Interfaces between Ferroelectric Ceramics and Superconducting Oxide

MEMOIRS OF SHONAN ]NSTITUTE OF TECHNOIiOGY VoL 29.No. 1,1995

Interfaces

between

Ferroelectric

Ceramics

and

Superconducting

Oxide

SunaoSUGIHARA*

Superconducting oxide of YiBa2Cu307-.was _pasted ina thickfilmon _piezo electronic ceramics, Pb

(Zr,Ti)03

and theelectrical _properties were evaluated from the temperatureof liq.N2 tothe room

temperature. They showed the semiconductive _property, although the resistivity was O,19･cm at 80

K without clear clitical temperature, Furthermore,Pb{Zr,Ti)03was sandwiched with YBCOs as _the electrodes tomeasure piezoelectricityof thesystem.

The YiBa2Cu307..fi1rnthicknesses were determinedby scanning electron microscope

(SEM).

An

electron probe microanalyzer(EPMA) revealed diffusionof Ba intoPb{Zr,Ti)03.The high density of

thick filmshould beachieved fornew composites with better_properties.

1.

Introduction

Inan electrode forceramics, wettability of a

metal on ceramics

is

of an

importance

for

a

good contact of them. A _glassfritisemployed

for

_joining

the metal with ceramics since

ce-ramics does not _generally bond with a metal.

Sugihara

et al.

have

widely studied the

wetta-bilityand bondability of rnetallceramics and

ceramicstceramics

for

the electronic ceramics

particularly.i}･2)

Joining

of superconductor and

semiconduc-torwas theoreticallystudied on the

boundary

effects

by

P.

G.

De

Gennes,3)

in

which

super-conducting electrons migrate toward

semicon-ductor

by

the proximity effects. The

issue

is

concerned with a nanometer order, so called

mesoscopical.

There

have

been

several studies

of the proximity effect of _{superconductor.4)}

The

Y-Ba-Cu-O

sy$tem

based

multilayer for

optoelectronic

devices

was

investigated

on the

R-plane sapphire and A1203 as IR detectors.5)

The

YBCO

films

were

hundreds

of nm, and

employed

for

counterelectrode and

base.

In

the more rnacroscopical view point,

Sriva-stava et at. reported YiBa2Cu307-. adhered

onto

BaTi03

and

Pb<Zr,Ti>03

(hereafter

PZT)

*

_utsFx\ig

_tztyrk

SPet ₆

Hi

₁₀

_n

₁₂

_EftN

tocharacterize electrical _properties of the

de-vices,6) Furthermore,

Moya

_et al.

formed

the

YiBa2Cu307-x composites on

Ce-TZP,

Y-TZP

and spinel substrate,T) The

interfaces

between

YiBa2Cu307-.

_{hereafter

YBCO)

and the other

ceramics are very important toform the device

or the composite when one uses

YBCO

as an

electrode.

The firstpurpose isto

join

YBCO

thick

film

with piezoelctronic ceramics, then to find

ap-propriate thickness and

better

contact of the

film

togive good piezoelctricity and

supercon-ductivity.

The

second aim

is

touse the

YBCO

electrode

for

field

effect transistorat the low

temperature, where the

film

works as

semi-conductive rnaterial even

if

the temperature

for

it's

operation

is

not

below

the transition

temperature.

Furthermore,

an operation of an

electronic circuit _at

lower

_temperature will

play a role of ma･king the system rnore

accu-rate.

2. Experimental

1)

FabricationofPZT

The

PZT

powder which

the

cornposition

is

Pb(Zro.s3,Tio,47)03has been supplied by

Fuji

Ti-tanium

Ind.

Co.

Ltd.

It

is

pressed at

180MPa

followed

by

sintering

for

2

hours

at 1503K.

The

sintering was carried out in the

Shonan Institute of Technology

ShonanInstitute of Technology

vaM=*iFJit\$est

rg

29

g

za

1

g

sizes of sintered _pelletswere 15mm

in

diame-terand

O.8-1.0mm

in

thickness.

The

sintered

density

was

95-96%

tothe theoreticalone.

2)

Slurry

of

YBCO

The YBCO powder supplied by

Seimi

Chem-ical

Co.,

Ltd.

was calcined at

873K

was milled

by Zr02 balls

₍₃

mm indiameter)

for

24

hours

in

the

solvent.

The

slurry was _pasted on the

PZT

fabricated

above, then sintered at

1193

K

in

an

oxygen atmosphere

(O.51itter/minJ

for

each

sintering tirne;5,60,420 minutes.

