Syntheses and structures of Li3ScF6 and high pressure LiScF4-, luminescence properties of LiScF4, a new phase in the system LiF-ScF3

Article abstract of DOI:10.1016/j.jssc.2005.04.038

Colorless single crystals of Li₃ScF₆ have been prepared by reacting the binary components LiF and ScF₃ at 820°C for 16 h in argon atmosphere. This complex fluoride is the only stable phase in the system LiF-ScF₃ under ambient pressure. According to a structure refinement based on single crystal X-ray diffraction data it crystallizes in the centrosymmetric space group P3c1 with a=8.78.3(1)A and c=9.518(1)A. The new structure of Li₃ScF₆ is a filled variant of the Na₂GeF₆ type structure and can be described in terms of a hexagonal close packing of fluorine in which 2/3 of the octahedral holes are occupied by Sc and Li. High pressure/high temperature studies of the system LiF-ScF₃ show that the new phase LiScF ₄ is formed at around 5.5 GPa and 575°C. According to Rietveld refinements of powder X-ray diffraction data LiScF₄ adopts the Scheelite type structure (space group I41/a) with a=4.980(1)A and c=10.074(1)A. A sample of LiScF₄ doped with 1% Er exhibits an intense luminescence in the far IR region.

Full text of DOI:10.1016/j.jssc.2005.04.038

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Journal of Solid State Chemistry 178 (2005) 2620–2625
www.elsevier.com/locate/jssc
Syntheses and structures of Li ScF and high pressure
3
6
LiScF , luminescence properties of LiScF , a new phase in the
4
4ꢀ
system LiF–ScF3
a
b,
Ã
b
¨
A.K. Tyagi , J. Kohler , P. Balog , J. Weber
c
a
Applied Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
b
Max-Planck-Institut f u¨ r Festk o¨ rperforschung, HeisenbergstraXe-1, D-70569 Stuttgart, Germany
Technische Universit a¨ t Dresden, Zellescher Weg 16, D-01069 Dresden, Germany
c
Received 18 February 2005; received in revised form 20 April 2005; accepted 24 April 2005
Available online 6 July 2005
Abstract
Colorless single crystals of Li
argon atmosphere. This complex fluoride is the only stable phase in the system LiF–ScF under ambient pressure. According to a
3 6 3
ScF have been prepared by reacting the binary components LiFand ScF at 820 1C for 16 h in
3
¯
structure refinement based on single crystal X-ray diffraction data it crystallizes in the centrosymmetric space group P3c1 with
(
(
a ¼ 8:78:3ð1Þ A and c ¼ 9:518ð1Þ A. The new structure of Li
described in terms of a hexagonal close packing of fluorine in which 2/3 of the octahedral holes are occupied by Sc and Li.
High pressure/high temperature studies of the system LiF–ScF show that the new phase LiScF is formed at around 5.5 GPa and
75 1C. According to Rietveld refinements of powder X-ray diffraction data LiScF adopts the Scheelite type structure (space group
3 6 2 6
ScF is a filled variant of the Na GeF type structure and can be
3
4
5
4
(
(
I41=a) with a ¼ 4:980ð1Þ A and c ¼ 10:074ð1Þ A. A sample of LiScF doped with 1% Er exhibits an intense luminescence in the far
4
IR region.
r 2005 Elsevier Inc. All rights reserved.
Keywords: Fluoride; Scandium; Structure; Luminescence; High pressure synthesis
3
M
þ
(
1
. Introduction
r
o0:8 A only the 3:1 phases with composition Li MF
3
6
+
3
(
M ¼ Al, Ga, Ti–Ni) [7–13] are found in which the M
ꢀ
Fluorides are excellent host materials for luminescent
ions are six-fold coordinated by F ions. Exceptions are
the systems LiF/MF with M ¼ Mn, Co or In, in which
ions because of their wide transmission wavelength
range and their low refractive index. In particular LiYF4
is widely used as host for trivalent rare-earth ions [1–5].
It is astonishing that not much is known about complex
lithium fluorides with the lighter homologue scandium.
