Superconducting properties of bulk Bi(Pb)-Sr-Ca-Cu-O with nanopowder CoFe2O4 addition.

t

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g E E F 3 e F

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F E E

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E E $ E F

SUPERCONDUCTING

PROPERTIES OF

BULK

Bi(Pb)-Sr-Ca-Cu-O

WITH

NANOPOWDER

CoFezO+

ADDITION

rK.

T. Lau*, rR-Abd shukor,

3M.

M. Awang

Kechik,

'Mohamad Nizam

Ayof,

- _{2,-, l- n r!}

rAgus

Setyo

Budi,

lSafarudin

Gazali

Herawan,

2Weesiong

Chiu,

rS.

Radiman

I _{Dept. of}

Science and Mathematics, Centre of Academic Services

Kolej Universiti

Tekrikal

Kebangsaan Malaysia, Locked Bag 1200, Ayer Keroh,75450 Melaka

* _{Email: ktlauriilkutkm.edu.rnr,}

2

School

ofApplied

Physics, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor

rDepartment _of

Physics, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor

a

Facu)ty of Mechanical Engineering

Kolej

Universiti Teknikal Kebangsaan Maiaysia, Locked Bag 1200, Ayer Keroh,75450 Melaka

Abstract:

The efforts to improve the superconducting properties of high temperature superconductor in the asp€ct

of

supercunent transport

ability

have been made

by

introducing

artificial pinning

sites. Several

techliques inciude healry

ion

bombardment,

proton irradiation, neutron irradiation and

atomic

substitutions had been used and found its own difficulties when applied in large-scale production. One

of solution to overcome these problems is the addition of nanometer size partic)es as pinning centres to the superconductor which had been found effective

to

improve the pinning strength

of

superconductor

In this paper, the superconducting properties

of bulk

Bi(Pb)-Sr-Ca-Cu-O

with

nano-powder CoFezOa

addition

will

be investigated by

f.

measurements and SEM micrograph

Keywords:

Nanopowder CoFezOr, bulk B i(Pb)-Sr-Ca-Cu-O, microstructure, superconducting property

I

Introduction

Much

effoft

has been don€

to

improve

the

superconducting

properties

of

high

t€mperature

superconductor (HTSc)

in

the aspect

of

supercurrent transport

ability, which

includes enhancing the

pinning strength

of

the materials. Thus stronger pinning properties

of

HTSc

will

give

way

to

mole applications using

high

magnetic

field.

Several techniques include

beara ion

bombardment, proton irradiation, neutron irradiation and atomic substitutions had been used

to

increase the pinning strength

ofHTSc

[1-5], y€t

addition

of

nanometer size particles

[6-9]

have been favoured

in

term

of theil

reliabiliby in the larg€ scale production.

It

was leported [6] that particle size of MgO nanoparticles may

play a significant role in the efliciency

ofthe flux

pinning centres. Contrast to the expectation,

ultfa-fine MgO (

l0

nm) did not enlarge the critical current density compared with 200 nm MgO.

It

is

believed

that

flux

iine

network and

magnetic

textule can intelact effectively

if

their characteristics scales are ofsame order ofmagnitude. ln a magnetic System with characteristic length

z,

where coherence length _E

<,

< penetration depth 1", strong interaction between

flux

line network

and magnetic subsystem can be expected

[10].

ln

our previous work, we had shown that addition

of

magnetic nanopowder y-Fe2O3

in

Bi-Sr-Ca-Cu-O/Ag superconductor tapes enhanced

its

self-field critical current derlsity J. to four times larger than the

J.

for

Bi-Sr-ca-cu-o/Ag

superconductor tapes

without the addition in the same heat-treatment

l7].

Thus

it

is interesting

to

investigate the effect

of

addition

of

other types

of

magneric nanopowder in the superconducting proPerties

of B!Sr-ca-cu-o

superconductor.

In this

paper, we reporl the effect

of

magnetic nanopowder CoFe2Oo addition on

superconducting propenies of bulk Bir Pb r-Sr-Ca-Cu-O iuperconductol

2

Experimental

Details

Bi(Pb)-Sr-Ca-Cu-O superconductor powder was prepared through co-plecipitatioll using n1etai acetates

of bismuth, strontnium, lead, calcium and copper (purity

>

99.99%), oxalic acid, de-ionized water and

2-proponal.

More detail

about rhe co-precipitation technique rvas described

in

[11]. The

calcined

429

t",-.,.,.i:,.'. .,r.'rJ,J'.,r.\.ri,i..&!tt1NlrcnnormInJLtl,l/tS:1'\'/:illr,//r'rxtiil

po\lders

\\erc

separare.i and then \.vere nlixed and ground fbr

hall

an hour rvith nanoporlder CoFelOl according

to

the

ibllowing

rveight per.centage

(",owt):

0. 0.01, 0.05 and 0.1.-The porvders were then

nade into pellers

of

ll

ntm diameter

underi

pressure

ofaround

5000

kgicrrr lor

5

ninutesand

were

labelled as sanrples

Bi-0.

Bi-0.01.

Bi,0.0i

and Bi-0.1.

All

the samples rvete heated at 8.1-5

"c

fbr

50 hours in air (:219,o

o:)

followed by lurnace cooling to room tetnperature. The sinthesis

ofCoFe:or

is

shorvn in

[

2].

Electrical resistance (dc) measurements rvere carried out using the stanclard four-Point probe rnethod Particle sizes and microstructures ofnano porvder CoFe:Or rvere studied by using transmission electron

microscope (TE1V1)

with

LEO

9I2AB

equipped

with

energy

filter.

