Poole Ch.P., Jr. Handbook of Superconductivity

366

Chapter 8: Crystal Structures of High-Tc Superconducting Cuprates

refinement of the average structure of

Co.32Ba2Ca3Cu4.68Oll.06, two

pairs of O

sites were considered in the

additional

and

bridging

layers, corresponding to an

occupation of the cation site in the

additional

layer by C and Cu, respectively

(Shimakawa

et al.,

1994a). A superconducting, carbon-free 1234 compound

(T c = 117.1 K) was reported for the nominal composition

Agl_xBa2Ca3Cu4+xOll_ • (Ihara

et al.,

1994a). The average structure was

described in space group

P4/mmm

(a= 3.8635, r 18.ILIA), but body-

centered tetragonal superstructures (2a, 2c) with ordered arrangements of

copper and silver atoms were suggested for x = 0.25 and x = 0.75. Wu

et al.

(1994b) and Matsuhata

et al.

(1994) stated that the amount of Ag in the

compound was negligible and explained the superstructure by the ordering of

vacancies on the Cu site in the

additional

layer. Cu-1234 compounds, with

structural features similar to those described earlier, were reported by Jin

et al.

(1994), Wu

et al.

(1994a), Ihara

et al.

(1994b), and Alario-Franco

et al.

(1994b).

In the last article, the superstructure was shown to be orthorhombic (2a, a, 2c),

but the same authors later detected small amounts of carbon in their samples

(Alafio-Franco

et al.,

1994a). In the refinement of the average structure of

Ba2Ca3Cu4.6Olo.8, not only the Cu site, but also the O sites in the

additional

and

bridging

layers were found to be partly vacant (Akimoto

et al.,

1995). The

orthorhombic space group

A2mm

(or monoclinic

Am

or

A2/m)

was proposed for

the description of a 4-fold superstructure by Matsuhata

et al.

(1995).

1245 HglBa2Ca4Cu5012.32

AB2C4D5012+8 ,

tP24, (123)

P4/mmm-ieh3 g 3 e(c)ba

-DO2-.

C-DO 2-" C-DO2-" C-DO2-. C-DO2-OB-A .-O B-

HgBa2Ca4CusO12.32, a T c = 101 K, PN, RT,

Rwp

= 0.0640 b

(Huang

et al.,

1994a)

(123)

P4/mmm,

a = 3.85151, c = 22.1049 A, Z = 1

Fig. 20

H. Crystallographic Data Sets

367

Atom WP PS x y z

Occ.

Hg l(a)

4/mmm 0 0 0

1 1

0.1269

Ba 2(h)

4mm ~ -~

Cu(1) 2(g)

4mm

0 0 0.2144

1 1

0.2854

Ca(l) 2(h)

4mm ~

Cu(2) 2(g)

4mm

0 0 0.3551

1 1

0.4254

Ca(2) 2(h)

4mm ~

1

Cu(3) l(b)

4/mmm 0 0

1 1 0

O(1) l(c)

4/mmm ~

0(2) 2(g)

4mm

0 0 0.0867

1

0.2149

0(3) 4(i)

2mm . 0

1

0.3562

0(4) 4(i)

2mm . 0

1 1

0(5) 2(e)

mmm . 0 ~

0.32

a

Prepared at 1.8 GPa.

b Multiphase refinement; sample also contained 20% Hg-1256 and 2% CaO.

Compound a (A) c (A) T c (K) Ref.

A1Sr2Ca4Cu5013

a

3.845 20.87 83 1

HgBa2Ca4CusO 12.32 b 3.85151 22.1049 101 2

Hgo.623Pbo.a44BaECa4CusO12.52 c

3.8529 22.172 116 3

Hgo.7Auo.3Ba2Ca4Cu5012+6 d

3.849 22.061 110 4

B Sr2Ca4Cu5013 e

3.837 20.22 85 5

a

Prepared at 5.5 GPa; nominal composition.

bprepared at 1.8 GPa.

c Prepared at 1 GPa.

d Prepared at 1.8 GPa; nominal composition.

e Prepared at 6 GPa; nominal composition.

References: 1, Isobe

et al.

(1994); 2, Huang

et aL

(1994a); 3, Schwer

et al.

(1995b); 4, Bordet

et al.

(1996); 5, Kawashima

et al.

(1995).