3
also phases with the composition LiMF or Li MF
5
4
2
3
exist [14–16]. The Sc ion is significantly smaller than
+
3
+
Y
with the above-mentioned criteria Li ScF is the only
or the trivalent lanthanide ions and in agreement
3
6
In systems LiF–MF with large ions M ¼ Y, Eu–Lu
stable phase in the system LiF–ScF3 under ambient
conditions [17]. According to X-ray powder diffraction
(XRD) studies the structure of Li ScF is not isotopic to
3
3
þ
r 40:80 A) only thermodynamically stable phases
M
(
(
with the composition LiMF exist at ambient pressure.
These fluorides crystallize all in the scheelite type
4
3
6
any known hexafluorometallate (III) and only a
similarity to the Na GeF type structure has been
3
+
structure [6] in which the M ions exhibit the
coordination number 8. For smaller ions with
2
6
proposed [18]. Here we report on the synthesis, structure
determination and refinement of Li ScF based on single
3
6
Ã
crystal X-ray diffraction data. Furthermore, we have
explored the possible existence of phases in the system
Corresponding author. Fax: +49 711 689 1091.
¨
E-mail address: J.Koehler@fkf.mpg.de (J. Kohler).
0022-4596/$ - see front matter r 2005 Elsevier Inc. All rights reserved.
doi:10.1016/j.jssc.2005.04.038

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A.K. Tyagi et al. / Journal of Solid State Chemistry 178 (2005) 2620–2625
2621
Table 1
Crystallographic data and experimental conditions for Li
LiF/ScF under high pressure–high temperature condi-
3
tions as structural changes under high static pressure are
a
3
ScF
6
often accompanied by an increase of the coordination
number of the constituent ions. Under such conditions
we have synthesized LiScF , and studied its suitability as
Name
Formula
Lithiumhexafluoroscandate
Li ScF
179.78
P 3¯ c1 (No. 165), 6
293 K
3
6
Formula weight
Space group; Z
Temperature
Unit cell dimensions:
4
host material for luminescent rare earth ions.
(
a ¼ 8:783ð1Þ and c ¼ 9:518ð1Þ A
3
(
V ¼ 635:8ð1Þ A
2
. Experimental section
.1. Li ScF
3
Density (calculated)
Crystal size (mm)
2.817 g/cm
0.01 Â 0.03 Â 0.03
2
ꢀ1
˚
1.77 mm , 0.71073 A
3
6
m(MoKa), l (MoKa)
Diffractometer, scan mode Enraf-Nonius, $-scan
Starting materials were LiF(Alfa, 99.9%) and ScF 3
Alfa, 99.9%) which were dried at 250 1C in a dynamic
Graphite-Monochromator, Scintillation
counter
(
vacuum of 10 Torr. LiFand ScF in a 3:1 M ratio were
ꢀ
5
Limiting indices
41o2yo611, ꢀ12oho12, ꢀ12oko12,
3
ꢀ
13olo13
well ground in an argon filled dry box, pressed into a
pellet and then placed in a platinum tube, which was
transferred to an argon filled sealed quartz glass tube. The
ampoule was heated to 820 1C with a heating rate of 5 1C/
min, held for 16h and then cooled to room temperature
with a rate of 2 1C/min. A white powder sample of the
Scan speed
Scan-width
Variable depending on I
1.11
9487
Reflections collected
Absorption correction
Refinement
c-scan with 10 reflections
Full-matrix least square method
SHELX-97 [20]
F(000)
Number of free
parameters
504
47
complex fluoride Li ScF was obtained which contained
3
6
also tiny transparent crystals. The powder XRD pattern
of Li ScF matched nearly perfectly with the reported
XRD pattern [18] which has led to a trigonal unit cell
2
Goodness-of-fit on F
Independent reflections
0.925
3
6
652 F
359 F
o
(hkl)
(
(
o
(hkl) with Ij42:0sðIÞ
with a ¼ 8:773ð3Þ A and c ¼ 4:750ð1Þ A. However, a
small reflection around 521 was observed which required
a doubling of the c-axis for a complete indexing. The
refinement of the trigonal unit cell of Li ScF resulted in
wR
R
2
(359 indep.refl.)
