Poole Ch.P., Jr. Handbook of Superconductivity
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356
Chapter 8: Crystal Structures of High-Tr Superconducting Cuprates
Pbo.sCdo.sSrl.8Euo.zGdl.4Ceo.6fu209
Pbo.sSrl.75Ndo.2sHOl.38Ceo.62Cu2.508.64
Hgo.4Pro.6Sr2.3Prl.7Cu209 a
Hgo.sPbo.ssr2Gdl.sCeo.sCu2Oya
3.8250 29.2235 23 b 12
3.82496 28.9862 10 r 13
3.8603 29.614 n.s. 2
3.846 29.418 38 r 14
a
Nominal composition.
b From resistivity measurements (zero resistivity).
c From resistivity measurements (onset).
References: 1, Liu
et al.
(1992a); 2, Hervieu
et al.
(1995b); 3, Chen
et al.
(1993d); 4, Chen
et al.
(1992a); 5, Chen
et al.
(1992b); 6, Iqbal
et al.
(1991); 7, Vijayaraghavan
et al.
(1993); 8, Adachi
et al.
(1992); 9, Li
et al.
(1992a); 10, Maeda
et al.
(1991b); 11, Maeda
et al.
(1990); 12, Luo
et al.
(1996);
13, Maeda
et al.
(1992); 14, Tang
et al.
(1995c).
A superconducting Cu-1222 compound (T c = 33 K) was first reported for
the composition Bal.34Eu2Ceo.66Cu308.54 (Sawa
et al.,
1989a). The structural
refinement, carried out in space group
I4/mmm
with all atom sites in ideal
positions, revealed vacancies on the Cu site in the
additional
layer (occupancy
0.85). For the refinement of the structure of Sr1.8Y1.sCeCu2.708.6 ((Cuo.7Ceo.3)-
(Sro.9Yo.1)2(Yo.65Ceo.35)2Cu208.6) ,
the cation site in the
additional
layer was split
(from 2(a) 0 0 0 into 8(i) 0.052 0 0) (Kopnin
et al.,
1994). The structure of Nb-
1222 compounds, first reported by Cava
et al.
(1992), is characterized by full
occupation of the O site in the
additional
layer, yielding an oxygen content of
NbSr2R2Cu2Olo
(Goodwin
et al.,
1992).
T1-1222 compounds were first reported for the compositions
Tll.32Bal.68Pr2Cu209 and Tll.3Srl.6Pr2Cu209 (Martin
et al.,
1989a). Structural
refinements were carried out in space group
I4/mmm
(a = 3.900, c=
30.273 A and a = 3.8635, c = 29.535 A). In both structures the T1 site, partly
vacant in the Sr-containing compound, was found to be located in the
ideal position (2(a)0 0 0). Superconductivity (T c = 40K) was observed for
Tlo.sPbo.5SraEUl.8Ceo.2Cu209 (Iqbal
et al.,
1991) and a short time later for
Pb-free
T1Ba2Eul.sCeo.5Cu20 9
(Liu
et al.,
1992a). The first Pb-
based 1222 compound, PbSrl.6Pr2.4Cu2.6Oy, was reported by Adachi
et al.
(1990a). A critical temperature of 25 K was measured for a sample of composi-
tion Pbo.5Sr1.75Eu1.75Ceo.sCu2.509 (Maeda
et al.,
1990). The structural
refinement considered splitting of both the cation and the oxygen site in the
additional
layer (cation in 8(i) 0.070 0 0 and O in 8(j) 0.18 89 0) (Maeda
et al.,
199 lb). For Pbo.5Srl.75Ndo.25HOl.38Ceo.62Cu2.508.64 an extra O site with very low
occupancy (4(r 1 0, occupancy 0.015) was detected in the
additional
layer
(Maeda
et al.,
1992).
H. Crystallographic Data Sets 357
1223
(Tlo.soPbo.50)l Sr2(Cao.94Tlo.03Pbo.03)2Cu309
AB2CzD309,
tP17, (123)
P4/mmm-ihZg2ecba
-002--~
C-D02-. C-DO2-OB-A O-OB-
Tlo.s6Pbo.s6SrzCal.88Cu309, Tc = 120 K, SX, RT,
R w
--0.047 (Subramanian
et al.,
1988e)
(123)
P4/mmm,
a -- 3.808, c -- 15.232/~, Z = 1 Fig. 17
Atom WP PS
Occ.
