Remarkable Influence of Heat Treatment on the Structural and Superconducting Properties of Y1-xPrxSrBaCu3O6+z

HAL Id: jpa-00247088

https://hal.archives-ouvertes.fr/jpa-00247088

Submitted on 1 Jan 1995

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Remarkable Influence of Heat Treatment on the Structural and Superconducting Properties of

Y1-xPrxSrBaCu3O6+z

A. Das, R. Suryanarayanan

To cite this version:

A. Das, R. Suryanarayanan. Remarkable Influence of Heat Treatment on the Structural and Super-

conducting Properties of Y1-xPrxSrBaCu3O6+z. Journal de Physique I, EDP Sciences, 1995, 5 (6),

pp.623-630. �10.1051/jp1:1995155�. �jpa-00247088�

Classification Physics Abstracts

74.62Bf 74.62Dh 74.72 Bk

Short Communication

Remarkable Influence of Heat llkeatment

_on

the Structural and

Superconducting Properties of Yi-zPrzSrBaCu306+z

A. Dos and R.

Suryanarayanan (*)

Laboratoire de Physique des Sofides de Bellevue, CNRS, 92195 Meudon, Fiance

(Received

22 February1995, rev~sed 27 March 1995, accepted 19 AprÙ

1995)

Abstract. Preparation, structural and superconducting properties of Yi-xPrxSrBaCu306+z

(YPSBCO)

_are reported.

Preheating

of the samples _{in argon paon} to oJçygen

annealing

trot only

increased the orthorhombic splitting but Tc also _was enhanced by 5 to 14 K depending _{on x.}

Furthermore, this _treatment induced superconductivity in the _x

= 0.70 sample and Tc _was found to be 14 K. The slope

dTc/dx

decreased considerably compared to Yi-xPrxBa2Cu306+z, where

superconductivity _was destroyed for _x > 0.55. The data _seem to mdicate that _a knowledge of the structural and defect chemistry _is essential to understand the behaviour of Pr in YPSBCO.

1. Introduction

The structural and

superconducting properties

of many-copper based oxides _are known for sometime to be

quite

^sensitive to trie heat treatment

employed

to prepare them. For

exarnple,

trie

compound LaBa2Cu306+z

sintered in air and annealed in oxygen bas _a Tc ^of 20

K,

whereas

sintering

in

nitrogen

followed

by

_oxygen

annealing

^{increased trie} Tc to 92 K

[1-3]. Recently

it _was shown that

preheating

trie

compounds LnSrBaCu306+z (Ln

=

Nd,Eu,Sm)

in argon followed

by annealing

in oxygen ^trot

only

increased trie Tc

by

_a maximum [4] of10 K

(for

Lu =

Nd),

but also trie

orthorhombicity

and the

irreversibility

line [Si. ^{Since tue} oxygen content

uardly changed following

this heat treatment, it _was

proposed

that trie observed

properties

may result from _a

reordering

of _oxygen in

O(4)

and

O(5)

sites.

Further, Lütgemeier

et ai.

[6] observed that Tc ^of

LnBa2Cu306+z depended

_ou the llumber of

chail1fragments

in Cu chain rather than _on the total _oxygen content. As _an extension of _our

investigation

of such

properties

_we would like _to report ^here on trie influence of heat _{treatment on} the structural and

superconducting properties

^of

Yi-~Pr~SrBaCu306+z (YPSBCO).

Let _us note the well-

established fact that 551~ of Pr

destroys superconductivity

in

Yi-~PrxBa2Cu306+z (YPBCO)

(*) Corresponding author Address after May 1, 1995: Laboratoire de Chimie des Solides, CNRS, URA 446, Bât. 414, Université de Paris Sud, 91405 Orsay, Fiance

© Les Editions de Physique 1995

624 JOURNAL DE PHYSIQUE I N°6

[7].

