Poole Ch.P., Jr. Handbook of Superconductivity

316 Chapter 8: Crystal Structures of High-Tc Superconducting Cuprates

Rakho

et al. (1988)

and its structural refinement was carried out in space group

P4mm

(a = 3.867, c = 7.656 A at T - 500 K) with two cation sites in the DO 2

layers, describing a partial ordering of copper and iron atoms. Splitting of the D

site (Cu and Fe site separation) in space group

P4/mmm

was proposed in

Caignaert

et al.

(1995).

0122

Ba1(Ndo.5oCeo.45)2(Cuo.45Feo.55)207

BC2D207,

ti24, (139) I4/mmm-ge2dba

-DO2-.C-O2-C.-O2D-BO -

BaNdCeo.9Cuo.9Fel.lO7, n.s., PX, R e -- 0.046 (Michel et al.,

1991a)

(139)

I4/mmm, a = 3.9025, c = 20.8955 A, Z - 2

Fig. 3

Atom WP PS x y z Occ.

Ba 2(a)

4/mmm 0

1

Cu a 4(e) 4mm

Nd b 4(e) 4mm 0

1

O(1) 2(b) 4/mmm

0(2) 8(g) 2mm . 0

O(3) a 4(d) ,~m2 0

0 0

! 0.0976

2

0 0.1876

1 0

1 0.1124

2

1 1

0.95 c

a Cu = Cuo.45Feo.55.

bNd = Ndo.5263Ceo.4737.

c Value taken from nominal composition.

a Site may be partly vacant.

(continued)

H. Crystallographic Data Sets 317

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

BaNdCeo.9Cuo.9Fe

1.107

3.9025 20.8955 n.s. 1

SrY2CuFeO6.5

a

n.s. 2

4-fold superstructure

(Ibam,

a = 5.4149, b = 10.7244, c = 20.2799 A).

References: 1, Michel

et al.

(1991 a); 2, Kim

et al.

(1991).

0122

compounds are known only with mixtures of Cu and Fe on the D site.

Pure samples of BaNdCeo.9Cuo.gFel.lO7_ 6 were obtained for rare-earth element

deficient compositions (Michel

et al.,

199 l a). A possible ordering of Cu and Fe,

or Nd and Ce, was not considered in the structural refinement. The oxygen

vacancies (~ _< 0.05) were suggested to be located in the 02 layer between the

two separating

(Nd, Ce) layers. The superstructure observed for SrY2CuFeO6.5

results from an ordering of oxygen vacancies in the corresponding layer (Kim

et

al.,

1991).

0132

Sr 1 (Yo.55Ceo.45)3

(Cuo.5

oFeo.5o)209

BC30209, tP15,

(123)

P4/mmm-i2hgdca

-O 2D--C.-O2-. C-O2-C.-O 2D-BO-

SrY1.65Cel.35CuFeO9, n.s., PX, R 8 -- 0.051 (Li

et al.,

1992b)

(123)

P4/mmm,

a = 3.830, c -- 12.960A, Z -- 1 Fig. 4

Atom WP PS x z Occ.

Sr l(a)

4/mmm 0

1

Cu a 2(h)

4mm

Y(1) b 2(g)

4mm 0

1

Y(2) b l(d)

4/mmm

1

O(1) l(c)

4/mmm

O(2) 4(i)

2mm . 0

0(3) 4(i)

2mm . 0

0

0.157

0.2955

1

0

0.186

0.395

a Cu ---

Cuo.sFeo. 5.

b y(1) = Y(2) = Yo.55Ceo.45.

318 Chapter 8:

0201

Crystal Structures of High-T~ Superconducting Cuprates

(Lao.92Sro.o8)2CulO4

BzOO 4,

tI14, (139)

I4/mmm-e2ca

-O2D-BO-OB-

Lal.85Sro.lsCuO4 (Tc = 37.5 K), PN, T = 300 K,

R e = 0.0371 (Cava

et aL,

1987c)

(139)

I4/mmm,

a = 3.7793, c = 13.2260 A, a Z = 2

Fig. 5

Atom WP PS x

Occ.

La b l(e)

4mm 0

1

Cu 2(a)

4/mmm

1

O(1) 4(e)

4mm

0(2) 4(c)

mmm . 0

0.36046

1

_

2

0.3176

1

_

2

a

Modification stable above 200 K.

bLa = Lao.925Sro.o75.

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

Ref.