(359 indep.refl.)
8.41%
3.75%
1
a
Further details of the crystal structure investigation may be
3
6
(
obtained from the Fachinformationzentrum Energie, Physik, Mathe-
matik, D-76344 Eggenstein-Leopoldshafen 2, on quoting the deposi-
tory number CSD-415135, the names of the authors, and the journal
citation.
a ¼ 8:783ð1Þ and c ¼ 9:518ð1Þ A.
Single crystals of Li ScF were picked up by physical
3
6
fragmentation from a sample under an optical micro-
scope. Their suitability for intensity data collection was
ascertained by recording a Laue photograph. Out of 5
one was found to have acceptable quality. The single-
crystal X-ray investigation was performed on a four-
circle diffractometer using MoKa radiation (graphite
monochromator). The intensities were corrected for
Lorentz and polarization effects, and a semi-empirical
absorption correction was applied on the basis of c-
scans. Table 1 contains the crystallographic data and the
experimental conditions of the data collection and
2.2. LiScF4
High pressure and high temperature (HP–HT) experi-
ments have been performed up to 12 GPa and 900 1C,
using a multianvil press (Voggenreiter GmbH, Ger-
many) and a belt uniaxial press (Dieffenbacher GmbH,
Germany). The multianvil press is equipped with a
Walker module, employing 32 mm edge size WC cubes,
with 11 and 8 mm truncation edge length, respectively.
Both presses have been previously pressure–temperature
calibrated. Temperature was controlled by Eurotherm
units, and was measured using NiCr/Ni and W5Re/
W26Re thermocouples, no correction being made for
the pressure effect on thermocouple wires. Thermal
gradient in the high pressure cell was minimized by using
stepped cylindrical heaters.
refinement. The structure was solved in the space group
2
P3c1 by direct methods and refined against the F data
¯
(
SHELX program [19,20]) to residuals wR ¼ 9:96%
2
and R ¼ 8:09% for all 652 independent reflections,
1
respectively, and wR ¼ 8:41% and R ¼ 3:75% for 359
2
1
reflections with I42sðIÞ, see Table 1. The displacement
factors of the atoms were taken into account in the
anisotropic harmonic approximation. Atomic scattering
factors and anomalous dispersion corrections were
taken from the ‘International Tables for X-ray Crystal-
lography’ [21]. The atomic position parameters and the
isotropic displacement factors for Li ScF are given in
Starting materials LiF(Merck, 99.9%), ScF 3 (Chem-
pur, 99.9%), ErF3 (REacton, Johnson Matthey,
99.99%), were dried at 250 1C in dynamic vacuum for
overnight. Intimate mixtures of the reactants in an
appropriate ratio were placed in tightly sealed Pt
3
6
Table 2. Listings of the observed and calculated
structure factors are available.

ARTICLE IN PRESS
A.K. Tyagi et al. / Journal of Solid State Chemistry 178 (2005) 2620–2625
2622
Table 2
Atomic coordinates and equivalent isotropic displacement parameters
2
4
˚
(
A Â 10 ) for Li
3 6
ScF
Atom Position x=a
y=b
z=c
B (is/eq)
Li1
Li2
Sc1
Sc2
F
6f
12g
2b
4d
g
0
0.7000(9) 1/4
0.6574(8)
0
0.0207(17)
0.4629(6) 0.0205(13)
0.0117(3)
0.6372(8)
0
0
2/3
1/3
0.2639(1) 0.0108(2)
0.1450(2) 0.0152(4)
0.3817(2) 0.0156(4)
0.1076(2) 0.0156(4)
1
2
3
12
12
12
0.7846(3)
0.5417(3)
0.1179(3)
0.5535(2)
0.4298(3)
0.2267(2)
F
g
F
g
4
Fig. 1. Rietveld refinement of the crystal structure of LiScF .
capsules in order to avoid contamination. The experi-
mental duration varied between 4 and 18 h at different
temperatures (550–900 1C). The desired product LiScF4
free from any byproduct was obtained at 575 1C,
Observed diffraction pattern (upper curve), difference between
calculated and observed intensities (lower curve). The tick marks
show the positions of the allowed Bragg reflections.
