Phase formation in Li2MoO4-K2MoO 4-MMoO4 (M = Ca, Pb, Ba) systems and the crystal structure of α-KLiMoO4

Article abstract of DOI:10.1134/S0036023611090075

Solid-phase interactions in Li₂MoO₄-K ₂MoO₄-MMoO₄ (M = Ca, Pb, Ba) systems were studied, and the subsolidus regions of these systems were triangulated. The lead and barium systems were studied in a more detailed way to discover that, along KLiMoO₄-K₂M(MoO₄)₂ (M = Pb, Ba), KLiMoO₄-PbMoO₄, and Li₂MoO₄-K ₂Ba(MoO₄)₂ quasi-binary sections, there are homogeneity regions reaching 6-11 mol % based on K₂M(MoO ₄)₂ and lead molybdate. Triple molybdates are formed in none of the systems, which is verified by experiments on spontaneous crystallization from solution in melt. Crystallization experiments yielded crystals of potassium dimolybdate and simple and double molybdates from the boundary systems. The crystal structure was solved for a hexagonal KLiMoO ₄ phase: (Na,K){ZnPO4}, a = 18.8838(7) ?, c = 8.9911(6)?, Z = 24, space group P6₃, R = 0.065. The structure comprises a three-dimensional tridymite framework built by an alternation of corner-sharing LiO₄- and MoO₄ tetrahedra wherein voids are occupied by potassium cations.

Full text of DOI:10.1134/S0036023611090075

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2011, Vol. 56, No. 9, pp. 1443–1452. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © I.A. Gudkova, Z.A. Solodovnikova, S.F. Solodovnikov, E.S. Zolotova, N.V. Kurat’eva, 2011, published in Zhurnal Neorganicheskoi Khimii, 2011, Vol. 56,
No. 9, pp. 1517–1526.
PHYSICOHEMICAL ANALYSIS
OF INORGANIC SYSTEMS
Phase Formation in Li2MoO4–K2MoO4–MMoO4 (M = Ca, Pb, Ba)
Systems and the Crystal Structure of ꢀKLiMoO4
α
I. A. Gudkovaa, b, Z. A. Solodovnikovaa, S. F. Solodovnikova, b, E. S. Zolotovaa, and N. V. Kurat’evaa, b
a Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 3, Novosibirsk, 630090 Russia
b Novosibirsk State University, ul. Pirogova 2, Novosibirsk 630090 Russia
eꢀmail: solod@niic.nsc.ru
Received April 8, 2010
Abstract—Solidꢀphase interactions in Li2MoO4–K2MoO4–MMoO4 (M = Ca, Pb, Ba) systems were studied,
and the subsolidus regions of these systems were triangulated. The lead and barium systems were studied in a
more detailed way to discover that, along KLiMoO4–K2M(MoO4)2 (M = Pb, Ba), KLiMoO4–PbMoO4, and
Li2MoO4–K2Ba(MoO4)2 quasiꢀbinary sections, there are homogeneity regions reaching 6–11 mol % based
on K2M(MoO4)2 and lead molybdate. Triple molybdates are formed in none of the systems, which is verified
by experiments on spontaneous crystallization from solution in melt. Crystallization experiments yielded
crystals of potassium dimolybdate and simple and double molybdates from the boundary systems. The crystal
structure was solved for a hexagonal KLiMoO4 phase: (Na,K){ZnPO4},
a = 18.8838(7) Å, c = 8.9911(6) Å, Z =
24, space group 63, = 0.065. The structure comprises a threeꢀdimensional tridymite framework built by an
P
R
alternation of cornerꢀsharing LiO4ꢀ and MoO4 tetrahedra wherein voids are occupied by potassium cations.