A critical temperature of 112 K was reached for Hg-1245 after optimization

(Loureiro

et al.,

1994). For Hgo.623Pbo.344Ba2Ca4CusO12.52, two distinct cation

sites were refined in the

additional

layer (Hg in l(a)0 0 0 and Pb in

8(/)) 0.044 0.087 0, occupancy 0.579 and 0.043) (Schwer

et al.,

1995b). Extra

Hg and Ba sites with low occupancy were introduced into the structural model to

take into account an intergrowth with 1234 and 1256.

368

Chapter 8: Crystal Structures of High-T~ Superconducting Cuprates

1256

Hg

1Ba2CasCu6014.40

AB 2

C5D6014+6 , tP28,

(123) P4/mmm-i

3 h 3 g4 d(c)a

-DOE-.C-DO2-.C-DOE-.C-

DO2-.

C-DO2-. C-DOz-OB-A .-OB-

HgBazCasCu6014.4, a T c = 114 K, PN, RT,

Rwp

-- 0.0640 b

(Huang

et al.,

1994a)

(123)

P4/mmm,

a = 3.8515, c = 25.3313/~, Z = 1

Fig. 21

Atom WP PS x y

Occ.

Hg l(a)

4/mmm 0 0

1 1

Ba 2(h)

4mm ~

Cu(1) 2(g)

4mm 0 0

1 1

Ca(l) 2(h)

4mm ~

Cu(2) 2(g)

4mm 0 0

1 1

Ca(2) 2(h)

4mm ~

Cu(3) 2(g)

4mm 0 0

1 1

Ca(3) l(d)

4 / mmm ~ -~

1 1

O(1) l(c)

4/mmm ~

0(2) 2(g)

4mm 0 0

1

0(3) 4(i)

2mm . 0

1

0(4) 4(i)

2mm . 0

1

0(5) 4(i)

2mm . 0

0

0.109

0.184

0.240

0.314

0.380

0.437

1

_

2

0

0.075

0.180

0.312

0.441

0.4

a

Prepared at 1.8 GPa.

b Multiphase refinement; sample also contained 78% Hg-1245 and 2% CaO.

H. Crystallographic Data Sets

369

2201

T12Ba2Cu]O6

A2B2D06,

ti22, (139) I4/mmm-e4cb

-DO2-OB-A O-OA-BO-

TlzBa2CuO6, T c = 90 K, SX, RT, R w -- 0.022

(Torardi

et al., 1988a)

(139)

I4/mmm, a = 3.866, c = 23.239 A, Z = 2 Fig. 22

Atom WP PS x y z

Occ.

T1 4(e)

4mm 0 0 0.29735

1 1 0.41699

Ba 4(e)

4mm ~

1

Cu 2(b) 4/mmm 0 0

1

0.2829 O(1) 16(n) .m. 0.405

0(2) 4(e) 4mm 0 0 0.3832

1 1

0(3) 4(c) mmm . 0 ~

0.25

Compound a (A) c (A) T c (K)

Ref.

T12Ba2CuO6

3.866 23.239 90

T1].75Cdo.25Ba2CuO6

3.851 23.313 90 a

T1HgBazCuO6 3.856 23.29 n.s.

aT c

given for

Tll.8Cdo.2Ba2CuO6

(nominal composition).

References: 1, Torardi et al. (1988a); 2, Parise et al. (1989b); 3, Nakajima et al. (1996).

2201

T12Ba2Cu]O6.1o

A2B2D06,

ti22, (139) I4/mmm-e4cb

-DO2-OB-A O-OA-BO-

TlzBa2CuO6.1o, T c -- 90 K,

PN, T = 4 K, R B -- 0.049 (Parise et aL, 1989c)

(69) Fmmm, a = 5.4604, b = 5.4848, c = 23.2038/~, Z = 4

a I +a2, --a 1 +a2, c

(continued)

370

Chapter 8: Crystal Structures of High-Tc Superconducting Cuprates

Atom WP PS x y z Occ.

T1 16(m) m.. 0 -0.025 0.2976 0.5

1 0 0.4172

Ba 8(i)

mm2

1

Cu 4(b)

mmm 0 0

1 1 1

0.07

O(1) a 8(f) 222 a a

1

--0.059 0.2895 0.49

0(2) 16(m) m..

