Synthesis and crystal structure of new complex sodium lanthanide phosphate molybdates Na2MIII(MoO4)(PO4)(M III = Tb, Dy, Ho, Er, Tm, Lu)

Article abstract of DOI:10.1134/S0036023607050014

New complex sodium lanthanide phosphate molybdates Na₂M ^III(MoO₄)(PO₄)(M^III=Tb, Dy, Ho, Er, Tm, Lu) have been synthesized by the ceramic method (T = 600°C, τ = 48 h), and their unit cell parameters ha

Full text of DOI:10.1134/S0036023607050014

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2007, Vol. 52, No. 5, pp. 653–660. © Pleiades Publishing, Inc., 2007.
Original Russian Text © M.A. Ryumin, L.N. Komissarova, D.A. Rusakov, A.P. Bobylev, M.G. Zhizhin, A.V. Khoroshilov, K.S. Gavrichev, V.P. Danilov, 2007, published in Zhurnal
Neorganicheskoi Khimii, 2007, Vol. 52, No. 5, pp. 717–724.
SYNTHESIS AND PROPERTIES
OF INORGANIC COMPOUNDS
Synthesis and Crystal Structure of New Complex Sodium
III
Lanthanide Phosphate Molybdates Na2M (MoO4)(PO4)
III
(M = Tb, Dy, Ho, Er, Tm, Lu)
M. A. Ryumina,b, L. N. Komissarovaa, D. A. Rusakova,b, A. P. Bobyleva, M. G. Zhizhina,
A. V. Khoroshilovb, K. S. Gavrichevb, and V. P. Danilovb
a Moscow State University, Vorob’evy gory, Moscow, 119992 Russia
b Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia
Received September 25, 2006
Abstract—New complex sodium lanthanide phosphate molybdates Na2MIII(MoO4)(PO4) (MIII = Tb, Dy, Ho,
Er, Tm, Lu) have been synthesized by the ceramic method (T = 600°C, τ = 48 h), and their unit cell parameters
have been determined. The structures of Na2MIII(MoO4)(PO4) (MIII = Dy, Ho, Er, Lu) were refined by the
Rietveld method. The compounds are isostructural: they are orthorhombic (space group Ibca, Z = 8) and have
layered structures. In the structures of phosphate molybdates, chains of MIIIO8 polyhedra and MoO4 tetrahedra
are linked by PO4 tetrahedra to form layers. The MoO2– anions are involved in dipole–dipole interaction. The
4
sodium ions are arranged in the interlayer space. The compounds melt incongruently at 850–870°C.
DOI: 10.1134/S0036023607050014
New materials based on inorganic phosphates have reaction of stoichiometric amounts of Na2MoO4 · 2H2O
(chemically pure, Russian State Standard), MI2II O3
been sought for many years. Information on individual
compounds containing, in addition to PO4 tetrahedra,
(chemically pure), and NH4H2PO4 (pure for analysis) or
other differently charged tetrahedral groups with two
by the reaction of sodium molybdate with MIIIPO4 ·
cations is rather scanty and only concerns compounds
of
three
compositions.
Phosphate
sulfates
xH2O precipitated from aqueous solutions. Samples
were ground every 24 h to ensure homogenization. The
completeness of the reaction was monitored by X-ray
powder diffraction. The highest synthesis temperature
was 750°ë. New compounds as polycrystalline sam-
ples were identified by X-ray diffraction even at the
stage of annealing at 600°ë.
KM3(SO4)2(PO4) (M = Sr, Ba, Pb) [1] have a cubic
eulitine-type
structure.
The
compound
Na3Ba(MoO4)(PO4) [2], as well as double phosphates of
singly and triply charged cations, have a glaserite-type
structure. Compounds MI2 MIII(EO4)(PO4) (MI = Na,
MIII = La, EO4 = S2O3; MI = Na, MIII = Y or Yb, EO4 =
X-ray powder diffraction analysis was carried out
on a Siemens D500 diffractometer (CuKα1 radiation,
λ = 1.5406 Å, reflection geometry, scintillation detec-
tor, SiO2 monochromator, scan step 0.02° (2θ), 2θ range
5°–60° with a counting time of 1 s per step). The
TREOR-90 program and the STOE WinXPOW soft-
ware were used for analysis and primary processing of
experimental data. Phase analysis was performed with
the use of the JCPDS PDF-2 database.