DOI: 10.1134/S0036023611090075
By now, numerous double molybdates have been these ternary systems, namely, KLiMoO4 palmieriteꢀ
synthesized; of them, rareꢀearthꢀcontaining comꢀ related K2M(MoO4)2 (M = Pb, Ba); structure has been
pounds have found the greatest application as laser solved only for monoclinic K2Pb(MoO4)2 [11]. Thereꢀ
matrices, luminophores, ferroelectrics, and other fore, the second task of this work was to study double
important engineering materials [1, 2]. The next molybdates in the boundary binaries.
important position is took by double molybdates of
alkali and divalent metals; of them, A4Zn(MoO4)3 (A =
K, Rb) and A2Pb(MoO4)2 (A = K, Rb, Cs) have ferroꢀ
EXPERIMENTAL
electric properties [3–5]. ALiMoO4 (A = K, Rb, Cs)
double molybdates are also of applied importance for
their ferroelectric and nonlinearꢀoptical properties
[4]. Double molybdates of alkali and polyvalent (diꢀ,
terꢀ, and tetravalent) metals have been studied fairly
well and characterized.
The initial components used were MoO3 (pure for
analysis grade); Li2MoO4, K2MoO4, PbMoO4, BaMoO4
(all of pure grade); and Li2CO3, K2CO3, CaCO3, and
BaCO3 (all of high purity grade). All reagents were
dried in a drier at 200
°
С
for 24 h (some of them were
for 3–24 h to
then calcined in a muffle at 450–600
°C
remove remnant water) and verified for a singleꢀphase
constitution by powder Xꢀray diffraction. Further
experiments used only those materials for which Xꢀray
diffraction characteristics agreed with the literature
data.
In the last two decades, many triple molybdates
have been prepared, but triple molybdates that contain
divalent Mg, Mn, Co, and Zn along with two alkali
elements, have been prepared only recently [6]. Triple
molybdates of this group containing other divalent
metals are yet unknown.
For a phaseꢀformation study, the initial compounds
were prepared by solidꢀphase reactions with the proꢀ
cess parameters as shown in Table 1.
The major task of this work was to search for triple
molybdates in Li2MoO4–K2MoO4–MMoO4 (M = Ca,
Pb, Ba) systems. These systems are attractive primarily
Phase equilibria and phase formation in air in subꢀ
for the fact that compounds with interesting physical solidus regions of Li2MoO4–K2MoO4–MMoO4 (M =
properties (see above) have already been prepared in Ca, Pb, Ba) systems were studied by inspecting powder
them, triple molybdates are expected to have these Xꢀray diffraction patterns for annealed samples, which
properties, and some double molybdates have not served to triangulate isothermal sections, i.e., to divide
been structurally studied. There are data [7–10] that them into secondary ternary systems. For the lead and
double molybdates are formed in boundary binaries of barium systems, the method of intersecting sections
1443

1444
GUDKOVA et al.
Table 1. Synthesis parameters and melting temperatures of the precursor molybdates
Compound
T
anneal, K/h
T
m, °C
Compound
T
anneal, K/h
Tm, °C
Li2MoO4
550–600/50
550–600/50
600–650/70
600–650/70
700*
926*
BaMoO4
600–650/70
450–500/70
550–600/70
450–460/50
1457*
570
K2MoO4
CaMoO4
PbMoO4
KLiMoO4
1445*
1060*
K2Pb(MoO4)2
K2Mo2O7
820
490
* Melting temperatures are given according to [2].
was employed; this method is employed when binary lytical experiments were carried out on an original
compounds are positioned in more than one of the design setup (Pt–Pt/Rhꢀthermocouples, Al2O3 referꢀ
boundary systems [12, 13].
ence, cold junctions thermostated at
vided recording of heating (cooling) DTA curves up to
1100 . A material weighing 0.3–0.5 g was placed in a
platinum or quartz crucible and heated at a rate of
10 K/min.
0°C), which proꢀ
Temperature ranges for solidꢀphase reactions were
selected with account of the incongruent melting of
double molybdates in the boundary systems (Table 1).
Sections inside triangles were studied in 2 mol % steps.
The compositions corresponding to the points where
binary sections of ternary systems meet, were prepared
in two ways: from constituent simple molybdates or from
double molybdates that belong to boundary systems.