Quite interestingly,

_we found

that, by adopting

our heat _treatment

procedure,

_we could induce

superconductivity

in the title

compound (YPSBCO)

with _x

(Pr)

= 701~.

2.

Experimental Techniques

The

polycrystalline sarnples

have been

prepared by

solid _state reaction of the

respective

^oxides

or carbonates and further

sintering. Y203, Pr203, SrC03, BaC03

and CUO _were

thoroughly

mixed in

required

proportions and calcined at 950 °C in air for _a

period

of12-18 h. The

resulting product

_was

ground, mixed, pelletized (two pellets

of 750 mg

each)

and heated in air _at 980 °C for _a

period

of 16-24 h. This _was

repeated

twice. For each

composition,

two

heat treatments _were carried out: 1) the

pellets

denoted _as

loi

_were annealed in oxygen ^at

450 °C for about 72 h and furnace

cooled; ii)

trie

pellets

denoted _as [ADI were annealed in argon ^at 850 °C for about 24 h and furnace cooled to 20 °C. Then trie _argon flow _was

shut

off,

trie _oxygen flow _was started and trie temperature of trie furnace _was increased to 450 ^° C.Trie furnace _was switched off alter about 72 h and trie

samples

_were furnace cooled in

flowing

_oxygen till 20 °C.

X-ray

diffraction

(XRD)

data of trie

samples

_were collected

using

_an

automatic

Philips

dilfractometer fitted with _a

secondary

bearn

graphite

monochromator and

using

Cu

K~ (40

kV

/20 mA)

radiation. Trie

angle

2@ _was varied from 20 to 80

degrees

in steps of o.025

degree

and trie

counting

time per step was 10 _sec. About 15 reflections _were taken into account to calculate trie lattice parameters _a, ^{b and} c

by least-squares fitting.

Bath trie real

(x')

and trie

imagmary (x")

parts of trie _ac

susceptibility

of trie

samples

_were recorded in

a field of o.Il De and _{at a}

frequency

of15oo Hz. Trie

x' signal

obtained at around 75 K with

a

fully oxygenated YBa2Cu307

_is taken _as -1. The size of each of the

samples

measured in

tuis work is tue _{sa~ne as} that of the

YBa2Cu307 sa~nple.

Tue _oxygen content of the

samples

was determined

by iodo~netry

titration ~nethod.

3. Results

Typical

XRII spectra ^for tue

(oo6)

and

(200)

reflections _m tue

region

of 46° < 2@ < 49° of tue

sa~nples

witu _x

=

oA,

o-à, o-G and o.7 _are suown in

Figure

1. Tue ortuoruo~nbic

splitting

was

clearly

seen m tue _case of

loi sa~nples only

for 0 < _x < o-Go- For _x > Q-SQ, a

tetragonal

sy~n~netry was observed in contrast to what _was

reported

in YPBCO [7]. However,

following

the heat treatment descnbed above, the

orthorhombicity

increased in the [ADI

samples starting

from _{x >} o.2. In

particular,

for the _x

= o.70

sample

_[OI which had _a

tetragonal

symmetry, an

orthoruombic

splitting

alter tue [ADI treatment _was apparent. ^In

general,

witu

increasing Pr,

tue volume of trie unit cell _was found to increase both in trie _case of

loi

and [ADI

samples

similar to that

reported

for trie YPBCO _case [7].

Further,

trie

cla

value _{as a} function of Pr decreased for both trie

loi

and [ADI

sarnples (Fig. 2). However,

this decrease _{was more}

pronounced

in tue _case of IDI sarnples. Trie oxygen ^content of trie IDI

samples

decreased

gradually

from 6.90 + o.03 for _{x =} o _to 6.83 for _x

= o.7. On tue other

hard,

after trie [ADI treatment for _a

given

_x, trie

change

_m trie oxygen ^{content was} less than o.5i~.

All tue IDI

samples

witu _x < o.65 showed

diamagnetic

transitions with

increasing

widtus with _x

(Fig.