5
.5 GPa and 4.5 h. After the experiment the Pt capsules
were extracted from the high pressure modules, and the
sample material was retrieved under controlled atmo-
sphere conditions. All samples resulting from experi-
ments in which the Pt capsule was found broken, were
eliminated from the final analysis.
XRD data for the Rietveld refinement were collected
on a STOE STADI-P powder diffractometer equipped
with a mini-PSD detector, with a rotating sample in
symmetric transmission mode (Ge monochromator,
Table 3
a
Crystallographic data and experimental conditions for LiScF
4
Name
Formula
Lithiumtetrafluoroscandate
LiScF4
Formula weight (g/mol)
Space group (Nr.), Z
127.9
I41=a (Nr. 88), 4
˚
Lattice constants (A)
a ¼ 4:980ð1Þ, c ¼ 10:074ð1Þ
3
Cell volume (A )
˚
249.92(2)
240
36
CuKa radiation). For LiScF , the atomic parameters
4
F(000) (electrons)
Number of atoms in cell
from LiYF were used as starting parameters and the
4
3
positional and thermal parameters were refined by full
powder profile method using the CSD software [22]. The
background scale, zero-shift and asymmetry parameters
were refined, together with the profile parameters. The
profile line shape was simulated by using a pseudo-Voigt
Calculated density (g/cm )
Absorption coefficient (cm
Radiation and wavelength
3.399(1)
25.31
ꢀ1
)
˚
CuKa, 1.54051 A
Stoe Stadi P, Ge
Diffractometer, monochromator
Mode of refinement, program
Number of atom sites
Full profile, CSD [22]
3
Number of free parameters
7
function. The calculated pattern of LiScF shows a good
4
2
D and sin y/l (max)
Reflections used in refinement
, wR
96.4, 0.484
55
agreement with the observed one, Fig. 1. The details of
the final Rietveld refinement for LiScF are given in
4
R
I
p
0.037, 0.081
0.33
Table 3. The atomic parameters are listed in Table 4.
Photoluminescence spectra of powder samples of
LiScF4 and LiScF :Er (1%) were recorded at room
Goodness of fit
Scale factor
1.79(2)
4
a
Further details of the crystal structure investigation may be
obtained from the Fachinformationzentrum Energie, Physik, Mathe-
matik, D-76344 Eggenstein-Leopoldshafen 2, on quoting the deposi-
tory number CSD-412050, the names of the authors, and the journal
citation.
temperature using the 488-nm line of an Ar ion laser
2
with a laser power of 50 mW/cm . The photolumines-
cence was analyzed with a grating monochromator and
detected by a cooled Ge diode. The spectral resolution
of the monochromator was 1 nm.
3
. Discussion
Table 4
Atomic coordinates and equivalent isotropic displacement parameters
2
4
˚
(
A Â 10 ) for LiScF
4
Systems LiF–MF with small ions M ¼ Al, Ga, Ti, V,
3
(
3þ
M
Cr, Fe (r o0:8 A) are characterized at ambient
Atom Position x=a
y=b
z=c
B (is/eq)
conditions by the existence of phases Li MF , which
all crystallize in the monoclinic b-Li VF type structure
3
6
a
Li
Sc
4b
4a
0
1/2
1/4
3/4
1/8
1/8
0.01
0.039(5)
3
6
[9]. With the larger rare earth elements (RE ¼ La–Lu,
Y) only compounds of the type LiREF are found in the
systems LiF–REF , but with the smallest rare earth ion
3
F16
f
0.2894(3)
0.0760(2)
0.0430(2) 0.099(7)
4
a
Fixed during refinement.

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A.K. Tyagi et al. / Journal of Solid State Chemistry 178 (2005) 2620–2625
2623
3+
Sc the 3:1 phase Li ScF is found which crystallizes in
5. Accordingly the coordination number of F(1) is 3+1
whereas F(2) and F(3) are surrounded by only 3 next
nearest cations.