Reaction mixtures were annealed for at least 200 h at
°C
Samples for Xꢀray crystallography were isometric
crystal chips 0.02 mm in size. Unit cell parameters
≈
and Xꢀray diffraction data for solving the KLiMoO4
structure were measured on a Bruker X8 Apex CCD
automated diffractometer at room temperature using a
400–550
°
C
with grindings once or twice a day. Temꢀ
every 50 h of
routine procedure (Mo
K radiation, graphite monoꢀ
α
perature was elevated by 10–50
°C
chromator,
ϕ
scans, Δϕ = 0.5°). Calculations to solve
annealing. The attainment of equilibrium was moniꢀ
tored by powder Xꢀray diffraction.
and refine the structure for KLiMoO4 were performed
using the SHELX97 program package [14].
Whether triple molybdates can form at higher temꢀ
peratures was checked using spontaneous crystallizaꢀ
tion from solution in melt. The solutes used were
annealed mixtures corresponding to the compositions
at the points where sections meet with addition of
appropriate alkali metal dimolybdates as solvents. The
homogenization temperatures of solution melts were
RESULTS AND DISCUSSION
The boundary binaries of the Li2MoO4–К2MoO4–
MMoO4 (M = Ca, Pb, Ba) ternary systems we studied
are described in the literature in a sufficiently detailed
way [2, 7–10, 15, 16]; therefore, we did not carry out
additional studies of these binaries. The literature
implies that, in the Li2MoO4–K2MoO4 system, there is
the only congruently melting double molybdate
KLiMoO4 [2, 7], and the Li2MoO4–MMoO4 (M = Ca,
Pb, Ba) and K2MoO4–CaMoO4 systems do not form
compounds [2, 7, 15, 16]. The K2MoO4–МMoO4
(M = Pb, Ba) boundary binaries form K2M(MoO4)2
compounds [2, 7–10], which belong to the palmierite
K2Pb(SO4)2 structure family [17].
500–600°С; cooling rates were 3–5 K/h.
Crystallization from solution in melt was also used
to obtain double molybdate crystals. The solutes used
were mixtures of simple or double molybdates preꢀ
pared by solidꢀphase reactions; the solvents used were
appropriate alkali dimolybdates. Double molybdate
crystals suitable for Xꢀray crystallography were preꢀ
pared from melts of singleꢀphase samples; melt
homogenization temperatures were 1000–1100
°С.
Samples prepared by solidꢀphase reactions and
In the Li2MoO4–K2MoO4–CaMoO4 ternary sysꢀ
solutionꢀmelt crystallization were studied by powder tem, double molybdate KLiMoO4 is formed only in
Xꢀray diffraction and thermal analysis. Powder patꢀ one boundary system and, therefore, there is a single
terns were recorded on a DRONꢀ3M diffractometer inner section: KLiMoO4–CaMoO4. For this reason,
(CuK
α
radiation; scan rate: 1 deg/min). Thermoanaꢀ only this section (it appeared to be quasiꢀbinary) was
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 56 No. 9 2011

PHASE FORMATION
1445
(а)
K2MoO4
T
= 400–700°C
KLiMoO4
Li2MoO4
CaMoO4
(b)
K2MoO4
(c)
K2MoO4
T
= 500°C
T
= 500°C
KLiMoO4
K2Pb(MoO4)2
KLiMoO4
K2Ba(MoO4)2
Li2MoO4
PbMoO4 Li2MoO4
BaMoO4
Fig. 1. Subsolidus phase relations in the Li MoO –K MoO –MMoO (M = Ca, Pb, Ba) systems: (a) triangulation of the
2
4
2
4
4
Li MoO –K MoO –CaMoO system, (b) triangulation of the Li MoO –K MoO –PbMoO system, and (c) triangulation of
2
4
2
4
4
4
2
4
2
4
4
the Li MoO –K MoO –BaMoO system;
2
2
4
4
studied in a detailed way in this ternary system (Fig. 1a), along the KLiMoO4–K2Pb(MoO4)2 and Li2MoO4–
as well as several points inside secondary triangles.
K2Ba(MoO4)2 sections reach 11 1 mol % in extent.