3

a,b).

Trie

sample

witu _~

= o.7 did _net show _any

diamagnetic

transition.

Compared

to

YBa2Cu307,

_we estimate 1ooÎ~

shielding

in trie _case of _x

= o and 30 to 401~

shielding

in trie _case of _x

= o.65. Remarkable

changes

_were observed when these

samples

were

ueated in argon followed

by

_oxygen

annealing (Fig. 4).

^All trie [ADI

samples

with _x > o.2, suowed _an increase in Tc

ranging

from 5 to 14 K. In

particular, superconductivity

_was induced in tue _x

= o.7 [ADI

sample

and tue Tc _was 14 K. We did _not observe _any sucu increase in Tc in

= 0.4

o 3

3

o 0.5

~

_

A O

é

tD

3 3

~

Îfi

^~~ i 2

~

Ii 3

ce A O

/ ^"~~~

~

l

_J

j ~

°

ç~

j / _~

x=0.7

AO

O

46~0 46.5 47,0 47,5 48.0 20

Fig. 1. Part of tue XRD diagram of Yi-~Pr~SrBaCu306+z for _x

= 0.4, 0.5, o-fi and 0.7 illustrating

trie elfect of trie heat treatment. [O] = samples annealed in _oxygen

(.);

[AO] = samples preheated in argon followed by _oxygen annealing

(A).

1, ² and 3 denote

(006)

and

(200)

reflections, respectively.

Note that, for _x

= 0.7, the

(006)

reflection _{is seen} clearly only alter trie [AO] treatment.

trie _case of YPBCO

samples.

Trie variation of normalized value

Tc(x)/Tc(x

=

o)

_{as a} function of

x(Pr)

is shown in

Figure

5 for both trie IDI and [ADI

samples.

Trie normalized values of

YPBCO [7] are also shown in

Figure

5 for _companson. It is

quite

clear that

by substituting

501~ of Ba

by

Sr, trie slope dT*

/dx

_[T*

=

Tc(x)/Tc (x

= o)] bas

considerably

decreased _up to x = o.2. Further decrease _m trie

slope

occurred _{as a} result of trie [ADI treatment for _{x up} to o.4.

626 JOURNAL DE PHYSIQUE I N°6

3.06

AO

m 3,02

É

o

2,98

0,0 0,2

0,4

0,6 0,8

x Pr

Fig. 2.

cla

of Yi-~Pr~SrBaCu306+z _{as a} function of _x

(Pr). [O]=samples

annealed in oxygen;

[AO]=

samples preheated in argon followed by _oxygen annealing.

~ÙW- f* ~ ^nr

$

7

1*

. .. a

-

j

~

j

^.

~

~/

^. , ^..

. ^.

~

:

_, .

. . , . ^.

~

. .

~ii

-# ~j j

_0.2.

- o~ ^. .

'~

_i o

~'~ ~'~

~')0.0

j ^~~~~~ ~j~

~

/ ,Î

£ ~fÎ

~

~

--

0 20 40 60 80100

T(K)

Fig. 3. The real

x'(a)

and imagmary

x"(b)

parts of the _ac susceptibility of Yi-xPrxSrBaCu306+z (0 < _x <

0.7)

_{as a} function of temperature. [OI = samples annealed in oxygen.

0.7f~ fyfr _r

. ~

- x

/ ^:

f j ^f _j

~w+~ j

to Ù.65

_j

H

Ù.6

~-l AO

~

0.4

AO j0.4

°6 Ù5

j

^b

~

0.65

j~ ^,~

~

_/ ~ £j ^fÎ ~[

~

/ j (

~

£ j/ Î, q~/

~

Î ~

~~ i ÎÎ%~-

0 20 40 60 80

T(K)

Fig. 4. Trie real

x'(a)

and imaginary

x"(b)

_parts of trie _ac susceptibility of Yi-xPrxSrBaCu306+z (0 <

x <

0.7)

_{as a} function of temperature.