Bal.2Sro.8CuO3.26 3.8988 12.815

a

Sr2CuO3 +6 b 3.764 12.548 c

Srl.81 Cuo.9o503. 4 3.7907 12.417

Srl.3Lao.vCu(O,F)4+6 e 3.9368 13.075

Srl.3Ndo.7Cu(O,F)4+~ e 3.9288 12.9630

SrECuO2CIE 3.9716 15.6126

Cal.8sKo.15CuOzC12 f 3.856 g 15.27 g

Cal.9Nao. 1 CUO2C12 h 3.8495 15.1729

La 1.945Rbo. o 55CUO4 3.7858 13.2759

Lal.8Nao.2CuO4 3.7796 13.1871

Lal.85Bao. 15CUO4 3.7873 13.2883

Lal.8sSro.lsCuO4 3.7793 13.2260

50

70 a

n.s.

55

44

n.s.

24

26

22

30 i

33

37.5

(continued)

1

2

3

4

5

6

7

8

9

10

11

12

H. Crystallographic Data Sets 319

Lal.8sCao.15CllO4 e

3.7791 13.166 20 / 13

La

1.95 B

io.o5 CuO4.o 8 k 3.799 g 13.22 g 35 14

a Additional reflections indicate 4-fold superstructure (monoclinic, a -- 15.60, b = 3.899,

c = 13.395 A, fl = 106.9~

b Prepared at 6 GPa; nominal composition, 6 --0.1 from chemical analysis.

c 32-fold superstructure

(P4/mbm,

a = 21.2900, c = 12.5611,3,) in Shimakawa

et al.

(1994b).

aT c

= 94 K in Han

et al.

(1994); according to Shaked

et al.

(1995), superconductivity should be

attributed to impurity phases Sr3Cu2Os+ ~ (0212) and/or Sr4Cu307+ 6 (0223).

e Nominal composition.

fPrepared at 5 GPa; nominal composition.

g Value taken from figure.

h Prepared at 6 GPa.

iT c

-- 36 K for Lal.59Nao.41CuO4_ ~ (Markert

et al.,

1988).

J From resistivity measurements (midpoint), value taken from figure.

k Nominal composition, oxygen content from TG analysis.

References: 1, Hodges

et aL

(1996); 2, Hiroi

et aL

(1993b); 3, Lobo

et al.

(1990); 4, Chen

et al.

(1995); 5, Yang

et al.

(1996); 6, Miller

et al.

(1990); 7, Tatsuki

et al.

(1995); 8, Argyriou

et al.

(1995);

9, Keane

et al.

(1994); 10, Torardi

et al.

(1989); 11, Jorgensen

et al.

(1987b); 12, Cava

et al.

(1987c);

13,

Oh-ishi

et al.

(1988); 14, Kato

et aL

(1996).

0201

(Lao.92Sr0.o8)2Cu 1 0 4

B2D04, tI14,

(139)

I4/mmm-e2ca

-02D-BO-OB-

Lal.ssSro.15CuO4, Tc --37.5 K, PN, T = 10K, R 8 =0.0341 (Cava

et al.,

1987c)

(64)

Bmab (Cmca),

a -- 5.3240, b -- 5.3547, c -- 13.1832A, a Z = 4

a 1 + a2, --a I -+- a2, C

Atom WP PS x y z

Occ.

Lab 8(f) m.. 0 --0.004964 0.36077

1 0 1

Cu 4(a)

2/m. . ~

1 -0.0255 0.31740

O(1) 8(f) m..

1 1

0.50573

0(2) 8(e) . .2 ~ a

a Modification stable below 200 K.

bLa -- Lao.925Sro.075.

0201

(Lao.93Bao.o7)2 Cu 1 0 4

I4/mmm-e ca

B2DO4,

tI14,

(139)

2

-02D-BO-OB-

Lal.855Bao.145CuO4, T c = 30 K, a PN, T -- 30 K, R~ = 0.0230 (Takayama-Muromachi

et al.,

1993)

(138)

P42/ncm

(origin at

2/m),

a = 5.34294, c = 13.2432A, b Z = 4

a 1 -f-a2, --a 1 -f-a2, C

(continued)

320

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

Atom WP

PS x y z Occ.

La c 8(i)

Cu 4(d)

O(1) 8(i)

0(2) 4(e)

0(3) 4(a)

9 .m 0.0036 0.0036 0.36074

1 0 1

9 .2/m ~

..m 0.4826 0.0174 0.31791

1 1

0.5074

2 .mm ~

2.22 ! ~ !

4 4 2

a

Value taken from figure.

b Modification stable below 60 K.

CLa = La0.9275Bao.0725.

0201

La2ful O4.08

B2DO4, tI14, (139) I4/mmm-e2ca

-O2D-BO-OB-

La2fuO4.o81, a T c = 42 K, PN, RT, Rwp -- 0.0643 (Radaelli et al., 1993a)

(69) Fmmm, a = 5.33794, b = 5.4106, c = 13.2155 A, b Z --- 4

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

Atom WP PS x y

Occ.