The Li2MoO4–K2MoO4–MMoO4 (M = Pb, Ba)
Subsolidus phase formation data for the Li2MoO4–
systems were studied in a more detailed way. For them К2MoO4–MMoO4 (M = Ca, Pb, Ba) ternary systems
to be triangulated, KLiMoO4–K2M(MoO4)2, were supplemented with the results of solutionꢀmelt
KLiMoO4–MMoO4 and K2M(MoO4)2–Li2MoO4 crystallization; however, search experiments, too,
(M = Pb, Ba) sections and their intersection points failed to succeed in preparing triple molybdates as
were studied comprehensively. Powder Xꢀray diffracꢀ crystals. The crystallization products under the chosen
tion analysis of samples with compositions correꢀ conditions were crystals of simple and double molybꢀ
sponding to the intersection points of these sections dates from boundary systems and potassium dimolybꢀ
showed that triangulation in the Li2MoO4–K2MoO4– date, which was used as a solvent in melt solution
MMoO4 (M = Pb, Ba) systems (Figs. 1b, 1c) is differꢀ experiments. The same crystals were obtained upon
ent; despite the similarity of their boundary systems, crystallization of own melts of double molybdates or
each ternary system is divided by quasiꢀbinary sections their mixtures with potassium dimolybdate. The crysꢀ
into three secondary triangles. Along KLiMoO4– tals reached several millimeters in size. Crystals of
K2M(MoO4)2, KLiMoO4–PbMoO4, and Li2MoO4– simple calcium, lead, and barium molybdates were
K2Ba(MoO4)2 quasiꢀbinary sections, homogeneity shaped as tetragonal bipiramids; crystals of double
regions based on K2M(MoO4)2 and lead molybdate molybdates of lead and barium grew into hexagonal
were discovered. The extents of these regions along the platelets. Potassium lithium molybdate KLiMoO4
KLiMoO4–PbMoO4 and KLiMoO4–K2Ba(MoO4)2 crystallized into hexagonal prisms, and potassium
sections were estimated at 6 1 mol % from powder dimolybdate crystals had an elongated prismatic
patterns for samples quenched from 500°C, and those shape.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 56 No. 9 2011

1446
GUDKOVA et al.
Table 2. Crystallographic data for the phases studied
Unit cell parameters
, Å
Compound
Space group, Z
a,
Å
b,
Å
c
angle, deg
–
KLiMoO4
P
63, 24
18.8909(6)
6.9649(1)
–
8.9884(6)
7.5519(1)
α
β
γ
= 82.162(1)
= 68.888(1)
= 86.016(1)
K2Mo2O7
P1, 2
7.2478(1)
K2Ba(MoO4)2
K2Pb(MoO4)2
R
3
m
, 3
6.0071(1)
–
23.3420(8)
15.6069(4)
–
C
2/
m
, 16
20.7532(9)
11.9635(4)
β
= 116.355(1)
All crystals we grew were identified with powder
Xꢀray diffraction; their unit cell parameters were meaꢀ
sured on a BrukerꢀNonius X8 Apex automated diffracꢀ
tometer equipped with a CCD square detector. The
crystal data we obtained for our studied compounds
are complied in Table 2. The unit cell parameters meaꢀ
sured for К2Ba(MoO4)2 and K2Mo2O7 agree with literꢀ
Table 3. Singleꢀcrystal Xꢀray diffraction data for αꢀKLiMoO4
Crystal system
Hexagonal
63
Space group
P
Unit cell parameters, Å
a
c
18.8909(6)
8.9884(6)
2777.9(2)/24
2.955
ature data [10, 18]; for K2Pb(MoO4)2 and KLiMoO4
,
we obtained new results. Inasmuch as the structure of
the latter was unknown, we undertook an Xꢀray crysꢀ
tallographic study.