[AO]=

samples heated in argon followed by annealing _m

oxygen.

1,o

Ii

1

<J

~ AO

*

~J Ba~

o,o

0,O x(Pr)

Fig. 5.

Tc(x)/Tc(x

= 0) of Yi-xPrxSrBaCu306+z and Yi-~PrxBa2Cu306+z

(Ba,

Ref. [7]) as a function of

«(Pr). [O]=

samples annealed in oxygen;

[AO]=

samples heated in _argon followed by

annealing _{in oxygen.}

628 JOURNAL DE PHYSIQUE I N°6

4. Discussion

In what

follows,

_a brief discussion of _our results is

presented

in trie

light

^of certain other data and theoreticalmodels. We recall that among trie various _rare earth substituted

YBa2Cu306+z (YBCO),

trie

properties

of

Yi-«Pr~Ba2Cu306+z (YPBCO)

bave been

extensively

^{studied but}

trie least understood [7]. ^In contrary to other trivalent _rare

earths,

Pr

destroys superconduc- tivity

_m this

compound

for _{x >} 0.55. Trie critical value of _x

(xcr)

for which Tc _goes to zero

depends

_on trie

specific

_rare earth

[9].To interpret

some of these

results,

mechanisms

involving

hole

filling

and

/or pair breaking

bave been

proposed.

In trie hole

filling

model

[8,10],

^Pr

adopts

a valence of 4+ and trie _extra electron

brought by

Y site could transfer to tue Cu-O

planes

to decrease trie hole

density

and uence tue Tc.

However,

from

M4,5-X-ray absorption edge

spectra [11], valence-band resonant

photoemission

_[12] and coulometric [13]

experiments,

trie valence of Pr _was found to be close to 3+

(for

ail _{x >}

0).

On trie other

hand, according

to trie

pair breaking

model

[14],

^trie decrease ofTc results from trie interaction of extended Pr~+ f orbitals with trie

charge

carriers in trie Cu-O

planes.

It has been

argued

tuat Tc

depression

_m YPBCO is similar to that observed in

YBa2Cu306+z

as a function of _z [15].

However,

it _was

pointed

out

recently

that the

NQR spectral

features of YPBCO _are

quite

dilferent from the oxygen

depleted YBa2Cu306+z

(16]. ^The contribution of Cu _wave function to the

quadrupole

interaction _is

largely changed

in trie

Cu(2) planar

site in trie Pr system

compared

to other cuprates [17]. ^This was

interpreted

_{as an} indication of

localization of holes

leading

to trie absence of

superconductivity Further, polarized optical

spectra on detwmned

PrBa2Cu307 single crystal

showed that it _was difficult _to

dope

mobile holes into trie Cu-02

Plane making

it an insulator [18]. ^And

finally,

Môssbauer data obtained

on

~7°Yb~+

substituted YPBCO

suggested

that

though

trie

superconductivity

_was

suppressed

at xcr when trie Pr~+ becarne

magnetically ordered,

trie suppression was not

directly

due _to this

ordering

but rather due to

changes produced by

trie Pr~+

on trie Cu-02

planes

_[19].

Though

trie theoretical models

[20-22]

^would account for _some of trie data discussed

above,

it cannot

quantitatively explain

_our data.

However,

it _was

pointed

out that trie _extreme

sensitivity

of trie 1D chains and trie Pr~~~

Pr~~

_{mixed valent state to O vacancies and other defects}

may

play

_a role [22]. ^{Dur results} seem to support ^this view

point. For,

_we did observe both trie Tc and trie

strength

^{of trie}

x' signal

increased for _{x >} 0A and that

superconductivity

_was

induced for _{x =} 0.7

by simply preheating

trie

samples

_{in argon} followed

by

_oxygen

annealing.

This

might

be due to _a proper organization of O vacancies _m the basai

plane.