They

were

cooled

down

to

a room

temperature

at the

speed of about 1.5

Ktmin,

The

surface of thick

filmswere examined

by

X

ray

diffraction

anal-ysis

(XRD).

3)

Interfaces

between

YBCO

and PZT

The

morphological analysis at the

interfaces

was carried out using scanning electron

micro-scope, and the element distributions through

the interfaceswere _{qualitatively}

investigated

a

mapping with an eletron _probe micro analyzer,

4) Electrical_properties

Electrical

resistivity was measured with a

four-probe method from the temperature of

liquid N2 to a room temperature. YBCO/PZT/

YBCO

(SuperconductorllnsulatorlSupercon-ductor) was

investigated

for

frequency

depend-ence of the composite by the impedance

analy-zer

(YHP

4192A).

3.

ResultsandDiscussion

1)

Interfaces

of YBCO/PZT and

YBCO

faces

Figures

1-a,

1-b

and 1-cshow the

SEM

photo-graphs at the interfacesof

YBCO/PZT

system

sintered for 420, 60 and 5 minutes at

1193K,

respectively. The necking of

YBCO

_grains are

formed

although there seems to

be

_porous

in

the sintered YBCO thick

film

of 420 minutes.

The

thickness of the

film

was about

17"m.

The

system maintained for 60 minutes

in-dicated

very _porous structure which

film

thickness was about

33ptm,

and the sintered

system of

5min

showed

the

denser

morphol-ogy.

The

SEM

_photographs on the surfaces of

a

b

cFig.

1. SEM photographs at the interfacesof

YBCOtPZT systems foreach sintering

time, a;420, b;60, c;5min,

the

YBCO/PZT

system are shown

in

Fig.

2-a,

2-b and 2-c

for

the sintered specimens of 420,

60

and 5min, respectively. As shown in Fig.

2-a,

the well-developed neckings of

YBCO

gen-erated with porous microstructures on the 17 ptm-film sintered

for

420min.

The

neckings

did

not develop inthe filmwith thickness of about

33ptm

for

the sintered system of

60min

as

shown

in

Fig.

2-b

and seemed to

be

more

porous with thedifferentmicrostructures

from

thesintered systems of

5min

and

420

min.

It

is

not clear at

this

mDment why the sintered

system of

60min

shows the

difference

of the

microstructure. Inthe only sintered system of

5min,

the

film

was

thinner

of 5pm and denser

(Fig,

2-c),

and thinner

film

seems to

be

better

inteT:facesbetweenRerroelectricCeramicsand SmperconductingQxide

a

b

cFig.

2.SEM _photographs on the surfaces in

YBCOiPZT systems for each sintering

time,a;420,b;60,c; 5min.

2)

Diffusion of

barium

from YBCO to PZT

Y2BaCuOs and BaCu02 besides YBCO were

found

by

XRD

analysis when sintered for420

minutes at

1193K,

and

Y2BaCuOs

of _green

colour and non-superconducting materials

were

detected

with

YBCO

_peaks

in

thesintered

film

of

5

minutes.

Figures

3-aand 3-bshow the

EPMA

line

analyses

indicating

the Ba

diffusion

distance

of

35"m

and

5um

into

the

PZT

from

the interfaces,respectively.

The

length

of

Ba

diffusionis

illustrated

inFig.4.

3>

Electrical

resistivity and _{piezoelectric}

properties

The resistivities were measured at the

tem-peratures

from

liq.

N2

to

296K.

They

indicated

the serniconductive resistivities with

tempera-turedependences a$shown

in

Fig.

5.

However,

xl en=c-o a

2

1

Xlo31.2

u)avO,6

bFig.

YB

o

Coe'PZT

O.070

mm

o

O

O.070

mm

3. EPMA line analysis at the interfaces

between YBCO and PZT ineach

ingtime,a;420,b;60,c; 5min.

theon-set temperature on 5"m

YBCO

filmwas

not clear _although

O.1

9･cm

was shown at the

temperature of

80

K,and the resistivity _at

296

K

was

O.089･cm.

BaCu02 _generated

in

the

sintered system of

60min

was

non-super-conductive materiaL More Ba _and

Y

_were

de-tected on the surface of

YBCO

than in bulk,

which cause was reported due to a large

amount of

C032-

ions.