La 8(i) mm2 0 0 0.3601

1 0 1

Cu 4(a) mmm ~

1 0.029 0.3180

O(1) 16(m) m..

0(2) 32(p) 1 0.546 0.124 0.313

1 1 1

0(3) 8(e) . .2/m ~ ~

1 1 1

0(4) 8(f) 222 ~ ~

0.4225

0.045

0.0155

a

Electrochemically oxidized; oxygen content La2Cu04.12 from TG analysis.

b Average structure; additional reflections indicate superstructure.

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

Ref.

Sr2CuO2F2.57 5.394 5.513

13.468

La2CuO4.o81 a

5.33794 5.4106 13.2155 b

46

42

a

Electrochemically oxidized; oxygen content La2CuO4.12 from TG analysis.

b Additional reflections indicate superstructure.

References: 1, A1-Mamouri et aL (1994); 2, Radaelli et al. (1993a).

0201 compounds are usually referred to as T phases. Superconductivity in

the La-Ba-Cu-O system was first reported by Bednorz and Mfiller (1986) with a

critical temperature close to 30 K. The superconducting compound was later

identified as La2_xBaxCuO4 (Takagi

et al.,

1987), and the first structural

refinement was carried out by Jorgensen

et al.

(1987b). Superconductivity

(T c = 36K) in the La-Sr-Cu-O system was reported by Cava

et al.

(1987d)

for the composition Lal.8Sro.2CuO4. At room temperature both the Ba- and Sr-

containing compounds crystallize with a tetragonal, K2NiFa-type structure

(I4/mmm)

(Balz, 1953). At low temperature (T ,~ 200 K for Lal.85Sro.15CuO4)

they undergo a structural phase transition from tetragonal to orthorhombic

(Bmab,

La2CuO4 type, Grande

et al.,

1977), caused by a tilting of the CuO6

H. Crystallographic Data Sets 321

Fig. 8.17.

~<

o

E

13.27

13.25

13.23

13.21

' I ' I ' 1

..O"

..o.I

O

b "

5.36 -

s.35 n_axr o

5.34 i

5.33 , I L I , I. , I L I ,

0 50 100 150 200 250

Temperature

(K)

300

Cell parameters vs temperature for Lal.882Ba0.118CuO4 (for the high-temperature tetragonal

modification v/2a is plotted) (Suzuki and Fujita, 1989).

Fig. 8.18.

13.24 ' i , i , i , i , i

~<

o

E

t~

13.22 . /

13.20. - C ~

]3.~8- %vv ---~-'~

5.34 -

5.33

5.32

ckx:ro--~ -''~

5.31 , t , I , I , i , I

,

0 50 100 150 200 250 300

Temperature

(K)

Cell parameters vs temperature for La1.ssSro.lsCuO4 (for the tetragonal modification vr2a is

plotted) (Day

et al.,

1987).

322

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

Fig. 8.19.

13.38

13.32

13.26

,~, 13.20

~ 13.14

'

I

'

I ~ I

7

C

7

J

5.42

5.40 b

5.38

5.36

.....

5.34

5.32

0.00 0.05 0.10 0.15

x in La2.xBaCuO4

J [ i

O .

1

0.20

~

O-

I

0.25

Cell parameters vs Ba content for La2_xBaxCuO4 (for the tetragonal modification ~/-2a is

plotted) (Suzuki and Fujita, 1989).

Fig. 8.20.

13.30

13.26

13.22

13.18

'~" 13.14

13.10

E

295 K

10K

5.40

5.38

5.36

5.34 q

5.32 .-- a ~--------L~ .

5.30

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

x in La2.xSrCuO 4

Cell parameters vs Sr content for La2_xSrxCuO4 (for the tetragonal modification ~/~a is

plotted) (Radaelli

et al.,

1994a).

H. Crystallographic Data Sets

323

octahedra. A similar transformation is observed on decreasing the Ba or Sr content

(x ~ 0.1 for Laz_xSrxCuO 4 at 295 K). Upon further cooling, the compounds undergo

a second structural transition, Laz_xBaxCuO 4 (T ~ 50 K for x = 0.1) to another

tetragonal

(P42/ncm)

(Axe

et al.,

1989) and La1.885Sr0.115CuO4 to another

orthorhombic modification

(Pccn)

(Koyama

et aL,

1995). For Lal.6_xNdo.4SrxCuO 4

three successive structural transformations were reported to take place upon

cooling, following the sequence

I4/mmm-Bmab-Pccn-P42/ncm

(Crawford

et aL,

1991). The cell parameters of

Laz_xMxCu04

vs the temperature and the

Ba(Sr)-content are presented in Figs. 8.17, 8.18, 8.19 and 8.20, respectively. The

superconducting transition temperature of Laz_xBaxCuO4 as a function of the

Ba content shows two maxima, with an intermediate suppression of the super-

conductivity at x = 0.125 (Fig. 8.21). For the Sr-containing compound, T c vs the Sr

content is shown in Fig. 8.22, suppression of the superconductivity being reported to

occur at x = 0.115 (Kumagai

et al.,

1994).