0(3) 8(i)

mm2 0 0

0.3837

1 1 1

0(4) 8(e)

. .2/m ~ ~

a

Extra O site located between the T10 layers.

2201

Bi2Sr2CulO6

A2B2D06,

ti22, (139)

I4/mmm-e4 cb

-DO2-OB-A O-OA-BO-

BiaSr2CuO6, T c = 9 K, SX, RT,

R w

= 0.130 (Torardi

et al.,

1988a)

(66)

Amaa (Cccm),

a = 5.362, b = 5.374, c = 24.622 A, a Z = 4

al + a2, -al + a:, e; origin shift 0 1

Atom WP PS x y z

Occ.

Bi 8(/) m.. 0 0.2758 0.0660

1 0.2479 0.1790

Sr 8(/) m..

1 1

Cu 4(e)

2/m . . 0 ~

1 0.334 0.064

O(1) 8(/) m..

0(2) 8(/) m.. 0 0.226 0.145

1 0 0.254

0(3) 8(h) . .2

a

Average structure, additional reflections indicate superstructure (5a, b, 3c).

Compound a (A) b (A) c (A) T c (K) Ref.

Bi2 Sr2CuO6 a 5.375 5.378 24.377 b 9.5 1

Bi2Srl.6Lao.4CuO6.3o 5.388 5.398 24.399 29.5 c 2

a Refined composition Bil.86Srl.56Cuo.83Os.98.

b Space group

A2aa.

C From resistivity measurements (midpoint); T c = 30.9K for sample annealed under reducing

conditions.

References: 1, Rajagopal

et al.

(1993); 2, Schlrgl

et al.

(1993).

2201

(B io.9oPbo.

10)2(Sro.85B

io.o6Pbo.o

1 )2 Cu 10 6

A2B2D06, ti22,

(139)

I4/mmm-eacb

-DOE-OB-A O-OA-BO-

Bil.924Pbo.216Srl.7ooCuO6, a T c --- 18 K, SX, T = 293 K,

R w

= 0.053 (Torardi

et al.,

1991)

(52)

Pnan (Pnna),

a = 5.2757, b = 5.3797, c = 24.558 A, Z = 4

a l+a 2 -a l+a 2, e; origin shift 0 1 1

,

~

(continued)

H. Crystallographic Data Sets 371

Atom WP PS x y

Occ.

Bi b 8(e) 1 0.9829 0.2681

Sr c 8(e) 1 0.9604 0.7530

3

Cu 4(d) 2.. 0.4640

O(1) 8(e) 1 0.9153 0.6643

O(2) 8(e) 1 0.4662 0.7667

0(3) 8(e) 1 0.7071 0.9998

0.06311

0.1772

1

4

0.0716

0.1454

0.2523

0.92

a

Cation content Bi1.78Pbo.2oSrl.70CuO 6 from microprobe analysis.

b Bi = Bio.899Pbo.lo 1.

c Sr -- Sro.9239Bio.0684Pbo.o077.

Compound a (A) b (A) c (A) T c (K) Ref.

BiPbBaLaCuO6 5.4028 5.4745 24.515

a n.s.

Bil.924Pbo.216Srl.7ooCuO6 b 5.2757 5.3797 24.558 18

Bi1.8Pbo.2Srl.8Lao.2CuO6.36 5.396 5.374 24.374 21

....

a Space group

Fmmm.

b Cation content Bil.78Pbo.2oSr1.7oCuO6 from microprobe analysis.

References: 1, Pham

et al.

(1993); 2, Torardi

et al.

(1991); 3, Rajagopal

et al.

(1993).

Superconductivity in the T1-Ba-Cu-O system was first reported by

Kondoh

et al.

(1988) and Sheng and Hermann (1988a). T1-2201 crystallizes

with two structural modifications, one tetragonal and the other orthorhombic, and

is superconducting with T c up to 90 K for an optimal oxygen content. The first

structural refinement on tetragonal TlzBazCuO6

(I4/mmm)

was reported with the

T1 site on the 4-fold rotation axis (Torardi

et al.,

1988a). In more recent articles

the T1 site was found to be displaced [16(n) 0.0406 0 0.29696 (Liu

et al.,

1992b),

32(0) 0.039 0.017 0.29735 (Opagiste

et al.,

1993a)], and a partial substitution up

to 7 at.% T1 by Cu was detected. The presence of an extra O site (8(g) 0 1 0.267)

with an occupancy ranging from 0.005 (T c = 73 K) to 0.028 (nonsuperconduct-

ing), located between the

additional

T10 layers, was suggested by Shimakawa

et al.

