On a lead nickel manganese tellurium oxide PbMn2Ni6Te3O18 containing Mn2+ in trigonal prismatic oxygen coordination

Article abstract of DOI:10.1016/S0025-5408(99)00231-7

A new lead manganese nickel tellurium oxide PbMn₂Ni₆Te₃O₁₈ is light green in color and crystallizes in hexagonal symmetry, space group C_6h² P6₃/m (no. 176), with cell parameters a = 9.294(1), c = 8.823(1) angstrom, and Z = 2. The structure was determined from a single crystal X-ray study and refined to the conventional values R = 0.026 and wR(F²) = 0.046. Ni²⁺ and Te⁶⁺ show octahedral and Mn²⁺ shows trigonal prismatic coordination by O^2-. The crystal structure is featured by a _∞²[Ni₆Te₃O₁₈]^6- network together with two kinds of channels along [001] with trigonal and hexagonal shape. Isolated face shared [Mn₂O₉]^14- trigonal prismatic polyhedra doubles are located in the trigonal channels, while one-dimensional infinite chains of [PbO₆₊₆]^22- oxygen cube dodecahedra are incorporated in the hexagonal channels.

Full text of DOI:10.1016/S0025-5408(99)00231-7

Materials Research Bulletin, Vol. 34, Nos. 14/15, pp. 2193–2199, 1999
Copyright © 2000 Elsevier Science Ltd
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0025-5408/99/$–see front matter
PII S0025-5408(99)00231-7
ON A LEAD NICKEL MANGANESE TELLURIUM OXIDE PbMn2Ni6Te3O18
CONTAINING Mn2؉ IN TRIGONAL PRISMATIC OXYGEN COORDINATION
B. Wedel1*, K. Sugiyama2, K. Hiraga2, and K. Itagaki1
1Tohoku University, Institute for Advanced Materials Processing (IAMP), Katahira 2-1-1,
Aoba-Ku, Sendai 980-8577, Japan
2Tohoku University, Institute for Materials Research (IMR), Katahira 2-1-1, Aoba-Ku,
Sendai 980-8577, Japan
(Refereed)
(Received February 5, 1999; Accepted March 8, 1999)
ABSTRACT
A new lead manganese nickel tellurium oxide PbMn2Ni6Te3O18 is light green
in color and crystallizes in hexagonal symmetry, space group C26h P63/m (no.
176), with cell parameters a ϭ 9.294(1), c ϭ 8.823(1) Å, and Z ϭ 2. The
structure was determined from a single crystal X-ray study and refined to the
conventional values R ϭ 0.026 and wR(F2) ϭ 0.046. Ni2ϩ and Te6ϩ show
octahedral and Mn2ϩ shows trigonal prismatic coordination by O2Ϫ. The
2
crystal structure is featured by a [Ni6Te3O18]6Ϫ network together with two
ϱ
kinds of channels along [001] with trigonal and hexagonal shape. Isolated face
shared [Mn2O9]14Ϫ trigonal prismatic polyhedra doubles are located in the
22Ϫ
trigonal channels, while one-dimensional infinite chains of [PbO6ϩ6
]
ox-
ygen cube dodecahedra are incorporated in the hexagonal channels. © 2000
Elsevier Science Ltd
KEYWORDS: A. inorganic compounds, A. oxides, C. X-ray diffraction, D.
crystal structure
INTRODUCTION
We have recently characterized the quaternary lead(II) nickel tellurium oxide
Pb3Ni4.5Te2.5O15 [1] with a stereo active lone pair located at Pb2ϩ and Pb(Mn,Te)O3 [2]. The
*To whom correspondence should be addressed.
2193