V
, Å3/
ρcalc, g/cm3
(Mo
), mm–1
Z
KLiMoO4 colorless crystals suitable for Xꢀray crysꢀ
tallography were grown from solution in melt during
studying phase formation in the Li2MoO4–K2MoO4–
MMoO4 (M = Pb, Ba) systems. The structure was
μ
K
3.613
α
Crystal size, mm3
angle range, deg
0.14
1.24–29.13
–21 25,
×
0.08 0.06
×
solved in terms of space group P63, which was conꢀ
θ
firmed in further structure refinement. The coordiꢀ
nates of heavy atoms (4Mo and 6K) for this group were
found by direct methods of structural amplitude sign
determination. Following the isotropic leastꢀsquares
Miller index ranges
≤ ≤
h
–25
≤
k
≤
25, –11
22768
4975
≤
l ≤ 12
Reflections measured
refinement of the revealed set of atoms to
R = 0.381,
Reflections used
n
[I
> 2
σ(I
)]
the positions of 16 basis atoms were found from elecꢀ
tronꢀdensity distribution. The model found in this way
was further refined with an experimental weighting
[R
(int) = 0.0508]
235
scheme in an isotropic version to
R = 0.135. The
Parameters refined
p
anisotropic refinement gave = 0.0958 and the posiꢀ
R
Goodness of fit
F2calc ]2/(n – p)]1/2
S
= [ w –
[(F2exp
Σ
1.051
tions of four lithium atoms, and the final anisotropic
refinement (the lithium atoms were refined isotropiꢀ
cally) with a correction for secondary extinction
applied in the final step, gave
R = 0.0650. Crystalloꢀ
R
(
F
) for
F2) for
) for all reflections
F2) for all reflections
Residual electron density, e/Å3
I
> 2
σ
(
I
)
0.0650
0.1583
graphic data are listed in Table 3, coordinates of basis
atoms are listed in Table 4, and selected interatomic
distances are in Table 5. The anisotropic temperature
factors are available from the authors. The adequacy of
the structural model is verified by the good converꢀ
gence of local valence strength balance (Table 6), as
calculated using data from [20].
wR
(
I
> 2
σ
(I)
R
(F
0.0788
wR
(
0.1696
3.396/–5.358
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 56 No. 9 2011

PHASE FORMATION
1447
Table 4. Basal atom coordinates and equivalent isotropic atomic displacement parameters in the
α
ꢀKLiMoO4 structure
eq, Å2
Atom
x
y
z
U
Mo(1)
Mo(2)
Mo(3)
Mo(4)
K(1)
0.15432(6)
0.01251(7)
0.51200(8)
0.33224(7)
0
0.16738(6)
0.34538(7)
0.34354(8)
0.48663(8)
0
0
0.0080(2)
0.0207(3)
0.0246(3)
0.0248(3)
0.029(2)
0.021(1)
0.052(2)
0.0232(7)
0.0224(5)
0.0254(7)
0.028(2)
0.021(3)
0.025(2)
0.031(3)
0.021(2)
0.025(2)
0.030(2)
0.021(3)
0.030(2)
0.016(2)
0.030(3)
0.030(2)
0.027(2)
0.033(3)
0.022(3)
0.028(2)
0.006(3)
0.013(4)
0.018(4)
0.017(4)
0.07087(18)
0.06154(20)
0.06418(20)
0.2690(7)
K(2)
1/3
2/3
0.2592(7)
K(3)
2/3
1/3
0.3303(8)
K(4)
0.17070(19)
0.49611(15)
0.33841(19)
0.1328(7)
0.2608(7)
0.1058(6)
0.1149(7)
–0.0539(7)
0.0898(6)
0.0521(6)
–0.0416(7)
0.5918(6)
0.4580(7)
0.4447(7)
0.5479(6)
0.2970(6)
0.4381(7)
0.2789(7)
0.3190(6)
–0.0093(11)
0.3384(12)
0.4862(13)
–0.1637(13)
0.32481(20)
0.49684(15)
0.17671(16)
0.1873(6)
0.220(7)
0.3242(4)
K(5)
0.2994(4)
K(6)
0.2570(4)
O(1)
–0.1754(12)
0.0330(10)
0.1299(11)
0.0224(13)
0.0597(12)
–0.0585(11)
0.2545(11)
0.0413(11)
–0.0610(12)
0.0242(9)
O(2)
O(3)
0.2002(6)
0.0603(7)
0.3830(6)
0.3951(5)
0.3662(6)
0.2382(7)
0.3934(6)
0.2385(6)
0.3831(7)
0.3600(6)
0.4030(6)
0.5562(8)
0.5411(8)
0.4515(7)
0.1617(12)
0.3258(11)
0.6569(13)
0.3284(12)
O(4)
O(5)
O(6)
O(7)
O(8)
O(9)
O(10)
O(11)
O(12)
O(13)
O(14)
O(15)
O(16)
Li(1)
Li(2)
Li(3)
Li(4)
0.0503(14)
0.2482(11)
–0.0540(12)
0.0395(14)
0.0343(10)
0.2539(9)
0.127(2)
–0.032(2)
–0.036(2)
–0.030(2)
Note:
U = 4(U + U + 0.75U – U )/9.
