STRUCTURE FAMILIES OF SUPERCONDUCTING OXIDES
J. Hauck and K. Mika
IFF, Research Center Jülich,
D-52425 Jülich, Germany
The Ising type analysis of superconducting
cuprates shows that the layered structures are composed from
perovskite, SrO and CaCuO2 structural units with
different interactions between oxygen atoms. The 45 structures
for a combination of a maximum of 8 structural units can be
classified in 13 structure families which are named by the
authors who synthesized the first compound or found
superconducting properties like the Ruddlesden-Popper,
Bednorz-Müller family with the sequence of coordination numbers
(CN) of metal atoms 12 62 122 62
92 6n 6'n (Table 1). The formula
Cu La2 O4 or Cu Ba2 Tl O5
indicate the sequence of metal atoms Cu La La, Cu or Cu Ba Tl Ba,
Cu with single Cu (or Tl) atoms at mirror planes and two La or Ba
atoms in between the mirror planes. Long sequences of CN values
increase with the possibility of segregation e.g. of La Cu2
La2 O7 (with CN values 12 62 92)
to La Cu O3 (12 6) and Cu La2 O4
(6 92). The final members Ca Cu O2 (8 4),
Sr O(6') and La Cu O3 or Ca Ti O3 (12 6),
which can be formed at segregation are underlined in table 1. The
composition Cu (La, Sr)2 O4 can be obtained
either with two trivalent La atoms (2 0 1) or one La and one Sr
atom (1 1 1). The formal valency of divalent copper atoms (C1)
in 2 0 1 is increased at (1 1 1) composition (C2). The
underlined value corresponds to the experimental compound. Most
superconducting oxides are within the first three families listed
in table 1. Some compounds of other families are non-metallic as
e.g. Ba (Cu, Fe)2 YO5. Other compounds as
e.g. Pb Sr2 Fe2 Sr2 O9
have the same composition MNC2 = 232 as Pb Fe2
Sr2 Bi2 O9. Both structures are
closely related. The sequence of the CN values of the Lucas,
Raveau series 6'n 92 62 92
6'n can be derived from 6'n 92
62 (122 62) 92 6'n
of the Ruddlesden-Popper family, if the part given in brackets is
omitted. The structures of the Cava, Subramanian series with CN
values 4 82 52 92 92
62 12 can be obtained from4 82
52 92 (6'2) 92 62
12 in a similar way. Other families can be obtained, if CuSr2O3
(4 72) of the Müller-Buschbaum series 8 42
72 6' is substituted in 4 82
52 92 6'2 92 62
12 for 4 82 52 92 72
42 8 of the Subramanian, Cava or 8 42
72 92 62 12 of the
Fu, Zandbergen series. No compounds are known for MNC1=403
or 242 with the corresponding CN values 4 102 62
92 or 6 92 6'2 72 4.
The Aurivillius phases with CN values 12 62 12'2
and the CeO2 containing phases with 6 122
52 8'n (Li, Cava), 8 42
102 52 8' (Sawa) can be obtained, if
92 6'n of 12 62 92
6'n is replaced by 6 12'2 (WBi2
O6) and 8 4 (Ca Cu O2) is replaced by 4 8'2
(Cu(Nd, Ce)2 O4).
Table 1: Composition of different
cuprates containing trivalent (M), divalent (N), formally
divalent (C1) or higher valent (C2) copper
atoms and coordination numbers of metal atoms
composition | MNC1 | MNC2 | CN |
CaCuO2 | 0 1 1 | 8 4 | |
SrO | 0 1 0 | 6' | |
Cu Sr2 O3 | 0 2 1 | 4 72 | |
La Cu O3 | 1 0 1 | 12 6 | |
(Ruddlesden-Popper, Bednorz-Müller) | 12 62 92 6'n | ||
Cu La2 O4 | 2 0 1 | 1 1 1 | 6 92 |
Cu Ba2 Tl O5 | 2 1 1 | 1 2 1 | 6 92 6' |
Cu Sr2 Bi2 O6 | 2 2 1 | 1 3 1 | 6 92 6'2 |
Pb Fe2 Sr2 Bi2 O9 | 4 1 2 | 2 3 2 | 12 62 92 6'2 |
(Nguyen, Cava) | 8 42 82 52 92 6'n | ||
Ca Cu2 La2 O6 | 2 1 2 | 1 2 2 | 8 52 92 |
Ca Cu2 Ba2 Tl O7 | 2 2 2 | 1 3 2 | 8 52 92 6' |
Ca Cu2 Sr2 Bi2 O8 | 2 3 2 | 1 4 2 | 8 52 92 6'2 |
Cu (Y, Sr)2 Cu2 (Pb, Ba)2 O8 | 2 2 3 | 1 3 3 | 4 82 52 92 |
(Raveau, Chu) | 8 42 102 52 82 4 | ||
Cu Ba2 Cu2 YO7 | 2 1 3 | 1 2 3 | 4 102 52 8 |
(Er-Rakho, Raveau) | 6 122 52 82 42 8 | ||
Ba (Cu, Fe)2 YO5 | 2 0 2 | 1 1 2 | 12 52 8 |
(Lucas, Raveau) | 6'n 92 62 92 6'n | ||
Pb Sr2 Fe2 Sr2 O9 | 4 1 2 | 2 3 2 | 6' 92 62 92 |
(Cava, Subramanian) | 4 82 52 92 92 62 12 | ||
Y Cu2 Sr2 Pb2 Cu O10 | 4 1 3 | 2 3 3 | 8 52 92 92 6 |
(Subramanian, Cava) | 4 82 52 92 72 428 | ||
Y Cu2 Sr2 Pb2 Cu O9 | 2 3 3 | 1 4 3 | 8 52 92 72 4 |
(Fu, Zandbergen) | 12 62 92 72 42 8 | ||
Cu (La, Sr)2 Pb2 Cu O7 | 2 2 2 | 1 3 2 | 6 92 72 4 |