Hydrothermal Crystal Growth of Mixed Valence Cs2SbBr6

Article abstract of DOI:10.1021/acs.cgd.9b00481

Mixed valence perovskite materials present an opportunity to understand how structural motifs influence electronic properties in semiconducting materials. Here, we report the preparation of high-quality single crystals of the mixed valence compound Cs

Full text of DOI:10.1021/acs.cgd.9b00481

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Article
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Hydrothermal Crystal Growth of Mixed Valence CsSbBr
Victoria E. Combs, Iain W. H. Oswald, and James R. Neilson
Cryst. Growth Des., Just Accepted Manuscript • Publication Date (Web): 22 May 2019
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Hydrothermal Crystal Growth of Mixed Valence
Cs2SbBr6
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∗
Victoria E. Combs, Iain W. H. Oswald, and James R. Neilson
Department of Chemistry, Colorado State University, Fort Collins, CO, 80523-1872
E-mail: james.neilson@colostate.edu
Abstract
Mixed valence perovskite materials present an opportunity to understand how structural
motifs influence electronic properties in semiconducting materials. Here, we report the prepa-
ration of high-quality single crystals of the mixed valence compound Cs2SbBr6, which can also
be written as Cs4SbIIISbVBr12. We have determined the solubility of Cs2SbBr6 under myriad
reaction conditions which permits prescription of conditions to grow large, high-quality single
crystals. Single crystal X-ray diffraction confirms the crystal structure of this material and
shows that the crystal structure is preserved from T = 100 to 380 K, and the heat capacity mea-
surements show an absence of any anomalies due to phase transitions between T = 2 to 150 K.
Furthermore, we illustrate that the mixed valence of the Sb centers in this material charge order
into interpenetrating diamond lattices. We also show that the habit of Cs2SbBr6 single crystals
is defined by well-formed faces along the close packed planes of bromine atoms.
Introduction
Semiconductors incorporating mixed valence ions continue to garner interest due to the variety
of fascinating properties that result from the complex electronic structures. The rich magnetic
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phase diagram and metal-insulator behavior of manganese oxide perovskites1 and the supercon-
ductivity of bismuth oxide based perovskites2 are two famous instances in which the emergent
electronic ground states result from the incorporation of mixed valence metals. Although the elec-
tronic ground states of mixed valence materials have been heavily studied, less is understood about
the nature of excited states resulting from mixed valence systems. For example, little is known
about the states created from the charge transfer between mixed valence species caused by vis-
ible light absorption. The excitement surrounding the high-performance halide semiconductors
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such as CH3NH3PbI3 and Cs2SnI6 encourages renewed interest in, and expansion of, the early
studies on antimony-based halides,5 such as in the vacancy-ordered double perovskite (VODP)
Cs2SbBr6.6
Mixed valence VODP halides can be described by the formula “A4BIIIBVX12”, as the formally
tetravalent B site metal charge disproportionates from B4+ into B5+ and B3+ when considering
formal charge.5 In Cs2SbBr6, this charge disproportionation is accompanied by distortion from Oh
symmetry of the [SbBr6] octahedra to D2h symmetry, where the axial bonds are elongated and the
equatorial bonds are shortened.7 The ordering of [SbX6]– and [SbX6]3 – octahedra results in the
tetragonal space group I41/amd. These materials also exhibit visible and near-IR light absorption
due to charge transfer from the fully occupied Sb3+ 5s orbitals to the unoccupied 5s orbitals of
Sb5+.8,9 The charge transfer processes have also been shown to be intimately coupled to vibrational
modes within the material.10 However, detailed investigations into electronic transport awaits the
synthesis of single crystalline specimens of these materials.
Here, we report the hydrothermal preparation of single crystalline mixed valence VODP Cs2SbBr6.
The solubility behavior of the system has been investigated under many different reaction condi-
tions. The results allow prescription of suitable concentrations which produce large crystal growth
at various temperatures, as experimentally verified. The crystal structure of Cs2SbBr6 was investi-
gated using single crystal X-ray diffraction (SCXRD) and is consistent with previous reports.
