Poole Ch.P., Jr. Handbook of Superconductivity
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326
Chapter 8: Crystal Structures of High-T~ Superconducting Cuprates
Lal.6Sro.4CaCu205.9o 8
3.8208 19.5993 55 9
Lal.82Cal. 18Cu206.o14 f 3.81604 19.4214 50 g 10
a
Prepared at 6 GPa; nominal composition.
b Prepared at 5.5 GPa; nominal composition.
c Prepared at 5 GPa.
d Prepared at 6 GPa.
eNominal composition, oxygen content from chemical analysis.
fPrepared at 0.2 GPa.
g Value taken from figure.
References: 1, Hiroi
et al.
(1993b); 2, Kawashima and Takayama-Muromachi (1996); 3, Kawashima
et
al.
(1996); 4, Jin
et aL
(1995); 5, Isobe
et al.
(1996a); 6, Huang
et al.
(1990); 7, Lightfoot
et al.
(1990b); 8, Seling
et al.
(1995); 9, Cava
et al.
(1990b); 10, Kinoshita
et al.
(1992).
0212 compounds are sometimes referred to as 326 or 2126 phases and were
first reported for
La2_xMl+xCu206_~
(M = Sr or Ca), with a complete structure
determination published by Nguyen
et al.
(1980). La2_xSrl+xCu206 and stoichio-
metric La2CaCu206 are not superconducting, but superconductivity occurs after
partial substitution of La by Sr or Ca in the latter and postannealing at high
oxygen pressure (Cava
et al.,
1990a; Kinoshita and Yamada, 1992b). The high-
pressure treatment is believed to increase the ordering of cations (Kinoshita
et al.,
1991; Shaked
et al.,
1993), superconductivity being suppressed for a high degree
of disorder, in particular when strontium atoms are present also in the
separating
layer, g partly occupied O site (2(a) 1 1 1) in the
separating
layer is often
reported and can be related to the substitution of Ca by Sr or La (occupancy 0.28
for Ca-free
Lal.85Srl.15Cu206.25 ,
Lightfoot
et al.,
1990b). Note that a full
occupation of this site would give a SraTi207-type structure (Ruddlesden and
Popper, 1958).
0222
(Ndo.59Sro.41)2(Ndo.73Ceo.27)2Cu207.84
B2C2D208,
tP14,
(129)
P4/nmm-fc4b
-DO2-.C-O2-C.-O2D-BO-OB -
Nd2.64Sr0.82Ceo.54Cu207.840, T c - 22 K, PN, RT,
R B
= 0.0332 (Izumi
et al.,
1989c)
(129)
P4/nmm
(origin at
2/m),
a = 3.8564,
c=12.4846A, Z=l Fig. 7
H. Crystallographic Data Sets 327
Atom WP PS x y z
Occ.
1 1 0.1107
Nd(1)a 2(c)
4mm -4
3 3 0.2490
Cu 2(c)
4mm ~
1 1 0.3965
Nd(2) b 2(c)
4mm ~ -~
O(1) 8(/) .. m 0.796 0.796 0.0709
1 3 0.2622
0(2) 4(f)
2mm . ~ -~
1 3 1
0(3) 2(b) 4m2 ~
4
0.230
aNd(l) = Ndo.59Sro.41.
bNd(2) = Ndo.73Ceo.27.
Compound a (A) c (A) T c (K)
Ref.
Sr2Nd2Cu206C12 a 3.956 13.880 n.s. 1
Srl.sBio.sYl.15Ceo.85Cu208 3.822 12.659 30 2
Lal.5 Sro.5 Sm2.oCu207. 9 3.8588 12.5725 20 b 3
Lal.8Sro.4EUl.8Cu208 c
. ..... 34 4
La1.8 Sro.4Gd 1.8Cu208 3.85344 12.53367 13 a 5
La2.sDy 1.5Cu207.5F 1.o e n.s. 6
Nd2.64Sro.82Ceo.54Cu207.84o 3.8564 12.4846 22 7
a Nominal composition.
b Tc = 37 K for
Lal.64Sro.36Sm2.oCu20 8
(nominal composition) prepared under 0.3 GPa
02
(Hundley
et al.,
1989).
c Prepared under 0.3 GPa 02; nominal composition.
aT c
= 33 K for sample prepared under 0.3 GPa 02 (Fisk
et al.,
1989).
e Space group
Cmma,
a = 5.4609, b = 5.5089 and r = 12.4842 A.