T1 a 4(/)
m2m.
Sr 2(h)
4mm
Cu(1) 2(g)
4mm
Ca b 2(h)
4mm
Cu(2) l(b)
4/mmm
O(1) 4(n)
m2m.
O(2) 2(g)
4mm
0(3) 4(i)
2mm.
0(4) 2(e)
mmm.
0.067
1
_
2
0
1
2
0
0.40
0
0
0
0
0.1709
0.2868
0.3928
1
_
2
0
0.1311
0.2924
1
_
2
0.25
0.25
a T1 = Tlo.sPbo. 5.
b Ca
= Cao.94Tlo.03
Pbo.o3.
Compound
a (A)
c (A)
T c (K)
Ref.
T11.1Ba 1.88Ca
1.9Cu3 09
T1Sr2Ca2Cu3Oy a
T11.16 Sr 1.zsBao.
72Ca 1.84Cu3 09
Tlo.6Vo.sSr2Ca2Cu3Oya
Tlo.8Ino.2Srl.6Bao.aCa2Cu309_6 a
Tlo.56Pbo.56Sr2Cal.88Cu309
Tlo.668Pbo.4o4Srl.6oafa2.324Cu309
Tlo.66oPbo.e B io.2 Sr 1.586Bao212Ca2.142
Cu3 09
Tlo.sB i0.5 S r2 Ca2 Cu3
O9 a
Tlo.68B io. 17 Sr1.6Bao.aCa2Cu3 09
A1Sr2Ca2Cu309.s e
Pbo.5 Sr2.51
Ca
1.74Cu3.250/
Geo.5 SrzCal.8Yo.zCu3.509.3 h
3.853
3.815
3.8274
3.824
3.8327
3.808
3.81516
3.81798
3.815 c
3.8211
3.836
3.831
3.8313
15.913
15.306
15.524
15.16
15.4713
15.232
15.2798
15.3223
15.31 c
15.4235 d
14.405
15.30 g
14.533
110
106
90 b
110
103
122
118.2
119.5
120
113
78
104
77
1
2
3
4
5
6
7
8
9
10
11
12
13
(continued)
358
Chapter 8: Crystal Structures of High-T c Superconducting Cuprates
B Sr2Ca2Cu309 h 3.821 13.854 75 14
Bo.6Co.4Sr2.7Cal.3Cu309 e 3.87 13.98 115 15
Co.sBa2Ca2Cu3.509 i 3.862 14.825 i 120 16
Po.5Sr2Cal.8Yo.2Cu3.509.45 e
3.845 14.29 / 74 17
h
So.5Sr2Ca3Cu4.5012.1 3.850 c 14.5 r 100 18
a Nominal composition.
b Tc =
110 K for sample annealed under reducing conditions.
c Value taken from figure.
d Superstructure (orthorhombic, 4a, 2a, 4c) reported for Tlo.75Bio.25Srl.6Bao.aCa2Cu309 (Lee
et al.,
1996).
e
Prepared at 5 GPa; nominal composition.
fPrepared at 6 GPa.
g Additional reflections indicate incommensurate modulation (q ~ a*/3.1).
h Prepared at 6 GPa; nominal composition.
/Prepared at 8 GPa; nominal composition.
J Additional reflections indicate superstructure (2a, a, 2c).
kAdditional reflections indicate superstructure (2a, a, 2c or 2a, a, c).
References: Subramanian
et aL
(1988b); 2, Morgan
et al.
(1993); 3, Martin
et al.
(1993b); 4, Li
et al.
(1994); 5, Hur
et aL
(1996); 6, Subramanian
et al.
(1988e); 7, Marcos and Attfield (1996); 8,
Gladyshevskii
et aL
(1996); 9, Subramanian
et al.
(1990a); 10, Hur
et al.
(1995); 11, Matveev and
Takayama-Muromachi (1995); 12, Wu
et al.