3
6
a new structure type, Fig. 2. The motifs of the mutual
adjunction [23] and interatomic distances are given in
Table 5. The crystal structure of Li ScF is according to
As mentioned above the structure of Li ScF is closely
3
3
6
6
Li(1) Li(2) Sc(1) Sc(2) F(1) F(2) F(3) based on the
6
related to the well-known structure of Li GeF [24]
2 6
3
6
1
2
6
6
treble of the formula. It can be described in terms of a
close packing of puckered layers of Fwhich are stacked
along [001] according to the motif yABABy Sc(1)
occupies 1/18th and Sc(2) occupies 2/18th of the
octahedral holes within neighboring F layers, i.e., a
total of 1/6th of the octahedral holes are occupied by Sc,
Fig. 2. Both, the Sc(1)F and Sc(2)F octahedra are
which crystallizes in the Na GeF type structure
2 6
and exhibits also a hexagonal packing of anion layers,
Fig. 3. In both structures the arrangements of the
ScF6 and GeF6 octahedra are nearly identical and
the main difference arises from the occupation of
the Li sites. As the scattering power of Li is rather
small it is not surprising that the XRD patterns of
both structures are very similar, see Section 2. However,
an essential difference is found for the charges
of the metal atom layers (along [001]) which in the
structure of Li GeF are+7 for Ge(1) +3 Li(2)
6
6
˚
nearly regular (d
¼ 2.00–2.03 A). Within the anion
ScꢀF
layers additional the Li occupy octahedral holes in such
a way that layers of 1 Sc(1) and 6 Li(2) alternate with 2
Sc(2) and 3 Li(1). However, it should be mentioned that
the polyhedra around the Li are rather distorted and
only for Li(1) the coordination number 6 is assigned
unambiguously. For Li(2) the assumption of the
coordination 6 is only a rough approximation as the
2
6
and+11 for 2 Ge(2)+3 Li(1), see Fig. 3, whereas the
structure of Li ScF exhibits a much more balanced
3
6
the charge distribution, i.e. both Sc/Li layers have
the charge +9, see Fig. 2. Nevertheless, due to the
similarity of the unit cell dimensions it is possible to
˚
Li(2)–Fdistances range from 1.944 to 2.495 A , see Table
synthesize members of the mixed series Li3
ꢀx
Ge Sc F ) which might be promising candidates for
(
Li ionic conductivity.
x
1ꢀx
6
The reaction of LiFwith ScF 3 under a pressure of
5.5 GPa at 575 1C for 4.5 h leads to white powder
samples and colorless transparent crystallites of LiScF4,
see Section 2. LiScF crystallizes in the scheelite type
4
structure, like LiYF , in accordance with the so-called
4
pressure homologue rule. Characteristic building units
are ScF bisdisphenoids with four short Sc–Fdistances
8
˚
of 2.101 A and four longer ones of 2.179 A, Fig. 3.
˚
Despite the fact that LiScF has been synthesized under
4
high pressure it is remarkable that it is the first
compound which contains eight-fold coordinated Sc.
The Li–Fdistances within the LiF
˚
tetrahedra are
.874 A and slightly shorter than the corresponding
4
1
distances in LiYF (1.899 A). As it can be seen from Fig.
˚
4
4
along the c-axis with four long edges (3.36 A) and two
˚
short ones (2.89 A). This squeezing becomes even more
the LiF tetrahedra in LiScF are highly squeezed
4 4
Fig. 2. Perspective view of the crystal structure of Li
circles represent F, small gray circles Li and large gray circles Sc. The
ScF octahedra are graphically emphasized.
3 6
ScF . Small light
˚
6
Table 5
Motifs of the mutual adjunction [23] together with interatomic
˚
3 6
distances (A), and coordination numbers (C.N.) for Li ScF
Atoms
12 F1
2/1
12 F2
12 F3
2/1
C.N.