eq 11 22 33 12
For hexagonal KLiMoO4 phase, the structure was cally independent oxygen atoms are in general posiꢀ
determined for the first time; the same structure is tions. The molybdenum and lithium atoms are coordiꢀ
known for (Na, K)ZnPO4 [21]. Three of the six potasꢀ nated tetrahedrally; Mo–O distances fall within
sium basis atoms are positioned on triple axes, and the 1.716–1.801 Å, and Li–O distances are within 1.78–
other 4Mo, 3K, 4Li, and all 16 of the crystallographiꢀ 2.07 Å. The coordination polyhedra around the K(1)
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 56 No. 9 2011

1448
GUDKOVA et al.
Table 5. Selected interatomic distances (Å) in the
α
ꢀKLiMoO4 structure
Mo(1)ꢀtetrahedron
Mo(2)ꢀtetrahedron
Mo(3)ꢀtetrahedron
Mo(1)–O(1)
Mo(1)–O(2)
Mo(1)–O(3)
Mo(1)–O(4)
1.716(11)
1.767(12)
1.776(10)
1.783(12)
1.761
Mo(2)–O(5)
1.721(11)
1.730(9)
1.773(9)
1.773(11)
1.749
Mo(3)–O(9)
1.719(10)
1.751(10)
1.771(11)
1.778(9)
1.755
Mo(2)–O(6)
Mo(2)–O(7)
Mo(2)–O(8)
Mo(3)–O(10)
Mo(3)–O(11)
Mo(3)–O(12)
〈Mo
(
1
)–O
〉
〈Mo
(2
)–O
〉
〈Mo
(3
)–O
〉
Mo(4)ꢀtetrahedron
1.736(9)
Mo(4)–O(13)
Mo(4)–O(14)
Mo(4)–O(15)
Mo(4)–O(16)
K(1)ꢀicosahedron
2.907(13)
2.954(13)
3.191(10)
3.508(11)
3.140
1.775(12)
1.783(11)
1.801(8)
K(1)–O(4)
K(1)–O(4')
K(1)–O(1)
K(1)–O(3)
×
3
×
3
×
3
3
〈Mo
(
4)–O
〉
1.765
×
K(2)ꢀoctahedron
2.738(11)
2.887(12)
2.813
〈K
(1
)–O
〉
K(2)–O(9)
K(2)–O(15)
)–
×
3
K(4)ꢀoctahedron
2.685(10)
2.691(11)
2.697(10)
2.789(11)
2.841(11)
2.845(11)
2.758
×
3
K(4)–O(3)
K(4)–O(8)
〈
K
(
2
O
〉
K(3)ꢀoctahedron
2.637(11)
2.759(12)
2.698
K(4)–O(16)
K(4)–O(7)
K(4)–O(2)
K(4)–O(10)
K(3)–O(12)
K(3)–O(15)
×
3
3
×
〈K
(
3)–O
〉
K(5)ꢀicosahedron
2.907(14)
2.914(11)
2.927(9)
〈K
(4
)–O
〉
K(5)–O(14)
K(5)–O(11)
K(5)–O(5)
K(5)–O(5')
K(5)–O(11')
K(5)–O(14')
K(5)–O(16)
K(5)–O(12)
K(5)–O(7)
K(5)–O(6)
K(5)–O(9)
K(5)–O(13)
K(6)ꢀoctahedron
2.684(10)
2.694(10)
2.791(11)
2.845(11)
2.864(11)
2.945(12)
2.804
K(6)–O(6)
K(6)–O(1)
K(6)–O(13)
K(6)–O(2)
K(6)–O(10)
K(6)–O(8)
2.984(13)
2.991(14)
3.024(12)
3.038(10)
3.223(11)
3.224(11)
3.384(11)
3.476(12)
3.633(11)
3.144
〈K
(6
)–O
〉
Li(1)ꢀtetrahedron
1.92(2)
Li(1)–O(3)
Li(1)–O(1)
Li(1)–O(8)
Li(1)–O(4)
〈K
(
5
)–O
〉
1.93(2)
Li(2)ꢀtetrahedron
1.88(2)
1.98(2)
Li(2)–O(2)
Li(2)–O(11)
Li(2)–O(13)
Li(2)–O(7)
1.99(2)
1.89(2)
〈Li(
1
)–O
〉
1.955
1.98(2)
2.03(2)
Li(4)ꢀtetrahedron
1.89(2)
〈Li
(2
)–O
〉
1.95
Li(4)–O(10)
Li(4)–O(9)
Li(4)–O(5)
Li(4)–O(16)
Li(3)ꢀtetrahedron
1.78(2)
1.94(2)
Li(3)–O(14)
Li(3)–O(15)
Li(3)–O(6)
Li(3)–O(12)
1.97(2)
1.95(2)
2.07(2)
2.00(2)
〈Li(
4)–O
〉
1.97
2.02(2)
〈Li
(3