MoO4; MI = K, MIII =Yb, EO4 = MoO4; MI = Li, MIII =
Fe, EO4 = SO4) [3–6] form original layered structures,
all phosphate molybdates being isostructural. Only
Li2Fe(SO4)(PO4) has a NASICON structure. A combi-
nation of two triply charged anions leads to the formation
of solid solutions K3MIII(PO4)x(VO4)2 – x (MIII = Y, La,
Eu, Gd, Yb) [7].
In the present paper, we report the results of study-
ing sodium lanthanide phosphate molybdates
Na2MIII(MoO4)(PO4) (MIII = Tb–Lu), their synthesis,
structure, and thermal stability.
A set of experimental data for X-ray crystallography
was collected on the same diffractometer in the 2θ
range 5°–100° with the scan step 0.02° and the counting
time 10 s per step. Corundum (Al2O3) was used as the
external reference.
EXPERIMENTAL
Crystal structures were refined by the full-profile
Sodium lanthanide phosphate molybdates were syn- Rietveld method [8] using the JANA 2000 program
thesized by the temperature-programmed solid-phase package [9].
653

654
RYUMIN et al.
Table 1. Unit cell parameters and the results of refinement of some structures of sodium lanthanide phosphate molybdates
(Na2MIII(MoO4)(PO4) (MIII = Tb–Lu)
Parameter
Tb
Dy
Ho
Er
Tm
Lu
2θ range, deg
5–120
0.02
44474
5–105
0.02
37740
5–105
0.02
34634
5–105
0.02
31657
5–60
0.02
2255
5–125
0.02
36804
scan step, deg
Imax, counts
Unit cell parameters:
a, Å
b, Å
c, Å
V, Å3
17.9849(2)
12.1989(2)
6.9129(1)
1516.70(3)
479
17.9927(2)
12.1553(1)
6.8775(1)
1504.17(3)
392
18.0010(2)
12.1162(1)
6.8543(1)
1494.97(3)
388
18.0104(1)
12.0825(1)
6.8256(1)
1485.34(2)
386
18.012(2)
12.053(1)
6.803(1)
18.0186(2)
11.9973(1)
6.7537(1)
1459.99(2)
549
1476.8(3)
Number of Bragg reflec-
tions
108
Reliability factors:
Rp, Rwp, %
F20
6.95, 9.25
5.43, 7.45
6.06, 8.13
4.48, 5.77
7.03, 9.20
175
The IR spectra were recorded as mineral oil or
hexachlorobutadiene mulls on a Perkin Elmer 1600
FTIR spectrophotometer in the range 400–4000 cm–1.
The refined atomic coordinates and isotropic ther-
mal parameters for the structures of some representa-
tives of this family are listed in Table 2, and the inter-
atomic distances are presented in Table 3.
Thermogravimetric (TGA) and differential thermal
analyses (DTA) were carried out on a Q-1500 deri-
vatograph and a Setaram DSC 2000K differential
scanning calorimeter. Sample weights were 100–150 mg
(Q-1500) and 10–20 mg (DSC 2000K). Samples were
heated in alundum crucibles under an inert gas flow at
a rate 20 K/min in the range 20–500°ë and 10 K/min in
the range 500–900°ë.
The lanthanide atoms in the structures of
Na2MIII(MoO4)(PO4) are located in special positions
(Fig. 3) and are bound to eight-vertex arrays of oxygen
atoms. The MIIIO8 polyhedra share an edge (along the c
axis) to form zigzag chains, their convex and concave
parts alternating. Neighboring chains of MIIIO8 polyhe-
dra are linked through êé4 tetrahedra by edge sharing
to form layers in the bc plane. In the layer, a convex part
of one chain is linked to a concave part of a neighboring
chain. With a decrease in the ionic radius of MIII, the
average MIII–O distance somewhat increases in the
range 2.38–2.45 Å, the average P–O distance (1.495–
1.51 Å) remaining virtually unaltered.
RESULTS AND DISCUSSION
Analysis of the X-ray diffraction patterns of all syn-
thesized sodium lanthanide phosphate molybdates
shows that they are isostructural and have a structure
similar to that of the first representative of this family
Na2Yb(MoO4)(PO4) [5]. The orthorhombic unit cell
parameters were determined in the course of primary
data collection (Table 1). The following trends in the
change in the crystal parameters of isostructural com-
pounds were observed: as the radius of the triply
charged cation decreases, the a parameter slightly
increases while the b and c parameters and, especially,
the unit cell volume linearly decrease to a significant
extent (Fig. 1). In X-ray diffraction patterns of the
series of the Tb–Lu derivatives, the reflections are
slightly shifted toward larger angles (Fig. 2).