6
6
1
2
4
Li1
2 Li2
Sc1
2/1
1.949 (2 Â )
2/1
1
.944 (2 Â )
2.226 (2 Â )
2/2
1.915+2.495
—
2/1
2.047+2.206
6/1
6
6
6
1.902+2.010
—
2.006(6 Â )
—
Sc2
3/1
3/1
2.027 (3 Â )
Fig. 3. Perspective view of the crystal structure of Na
2
6
GeF . Small
2
4
.022 (3 Â )
light circles represent F and large gray circles Na. The GeF
are graphically emphasized.
6
octahedra
C.N.
3
3

ARTICLE IN PRESS
A.K. Tyagi et al. / Journal of Solid State Chemistry 178 (2005) 2620–2625
2624
the corresponding sum of the MAPLE values of the
binary components LiFand ScF 3 [26].
MAPLE(ScF )+3ꢀMAPLE(LiF) ¼ MAPLE .(Li ScF )
3
calc
3
6
1
476.8
3 Â 288.7
¼ 2342.9 kcal/mol
MAPLE(ScF3) MAPLE(LiF)
476.8 +288.7
¼ MAPLE (LiScF )
calc.
4
1
¼ 1765.5 kcal/mol
The differences are rather small (o1.3%) and indicate
that the MAPLE concept holds for highly ionic
compounds even when comparing the structures of
high pressure and normal pressure phases. In addition,
it reflects the excellent quality of the structure refine-
ments.
As mentioned in Section 1 fluorides like LiYF are
4
good host materials for luminescent ions such as the
lanthanides. Matrix effects are very important for
optical transitions and therefore we have made attempts
to prepare LiY0.95Sc0.05F , under high temperature–
4
Fig. 4. Perspective view of the crystal structure of LiScF
circles represent F, large dark gray circles Li and large gray circles Sc.
The ScF polyhedra and the LiF tetrahedra are graphically
emphasized.
4
. Small black
ambient pressure conditions. However, we found that
not even 5 mol% of Y in the lattice of LiYF can be
8
4
4
substituted by Sc and obviously the size difference of Sc
and Y is too large. We have used LiScF itself as host
4
material and measured the photoluminescence spectrum
of a sample LiScF doped with 1 mol% Er, see Fig. 5.
Two intense groups of sharp luminescence lines around
4
evident from the F–Li–F angles, which are 101.21 and
27.81, respectively.
LiScF is a stable phase at room temperature as could
1
1500 nm are observed. This spectrum is similar to what
has been found for LiYF :Er [27], however, due to the
4
4
be seen from an XRD pattern recorded more than three
months after the synthesis. However, LiScF decom-
smaller sites for Er in LiScF4 the lines are shifted
towards shorter wavelengths by approximately 20 nm.
Considering the large difference in the molar volumes
4
poses into ScF3 and Li ScF on heating at 250 1C.
3
6
3
3
This observation clearly indicates that though it is
thermodynamically metastable it is kinetically
stable phase, like most of the recovered high pressure
phases. Li ScF , on the other hand, is not stable under
V(LiScF ) ¼ 37.6 cm /mol and V(LiYF ) ¼ 43.3 cm /
4
4
a
mol mixed samples with compositions LiY Sc F :RE
1
ꢀx
x 4
(
RE ¼ rare earth element) prepared under high pressure
3
6
appear promising candidates for the access of emission
lines in an intermediate spectral range compared to pure
doped LiYF and LiScF samples. Furthermore, the
high pressure–high temperature conditions and decom-
poses into LiFand LiScF 4, as shown in a separate
experiment (5.5 GPa, 400 1C). This appears reasonable
4
4
spectra of LiScF :RE can be also used to estimate
4
3
as the molar volume V(Li ScF ) ¼ 63.8 cm /mol is
3
6
pressure effects on the optical properties of LiYF :RE
4
approximately 10% larger than the sum of the molar
3
[
28].
volume V(LiScF )+2 Â V(LiF) ¼ 37.6 cm /mol+2 Â
4
3
3
9
.76 cm /mol ¼ 57.12 cm /mol. One can also conclude
that there is no pressure/temperature range where both
phases, Li ScF and LiScF , coexist. It is worth
mentioning that Li ScF does not get converted to
3
6
4
3
6
LiScF and LiFon applying high pressures up to 10 GPa
4
for 50 h at ambient temperature. Therefore, it can be
inferred that the decomposition mechanism of Li ScF
into LiScF4 and LiFis reconstructive rather than
3
6
displacive.