Of _course, this argument _may not hold for YPBCO since _we did not observe any such elfect

following

similar heat treatments. As mentioned earlier [4], a similar treatment [ADI ^{increased the} Tc

by

10 K in trie _case of

NdSrBaCu306+z

and neutron diffraction _and Seebeck data showed

respectively

_no

change

in _oxygen content and _an increase _m trie hole

density following

the [AO]

treatment [23]. ^{In trie} present _case, trie [ADI ^{treatment increased trie} orthorhombic

splitting resulting

_{m an} increased number of Cu chain

fragments

whicu would increase tue hole

density

as a result of increased

charge

transfer. However, this increase in the hole

density

did not arise out of _an increase in the oxygen content since _our

iodo~netry

~neasurements showed that trie increase in

(6

+

z)

_was less than 0.51~

following

trie [ADI treat~nent. We believe that trie

increase in trie hole

density

_may bave res.ùlted from _a rearrangement ^of oxygen defects in trie basal

plane.

That trie defects

play

_a role in

counteracting

trie Pr-f

hybridization

_con also be inferred

by

recent data [24] ^{which showed} that

by opti~nizing

trie

growth

conditions of

single crystals

of

YPBCO,

Tc could be increased

by

about 20 K

co~npared

to

polycrystalline sa~nples

for _x

= o.5. And

finally,

to understand trie role

played by Sr,

_we would like to look at tue data

on tue

non-superconducting sa~nples

of

TlBa2-ySryPrCu206+z

_{system [25].} Let _{us note} tuat tuis

compound

_can be written _as

PrBa2-»Sry (TlCu2)06+z

and uence is

structurally

similar

to YPSBCO. It _was found that TN decreased from 8 K for _y

= o _to around 3.6 K for _y

=

due _to tue modification of Pr-f

uybridization resulting

from tue _presence of trie smaller Sr [25].

In _{our case} it is

quite possible

tuat trie AF interaction of Pr _was much reduced due _{to a}

weakening

of Pr

(f) Cu-02 hybridization

_{even up} to a concentration of 701~ of Pr

preserving

superconductivity.

However, it is important to obtain _more structural data based _on neutron diffraction and

magnetic

measurements in order to understand trie role

played by

Sr in _our

samples.

5. Conclusions

In

conclusion,

_we bave shown that

by substituting

^501~ of Ba

by

Sr in

Yi-«Pr~Ba2Cu306+z,

_we

bave weakened tue

Pr(f)-Cu hybridization

elfects.

Furtuermore, by preheating

the

samples

_in

argon

prior

to oxygen

annealing,

tue Tc could be increased

by

5 to 14 K and

superconductivity

was induced in tue

sample

witu

a~(Pr)

₌

o.7,

whereas _one obtains _an insulator for the _same concentration in YPBCO. Dur data _seem to indicate the role

played by

defects

especially

_m

the basal

plane.

Additional structural and

magnetic

data _are necessary in order to understand the mechanism of suppression ofT~

by

Pr in this

compound

before

applying

_any

specific

model

to account for the behaviour of Pr. And

finally

_we would like to add that while this work

was in progress, we became _aware of the results

by Guanguan

Cao _et ai. [26] ^wuo

reported

zero

resistivity

in YPSBCO but

only

for _{x up} to o.65.

However, they

have not used tue

[ADI ^heat treatment

employed by

_us and further the Tc values of their

oxygenated samples

(QI

< _x <

0.65)

_are lower than _ours.

References

[1] Maeda A., Noda T., Matsumoto H., Wada T., Izumi M., Yabe T., Uchinokura K. and Tanaka S., J. Appt. Phys. 64

(1988)

4095.

[2] Wada T., Suzuki N., Uchida S. and Takeda S., Phys. Reu. B 39

(1989)

9126.

[3] ^Izumi M., Yabe T., Wada T., Maeda A., Uchinokura K., Takeda S. and Asano H., Phys. Reu. B 40

(1989)

6771.

