results

analysis parameter

This

reduced

in

solution. emerges dark

increases that

field image

from

that

diffraction

and

quenched

sample

annealed

aging

solid

of this sample

samples

was

The

normal

transition

X-ray

diff rac-

sample

decreased

granules

are Si

4.2 K.

T, for The

rapidly transition

AT, = 0.8K and the resistance ratio R&R4? = 1.66. After annealing at 100°C for 50 h, T,= 1.88K, AT, = 0.07 K and Rioo/RJ,z = width

for

100 h r, =

in the resistance magnetic

100°C for bath

50 h. The

tem-

was maintained

an anomalous

current a certain range

at

behaviour

was larger than superconducting-

the

resistance

with increasing

In this case the magnetic

of the

magnetic

field.

field did not tend

to

but to promote

it.

the superconductivity,

The same sample

with

field for the

that the magnetoresistivity

exhibited

when the transport several mA. Over

of selec-

at 200°C for 100 h the specimens completely.

at

of the helium

quench

precipitated

at 200°C

of the applied

1.47 K. We observed

is

crystals. After

the intensity

content

a AI

dispersive

annealing

perature

(fig. 2(a)). The results these

of AIL.5

1.10 K, AT, = 0.01K and R3&RJ2 = 5.40.

4.042 A to

the silicon

supersaturated

electron

show

After

properties

Fig. 3 shows the change

In the amorphous phase a new phase which seems to be a bright point in the

ted area tion

shows the

2.50.

of alu-

at 100°C for SO h. X-ray the lattice indicate that

of a Al(Si)

4.047A.

We believe

phase

on .superconducting

2.47 mg of 14 ribbons

on a thin slab of sapphire

was measured

glued by a.c

temperature calorimetry [S]. The heat capacities of the sample holder and addenda were measured

separately

and

substracted

from

the

data. Fig. 4 presents our results in the standard plot of C&/T versus T (C,,= superconducting electronic heat capacity). curve

It must be noted

is different

from

that

that the form of of

conventional

sample. ~zf.47K

I

fO0 mA R

t

-/

‘rA

0

Fig. 2. Al-113at% Si, heat treated at 100°C for 50 h. (a) Transmission electron micrographs (JEM-IWO) 30 ()()0X (dark field). (b) Selected area diffraction pattern of region 1. (c) Selected area diffraction pattern of region 2.

40

20

60 H (Oe)

80

100

Fig. 3. The change in the resistance with the intensity of the applied magnetic field for Al-l13at% Si alloy prepared by splat cooling and annealed at 100°C for SO h. HllZll the plane of the sample.

Zero

of ordinate

for each curve is shifted.

3 H=O

H=O

. 0 0

0.5

'*OTIKI 'S

Fig. 4. C&/T versus T. Al-l 1.3 at% Si alloy splat cooling and annealed at 100°C for SO h.

If the

situation

substantial

is conceived

assume

that

adequately

sample

function

the sample

f(Tc)

having

obeys

by

can of

where

heat coefficient

and depends

C, can be written

only upon

are two striking

1.992 and 1.376 K, respectively.

of for

specific T,. Thus,

as:

Our

Cc = yT I ,I

f(Tc) dT,

+ 3yT’

dispersive

and the electronic

entropy

7

S, = yT

I 0

Consequently,

+ yT” I T

that

normal

the magnetic is

1.3 at%

II). Then,

increase

Si alloy

of phase centres

field, the I will act as

of the matrix

superconducting current

increasing

field

of new of phase

pinning II, and

pre-

of one (phase

the critical

with

are

at 100°C for

in a magnetic

granules second

peaks

are two super-

and annealed

flux pinning the

temperatures

lower

there

in Al-l

is quenched

we observed

phase of phase

due

II

to the

centres. Also, the that of the whole

(fig. 3).

f(TJT;‘dT,

the distribution

f( Tc) = [ 4C, - 3,

and

by splat

sample, will decrease with increasing magnetic field for a certain region of the magnetic field, as

as a

f(Tc) dT,

The

the superconductivity

I) of them

appearance resistance

I T

suggest

phases

50 h. When

will f(TJT;*dT,,

results

higher

by rapid cooling

(phase cz

to

conducting pared

which

7

peaks.

corresponding

region

y is electronic

there

be

value of T,. In

also the effect proximity

Fig. S. f(Tc) versus T,. Al-l 1.3 at% SI alloy prcpart‘d cooling and annealed at IOO”C for 51) h.

we

a dis-

the fraction

The C, of any superconducting

.?yT’/Tf,

by

to a

the sample,

means

yielding

some particular

this case we ignore simplicity.

prepared

inhomogeneity

characterized

tribution

25

of as due

in T, within

variation

I

20

References function

is

- T 3]/(2yT2)

The curve of fig. 5 is f(TJ method from our experimental

obtained in this data. Evidently

ItI A. Fontaine

and F. Meunier, Phys. Konden\. Mater. IJ (1972) 119. PI C.C. Tsuei and W.L. Johnson, Phys. Rev. B9 (1974) 4742. F. Lalu, F. Meunier and H. [31 A.M. Lamose, J. Chaumont, Bernas, J. de Phys. Lett. 37 (1976) L-287. [41 C.S. Ting, D.W. Talwar and K.L. Ngai. Phys. Rev. Lett. 45 (1980) 1213. H. Niedoba and J.J. Veyssik Rev. Phys. [51 P. Manuel, Appl. 7 (1972) 107.