(1996c); 13, Matveev
et al.
(1996); 14, Kawashima
et al.
(1995); 15, Uehara
et al.
(1994b); 16, Chaillout
et al.
(1996); 17, Isobe
et aL
(1996b); 18, Takayama-
Muromachi
et al.
(1995b).
1223 Gal Sr2Ca2Cu30
9
AB2C2D309, tP17,
(123)
P4/mmm-ih2g2ecba
-DO 2-.
C-DO 2-. C-DO 2-OB-A O-OB-
GaSr2Ca2Cu309, a T c -- 73 K, PN, RT, R B = 0.0263 (Khasanova
et al.,
1996b)
(74)
Imam (Imma),
a = 5.4041, b = 5.4615, c = 29.355/~, Z = 4
a 1 q- a 2, --a 1 d- a 2, 2c; origin shift 0 88 1
Atom WP PS x y
Occ.
Ga 8(i) . .m 0.059
1
Sr 8(h) m..
Cu(1) 8(h) m.. 0
1
Ca 8(h) m..
Cu(2) 4(a)
2/m . . 0
O(1) 8(i) . .m 0.399
0(2) 16(/) 1 -0.047
1
0(3) 8(g) . .2
1
0(4) 8(g) . .2
1
0(5) 8(g) . .2
-0.073
0.013
0.0039
-0.001
0
-0.112
0.020
3
4
1
_
4
1
_
4
1
4
0.3288
0.3865
0.4434
1
_
2
1
_
4
0.3060
0.3898
0.3928
0.5008
0.5
0.5
0.5
a
Prepared at 6 GPa.
H. Crystallographic Data Sets 359
1223
HglBa2Ca2Cu308.44
AB2C2D3Os+~, tP16, (123) P4/mmm-ih2g2e(c)ba
-DO2-. C-D02-. C-DO2-OB-A .-OB-
HgBa2CazCu3Os.44, a T c -- 133 K, PN, RT, Rwp -- 0.0815 (Chmaissem et al., 1993)
(123) P4/mmm, a = 3.8502, c -- 15.7829 A, Z = 1
Atom WP PS x y z
Occ.
Hg l(a) 4/mmm 0 0 0
1 1 0.1773
Bab 2(h) 4mm ~
Cu(1) 2(g) 4ram 0 0 0.2979
1 1 0.3954
Ca 2(h) 4mm ~
1
Cu(2) l(b) 4/mmm 0 0
1 1 0
O(1) l(c) 4/mmm ~
O(2) 2(g) 4mm 0 0 0.1236
1 0.2994
0(3) 4(i) 2mm . 0
1 1
0(4) 2(e) mmm . 0 ~ -~
0.44
a Prepared at 1.8 GPa.
bTwo Ba sites (2(h) 89 89 0.1865 and 2(h) 89 89 0.1613, occupancy 0.59 and 0.41) proposed in second
refinement.
Compound a (/~) c (A) T c (K) Ref.
HgBa2Ca2Cu308.44 a 3.8502 15.7829 133 1
Hgo.6Tio.4Ba2Ca2Cu308.4 b 3.8507 15.707 134 2
Hgo.gVo.zBa2Ca2Cu308.3 b 3.8629 15.652 127 2
Hgo.gCro.zBazCazCu308.l b 3.8631 15.625 110 2
Hgo.8Moo.2B azCazCu3 O8.4 b 3.8537 15.731 134 2
Hgo.9Reo. 1B azC azCu30y b ...... 134
3
Hgo.6Tlo.4BazCazCu308.33 3.8489 15.816 138 r 4
Hgo.618Pbo.382BazCazCu308.45o 3.8457 15.8252 130 a 5
Hgo.8Bio.2Ba2CazCu308.2 b 3.8504 15.813 130 6
Hgo.69Auo. 17BazCazCu308.3o a 3.8464 15.739 131 7
Hgo.68Reo.32SrzCazCu308.9o e 3.8265 15.2126 f 120 8
a Prepared at 1.8 GPa.
b Nominal composition.
C T c given for Hgo.8Tlo.zBazCazCu308+ 6.
d From resistivity measurements (zero resistivity).
e Prepared at 6 GPa.