[4] Suryanarayanan R., Nafidi A. and Das A., J. Appt. Phys. 76

(1994)

598.

[Si Suryanarayanan R. alld Nafidi A., Physica C 225 (1994) 104.

[6] Lütgemeier H., Hein~naa I., Wagener D. and Hosseini S. M., Workshop _on Phase Separation _in Cuprate Superconductors, E. Sigmund and K. A. Müller, Eds.

(Berlin,

Spnllger Verlag,

1994)

_pp.

225-232.

[7] ^For a general review and additional references _see Radousky H. B., J. Mater. Res. 7

(1992)

1917.

[8] Gonçalves A. P., Santos I. C., Lopes E. B., Hennques R. T. and Almeida M., Phys. Reu. B 37

(1988)

7476.

[9] For _a detailed discussion and earlier references _see, Weiyan Guan, Xu Y., Sheen S. R., Chen Y.

C., Wei J. Y. T., Lei H. F., Wu M. K. and Ho J. C.

,

Phys. Reu. B 49 (1994) 15993.

[loi

Matsuda A., Kineshita K.,

Isiii

_{T., Shibata H., Watanabe T. and}

iamada

_{T., Phys. Reu. B 38}

(2910)

1988.

[Il]

Neukirch U., Simmons C. T., Sladeczek P., Laubschat C., Strebel O., Kaindl G. and Sarma D.

D., Europhys. Lent. 5

(1988)

567.

[12] Kang J. S., Allen J. W., Shen Z. X., Ellis W. P., Yen J. J., Lee B. W., Maple M. B., Spicer W.

E. and Lindau I., J. Less-Common Met. 148

(1989)

121.

630 JOURNAL DE PHYSIQUE I N°6

[13] ^Kato M., Saga N., Sawamura T., Yoshimura K, and Kosuge K., Physica C 235,340

(1994)

815.

[14] ^{Neumeier J.} J., Maple M. B. and Torikachvilh M. S., Physica C156

(1988)

574; Kebede A., Jee C. S., Schwelger J., Crow J. E., Mihalsm T., Meyer G. H., Salomon R. E., Schlottmann P., ^Kunc M. V., Bloom S. H. and Guertin R. P., Phys. Reu. B 40

(1989)

4453.

[15] ^Fisher B., Genossar J., Patlagan L. and Adams T. R., Phys. Reu. B 43

(1991)

2821.

[16] ^Ohno T., Koyama K. and Yasuoka H., Physica B 199,200

(1994)

257.

[17] ^Yoshimura K., Saga N., Kato M., Shimizu T. and Kosuge K., Physica C 235-240

(1994)

1701.

[18] ^Takenaka K., Imanaka Y., Tamasaku K., Ito T. and Uchida S., Phys. Reu. B 46

(1992)

5833.

[19] Hodges J. A., le Bras G., Bonville P., Imbert P. and Jéhanno H., Physica C 218

(1994)

283.

[20] Guo G. Y. and Temmerman W. M., Phys. ^{Reu. B} 41 (1990) 6372.

[21] Singh D. J., Phys. Reu. B 50

(1994)

4106.

[22] Fehrenbacher R. and llice T. M., Phys. Reu. Lent. 70

(1993)

3471.

[23] Zelenay I., Nafidi A., Greaves C. and Suryanarayanan R., Physica C 231

(1994)

207.

[24] ^{Paulius L.} M., Lee B. W., Maple M. B., and Tsai P. K., Physica C 230

(1994)

255.

[25] ^{Lai C.} C., Lee T. J., Fun H. K., Ku H. C. and Ho J. C., Phys. Reu. B 50

(1994)

4092.

[26] Guanghan Cao, Yitai Qian, Zuyao Chen, Xiaojun Li; Hongkai Wu and Yuheng Zhang, Phys. Lent.

A 196

(1994)

263.