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B. WEDEL et al.
Vol. 34, Nos. 14/15
lead manganese tellurium oxide shows a spherical symmetry of the lone pair, which indicates
a s2 character, and this compound crystallizes in the cubic perovskite type.
Reported quaternary nickel tellurium oxides are rare; only a few compounds have been
reported. BaMn2NiO6 [3], Ba2NiTeO6 [4], and Sr2NiTeO6 [5] should be mentioned.
Sr2MnTeO6 [6], Ba2MnTeO6 [2], and (Mn2,4Cu0.6)TeO6 [2] have to be named in the case of
manganese(II) compounds.
The earth alkaline metal compounds crystallize in a small number of perovskite variants.
It was our aim to study the character of the lone pair in a lead tellurium oxo-compound
containing manganese(II) and nickel(II) and to compare the character of the stereo active lone
pair in Pb3Ni4.5Te2.5O15 with the character of the spherical lone pair in Pb(Mn,Te)O3.
EXPERIMENTAL
The hitherto unknown compound PbMn2Ni6Te3O18 was synthesized as a polycrystalline
powder and as single crystals in a solid-state reaction in air. Yellow PbO (Kanto Chemical
Co. Inc.), basic NiCO3 (Kanto Chemical Co. Inc.), basic MnCO3, and TeO2 (prepared by
oxidation of tellurium metal (Kanto Chemical Co. Inc.) by concentrated HNO3 in air at 473
K for 6 h [7]) were intimately mixed in the ratio 1:5:3:5 and ground thoroughly before being
placed in a platinum crucible. This crucible was placed in a furnace and heated in air to 1073
K for 336 h. The furnace was allowed to cool to room temperature and the samples were then
removed from the furnace. The high ratio of TeO2 was necessary because of evaporation
losses.
After cooling, many single crystals with different shapes and colors were found in the
inhomogeneous reaction product. Besides a few light-green single crystals, there were
various yellow, dark-red, and dark-green crystals. By energy-dispersive X-ray spectroscopy
(Hitachi X650S, EDX system KEVEX 7000Q) and X-ray diffraction (XRD; Rigaku X-ray
diffractometer RINT 2000), these crystals were identified as PbTeO3 [8], Mn3TeO6 [9], and
Pb3Ni4.5Te2.5O15 [1]. The light-green crystals were stable in air and suitable for single crystal
X-ray diffraction analysis. They were selected for use under a polarized light microscope; one of
them, with trigonal shape (0.10 ϫ 0.09 ϫ 0.06 mm), was selected for this study. By energy-
dispersive X-ray spectroscopy, a ratio Pb:Ni:Mn:Te ϭ 1.1:6.3:2.0:3.1 was determined.
The symmetry and the lattice parameter were determined with oscillation and Weissenberg
photographs, and imaging plate measurements (Rigaku Imaging plate CS, modified for the
Institute of Material Research (IMR)). The crystal used for the final intensity measurement
was mounted on the top of a glass fiber. Diffraction measurements at 293 K were made on
a Rigaku AFC6S four-circle diffractometer using Mo K␣ radiation. The unit cell was
determined by the least-squares procedure, applied to 25 randomly selected reflections (range
27.22° Ͻ 2␪ Ͻ 34.84°) obtained by using the AFC6 automatic search. Crystal data, data
collection parameters, and the results of the analysis of PbMn2Ni6Te3O18 are listed in Table 1.
The compound PbMn2Ni6Te3O18 crystallizes in the hexagonal crystal system. The patterns
observed in the data were consistent with the space groups P63, P63/m, or P6322. The centric
space group P63/m was assumed and confirmed by the successful solution and refinement of
the structure.
The structure was solved by a combination of direct methods and difference Fourier
syntheses (SHELX package [10,11]). All atoms were refined with anisotropic thermal
parameters. The positional parameters in PbMn2Ni6Te3O18 are listed in Table 2 and the