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Methods and Materials
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Preparation of Cs2SbBr6 Powder
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Polycrystalline powders of Cs2SbBr6 were synthesized via solution precipitation following previ-
ous reports.7 Sb powder (∼0.060 g, NOAH, 99.5%) was added to ∼5 mL aqueous HBr (Sigma-
Aldrich, 48%) with stirring, after which ∼100 µL of Br2 (Alfa Aesar, 99.8%) liquid was pipetted
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into the mixture. The mixture was then heated to ∼60 C with magnetic stirring until all Sb pow-
der dissolved. A solution of Cs2CO3 (∼0.160 g, Alfa Aesar, 99.9%) dissolved in 3 mL aqueous
HBr (to produce a CsBr solution) was then added to the Sb solution with stirring. A fine black
precipitate formed upon addition of the CsBr solution and the reaction was stirred for an additional
30 min. The powder was allowed to settle before the supernatant was removed. The powder was
then dried in a desiccator that also contained a beaker of concentrated H2SO4 (EMD, Millipore,
98%) and a beaker containing ∼100 µL of Br2 liquid. Cs2SbBr6 powder was synthesized up to a
purity of 99.1(1) wt% , and powder X-ray diffraction (PXRD) data are consistent with the reported
crystal structure.7 The purity of powder was calculated from Reitveld refinement. The major im-
purities determined by Rietveld refinement are the cesium and bromine deficient phase Cs3Sb2Br9
and CsBr. Allowing the powder to dry in air or under N2 results in decomposition to the yellow
competing phase Cs3Sb2Br9 and CsBr.
Hydrothermal Growth
Hydrothermal crystallization was carried out in Parr Instrument Company Model 4749 and 4745
acid digestion vessels (23 mL and 45 mL capacity respectively) in a Binder APT.line FP convection
oven. To ensure the vessels were free of contamination prior to crystallization experiments, the
◦
autoclaves were treated with ∼8 mL HNO3 and heated at 150 C for 24 h. The vessels were
◦
subsequently charged with ∼8 mL unpurified H2O and heated at 150 C for 24 h to rinse. This
rinse was repeated until contents of the vessel were pH neutral. Each autoclave was charged with
previously-prepared Cs2SbBr6 powder, 2-8 mL HBr, and 4 molar equivalents of Br2 relative to
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Cs2SbBr6. The reactions were heated to 150 C over 1 h and then dwelled at temperature for 5 h
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before being slowly cooled over 7 days. All crystals were stored in a desiccator that also contained
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a beaker of concentrated H2SO4 and a beaker containing ∼100 µL of Br2 liquid. To clean the
◦
vessels after each reaction the vessels were charged with unpurified H2O and heated at 150 C for
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24 h.
Solubility Experiments
Between 10 mg to 250 mg of Cs2SbBr6 powder were placed in each of 6 autoclaves. 2.0 mL of
HBr was added to each autoclave followed by 4 molar equivalents (with respect to powder) of
Br2. The estimated nominal concentrations of Cs2SbBr6 ranged from 0.000012-0.28 M. Reaction
◦
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vessels were heated to 125 C, 150 C, and 175 C and allowed to dwell for 1 h before being
cooled to room temperature. The vessels were then opened and inspected for undissolved powder.
Solubility behavior was assessed by the presence of undissolved powder or the lack thereof.
Characterization
Laboratory powder X-ray diffraction (PXRD) data were collected on a Bruker D8 Discover X-ray
diffractometer using Cu Kα radiation and a Lynxeye XE-T position sensitive detector. All samples
were ground in an agate mortar and pestle before being affixed to a “Zero Diffraction” silicon
R
wafer with a small amount of Vaselineꢀ. Quantitative analysis of PXRD data was accomplished
by the Rietveld method as implemented in GSAS/EXPGUI11 (Figure S3).