/Superstructure (Fmmm, Fmm2 or F222, 2a, 4a, 2c) reported for Hgo.vsReo.zsSrzCazCu3Oy (nominal
composition) (Yamaura et al., 1995).
References: 1. Chmaissem et al. (1993); 2, Maignan et al. (1995a); 3, Wolters et al. (1996); 4, Dai et
al. (1995); 5, Wu et al. (1996b); 6, Michel et aL (1995); 7, Bordet et al. (1996); 8, Chmaissem et al.
(1996).
360
Chapter 8: Crystal Structures of High-Tr Superconducting Cuprates
A superconducting T1-1223 compound (T c = 110 K) was identified for the
composition T1Ba2Ca2Cu309. A structure model was proposed in space group
P4/mmm
(a = 3.8429, c = 15.871A) (Parkin
et al.,
1988b) and the first
refinement was carried out by Martin
et aL
(1988). For Tll.1Bal.88Cal.9Cu309,
the T1 site was found to be displaced from the ideal position along the short
translation vectors (from l(a) 0 0 0 into 4(/) 0.085 0 0), vacancies were detected
on the Ba site (occupancy 0.94), and a small amount of T1 was found on the Ca
site (5 at.%) (Subramanian
et aL,
1988b). For T1Ba2Ca2Cu308.62 two partly
occupied T1 sites in the
additional
layer were considered (Morosin
et aL,
1991 c).
The two sites, one in the ideal position on the 4-fold rotation axis and the other
one off-centered (4(/) 0.1138 0 0), were associated with oxidation states T1 + and
T13+, respectively. In addition, vacancies were detected on the O site (occupancy
0.62) in the same layer. A superconducting Sr analogue, with 50% of the thallium
atoms substituted by Pb, was reported in Subramanian
et aL
(1988e). Aranda
et aL
(1994) found the T1 and O sites in the
additional
layer, as well as the O site
in the
bridging
layers, to be off-centered in the [1 1 0] direction (T1 in
4(/)
0.0451 0.0451 0, O in
4(i)
0.553 0.553 0 and 8(r) 0.049 0.049 0.1321).
The refinement also showed partial substitution of Sr by Ca (21.1 at.%).
A superconducting (C,Cu)-1223 compound (T c = 67 K) was first reported
for the composition C0.5Ba2CazCu3.509 (a -- 3.859, c = 14.766 A) (Kawashima
et aL,
1994a). By applying a thermal treatment under reducing conditions the
superconducting transition temperature was raised to 120 K (Chaillout
et aL,
1996). No structural refinements are available; however, models have been
proposed. In particular, two possible models for a superstructure (2a, a, 2c)
with an ordered arrangement of the carbonate groups were discussed by Chaillout
et al.
(1996). A boron-containing 1223 oxycarbonate without Cu in the
additional
layer has also been reported (Uehara
et aL,
1994b).
A superconducting Ga-1223 compound (T c = 70 K), GaSrzCazCu309, was
first reported by Takayama-Muromachi and Isobe (1994), who proposed space
group
I2cm
(a = 5.391, b = 5.454, c = 29.371A). A 2-fold superstructure (a,
2b, c) with two kinds of chains, built up from differently oriented corner-sharing
GaO4 tetrahedra, was proposed by Ramirez-Castellanos
et aL (1995).
A superconducting Hg-1223 compound (T c = 133 K), HgBazCazCu308+~,
was first reported by Schilling
et al.
(1993) and a tetragonal structure was
proposed (a = 3.93, c = 16.1 A). The first refinement was carried out by
Chmaissem
et aL
(1993). Takahashi
et aL
(1993), Chu
et al.
(1993), and
Nufies-Regueiro
et aL
(1993) observed a significant increase of the super-
conducting transition temperature at high pressure: T c --150K at 11 GPa,
153K at 15GPa, and 157K at 23.5GPa. The cell parameters of Hg-based
compounds vs the pressure are shown in Fig. 8.35. Finger
et al.