References: 1, Fuller and Greenblatt (1991); 2, Chen
et al.
(1993a); 3, Tokura
et al.
(1989c); 4, Fisk
et
al.
(1989); 5, Kwei
et al.
(1990); 6, Lightfoot
et al.
(1990a); 7, Izumi
et al.
(1989c).
0222 compounds are usually referred to as T* phases. Superconductivity
was first reported in the Nd-Sr-Ce-Cu-O system (Akimitsu
et al.,
1988). The
superconducting compound was identified as Nd2.64Ceo.54Sro.s2Cu2Oy and a
structural model was proposed by Takayama-Muromachi
et al.
(1988a). The
rare-earth metal and strontium atoms occupy two cation sites, with coordination
numbers 9 and 8, which correspond to the B site in the 0201 structure (T phase)
and the C site in 0021 (T'), respectively. The 0222 structure may thus be
described as an intergrowth of these two structures. The first refinement was
reported by Sawa
et al.
(1989b), who stated that the Nd site in the
bridging BO
layers was occupied by a statistical mixture of Nd, Sr, and Ce. Partial ordering of
R 3+ and Sr 2+ was shown by Izumi
et al.
(1989c) and confirmed by a refinement
on Lal.sSro.4Gdl.sCu208 ((Lao.sSro.2)2(Gdo.9Lao.1)2Cu208) by Kwei
et al. (1990).
The cell parameters and the critical temperature vs the Sm content in
La3.6_xSro.4SmxCu20 8 are presented in Figs. 8.23 and 8.24, respectively. Partial
oxygen pressure during the synthesis was shown to have a positive effect on the
critical temperature (Tokura
et al.,
1989c).
328
Chapter 8: Crystal Structures of High-Tc Superconducting Cuprates
Fig. 8.23.
12.70 l
12.67
' I ' I ' I ' I ' I ' I '
12.64
1" 12.61
E 12.58
3.87
a
o
3.86 i , I , I , I , t 7
0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
x in La3.6.xSro.4SmxCu20 s
Cell parameters vs Sm content for
La3.6_xSro.4SmxCu208
(T* phase; Fisk
et al.,
1989).
Fig. 8.24.
25
' I ' 1 ' I ' I ' I ' i , I ' I , ,
I
T+T* I T* T'"
I i
15
~ 10
5
0 , I ~ , I , I , I , I , I , I I
0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8
x
in La3.6_xSro.4SmxCu208
Superconducting transition temperature vs Sm content for
La3.6_xSro.4gmxCu208
(Fisk
et al.,
1989; Tan
et al.,
1991).
H. Crystallographic Data Sets 329
0223
(Sro.90Cao. 10)2( Cao.50Sro.50)2Cu3(
0o.85Clo.
15)8
B2C2D308,
tI30,
(139)
I4/mmm-ge4ca
-02DL-C.-O 2/)--C.-O 2D-BO-OB-
Sr2.sCal.2Cu306.8Cll.2, a T c : 46 K (Wu
et al.,
1996a)
(139)
I4/mmm,
a = 3.877, c = 28.65 A, Z = 2 Fig. 8
Atom WP PS x
Occ.
Sr b 4(e)
4mm 0
1
Cu(1) 4(e)
4mm
Ca c 4(e)
4mm 0
1
Cu(2) 2(a)
4/mmm
1
C1 a 4(e)
4mm
0(1) 8(g)
2mm . 0
0(2) 4(c)
mmm . 0
0.3284
0.3881
0.4448
1
0.2828
0.3881
1
_
2
a
Prepared at 5 GPa; sample also contained 0212 compound.
b Sr = Sr0.9Ca0.1.
c Ca = Cao.5 Sro. 5.
d C1 = Clo.60o. 4.
Compound a (A) c (A) T c (K) Ref.
Sr4Cu308 a
3.8730 27.39 1 O0 1, 2
b
Sr2CaCu205.5 3.863 27.22 109 3
Sr2Ca2Cu306.2F3.2 b 3.840 26.17 111 4
Sr2.8Ca1.2Cu306.8C11.2 c
3.877 28.65 46 5
a
Prepared at 5.7 GPa; sample also contained 0212 compound.
b Prepared at 5.5 GPa; nominal composition.