(1990). Orthorhombic T1-2201 (a -- 5.4451, b = 5.4961, c-- 23.153 A,

nonsuperconducting) was first reported by Huang

et al.

(1988), who proposed

space group

Fmmm.

The crystal structure was also refined in subgroups of

Fmmm,

in order to take into account distortions in the

additional

layers

[A2aa

(Hewat

et al.,

1988);

Abma

(Parise

et al.,

1988; Str6m

et al.,

1994)]. Note that in

the latter refinements no O site between the T10 layers was considered. It is

generally agreed that the tetragonal structure is favored for Tl-deficient composi-

tions, whereas the orthorhombic structure is formed for higher T1 contents

(Shimakawa, 1993) (Fig. 8.36). To a minor extent, the transition from the

tetragonal to the orthorhombic modification also depends on the oxygen content,

a high oxygen content favoring the orthorhombic structure (Jorda

et al.,

1993;

Str6m

et al.,

1994). Stoichiometric compounds (with respect to the T1 content)

could be obtained by high-pressure synthesis for both structural modifications

(Opagiste

et al.,

1993b; Jorda

et al.,

1994).

372

Chapter 8: Crystal Structures of High-To Superconducting Cuprates

Fig. 8.36.

~<

23.28

23.24

23.20

5.50

5.49

5.48

5.47

5.46 (

5.45

5.44

' I ' I ' I ' I '

s

I ' I ' I"

C

- b

d

J

/

, d

I j

~ a

, I , I , I , I , I , I i I i

1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00

x in

TlxBa2CuO6. a

Cell parameters vs T1 content for TlxBa2CuO6_ ~ (nominal composition; T c = 76K for

x - 1.85 and 1.95, T c - 60 K for x - 2.00; for the tetragonal modification ~/2a is plotted)

(Str6m

et al.,

1994).

The Bi-Sr-Cu-O system contains two distinct phases with the approximate

composition Biz+xSr2_xCuO6+ 6. The structure of the semiconducting compound

BizSr2CuO6 was found to be monoclinic (Roth

et al.,

1990) and was refined in

space group

C2/m

(a = 24.451, b = 5.425, c = 21.954 A, fl = 105.41 ~ (Darriet

et aL,

1993). It contains stepped CuO2 layers, the monoclinic angle resulting from

a periodic crystallographic shear. The structure of the superconducting, nonstoi-

chiometric, Bi-rich compound contains infinite CuO2 layers. Superconductivity in

the Bi-Sr-Cu-O system (T c = 22 K) was first reported for a sample of nominal

composition

BizSr2Cu207+ 6

(Michel

et aL,

1987). An orthorhombic subcell

(a = 26.6, b = 5.32, c = 48.8 A) was found and a giant supercell was proposed.

Later on, a pseudotetragonal cell (a = b = 5.38, c = 24.6 A) was reported for the

composition BiSrCuOy (T c = 8K) (Akimitsu

et aL,

1987), but the authors

suggested a monoclinic superstructure with a 5-fold periodicity along [1 0 2].

The compound was identified as Bi2SrzCuO6 with some Sr deficiency and the

structure was refined in space group

I4/mmm

(Torrance

et al.,

1988). Von

Schnering

et al.

(1988) chose space group

Amaa

and obtained composition

BizSr2CuO6. 4.

The Bi site was found to be displaced from the ideal position and

two O sites (one partly occupied) were found in the

additional

layers. Torardi

et

aL

(1988a) considered only one O site in the BiO layers, but detected a slight

monoclinic distortion and a large supercell was proposed. Similar results were

obtained by Rajagopal

et al.

(1993); however, they preferred the noncentrosym-

H. Crystallographic Data Sets 373

metric space group

A2aa,

also used for the structural refinement on Ca-containing

Bi-2201 (Imai

et al.,

1988). A refinement in the monoclinic space group A2

(a- 26.908, b- 5.380, c-26.856A, t3-113.55 ~ gave the composition

Bi10SrloCusO29, because of oxygen vacancies in the

additional

layers (Onoda

and Sato, 1988). The same authors also reported Sr deficiency, based on

microprobe analysis. Zandbergen

et al.