Structural refinements on SrzCuO3+ 6 showed oxygen vacancies in the

CuO2 layers (Shimakawa

et aL,

1994b). Studies of Bal.zSro.sCuO3+ 6 led to

similar conclusions, and a monoclinic superstructure with an ordered arrange-

ment of vacancies was proposed (Hodges

et al.,

1996). Note that a Cu-free

compound, SrzRuO4, crystallizing with a KzNiF4-type structure and supercon-

ducting below 1 K, has also been reported

(I4/mmm,

a = 3.87, c = 12.74 A,

T c = 0.93 K) (Maeno

et al.,

1994).

Fig. 8.21.

30

' I ' I ' ' I '' ...... I '

25

o o

20 0

15

10

O~ ' 6 , _l ........ l , I

0.00 0.05 0.10 0.15 0.20 0.25

X in La2.xBaCuO 4

Superconducting transition temperature vs Ba content for

La2_xBaxCuO 4 (Axe

et al.,

1989).

Fig. 8.22.

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

45

' I ' I ' I ' i

i

'

1

40

35

30

25

~.. ,,, 20

15

I0

0

0.00

324

,

I I

,

I

, ~1

g

1

0.25

i

0.05 0.10 0.15 0.20 0.30

x in La2.xSrCuO 4

Superconducting transition temperature vs Sr content for La2_xSrxCuO4 (Radaelli

et al.,

1994a).

Superconductors can be obtained not only by doping La2CuO4 with

alkaline-earth cations, but also by introducing excess oxygen. The compound

La2CuO4+ a with 6 < 0.02 (at 300K) crystallizes in space group

Bmab.

In

Chaillout

et al.

(1990) the structure of the oxygen-rich compound with

6 > 0.04 is also described in space group

Bmab

with two extra O sites, located

in and between the

bridging

layers, respectively (16(g)0.533 0.105 0.315 and

8(e) 1 88 0.258, occupancy 0.040 and 0.024), the original O site being partly

vacant (occupancy 0.922). Approximately the same structure was also refined in

space group

Fmmm

(Radaelli

et al.,

1993a) (filled-up variant of the "La2CuO4"

type; Longo and Raccah, 1973).

H. Crystallographic Data Sets

325

0212

(Lao.71Sro.2oCao.o9)2(Cao. 81Lao. 19)1Cu205.91

B2CD206,

ti22, (139)

I4/mmm-ge3b

-02D-C.-O2D-BO-OB -

Lal.6Sro.4CaCu2Os.9o8,

aT c

= 55 K, PN, RT, R e = 0.0627

(Cava

et al.,

1990b)

(139)

I4/mmm,

a = 3.8208, c = 19.5993 A, Z -- 2 Fig. 6

Atom WP PS x

Occ.

La b 4(e)

4mm 0

1

Cu 4(e)

4mm

Ca c 2(b)

4/mmm 0

1

O(1) 4(e)

4mm

O(2) d 8(g)

2mm. 0

0.32334

0.41344

1

_

2

0.2964

0.41789

0.954

a Oxygen content Lal.6Sro.4CaCu2Os.94 from TG analysis.

b La = Lao.7o6 Sro. 2

Cao.o94.

c Ca = Cao.812Lao.188 .

a Full occupation confirmed.

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

Ref.

Sr3Cu205+6 a

3.902 21.085

Sr2CaCu205.5 b 3.821 20.74

Sr2CaCuzO4.6F2.o b 3.843 19.88

Sr2.3Cao.7Cu204.76C11.24 c

3.8679 22.161

Sr2Cao.sNdo.zCuzOsF d 3.8606 20.1130

Ca3Cu204C12 3.861 21.349

La1.85Srl.15Cu206.25 3.8530 20.0833

Lal.zSrl.3Pbo.4Bio.zCUl.9Os.78 e 3.867 20.01

100

77

99

8O

85

n.s.

75

1

2

3

4

5

6

7

8

(continued)

Poole Ch.P., Jr. Handbook of Superconductivity

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