(1994) refined a
substantial amount of Cu on the Hg site (10-18 at.%) and detected two partly
occupied O sites, the occupancies of which were found to depend on the Cu/Hg
ratio in the
additional
layer (2(f) 0 89 0 and 4(n) 0.36 89 0, occupancy _> 0.10 and
< 0.0625). Samples with three different oxygen contents were studied by Wagner
H. Crystallographic Data Sets
361
Fig. 8.35.
15.81
15.77
15.73
3.85
3.84
*~ 12.64
ra~
12.61
E
~ 3.85
3.84
' I ' I ' I '
c
" i HgBa2Ca2Cu3Os+~ J
.--
a
--O-- ----O
l I i I i i I I I I I
c
"-o..---...._.
HgBa2CaCu206+a J
a
---C---
i I i I a I i I I I l
9.51
9.49
3.88" :
~ a
-"
3.87
3.86
0.0 0.1 0.2 0.3 0.4 0.5 0.6
Pressure
(GPa)
Cell parameters vs pressure for 1201, 1212, and 1223 in the Hg-Ba-Ca-Cu-O system (Hunter
et al.,
1994).
et al.
(1995). Vacancies were detected on the Hg site (occupancy 0.90-0.95) and
two partly occupied O sites in the
additional
layer were reported also here: one in
2(f) with an occupancy of 0.08-0.09, the other in l(c). The occupancy of the
second site (0.18, 0.13, and 0.10) could be correlated to the critical temperature
(135, 107, and 94 K).
362 Chapter
8:
1232
Crystal Structures of High-T~ Superconducting Cuprates
(Bio.50Cuo.50)I Sr2(Ceo.67Ndo.33)3Cu2011
AB2C3D2011,
tP19, (123)
P4/mmm-iZh2gZcba
-DO2
-~ C-O2-C .-O2--
C-DO2-OB-A O-OB-
Bio.sSrzCezNdCu2.5011, T c -- 15 K, PX, R e --0.077
(Chen
et aL,
1993b,c)
(123)
P4/mmm,
a = 3.848, c = 17.246A, Z = 1 Fig. 18
Atom WP PS x y z Occ
Bi a 4(]) m. 2m 0.065 0.065 0
1 1
0.141
Sr 2(h)
4mm ~
Cu 2(g)
4mm 0 0
0.245
1 1 0.3485
Ce(1) b 2(h)
4mm ~
1
Ce(2) b l(b)
4/mmm 0 0
1 1 0
O(1) l(c)
4/mmm ~
0(2) 2(g)
4mm 0 0
0.116
1 0.256
0(3) 4(i)
2mm . 0
1 0.4175
0(4) 4(i)
2mm . 0
0.25
a
Bi = Bio. 5 Cuo. 5.
b Ce(1) = Ce(2) = Ceo.6667Ndo.3333.
Compound a (A) c (A) T c (K) Ref.
Tlo.596Sr2Ce2HoCu2.2011 3.8221 17.2855 n.s. 1
Pbo.5 Sr2Ce2HoCu2.5011.122 3.82615 17.2028 n.s. 1
Bio.5Sr2Ce2NdCu2.5011 3.848 17.246 15 2, 3
Bio.sSr2Ce2GdCu2.5011_6
a
3.847 17.198 20 2, 3
Sr2Ce2HoCu3011 a
3.824 17.22 n.s. 4
a Nominal composition.
References: 1, Wada
et al.
(1991a); 2, Wada
et al.
(1991b); 3, Chen
et al.
(1993b); 4, Chen
et al.
(1993c); 5, Wada
et aL
(1990b).
Nonsuperconducting 1232 compounds were reported for the composition
MxSr2Ce2HoCu3_x011,
where Cu could be partly substituted by Pb, Fe, or A1
H. Crystallographic Data Sets
363
(Wada
et al.,
1990b). A structural refinement on Pbo.sSr2Ce2HoCu2.5Oll
((Cuo.sPbo.5)Sr2(Ceo.67Hoo.33)3Cu2011)
in space group
P4/mmm
(a = 3.82246,
c= 17.2082A) indicated that the atoms in the
additional
layer were
displaced from the ideal positions along the short translation vectors (cation
from l(a)0 0 0 into 4(/)0.072 0 0 and O from l(c) 89 1 0 into 4(n)0.32 1 0).