The molybdenum atoms, like the phosphorus and
lanthanide atoms, are located in special positions. Two
neighboring polyhedra in lanthanide chains are linked
by edges of two MoO4 tetrahedra. The MoO4 tetrahedra
are linked only to MIIIO8 polyhedra and are not con-
nected with each other. The other two vertices point to
the interlayer space and do not link two layers. The
change in the ionic radius of the triply charged cation
has no effect on the average Mo–O distance in tetrahe-
dra. The Mo–O distances, as well as the P–O distances,
are pairwise identical; correspondingly, the MIII–O dis-
tances are also pairwise identical since the MIIIO8 poly-
hedra are formed by six oxygen atoms from PO4 tetra-
hedra and two oxygen atoms from MoO4 tetrahedra.
Based on systematic absences (h + k + l = 2n; hk0:
h, k = 2n; h0l: h, l = 2n; h00: h = 2n; 00l: l = 2n), the
structures of the compounds Na2MIII(MoO4)(PO4)
(MIII = Tb, Dy, Ho, Er, Lu) were refined in space
group Ibca (no. 73) (Table 1). The atomic coordinates in
sodium ytterbium phosphate molybdate [5] were used
as the initial positional parameters in the refinement.
Sodium cations in the structures occupy the inter-
layer space and are located in the general position. The
average Na–O distance in NaO6 polyhedra decreases
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 5 2007

SYNTHESIS AND CRYSTAL STRUCTURE OF NEW COMPLEX
655
a, Å
b, Å
12.25
18.15
Tb
18.10
18.05
18.00
17.95
17.90
17.85
12.20
12.15
Yb*
Tm
Er
Dy
Dy
Er
12.10
12.05
12.00
11.95
Lu
Ho
Ho
Tb
Yb*
Tm
Lu
V, Å3
1520
c, Å
7.00
Tb
1510
6.95
6.90
6.85
6.80
6.75
6.70
Tb
1500
1490
1480
1470
1460
1450
Dy
Er
Ho
Dy
Er
Ho
Tm
Lu
Lu
Tm
Yb*
Yb*
1.05 1.04 1.03 1.02 1.01 1.00 0.99 0.98 0.97
1.05 1.04 1.03 1.02 1.01 1.00 0.99 0.98 0.97
3+
rM , Å
III
III
Fig. 1. Unit cell parameters of Na M (MoO )(PO ) vs. the radius of the M cation (CN = 8). * Parameters were taken from [5].
2
4
4
with a decrease in the radius of a triply charged cation. is typical of glaserite- and arcanite-type compounds
MI3 MIII(PO4)2 [14]. Changing the anionic part by com-
This change is contributed by the distances to the oxy-
gen atoms from åÓé4 tetrahedra (O(1) and O(2)). The
bination of the PO34 anion with differently charged tet-
sodium polyhedron is formed by three oxygen atoms
from two êé4 tetrahedra and three oxygen atoms from
rahedral anions makes it possible to obtain compounds
with a layered structure. This structure contains the
chains of MIIIO8 polyhedra linked by êé4 tetrahedra to
form layers as in xenotime. In the structures of
Na2MIII(åÓO4)(êO4), sodium ions loosen the initial
xenotime framework and occupy the interlayer space.
Hence, the complication of the composition by the
introduction of differently charged anions into the
xenotime structure leads to the formation of layered
phases in which chains of lanthanide polyhedra persist.
This results in lowering of the unit cell symmetry (tet-
ragonal–orthorhombic) while I centering is retained.
In these phases, the a (17.98–18.02 Å) and b (11.99–
12.19 Å) unit cell parameters are multiples of those in
xenotime phosphates, while the c parameter (6.75–
6.91 Å) is retained (Table 2), again as in xenotime
phosphates (a = 6.79–6.94 Å, c = 5.95–6.07 Å).
three MoO4 tetrahedra (Fig. 4). In the structures of
Na2MIII(MoO4)(PO4), the NaO6 polyhedra are com-
bined into two parallel chains (along the c axis) by edge
sharing.