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TABLE 1
Crystallographic Data for PbMn2Ni6Te3O18 [23]
Formula
Crystal size (mm)
Formula weight
Crystal system
PbMn2Ni6Te3O18
0.10 ϫ 0.09 ϫ 0.06
1340.13
hexagonal
Lattice parameters
a (Å)
9.294(1)
c (Å)
8.823(1)
V (Å)
659.95(1)
Space group
Z value
P63/m (no. 176)
2
Index ranges
␳calc (g/cm3)
␭ (Mo K␣) (mmϪ1
Temperature (K)
2␪ max. (°)
0 Ͻ h Ͻ 14; Ϫ14 Ͻ k Ͻ 12; 0 Ͻ l Ͻ 14
6.744
29.525
293
)
70
Number of observations (I Ͼ 4␴)
Number of variables
817
52
Goodness of fit
1.043
Residuals: R; Rw
0.026; 0.046
⌿-scan [24]
0.6481/0.9843
1.185 and 1.116
Absorption correction
Min/max absorption
Largest final peak and hole (e/Å3)
selected interatomic bond distances and angles can be found in Table 3. The anisotropic
thermal parameters are summarized in Table 4. The space group was determined by using the
ABSEN program [12]; all structure plots appearing in this paper were performed by an
ORTEP program [13] and STRUPOL [14].
DESCRIPTION OF THE STRUCTURE
3
The PbMn2Ni6Te3O18 crystal structure is a [Ni6Te3O18]6Ϫ network consisting of edge and
ϱ
corner connected octahedra. Figure 1 shows a typical plane of the network composed by the
TABLE 2
Positional Parameter and U(eq) for PbMn2Ni6Te3O18
Atom
Site
x
y
z
U(eq)
Pb
Te
Ni
Mn
O(1)
O(2)
O(3)
O(4)
2b
6h
12i
4f
12i
12i
6h
6h
0
0
0
3/4
23(1)
4(1)
6(1)
7(1)
8(1)
7(1)
6(1)
7(1)
0.3375(1)
0.9880(1)
1/3
0.1011(3)
0.1296(3)
0.5810(5)
0.1073(5)
0.3622(1)
0.3482(1)
2/3
0.3060(4)
0.6074(3)
0.4485(5)
0.2923(5)
0.9110(1)
0.0602(1)
0.0915(2)
0.9120
3/4
3/4

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TABLE 3
Interatomic Distances (Å) for PbMn2Ni6Te3O18
Pb–O(1) 6ϫ
Pb–O(4) 6ϫ
Te–O(4)
Te–O(1) 2ϫ
Te–O(2) 2ϫ
Te–O(3)
2.636(3)
3.250(3)
1.904(3)
1.936(2)
1.938(2)
1.987(3)
Mn–O(2) 3ϫ
Mn–O(3) 3ϫ
Ni–O(4)
Ni–O(1)
Ni–O(2)
Ni–O(2)
Ni–O(1)
Ni–O(3)
2.138(2)
2.335(2)
2.017(3)
2.046(3)
2.067(3)
2.094(3)
2.102(3)
2.117(3)
Esd’s given in parentheses.
10Ϫ
edge and corner connection of the NiO6
and TeO66Ϫ. Along the c axis these oxygen
octahedra are connected so as to make double chains by showing their edges. The sequence
of the metals in one chain is Ni2ϩ–Ni2ϩ–Te6ϩ–Ni2ϩ–Ni2ϩ–Te6ϩ; the second chain is
connected over edges with the first and shifted by one octahedron. Figure 2a shows a double
chain of the (Ni2ϩ,Te6ϩ) octahedra.
In the plane, the double chains are connected by corners and edges. Three oxygen
octahedra of Ni2ϩ and three oxygen octahedra of Te6ϩ form a ring with trigonal shape. These
rings build up channels parallel to [001] in which the Mn2ϩ ions are located. Three oxygens
of NiO610Ϫ and three oxygens of TeO66Ϫ are connected by corners to form hexagonal rings.
The Pb2ϩ ions are incorporated into the hexagonal channels formed by the double chains of
10Ϫ
6Ϫ
NiO6
and TeO6 octahedra rings, which gives Pb2ϩ a 6 ϩ 6 coordination by oxygen,
consisting of six inner and six outer O2Ϫ ions, forming a stretched cube octahedron. The high
thermal parameter of Pb2ϩ found in the channel structure of PbMn2Ni6Te3O18 is not unusual
for channel structures.
The manganese ions obtain a trigonal prismatic oxygen coordination in the channels,
which is unusual for common Mn2ϩ coordination. Only a few examples of this trigonal
prismatic coordination of Mn2ϩ are known so far, e.g., Mn5(PO4)3Cl0.9OH0.1 [15],
Mn2GeO4 [16], and (Cu,Mn)3.66Mo3O12 [17]. Nevertheless, the coordination prisms are
connected by their edges in these compounds. In PbMn2Ni6Te3O18, the prisms share a
TABLE 4
Anisotropic Displacement Factor [Å2 ϫ 103] for PbMn2Ni6Te3O18
Atom
U11
U22
U33
U23
U13
U12
Pb
Te
Ni
Mn
O1
O2
O3
O4
13(1)
4(1)
6(1)
7(1)
7(1)
7(1)
3(2)
4(2)
13(1)
4(1)
6(1)
7(1)
12(1)
6(1)
45(1)
3(1)
5(1)
7(1)
6(1)
6(1)
8(2)
5(2)
0
0
0
0(1)
0
0(1)
Ϫ2(1)
0
6(1)
2(1)
3(1)
3(1)
6(1)
2(1)
3(1)
2(1)
0
1(1)
0
Ϫ1(1)
Ϫ1(1)
0
6(2)
10(2)
0
0
Esd’s given in parentheses.