For an electrostatic analysis and a check the quality of
the refinements, especially with respect to the Li
positions, we have calculated the Madelung Parts of
Lattice Energy, MAPLE [25] for Li ScF and LiScF
4
3
6
and obtained 2312.6 kcal/mol and 1746.6 kcal/mol,
respectively. These values have to be compared with
Fig. 5. Photoluminescence spectra of: (a) a sample of LiScF
4
doped
with 1% Er and (b) an undoped LiScF sample.
4

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A.K. Tyagi et al. / Journal of Solid State Chemistry 178 (2005) 2620–2625
2625
4
. Summary and outlook
[8] M.K. Chaudhary, N. Roy, Synth. React. Inorg. Met.-Org. Chem.
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9] W. Massa, W. Ru
10] A.K. Tyagi, R. Po
1996) 1329.
[11] A.K. Tyagi, J. Ko
[12] J. Kohler, A.K. Tyagi, Z. Kristallogr. 214 (1999) 25.
13] A.K. Tyagi, J. Kohler, Mater. Res. Bull. 35 (2000) 135.
1
[
¨
dorff, Z. Naturforsch. 26b (1971) 1216.
ttgen, J. Kohler, Z. Anorg. Allg. Chem. 622
The main focus of this contribution lies in the
preparative and chemical aspects of phases in the system
LiF/ScF . However, the new phases in the system LiF/
3
[
¨
¨
(
¨
hler, Mater. Res. Bull. 32 (1997) 1683.
ScF call for studies of structure property relationships,
3
¨
[
[
¨
such as Li ionic conductivity of the mixed series
Li (Ge Sc F ), which are in progress. The intense
luminescence in the far IR region of a LiScF sample
14] P. Lacorre, J. Pannetier, F. Averdunk, R. Hoppe, G. Ferey, J.
Solid State Chem. 79 (1989) 1.
x
x
1ꢀx
6
4
[15] K.-H. Wandner, R. Hoppe, Z. Anorg. Allg. Chem. 546 (1987)
doped with 1% Er is given as an example to show the
potential of LiScF as a host material for studies of
1
13.
[16] P. Gravereau, J.P. Chaminade, T. Gaewdang, J. Gannec, M.
Pouchard, P. Hagenmuller, Acta Crystallogr. C 48 (1992) 769.
17] E.P. Babaeva, G.A. Bulhalova, Zh. Neorgan. Khim. 11 (1966)
48;
E.P. Babaeva, G.A. Bulhalova, Russ. J. Inorg. Chem. (1966)
52.
18] M.D. Val’kovskii, P.P. Fedorov, Russ. J. Inorg. Chem. 39 (1994)
380.
19] G.M. Sheldrick, SHELXS-86, Program for the Solution of
Crystal Structures, Universitat Gottingen, 1986.
20] G.M. Sheldrick, SHELXL-97, Program for the Refinement of
Crystal Structures from Diffraction Data, Universitat Gottingen,
997.
4
¨
optical properties, possibly also for some optical
applications. Detailed structural studies of LiScF based
[
4
6
on high pressure in situ experiments have already been
performed and will be reported in the near future [29].
3
[
[
[
1
Appendix A. Supplemental Data
¨
¨
The online version of this article contains additional
supplementary data. Please visit doi:10.1016/
j.jssc.2005.04.038.
¨
¨
1
[
21] T. Hahn (Ed.), International Tables of Crystallography, Vol. A,
fourth ed. Kluwer, Dordrecht, 1995.
[22] L.G. Akselrud, P.Y. Zavalii, Y. Grin, V.K. Pecharsky, B.
¨
Baumgartner, E. Wolfel, CSD, a universal program package for
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