The structure of sodium lanthanide phosphate
molybdates is a derivative of the xenotime (YPO4)
structure [10], typical of late lanthanide orthophos-
phates.
In the xenotime framework structure, layers can be
discerned that are made of chains of MIIIO8 polyhedra
in the ac and bc planes, the chains being connected to
one another by edges of êé4 tetrahedra. This type of
layer is typical of the framework structures of the min-
erals zircon ZrSiO4 [11] and anhydrite CaSO4 [12] and
sodium perchlorate NaClO4 [13]. The complication of
the cationic component of the xenotime structure by the
introduction of alkali-metal cations leads to loosening
of the initial framework and formation of layered struc-
tures with discrete MIIIO8 1 polyhedra. Such a structure
The IR spectra of the synthesized compounds show
absorption bands due to internal vibrations of PO43–
and MoO24– ions (Table 4) [15–17]. The splitting of
absorption bands of tetrahedral anions corresponds to
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 5 2007

656
RYUMIN et al.
I × 5000, arb. units
8
7
6
5
4
3
2
1
‡
7
6
5
4
3
2
1
b
8
7
6
5
4
3
2
1
c
8
7
6
5
4
3
2
1
d
9
7
5
3
1
e
1
3
2
5
15
25
35
45
55
65
2θ, deg
III
III
Fig. 2. Portions of the experimental X-ray diffraction spectra and positions of Bragg reflections of Na M (MoO )(PO ) for M
=
2
4
4
(a) Lu, (b) Er, (c) Ho, and (d) Dy and (e) a portion of the (1) experimental and (2) difference X-ray diffraction spectrum and
(3) positions of Bragg reflections of Na Tb(PO )(MoO ).
2
4
4
symmetry C2 of the position occupied by the PO34– and
degenerate vibrations should be split into two compo-
nents.
MoO24– anions in the unit cell. For this site symmetry,
each of the bands of triply degenerate vibrations should
be split into five components and the bands of doubly
The band of the triply degenerate antisymmetric
stretching vibration (ν3 F2) of the tetrahedral PO43–
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SYNTHESIS AND CRYSTAL STRUCTURE OF NEW COMPLEX
657
Table 2. Atomic coordinates and thermal parameters in the structures of Na2MIII(MoO4)(PO4) (MIII = Tb, Dy, Ho, Er, Lu)
Atom
Tb
Dy
Ho
Er
Lu
Na
x
0.5963(2)
0.1884(5)
0.272(1)
0.029(2)
0.75
0.5992(3)
0.1886(5)
0.2719(9)
0.043(2)
0.75
0.5972(2)
0.1905(5)
0.265(1)
0.030(2)
0.75
0.5948(2)
0.1910(5)
0.2612(9)
0.030(2)
0.75
0.5904(3)
0.1904(6)
0.262(1)
0.031(2)
0.75
y
z
Uiso
MIII
Mo
x
y
0.0716(1)
0
0.0719(1)
0
0.0719(1)
0
0.0721(1)
0
0.0715(1)
0
z
Uiso
0.0054(8)
0.4292(1)
0
0.0096(4)
0.4290(1)
0
0.0116(5)
0.4296(1)
0
0.0065(4)
0.4295(1)
0
0.0063(4)
0.4290(1)
0
x
y
z
0.25
0.25
0.25
0.25
0.25
Uiso
0.0145(9)
0.25
0.0176(7)
0.25
0.0199(7)
0.25
0.0119(6)
0.25
0.0112(6)
0.25
P
x
y
0.1727(5)
0
0.1771(5)
0
0.1839(5)
0
0.1856(5)
0
0.1898(6)
0
z
Uiso
0.011(1)
0.3773(5)
0.0257(6)
0.473(1)
0.030(2)
0.4895(4)
0.1202(9)
0.195(2)
0.030(2)
0.1844(4)
0.2553(5)
–0.009(2)
0.008(2)
0.2476(4)
0.1087(6)
0.183(1)
0.008(2)
0.008(1)
0.3759(3)
0.0256(5)
0.4605(8)
0.013(2)
0.4805(4)
0.1195(5)
0.198(1)