C prepared at 5 GPa; sample also contained 0212 compound.
References: 1, Shaked
et al.
(1995); 2, Hiroi and Takano (1994); 3, Kawashima and Takayama-
Muromachi (1996); 4, Kawashima
et al.
(1996); 5, Wu
et al.
(1996a).
330
Chapter 8: Crystal Structures of High-Tr Superconducting Cuprates
A 0223 compound was first reported in the Sr-Ca-Cu-O system for the
nominal composition
Sro.6Cao.333CuO2.1o (a =
3.86, c = 27.2A, T c = 90K;
Adachi
et aL,
1993). All compounds known so far were prepared at high
pressure. The isotypic compound without calcium, Sr4Cu308, was also obtained
(Hiroi
et aL,
1993b; Shaked
et al.,
1995); however, the only structural refinement
was carried out on a compound with oxygen partly substituted by chlorine. Note
that PbBaSrYCu307+ a is sometimes referred to as 0223 (Rouillon
et aL,
1989,
1992a), but that according to the classification criteria proposed here it corre-
sponds to the 2212 structure.
0232
Sr2(Ceo.53Yo.47)3 (Cuo.50Feo.50)2010
B2C3D201o, ti34, (139) I4/mmm-g2e4a
-0 2D-C.-O2-. C-O2-C.-O 2D-BO-OB-
Sr2Cel.599Y1.4olCuFeOlo ,
n.s., PX,
R B
-- 0.066
(Tang et al., 1993)
(139) I4/mmm, a = 3.828, c = 30.560 A, Z = 2 Fig. 9
Atom WP PS x
y z Occ.
Sr 4(e) 4mm 0
1
Cu a 4(e) 4mm
Ce(1) b 4(e) 4mm 0
1
Ce(2) b 2(a) 4/mmm
1
O(1) 4(e) 4mm
0(2) 8(g) 2mm . 0
0(3) 8(g) 2mm . 0
0 0.287
1 0.356
2
0 0.409
1 1
2
2
1 0.284
2
1 0.364
2
1 0.458
2
a CU =
Cu0.5Fe0. 5.
b Ce(1) = Ce(2) -- Ce0.533 Y0.467.
H. Crystallographic Data Sets 331
0234
B2C30401o, ti38, (139) I4/mmm-g2eSb
-02D-C.-O 2 D--C,-O
2D--C.-O 2D-BO-OB-
SrzCa3Cu40]o, a T c -- 70 K b (Adachi et al., 1993)
(139)
I4/mmm, ~ a = 3.86, c = 34.0A, Z = 2 Fig. 10
Sr2Ca3Cu4Olo
Atom WP PS x y z Occ.
Sr 4(e)
4mm 0 0 0.29
1 1
0.35
Cu(1) 4(e)
4mm ~
Ca(l) 4(e) 4mm 0 0 0.40
1 1 0.45
Cu(2) 4(e) 4mm ~ -~
1
Ca(2) 2(b) 4/mmm 0 0
1 1 0.28
O(1) 4(e) 4mm -~
1 0.35
0(2) 8(g)
2mm . 0
1 0.45
0(3) 8(g)
2mm . 0 -~
a prepared at 5 GPa; nominal composition Sr0.65Cao.3CuO2.10; sample also contained infinite-layer
compound; a = 3.901, c-33.82A and T c =83K for Sr3CaCu2.807. 5 (nominal composition)
prepared at 5.5 GPa (Kawashima and Takayama-Muromachi, 1996).
b Value taken from figure.
c Atom coordinates for ideal structure derived from drawing.
332 Chapter 8:
1201
Crystal Structures of High-T c Superconducting Cuprates
(T10.92) 1 (Bao.60Lao.40)2Cu 104.86
AB2DOs, tP9, (123) P4/mmm-hgecba
-00 2-OB-A
O-OB-
Tlo.92oBal.2Lao.8CuO4.864, T c -- 52 K, PN, T = 305 K,
Rwp
= 0.0369 (Subramanian
et aL,
1990c)
(123)
P4/mmm,
a = 3.8479, c = 9.0909 A, Z = 1 Fig. 11
Atom WP PS x y z Occ.