Those _elements and the

esti-Shonan Institute of Technology ShonanInstitute of Technology

maMI*iFJi<#ept

n

29

g

eg

1

g

Z

503ka-40.!gts 30

g-=.20

s.as

1.0 2.0 time , iog t

Fig.4. Change of Ba diffusion length in PZT

with sintering timeat 1193K.

iO.19qon-tsy.)D.1;-!ut

O,1yfi D.Iv.:c e.oem O.0 3A E oeVh -.-`22

:m-eEt6',u-.V

Teinperature xlo2K

Fig. 5. Electricalresistivity changes with perature.

mated to reduce superconductivity.8}

The

piezoelectricity on the electrodes of 5

"m thickness

YBCO

was measured.

Absorp-tion

of energy

by

PZT

coated with

YBCO

thick

film

was not much at the

frequency

around

190

kHz according to

the

re$ults

by

impedance

ana-lysis

which meant the _{poor piezoelectricity.}

Ba

was

doped

at the

distance

of approximate

16

"m

from

the surface of

PZT

so thattheeffect of

Ba

could be _{estimated on}

the

_{piezoelectricities}

with Ag electrodes.

Figures

6-a

and

6-b

show

the resonance and antiresonance absorptions

on t'hestandard PZT

(or

starting material) _and

Aorvvv=qvmpt"H a le5 to4 ID3 o! oT oa

fiimpdance

leS -' _lo4s: lo3s:cu loZHlol-Zl loO !abFig, 6. so ISO !31 3DO

uo zEo 3sa figo

Frequency (kHz)

Impedance analyses with frequency,

a; starting material, b;Ba-doped PZT

(electrodes

were Ag),

the Ba-doped PZT, respectively. At _the

reso-nance

frequencies

around

280kHz

for both

standard

PZT

and Ba-doped one, the capaci-tances

increase

indicating reversal _peak since

frequency

_phase was

inverted,

and hence the

reactances

(1/wC)

was nearly zero, as shown

in

Fig.6-a and

6-b.

Electromechanical

coupling

factors

_(Kp)

can

be

calculated by resonance _and

+antrresonance

frequencies. As shown inTable

1,Ba

did

not significantly seem to affect the

piezoelectricconstants such as

d3i

_and

_g3i.

So

the film density and

Ba

diffusion

seem to

cuase the _{poor piezoelectricity}on the

YBCOt

PZTIYBCO system,

From

_these

facts,

it

is

sug-gested that the

density

of

YBCO

thick film is

not

high

enough as theelectrode of

YBCO

for

a

device

according to SEM _analysis.

The

cause

of insuMcient

function

as the elctrodes of

interft2cesbetween E2rroelectn'cCeramics and Smperconducting Oxide

Table 1Piezoelctric _properties forstandard material and Ba-doped PZT.

kp dsi ×10-i2 gsl × 10-3 Er Frequency

(kHz)

resonance anti-reson, Standard PZT Ba-doped PZT O.57O.38 85.538,5 8.05,8 1215 752 281.6286.6 292.2304.0 le,;electro-mechanical coupling factor,d3i;piezoelectric

(V･mtN), E,;relative _{permittivity,}

constant(mtV}, g3]; piezoelectricoutput coeMcient

effect of

C032'

ions

in

the next step.

4.

Conclusions

The superconducting ceramics and

piezoel-ectric ceramics can be

joined

infilmand bulk,

and

hence

theirfunctions will

be

_possible for

the electrode and new

device.

1)

2)

3)

YBCO

thick films

_(5-33"m)

adhered onto

PZT,

The

investigation

of the

interfaces

revealed the diffusionof Ba from YBCO to

PZT,

and the

length

of

the

diffusion

depen-ded on the sintering time at 1193K.

YBCO

thick filmof

5"m

indicated rather

semiconductive _properties than

supercon-ductivity

which critical temperature was

not clear.

The thickfilmshould be denser tofunction

as the electrodes forthe composites of

sup-erconductortPZTIsuperconductor, and also

the film thickness of 5"m or

less

can

be

suggested as well as a short sintering time.

References

1}

S,

Sugihara and K. Okazaki,Proc.

of

the 7th

internationatSym.

of

Appticationon

ics,pp. 429-431, June 6-9, 1993, Champaign, USA,

2) S.Sugihara and K. Okazaki,Proc.

_of

the 7th

inteTnationalSym,

of

APPIicationon

tn'cs,pp. 432-434,

June

6-9,1993, Champaign, USA,

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J,

C.Villegier,H,Moriceau, H.Boucher, L. Ciocio, A.Ghis, A.Jaeger,M. Levis,F.Pourtier, M.Schwerdtfeder,M.Vabre and C.Villard,Mdt

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