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FIG. 1
Perspective view along [001] in PbMn2Ni6Te3O18. Light octahedra ϭ NiO610Ϫ; dark octa-
hedra ϭ TeO66Ϫ; big sphere with cross ϭ Pb2ϩ; small sphere with cross Mn2ϩ; open
sphere ϭ O2Ϫ
.
common triangular face to form Mn2O6 dimers, a feature not previously observed in any
compound. The Mn2O6 double prisms are connected by two empty prisms on each side,
to form a 1ϱ[Mn2O6 [empty]]8Ϫ chain. This sequence along [001] is demonstrated in
Figure 2b.
FIG. 2
1
1
Chains in PbMn2Ni6Te3O18. (a) [Ni6Te3O18]6Ϫ chain; (b) [Mn2O6 [empty]]8Ϫ chain; (c)
ϱ
ϱ
1ϱ[PbO9]16Ϫ chain along [001]. The symbols correspond to the symbols of Figure 1.

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Vol. 34, Nos. 14/15
FIG. 3
(a) [001] plane of edge- and corner-connected octahedra of hexagonal tungsten bronze type
structure; (b) of Pb3Ni4.5Te2.5O15.
According to a calculation of ECoN [18] values, the Pb2ϩ ions are coordinated by 12
oxygen ions. Six of them form an inner coordination sphere, the other six an outer sphere,
resulting in [6 ϩ 6] coordination. These PbO6ϩ6 polyhedra share trigonal faces with two
neighbors forming a 1ϱ[PbO9]16Ϫ chain along [001] (Fig. 2c). Because of the symmetric shape
of the oxygen coordination of Pb2ϩ, it is not possible to find a reasonable position of the lone
pair in the coordination polyhedron with geometric or MAPLE [19,20] methods. Therefore
we assume that the lone pair has a spherical s-orbital shape.
Finally, a similarity is noted between the present PbMn2Ni6Te3O18 structure, the well-
known hexagonal tungsten bronze type structure [21,22], and the Pb3Ni4.5Te2.5O15 structure
[1]. All of these three structures crystallize in hexagonal space groups, which are related to
each other as subgroups and supergroups. The systematic absence conditions of them are the
same. In Pb3Ni4.5Te2.5O15, there are only hexagonal channels along [001], while the tungsten
bronze type structure contains hexagonal and trigonal channels like those in the
PbMn2Ni6Te3O18 structure, except, in this case, the rings are built up by three polyhedra only
and the atoms in these smaller rings do not have a trigonal prismatic oxygen coordination.
Figure 3 shows the comparison of these structure types.
ACKNOWLEDGMENTS
The generous support given by the Japanese Ministry of Education is gratefully acknowl-
edged. Special thanks is given to Mr. Y. Sato for the EPMA analysis and Dr. L. Wulff for

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helping to calculate the Coulomb part of the lattice energy and helpful discussions to prepare
this paper.
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