T1 4(/)
m2m.
0.0801 0 0
1 1
0.2942
Ba a 2(h)
4mm ~
1
Cu l(b)
4/mmm 0 0
1 0
O(1) 4(n)
m2m.
0.4281
0(2) 2(g)
4mm
0 0 0.2250
1 1
0(3) 2(e)
mmm . 0 ~
0.230
0.216
"Ba = Bao.6Lao. 4.
Compound a (A) c (A)
T c (K) Ref.
T1Ba2CuO5 a 3.869 9.694 n.s. b 1
T1BaSrCuO5_6 c 3.805 9.120 43 d 2
Tlo.92oBa 1.2 Lao.8CuO4.864 3.8479 9.0909 52 3
T1Ba2CuOa.7Fo.3 3.836 9.590 75 4
T1Sr2CuO5 3.7344 9.007 e n.s. 5
Tlo.sPro.6Srl.6CuO5 3.741 8.875 40 6
Tlo.sCro.sSr2CuO5 3.795 8.880 c 50 7
Tlo.sPbo.sSr2CuO5 3.7405 9.0097 n.s. g 8
Tlo.sPbo.sSrl.sNdo.sCuOs.o7 3.76 h
8.88 h
40 9
T1SrLaCuO5 3.765 8.838 46 10
Pbo.sSrLaCul.5Os.o3 i 3.77305 8.6876 35 11-14
a
Composition Tll.2Ba2Cuo.704.8 from microprobe analysis.
b a = 3.859, c -- 9.261 A and T c = 9.5 K (from resistivity measurements, zero resistivity) for sample
prepared under reducing conditions (Gopalakrishnan, 1991).
c Prepared under reducing conditions; nominal composition.
d From resistivity measurements (zero resistivity).
e
Space group
Pmmm,
a = 3.661, b = 3.793, and c = 8.99 A reported for oxygen-deficient compound
(Ganguli and Subramanian, 1991); 2-fold superstructure
(Pmmm, a=
3.6607, b= 7.5709,
c = 8.9672 A) reported for T1Sr2CuO4.515 (Ohshima
et al.,
1994).
f8-fold superstructure
(A2mm,
a = 3.7803, b = 15.2573, c = 17.6737A) reported for
Tlo.75Cro.25Sr2CuO4.975 (Michel
et al.,
1996).
g T c = 60 K in Pan and Greenblatt (1991).
H. Crystallographic Data Sets 333
h Value taken from figure.
;Oxygen content from chemical analysis.
References: 1, Parkin
et al.
(1988c); 2, Gopalakrishnan
et al.
(1991); 3, Subramanian
et al.
(1990c); 4,
Subramanian (1994); 5, Kim
et al.
(1989); 6, Bourgault
et al.
(1989); 7, Sheng
et al.
(1992); 8, Kaneko
et al.
(1991); 9, Ohshima
et al.
(1993); 10, Subramanian (1990); 11, Khasanova
et al.
(1996a); 12,
Nakahigashi
et al.
(1990); 13, Adachi
et al.
(1990b); 14, Sasakura
et al.
(1990).
1201 Ga
1 (Sro.5oLao.5o)2Cu
10 5
ABzDO s, tP9,
(123)
P4/mmm-hgecba
-DO2-OB-AO-OB-
GaSrLaCuOs, n.s., SX, RT,
R w
= 0.077 (Roth
et al.,
1992)
(46)
I2cm (Ima2),
a = 5.369, b = 5.510, r -- 16.51 A, Z = 4
al + a2, -al + a2, 2c; origin shift 0 88 -~
Atom WP PS x y
Occ.
Ga 4(b) . .m 0.038 -0.065
Sr a 8(c) 1 0.5 0.0164
Cu 4(a) 2.. -0.001 0
O(1) 4(b) . .m 0.381 -0.141
0(2) 8(c) 1 -0.01 0.063
0(3) 8(c) 1 0.25 0.25
1
4
0.3932
1
2
1
4
0.354
0.49
a
Sr = Sro.sLao. 5.
1201
HglBa2CulO4.18
AB2D04+ 6, tP8,
(123)
P4/mmm-hge(c)ba
-DO2-OB-A .-OB-
HgBazCuO4.18, T c -- 95 K, PN, T -- 296 K,
Rwp
= 0.0687 (Huang
et al.,
1995)
(123)
P4/mmm,
a = 3.88051, c - 9.5288 A, Z = 1
Atom WP PS x y z
Occ.