Wada
et al.
(199 l b) detected an extra O site in the
additional
layer (2(f) 0 89 0,
occupancy 0.061). The only superconducting 1232 compounds known so far are
Bio.sSr2Ce2RCu2.5Oll with R = Nd or Gd (Chen
et al.
1993c).
1234 T11Ba2(Cao.98 )3 Ct14011
AB2C3D40]] ,
tP21, (123)
P4/mmm-i2h2g3dca
-D O 2-. C-DO 2-. C-DO 2-. C-DO 2-O B-A O-O B-
Tlo.996Ba2Ca2.96Cu4Oll , T c --
114 K, PX, RT, Re = 0.044
(Ogborne and Weller, 1994c)
(123)
P4/mmm,
a = 3.84809, c = 19.0005 A, Z = 1 Fig. 19
Atom WP PS x
Occ.
T1 4(/)
m2m.
Ba 2(h)
4mm
Cu(1) 2(g)
4mm
Ca(l) 2(h)
4mm
Cu(2) 2(g)
4mm
Ca(2) l(d)
4/mmm
O(1) l(c)
4/mmm
O(2) 2(g)
4mm
0(3) 4(i)
2mm.
0(4) 4(i)
2mm.
0.086
1
2
o
1
2
o
1
2
1
2
0
o
o
0
0.1437
0.2487
0.3292
0.4158
1
2
o
0.1099
0.2515
o.4156
0.249
0.98
364 Chapter
8:
1234
Crystal Structures of High-T~ Superconducting Cuprates
(Hgo.73Pbo. 18)lBa2Ca3 Cu401 o. 14
AB2 C3D4 01o+6 , tP20, (123)
P4 /mmm-i2 h2 g3 d(c)a
-DO2-.
C-DO 2-" C-D02-" C-DO2-OB-A .-OB-
Hgo.7336Pbo.1834BazCa3Cu4Om.14, a T c -- 129 K, SX,
R w
-- 0.0239 (Schwer
et al.,
1995a)
(123)
P4/mmm,
a = 3.8530, c = 18.968 A, Z = 1
Atom b WP PS x y z
Occ.
Hg c l(a)
4/mmm 0 0 0
1 1 0.14375
Ba a 2(h)
4mm ~
Cu(1) 2(g)
4mm
0 0 0.24840
1 1 0.32976
Ca(l) 2(h)
4mm ~
Cu(2) 2(g)
4mm
0 0 0.41592
1 1 1
Ca(2) l(d)
4/mmm ~ ~
1 1 0
O(1) l(c)
4/mmm ~
0(2) 2(g)
4ram
0 0 0.1059
1 0.2507
0(3) 4(i)
2mm . 0
1
0.4167
0(4) 4(i)
2mm . 0
0.917
0.14
a
Prepared at 1 GPa.
bSites with occupancy 0.019 (Hg in 2(g)0 0 0.1654, Ba in 2(h) 1 89 0.0266 and 2(h) 89 89 0.3102)
ignored here.
c Hg = Hgo. 8 Pbo. 2.
d Refined occupancy 0.962.
Compound a (A) c (A) T c (K) Ref.
Hgo.84Ba2Ca3 Cu4010.4
Hgo.7336Pbo. 1834Ba2Ca3 Cu401 o.
14 a
3.8495 19.003 125 1
3.8530 18.968 129 2
a
Prepared at 1 GPa.
References: 1, Paranthaman and Chakoumakos (1996); 2, Schwer
et al. (1995a).
1234
(C0.32Cu0.68) 1Ba2Ca3Cu4011.06
AB 2
C3D4On,
tP21,
(123) P4/mmm-i
2 h2g3fda
-DO 2-. C-DO2-. C-DO2-. C-DO2-OB-A O"-OB-
Co.32Ba2Ca3Cu4.68Oll.O6, a T c = 117 K, PN, RT,
Rwp
= 0.10686 (Shimakawa
et al.,
1994a)
(123)
P4/mmm,
a = 3.86192, c = 17.9512A, c Z = 1
Atom WP PS x y z
Occ.