(1988a, 1990b) explained the modulation

in the structures of Bi-based superconducting cuprates by the difference between

the translation periods of the BiO and CuO2 layers, which is reduced by

cooperative displacements of the atoms from the ideal positions and by the

incorporation of extra oxygen atoms into the former layers. A refinement of the

incommensurate structure in superspace group pA_2/~ (a- 5.3791, b- 5.3811,

c - 24.589 A, t3 - 89.93 ~ q - 0.2030a* + 0.467c*) was carried out by Leligny

et al.

(1992). Beskrovnyi

et al.

(1994) used space group

A2/a

to refine the

average structure, the 5-fold superstructure being described in A2.

Studies on the substitution of Sr by La in BizSr2_xLaxCuO6+ 6 showed that

single-phase samples can be prepared for 0.3 < x _< 1 (Schl6gl

et al.,

1993)

(0.2 < x _< 0.8; Khasanova and Antipov, 1995). An increase of the La content

causes a reduction of the c-parameter, accompanied by an expansion of the two

short cell parameters (Fig. 8.37), the structure remaining incommensurately

modulated. The oxygen content increases linearly with x (6- 0.5 for x- 1),

but the superconducting properties are suppressed at x > 0.7 (SchlSgl

et al.,

Fig. 8.37.

24.64

24.56 (

24.48

,--, 24.40

o<

24.32

ra~

r 24.24

~. ' I ' I ' 1 ' 1 ' I '

24.16 -

a

-

5.38 - ..... . . 1

5 36

0.2 0.3 0.4 0.5 0.6 0.7 0.8

x in Bi2Sr2_xLaxCuO6+6

Cell parameters vs La content for Bi2Sr2_xLaxCuO6+ 6 (0.25 _< 6 _< 0.42) (Khasanova and

Antipov, 1995).

374

Chapter 8: Crystal Structures of

High-Tc

Superconducting Cuprates

Fig. 8.38.

40 ' I ' i , i ,

35

30

25

20

15

O

10-

5-

0

0.2

i

I J I

n

I ,

0.3 0.4 0.5 0.6

x in

Bi2Sr2_xLaxCuO6+ 6

Superconducting transition temperature (from resistivity measurements, onset) vs La content

for BizSrz_xLaxCuO6+ ~ (0.25 < fi < 0.42) (Khasanova and Antipov, 1995).

1993) [x _> 0.6 (Khasanova and Antipov, 1995), Fig. 8.38], the critical tempera-

ture having passed through a maximum at x = 0.4.

Partial substitution of Bi by Pb in Biz_xPbxSrzCuO 6 can reach x = 0.25

(Torardi

et aL,

1991). The crystal structure of this and other (Bi,Pb)-2201

compounds is primitive orthorhombic

(Pnan)

and, contrary to the structures of

the Pb-free Bi-2201 compounds, does not show any modulation. Superconduct-

ing

Biz_xPbxSrz_yLayCuO 6

compounds with y _< 0.8 were identified in the region

x ~ y + 0.2 (Tarascon

et aL,

1990).

H. Crystallographic Data Sets 375

2212

Cu2Ba2YiCu208

A2B2DC208, oS30, (65) Ammm-j2iSd

-D02-.

C-DO2-OB-A O'-O' A-BO-

Ba2YCu4Os, Tc = 80 K, PN, T -- 293 K, R e = 0.080

(Fischer

et al., 1989)

(65)

Ammm (Cmmm), a = 3.8411, b = 3.8718,

c = 27.240 A, Z -- 2 Fig. 23

Atom a WP PS x

Occ.

Cu(1) 4(i)

mm2 0

1

Ba 4(/') mm2

Cu(2) 4(i) mm2 0

1

Y 2(d) mmm

O(1)b 4(i) mm2 0

O(2) 4(i) mm2 0

1

0(3) 4(]) mm2

0(4) 4(/) mm2 0

0.2873

0.3644

0.4386

1

2

0.2813

0.3546

0.4476

0.4472

a o site with occupancy 0.032 (4(j) 1 0 0.246) ignored here.

b Full occupation confirmed.

(continued)

Poole Ch.P., Jr. Handbook of Superconductivity

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