)–O
〉
1.94
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 56 No. 9 2011

PHASE FORMATION
1449
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 56 No. 9 2011

1450
GUDKOVA et al.
b
a
K
MoO4
LiO4
Fig. 2.
α
ꢀ
KLiMoO structure as projected along axis
c.
4
and K(5) atoms are distorted oxygen icosahedra, and works approximately at levels of
z = 0.25 and z = 0.75
the K(2), K(3), K(4), and K(6) atoms have octahedral (Fig. 3). The inꢀlayer links of potassium polyhedra are
coordination with different degrees of distortion; the
overall range of K–O distances is 2.637–3.633 Å. In
isostructural (Na, K)ZnPO4 [21], octahedra are occuꢀ
pied by sodium cations and icosahedra by larger potasꢀ
sium ions.
accomplished by corner sharing, and layers are stacked
by faces.
KLiMoO4 experiences several polymorphic transiꢀ
tions [22, 23], but the structures of all phases are
derived either from tridymite or from cristobalite, and
this means that all types of structures comprise threeꢀ
dimensional frameworks of alternating MoO4ꢀ and
LiO4 tetrahedra. Evidently, our tridymiteꢀrelated
KLiMoO4 crystals belong to a lower temperature phase
compared to cristobaliteꢀtype crystals, which are
known for highꢀtemperature cubic phases of ALiMoO4
(A = K, Rb, Cs) [22–24]. Indeed, comparing a meaꢀ
sured Xꢀray diffraction pattern of KLiMoO4 with the
pattern calculated by our structural data and comparꢀ
ing with the interplanar distances calculated using the
In our studied KLiMoO4 structure, alternating
MoO4 and LiO4 tetrahedra are linked via shared corꢀ
ners to a threeꢀdimensional framework (Fig. 2), which
resembles the
plex. As in
β
ꢀtridymite structure but is more comꢀ
β
ꢀtridymite, here hexagonal tetrahedral
networks contacting by their corners are recognized in
the framework. In the potassium lithium molybdate
structure, there are two symmetrically equivalent netꢀ
works per unit cell lying at the levels z = 0 and z = 0.5.
However, along with the same sixꢀmembered rings as
in tridymite (where tetrahedra are turned by their apiꢀ
ces upward and downward in an alternating order), in
KLiMoO4 there are rings with another order of the oriꢀ
entation of tetrahedra. A more detailed description of
this type of framework and its relations to other
tridymiteꢀrelated structure is found in [21]. Potassium
cations reside in voids within the framework of the
KLiMoO4 structure; their coordination polyhedra also
unit cell parameters of
we see that the structure we studied corresponds preꢀ
cisely to the lowꢀtemperature phase.