Cu(1) a l(a)
4/mmm 0 0
1 1
Ba 2(h)
4mm ~
Cu(2) 2(g)
4mm 0 0
1 1
Ca(l) 2(h)
4mm ~
Cu(3) 2(g)
4mm 0 0
1 1
Ca(2) l(d)
4 /mmm ~
1
O(1) 2(f)
mmm. 0
O(2) 4(/)
mZm.
0 0.318
0(3) 2(g)
4mm 0 0
0
0.1219
0.2332
0.3187
0.4117
1
2
0 0.37
0 0.08
0.1000 0.68
(continued)
H. Crystallographic Data Sets 365
0(4) 8(s) .m. 0 0.159
1
0(5) 4(i)
2mm . 0
1
0(6) 4(i)
2mm . 0
0.0593
0.2376
0.4130
0.08
a
Prepared at 5 GPa.
b Multiphase refinement; sample also contained small amounts of Ag and Ag20.
c Average structure; additional reflections indicate superstructure (2a, a, 2c).
a Cu(1 )
- Cu0.68 C0.32.
Compound a (A) c (A) T c (K) Ref.
A1Sr2Ca3Cu4011 a
3.839 17.72 110 1
GaSr2Ca3Cu4010.8 b c 93 d 2
Ba2Ca3Cu4.6Olo.8 e 3.8526 17.974 f 116 3
Co.32Ba2Ca3Cu4.68011.o6 e
3.86192 17.9512 g 117 4
BSr2Ca3Cu4011
b 3.8359
17.082 110 5
Po.5 Sr2Cal.9Yo. 1 Cu3.509.3 h 3.851 17.49 g 84 6
So.5Sr2Ca3Cu4.5012 b 3.854 i 17.5 ~ 1 O0 7
a prepared at 5.5 GPa; nominal composition.
b Prepared at 6 GPa; nominal composition.
c Space group
I2cm,
a - 5.417, b - 5.462, and c = 35.78 A.
a Tc = 107 K for GaSr2Ca3Cu4011.1.
e
Prepared at 5 GPa.
f Additional reflections indicate superstructure (2a, 2a, 2c).
g Additional reflections indicate superstructure (2a, a, 2c).
h Prepared at 5 GPa; nominal composition.
i Value taken from figure.
J Additional reflections indicate superstructure (2a, a, 2c or 2a, a, c).
References: 1, Isobe
et al.
(1994); 2, Takayama-Muromachi and Isobe (1994); 3, Akimoto
et al.
(1995); 4, Shimakawa
et al.
(1994a); 5, Takayama-Muromachi
et al.
(1995a); 6, Isobe
et al.
(1996b);
7, Takayama-Muromachi
et al.
(1995b).
A superconducting T1-1234 compound (T c = 122K) with a tetragonal
structure (a - 3.85, c-- 19.1 A) was first reported for the composition T1Ba2-
Ca3Cu4Oll (Ihara
et al.,
1988).
A superconducting Hg-1234 compound (T c = 126 K) was first reported for
HgBa2Ca3Cu4010+6 and a tetragonal structure was proposed (a- 3.8540,
c - 19.006 A) (Antipov
et al.,
1993). Structural refinements indicated vacancies
on the Hg site (occupancy 0.79 or 0.84) and a relatively high occupancy of the
extra O site in the
additional
layer (occupancy 0.60 or 0.40) (Loureiro
et al.,
1996a; Paranthaman and Chakoumakos, 1996). For Hg0.7336Pb0.1834Ba2Ca3-
Cu4Olo.14 extra cation sites with very low occupancy, corresponding to a small
fraction of intergrowth of 1234 with 1223 and 1245, were refined (Schwer
et al.,
1995a).
A critical temperature of 117 K was reported for the first (C,Cu)-1234
compound
(P4/mmm,
a- 3.855, c- 17.930A) and an orthorhombic super-
structure (2a, a, 2c) was proposed (Kawashima
et aL,
1994a). The superstructure,
also observed by Alario-Franco
et al.
(1994a) and Matsui
et al.
(1994), is caused
by the ordering of carbon and copper atoms in the
additional
layer. In the