0.013(2)
0.1851(3)
0.2540(4)
–0.004(2)
0.013(2)
0.2424(5)
0.1057(5)
0.1775(9)
0.013(2)
0.013(2)
0.3770(3)
0.0263(6)
0.4583(8)
0.011(2)
0.4841(4)
0.1196(5)
0.207(2)
0.011(2)
0.1812(4)
0.2531(4)
–0.011(2)
0.011(2)
0.2386(6)
0.1073(5)
0.170(1)
0.011(2)
0.008(1)
0.3803(3)
0.0255(5)
0.4658(7)
0.006(1)
0.4844(3)
0.1190(5)
0.203(1)
0.006(1)
0.1793(2)
0.2475(4)
–0.010(2)
0.006(1)
0.2610(5)
0.1077(5)
0.1661(9)
0.006(1)
0.008(2)
0.3845(4)
0.0247(7)
0.4732(9)
0.017(2)
0.4827(4)
0.1210(6)
0.212(2)
0.017(2)
0.1754(3)
0.2510(5)
–0.007(4)
0.012(2)
0.2351(5)
0.1089(6)
0.162(1)
0.012(2)
O(1)
O(2)
O(3)
O(4)
x
y
z
Uiso
x
y
z
Uiso
x
y
z
Uiso
x
y
z
Uiso
anion is split into three components (978–985, 1082–
Sodium lanthanide phosphate molybdates are rather
thermally stable. The temperature range of their incon-
gruent melting is 790–918°ë with a maximum at
850−870°ë. Their cooling curves show several exo-
therms, none of which corresponds to the formation of
the solid phase Na2MIII(MoO4)(PO4). Comparison of
the temperatures of the peaks with the data of the data-
base “Thermal Constants of Substances” [18] showed
that they correspond to the phase transitions of sodium
molybdate. Hence, the decomposition of phosphate
molybdates proceeds according to the scheme
1084, 1092–1099 cm–1), whereas, for the MoO24– tetra-
hedron in the IR spectra of Na2MIII(PO4)(MoO4), this
band is split into four components and is observed in
the range 780–860 cm–1.
The spectra show absorption bands due to the sym-
metric stretching vibrations of êé4 tetrahedra (1006–
1020 cm–1) and åÓé4 tetrahedra (913–916 cm–1). The
band splitting pattern allows us to draw the conclusion
MoO24–
that the
anions are involved in dipole–dipole
Na2MIII(MoO4)(PO4)
Na2MoO4 + MIIIPO4.
interaction with one another.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 5 2007

658
RYUMIN et al.
Table 3. Interatomic distances in the structures of Na2MIII(MoO4)(PO4) (MIII = Tb, Dy, Ho, Er, Lu)
Bond (Å),
Na2Tb(MoO4)(PO4) Na2Dy(MoO4)(PO4) Na2Ho(MoO4)(PO4) Na2Er(MoO4)(PO4) Na2Lu(MoO4)(PO4)
angle (deg)
Na–O(1)
2.91(1)
2.16(1)
2.85(1)
2.60(1)
2.34(1)
2.91(1)
2.63
2.95(1)
2.35(1)
2.78(1)
2.35(1)
2.51(1)
2.78(1)
2.62
2.93(1)
2.25(1)
2.76(1)
2.39(1)
2.40(1)
2.77(1)
2.58
2.87(1)
2.21(1)
2.73(1)
2.40(1)
2.39(1)
2.83(1)
2.57
2.82(1)
2.14(1)
2.64(1)
2.36(2)
2.41(2)
2.83(1)
2.53
Na–O(2)
Na–O(2')
Na–O(3)
Na–O(3')
Na–O(4)
〈Na– O〉
MIII–O(1) × 2
MIII–O(3) × 2
MIII–O(4) × 2
MIII–O(4') × 2
〈MIII–O〉
2.37(1)
2.42(1)
2.54(1)
2.24(1)
2.39
2.35(1)
2.42(1)
2.48(1)
2.26(1)
2.38
2.37(1)
2.45(1)
2.47(1)
2.31(1)
2.40
2.42(1)
2.47(1)
2.46(1)
2.33(1)
2.42
2.50(1)
2.52(1)
2.44(1)
2.34(1)
2.45
Mo–O(1)
Mo–O(2)
〈Mo–O〉
1.79(1)
1.76(1)
1.775
1.76(1)
1.76(1)
1.76
1.74(1)
1.78(1)
1.76
1.75(1)
1.77(1)
1.76
1.73(1)
1.76(1)
1.745
O(1)MoO(1)
O(1)MoO(2)
O(1)MoO(2)
O(2)MoO(2)
P–O(3)
117.7(4)
107.1(5)
109.1(4)
106.1(3)
1.49(1)
1.55(1)
1.52
114.3(3)
107.9(4)
105.3(4)
116.4(4)
1.49(1)
1.50(1)
1.495
114.2(3)
106.7(4)
108.2(4)
112.9(4)
1.50(1)