αꢀKLiMoO4 taken from [22],
α
ACKNOWLEDGMENTS
The authors are thankful to I.Yu. Filatova and
form a threeꢀdimensional framework; this framework D.S. Pantsurkin for carrying out the thermal analysis
is divided into layers lying between tetrahedral netꢀ of the compounds. This study was supported by the
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 56 No. 9 2011

PHASE FORMATION
1451
(a)
b
K1
a
K6
K3
K4
K5
K2
(b)
b
K1
a
K4
K2
K6
K3
K5
Fig. 3. Layers of potassium coordination polyhedra in the
at the 0.75 level.
α
ꢀ
KLiMoO structure: (a) a layer at the
z
≈
0.25 level and (b) a layer
4
z
≈
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 56 No. 9 2011

1452
GUDKOVA et al.
12. W. Guertler, Z. Anorg. Allg. Chem. 154 (1–4), 439
Russian Foundation for Basic Research (project no. 08ꢀ
03ꢀ00384).
(1926).
13. A. M. Zakharov, Phase Diagrams for Binary and Ternary
Systems (Metallurgiya, Moscow, 1978) [in Russian].
REFERENCES
14. G. M. Sheldrick, SHELX97, Release 97ꢀ2 (Univ. of
1. M. V. Mokhosoev, F. P. Alekseev, and V. L. Butukhanov,
Double Molybdates and Tungstates (Nauka, Novosiꢀ
birsk, 1981) [in Russian].
2. M. V. Mokhosoev and Zh. G. Bazarova, Complex
Oxides of Molybdenum and Tungsten with Group I–IV
Elements (Nauka, Moscow, 1990) [in Russian].
3. S. F. Solodovnikov, R. F. Klevtsova, and P. V. Klevtsov,
Zh. Strukt. Khim. 35 (6), 145 (1994).
4. V. A. Isupov, Ferroelectrics 322, 83 (2005).
Göttingen, Göttingen, 1997).
15. A. S. Trunin, I. K. Garkushin, and S. A. Datsyuk,
Zh. Neorg. Khim. 21 (10), 2770 (1976).
16. N. N. Verdiev, B. D. Babaev, and A. M. Gasanaliev,
Zh. Neorg. Khim. 41 (2), 309 (1996) [Russ. J. Inorg.
Chem. 41 (2), 296 (1996)].
17. C. K. Moller, Acta Chem. Scand. 8 (1), 81 (1954).
18. S. A. Magarill and R. F. Klevtsova, Kristallografiya 16
(4), 742 (1971).
5. E. F. Dudnik and I. E. Mnushkina, Ukr. Fiz. Zh. 22
19. Yu. A. Pyatenko, Kristallografiya 17 (4), 773 (1972).
(10), 1737 (1977).
20. I. D. Brown and D. Altermatt, Acta Crystallogr., Sect.
6. S. F. Solodovnikov, E. G. Khaikina, Z. A. Solodovnikꢀ
B
41 (4), 244 (1985).
ova, et al., Dokl. Akad. Nauk 416 (1), 60 (2007).
21. O. V. Yakubovich and O. K. Mel’nikov, Kristallografiya
34 (1), 62 (1989).
22. P. V. Klevtsov, S. V. Mel’nikova, R. F. Klevtsova, and
7. I. N. Belyaev, Zh. Neorg. Khim. 6 (5), 1178 (1961).
8. I. N. Belyaev and N. N. Chikova, Zh. Neorg. Khim.
(12), 2754 (1964).
9
A. I. Kruglik, Kristallografiya 33 (5), 1168 (1988).
9. V. K. Trunov, Zh. Neorg. Khim. 16 (2), 553 (1971).
23. K. Okada and J. Ossaka, J. Solid State Chem. 37 (3),
10. A. S. Trunin, G. E. Shter, and V. N. Serezhkin,
325 (1981).
Zh. Neorg. Khim. 20 (8), 2209 (1975).
11. V. A. Efremov and V. K. Trunov, Dokl. Akad. Nauk 24. K. S. Aleksandrov, D. H. Blat, V. I. Zinenko, et al., Ferꢀ
SSSR 235 (4), 820 (1977).
roelectrics 63, 13 (1985).
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 56 No. 9 2011