Hg l(a)
4/mmm 0 0
1 1
Ba 2(h)
4mm ~
Cu l(b)
4/mmm 0 0
1 1
O(1) l(c)
4/mmm ~
0(2) 2(g)
4mm 0 0
1
0(3) 2(e)
mmm . 0
0
0.2981
1
_
2
0
0.2076
1
_
2
0.18
Compound a (A) c (A) T c (K) Ref.
HgBa2CuO4.1 o 3.8766 9.5073
Hgo.85Ceo.15Ba2CuO4.15 3.8801 9.495
Hgo.sWo.zBa2CuO4.4 a 3.8713 9.416
Hgo.8Moo.2BazCuO4.4 a 3.8819 9.378
Hgo.vTlo.3BazCuO4+6 3.885 b 9.53 b
Hgo.743So. 184Ba2CuO4.486 3.8986 9.2466
Hgo.4Pro.65Srl.95CuO4+6 d
Hgo.5oCro.5oSr2CuO4.s8 3.85000 8.6961
94
90
45
74
41 b
62 C
n.s.
6O
1
2
3
3
4
5
6
7
(continued)
334
Chapter 8: Crystal Structures of High-Tc Superconducting Cuprates
Hgo.66Vo.34Srl.8Lao.2CuO4.82 3.8170 8.7564 41 b 8
Hgo.5Pbo.5Sr1.2Lao.8CuO5 3.7908 8.6915 32 9
Hgo.sBio.sSrl.sLao.sCuO5 3.7769 8.8252 27 10
a
Nominal composition.
b Value taken from figure.
c Tc = 77 K for sample annealed under reducing conditions.
d 2-fold superstructure (primitive orthorhombic, a = 7.606, b = 3.6827, c = 8.881 A).
References: 1, Putilin
et al.
(1993a); 2, Letouz6
et al.
(1996); 3, Maignan
et al.
(1995a); 4, Nakajima
et
al.
(1996); 5, Loureiro
et al.
(1996b); 6, Goutenoire
et al.
(1993a); 7, Chmaissem
et al.
(1995); 8,
Mandal
et al.
(1996); 9, Liu
et al.
(1993b); 10, Pelloquin
et al.
(1996a).
1201 Cl(Bao.50Sro.50)2Cu105.05
AB2DO s, tP9,
(123)
P4/mmm-hgfeba
-DO2-OB-A On-OB -
CBaSrCuO5.o5, n.s., PN, RT, R e = 0.0670 (Chaillout
et aL,
1992)
(127)
P4/mbm,
a -- 5.5899, c = 7.7153 A, Z = 2
al + a2, -a + a2, c
Atom WP PS x y
z Occ.
1 0
C 2(d)
m.mm 0
Sr 4(e) 4.. 0 0 0.2577 0.5
Ba 4(e) 4.. 0 0 0.2885 0.5
1 1
Cu 2(c)
m .mm 0 ~
O(1) 8(k) .. m 0.1566 0.3434 0.0447 0.2625
0(2) 8(k) . . m 0.0860 0.4140 0.1229 0.25
0(3) 8(k) . .m 0.0328 0.4672 0.1714 0.25
0(4) 8(k) . . m 0.2491 0.2509 0.4813 0.5
Compound Space group a (A) c (A) T c (K) Ref.
BBaLaCuO5 P4/mmm 3.94 a 7.50 a n.s. 1
CBaSrCuOs.o5
P4/mbm
5.5899 7.7153 n.s. 2
Co.9Bal. 1Sro.9CUl. 1 O4.9+ 6 P4212 5.5639 7.8567 26 3, 4
CSr2CuO5
P4/mmm
3.9033 7.49256 n.s. 5
Co.85Bo.15Sr2CuO5 I4 7.7881 14.9681 32 6
Co.7Bo.3Sr2CuO5 c
P4/mmm
3.86 7.40 50 7
CSrl.6Ko.aCuOS
P4/mmm
3.8907 7.522 e 23 8
a
Value taken from figure.
b 8-fold superstructure (I4, a = 7.8045, c = 14.993 A) in Miyazaki
et al.