1.51(1)
1.505
119.0(3)
106.9(4)
105.9(4)
112.2(3)
1.51(1)
1.49(1)
1.50
124.9(4)
103.9(5)
105.5(5)
113.4(4)
1.53(1)
1.49(1)
1.51
P–O(4)
〈P–O〉
O(4)PO(4)
O(4)PO(3)
O(4)PO(3)
O(3)PO(3)
116.7(7)
106.5(6)
113.3(6)
99.1(6)
102.7(5)
107.5(6)
114.9(7)
109.5(5)
103.9(6)
105.9(6)
114.7(7)
111.8(6)
101.5(5)
105.2(6)
115.3(5)
114.5(6)
98.6(6)
100.1(9)
116.7(9)
122.7(6)
Table 4. Maximum absorption frequencies in the IR spectra of Na2MIII(MoO4)(PO4)
Tb
Dy
Ho
Er
Tm
Lu
Assignment
530 s
530 s
529 s
527 s
526 s
526 s
ν4 F2 PO4
ν MIII–O
537 sh
559 sh
537 sh
555 sh
538 sh
556 sh
538 sh
556 sh
538 sh
574 s
614 s
783 s
809 w
575 s
616 s
780 s
809 w
575 s
617 s
782 s
809 w
573 s
618 s
783 s
806 w
829 sh
572 s
616 s
782 s
806 w
574 s
621 s
782 s
811 sh
827 sh
ν4 F2 PO4
ν4 F2 PO4
ν3 F2 MoO4
ν3 F2 MoO4
ν3 F2 MoO4
846 sh
860 s
846 sh
857 s
848 sh
860 s
862 s
915 s
858 s
914 s
980 s
861 s
915 s
916 m
978 s
915 s
981 s
914 s
980 s
ν1A1 MoO4
ν3 F2 PO4
ν1A1 PO4
ν3 F2 PO4
983 s
985 s
1006 sh
1015 sh
1082 s
1020 sh
1082 s
1094 sh
1084 s
1099 s
1082 s
1082 s
1092 s
1094 s
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 5 2007

SYNTHESIS AND CRYSTAL STRUCTURE OF NEW COMPLEX
659
MIIIO8
PO4
MoO4
b
a
Na
III
Fig. 3. General view of the structure of Na M (MoO )(PO ).
2
4
4
MoO4
Na
b
PO4
c
Fig. 4. Sodium ions surrounded by MoO and PO tetrahedra.
4
4
The formation of Na2MoO4 and MIIIPO4 is sup-
ported by X-ray powder diffraction analysis of the sam-
ples after thermal analysis. Complication of the compo-
sition impairs the thermal stability of the compounds.
The melting point of framework lanthanide orthophos-
phates is as high as 2000°ë, whereas the thermal stabil-
ity range of Na2MIII(åÓO4)(êO4) with a layered struc-
ture extends no higher than 900°ë.
Thus, representatives of a new family of complex
phosphates—sodium lanthanide phosphate molybdates
Na2MIII(MoO4)(PO4) (MIII = Tb, Lu)—were synthe-
sized. They were found to be isostructural with the pre-
viously obtained Na2Yb(MoO4)(PO4). They are orthor-
hombic crystalline compounds with a layered structure.
The structure of the new sodium lanthanide phosphate
molybdates turned out to be a derivative of the xeno-
time structure. Complication of the composition of the
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 5 2007

660
RYUMIN et al.
6. A. K. Padhi, V. Manivannan, and J. B. Goodenough,
initial structure leads to a reduction in symmetry and a
multiple increase in crystallographic parameters.
J. Electrochem. Soc. 145, 1518 (1998).
7. A. N. Kirichenko, ExtendedAbstract of Candidate’s Dis-
sertation in Chemistry (Moscow, 1999).
8. H. M. Rietveld, J. Appl. Crystallogr. 2, 65 (1969).
ACKNOWLEDGMENTS
We are grateful to B.I. Lazoryak for providing us the
opportunity to perform X-ray diffraction studies.
This work was supported by the Russian Foundation
for Basic Research, (project no. 03-03-32994).
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bin/tkv.
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