The nicrostluctures study-

of

bulk

Bi(pb)-Sr-ca-cu-o

superconducror was done using scanning eletron microscope

(sEM)

model

LEo

1.15 0v P

[image:3.595.163.445.344.601.2]

Result

and Discussion

Figure

I

shorvs microstructure of CoFe2Ol nanoparticles before

ii

rvas added to lhe bulk

Bi(Pb)-Sr-Ca-cu-o

superconductor. The particles have spherical-like shape

with

an average diammetel less than 50.

nm and are believe

to

shorv significant ferromagnetic behaviour. More detail about the properties

of

CoFerol nano particles are shown in 1121.

Figure

l.

Microstructure of CoFe:Or nano particles

The dependences

ofelectrical

resistance on the temperature

ofthe

sarrples are

sho*n

in Figure

2..All

the

sanDles sho\.v metallic normal state behaviour beibre their resistance staft to drop at onset criticai

temperature r.,,,,.,,. Offset

critical

temperature 1. ,",., (the temperature when resistance reach zero) tor

Bi-d. Bi-6. Bi-0

and

Bi-0.1

ar.e

96

K,95 K.95 K

and

32

K.

Anlqa).

the

resistances

at

raties tempefature

(during the normal

state)

are

noticed

highel

for

samples

with

higher %wt

CoFelOl addjtion. except for sanple Bi-0.01 which is slightly lor'"er than Bi-0. Consistenl lvith tlle change in the

normal state resistance.

critical

temperature

I..,,,, ol

the samples is smaller for higher ou;wt CoFelO' addition. These results indicate that CoFerOr suppless superconductivily

in bulk

Bi(Pb)-Sr-Ca-Cu-O

Pbsrcs Chen6tD & Brctechnotogl

0 00012

0.00010

0 00008

0.00006

0.00004

0.00002

0.00000

[image:4.595.114.504.71.357.2]

TemPerature (K)

Figure 2. The dependence ofelectlical resistance on the temperature

ofthe

samples

In order to inv€stigate the effect of coFezor addition on the microstluctule of bulk

Bi(Pb)-sr-ca-cu-o

superconductor to-ils superconducting ploperty, SEM micrograPhes were taken for sample Bi-0 01 and gi'-0.

i.

fh.

_{micrographis in} Figure 3"(a) una

iigu'"

3(b) show clearly the reduction

of

average size

of

superconductor

grilni

fot Bi-o

1 compared with the grains in

Bi-o

01

Large plates

of

superconductor

g;;ins

(t

l0

nm"long) which

u,.

'undotly

distributJd around

th-e sample Bi-0 01 can not be seen in

iample Bi-0.1.

Averige

grains size

ofBi-0.1

are found less than 5

nm

Both samples do not show sign

oi gl";n,

uiignn

"nt,ihi-"h

indi.at",

majority

of

supercunent

links

are consisted

of

weaklinks.

lt

is

.Lirfv

,}ro*l

that

CoFe2oa addition obstructs

thi

growth

of

large superconductor grains' which

deteriotes the quality

ofthe

connectivity

ofthe

grains

It

is

commonly known that the superconducting properties

of

superconductors are affected

by

thetr microstructures which have a big role in the connectivitiy between superconductor grains and pinning

rn"allunira

of

superconductor. Good connectivity

is

important

as.it

will

determine

the

maximum

amount of sup"rcunent allowed to flow tiom one superconductor grains to another without dissipation'

ei*'ing

,tr"ngtlt

is relat€d to the strength

of

pinning centres (rvhich are non-superconducting) in the

trp.r.i,J""tJ,

,"

hold magnetic fluxes-tlom causing dissipation The change in the microstrxcture due

tocoFeroaadditionmaybethereaSonforthedeteri,orationofsuperconductivifyinbulkBi(Pb)-Sr-Ca-Cu-O superconductor where its

1

..,, reduced from 96 K to 32

K

150

100

t,

:

:

A3l

G

Praceedtngs ofThe Se)tttnar ttn Suence & tts lpph'dtrcn n lndustrf ISSASI :0A6) t illnt?

l

Figure 3. Microstructure of bulk Bi(Pb)-Sr-Ca-Cu-O superconductor (a) Bi-0 01

(b)

Bi-0

1

Conclusion

our

offset critical temperatures 7:..",., indicate that coFezoa addition suppress supercolgt-"-tility^

il

:)t\

Bi(Pb)-Sr-Ca-Cu-O,up"r.ono,tto'l'I,-.-

O"tttut"'

from 96 K for 0 9'"wt addition to 32 K for 0

l

%wt

addition. The change m

,n"

.ta'o't'u"iuit

of

the superconductor

at

the same time may be the reason

for

the deteriorarion

ot

,up.r.onou.iiuity in bulk

tilleu;sr-cu-cu-o

superconductor' Further

study

need

to

be

done

to

investlgatt

tnt

tuust

of

microstructures change

of

the

superconductor'

Ooe

Dossibility is that the

air..tion

ot

iiurJ*t-rotion

in the sample had'been altered'by addition

of

the

boFe.O, nanopor der to lorm other non superconddcling phascs'

Acknotvledgement

The authors are grateful

to

KoleJ UniYemiti Teknikal Kebangsaan Maiaysia

for

supponing

this

work

under the universiti shon term grant

No PJP/2005/PPA(1)

S116'

r

_E

;:

:

:

..

.::]

'i

..

[image:5.595.181.459.54.482.2]

Section .1: PUsrcs. Chen$|ry & DiDtechnolagl

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i-l