(1992a).
c Prepared at 5 GPa.
a Prepared at 4 GPa; nominal composition.
e Additional reflections indicate superstructure (2a, 2a, 2c).
References: 1, Li
et al.
(1993); 2, Chaillout
et al.
(1992); 3, Kinoshita and Yamada (1992a); 4, Izumi
et
al.
(1992); 5, Babu
et al.
(1991); 6, Uehara
et al.
(1993a); 7, Uehara
et al.
(1994b); 8, Kazakov
et al.
(1995).
H. Crystallographic Data Sets 335
1201
(Co.50Tlo.25Pbo.25)l
Sr2CulO5
AB2DO5, tP9, (123) P4/mmm-hgfeba (hgecba)
-DO2-OB-AO" (AO)-OB-
CTlo.sPbo.sSr4Cu2Olo, T c = 60 K, a PX, R e -- 0.0655 (Huv6 et al., 1993b)
(123) P4/mmm, a = 3.8244, c = 16.516A, Z -- 1
al, a2, 2c
Atom WP PS x y z
Occ.
C l(a) 4/mmm 0 0 0
1 1
0.1275
Sr(1) 2(h) 4mm ~
Cu 2(g) 4mm 0 0 0.2346
1 1
0.3404
Sr(2) 2(h) 4mm ~
1
T1 b 4(m) m2m. 0.083 0
O(1 ) 4(/) m2m. 0.316 0 0
0(2) 8(s) .m. 0.162 0 0.086
1
0.223
0(3) 4(i) 2mm . 0
0(4) 2(g) 4mm 0 0 0.379
1 1
0(5) 4(0) m2m. 0.330 ~
0.25
0.25
0.25
0.25
aT c ---
70 K for sample annealed under reducing conditions.
b T1 -- T10.sPb0. 5.
Compound a (A) c (A) T c (K) Ref.
CT1Ba2SrzCu2Olo
a
62 1
CTlo.8Hgo.2Ba2 SrzCu2Oy b 60 c 2
CHgBazSrzCu209+ 6 3.88 16.94 a 66 3
CTlo.8Moo.2Sr4Cu2Olo 3.8251 16.429 80 4
CTlo.sPbo.s Sr4Cu201o 3.8244 16.516 60 e 5
CTlo.sBio.5 Sr4Cu2Olo 3.8309 16.518 54 6
CPbo.7Hgo.3 Sr4Cu2Olo 3.8242 16.4681 70 7
Co.955Bio.5Hgo.545Sr4Cu209.72 3.8265 16.4742 f 17 8
CUgo.57Vo.43 Sr4Cu209. 6
3.8505 16.240 76 9
CUgo.46Cro.54Sr4Cu209.88 3.8747 16.1555 37 10
CHgo.52Moo.4sSr4Cu209.21 3.8448 16.3173 74 10
a
8-fold superstructure (Ammm or Amm2, a = 3.839, b = 31.003, c-- 16.930 A); incommensurate
modulation (q ~ b*/6 to b*/7.4) and T c = 73 K in Matsui et al. (1993).
b Orthorhombic, a = 3.85, b = 3.87 and c = 16.95 A (values taken from figure).
c From resistivity measurements (zero resistivity), value taken from figure.
d Additional reflections indicate superstructure (orthorhombic, a -- 5.49, b = 24.71, r = 16.94 A).
e Tc = 70 K for sample annealed under reducing conditions.
f Additional reflections indicate superstructure (a, 8a, c).
References: 1, Goutenoire et al. (1993b); 2, Noda et al. (1995); 3, Uehara et al. (1994a); 4, Letouz6 et
al. (1995); 5, Huv6 et al. (1993b); 6, Maignan et al. (1993c); 7, Martin et al. (1994); 8, Pelloquin et al.
(1994); 9, Maignan et al. (1995b); 10, Pelloquin et al. (1995).
Stoichiometric T1Ba2CuO5 is nonsuperconducting (Parkin et al., 1988c);
however, superconductivity may be induced by partial substitution of Ba 2+ by
La 3+ (T1Bal.2Lao.gCuOs, T c - 40 K) (Manako et al., 1989) (Figs. 8.25 and 8.26).
The structure is tetragonal (P4/mmm), whereas that of the Sr analogue,