Single-crystal X-ray diffraction (SCXRD) was performed using a Bruker D8 Quest single crys-
tal X-ray diffractometer with a microfocus Mo Kα radiation source and Photon 50 CMOS half-
plate detector. Data collected at T = 100 K were from a single crystal mounted on a MiTeGen
R
tip using Paratoneꢀ oil. Both T = 300 K and T = 380 K measurements were performed using a
single crystal affixed to a glass fiber with epoxy.
The initial structural model was obtained from the previously reported crystal structure which
was further refined using SHELXTL Version 2017/1.12 Bruker SAINT was used for integration
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and scaling of collected data and SADABS was used for absorption correction.13 VESTA was
used to render all crystal structures.14
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Heat capacity measurements were performed on pelleted samples using the quasi-adiabatic
heat-pulse technique implemented in the Quantum Design, Inc., PPMS at T = 2-150 K, equilibrat-
ing for four time constants. Laue diffraction was performed on a back-reflection Laue diffractome-
ter from Photonic Science and Engineering, Ltd. with a source to sample distance of 46.41 mm.
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Results and Discussion
The solubility behavior of Cs2SbBr6 was investigated to provide insight into the crystallization
process under hydrothermal reaction conditions. The reactions with the highest concentration of
powder that fully dissolve at a specific temperature comprise the solubility curve of the system, as
shown in Figure 1. From this curve, we estimate the molar solubility at each reaction temperature
(Table 1).
Figure 1: Solubility behavior of Cs2SbBr6 during hydrothermal reactions at various temperatures
As the reaction temperature increases, the concentration at which full solubilization of powder
occurs also increases. We find that the largest crystals form just below the solubility curve. The
largest crystals produced at 125◦C were grown around concentrations of 0.1 M (Fig 1b).
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Table 1: Molar solubility of Cs2SbBr6 for each hydrothermal crystal growth reaction temperature
Temperature (◦C) Molar Solubility (M)
125
150
175
0.01447
0.02883
0.05767
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Preparation of large single crystals also requires sufficient volume of mother liquor. Crystal
growth experiments in volumes ranging from 1 mL to 8 mL while concentration was constant
suggest that larger, higher quality crystals are formed with a higher volume. We hypothesize that
this is due to increased convective mixing which occurs in higher volume samples compared to
lower volume samples.
Crystal growth experiments performed at 175◦C with a concentration of 0.028 M reproducibly
yields 3 to 4 mm on-a-side single crystals(Fig 1c). At concentrations of 0.057 M, agglomerated
crystals are produced along with several small single crystals (Fig 1d). This is likely due to the high
concentration precluding all powder from dissolving during heating and results in powder-induced
nucleation points.
Cs2SbBr6 crystallizes in the tetragonal I41/amd space group and adopts a VODP structure
where each Sb center is octahedrally coordinated to six Br– with Cs+ situated at the A site. In their
report of the crystal structure of Cs2SbBr6, Prassides and Day determined that the bond lengths
of Sb-Br differ between the SbIII and SbV sites, making each Sb site crystallographically distinct,
suggesting a chemical formula of “Cs4SbIIISbVBr12”.7 The slight differences in bond length be-
tween SbIII-Br and SbV-Br order crystallographically and cause the cubic unit cell to double along
the c axis, forming a supercell and an overall tetragonal unit cell. Precession images produced
during SCXRD data collection are shown in Figure 3 and feature intense spots corresponding to
a nominally cubic cell while the weaker reflections in between are evidence of the superlattice
reported in this material.8
To determine the crystal structure, Prassides and Day relied on powder neutron diffraction data
collected at T = 4.7 K. The authors reported several peaks in their diffraction pattern which could
not be identified as impurities or the lower symmetry space group I41/a.7 SCXRD data was ob-
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Figure 2: a Crystal structure of Cs2SbBr6 showing one slice of octahedra and b showing the
absence of covalent connectivity between octahedra. c Lines drawn between like Sb centers to
show the interpenetrating diamond lattices created by the charge ordering of Sb centers. Cs is light
gray, SbIII is dark blue, SbV is magenta, and Br is orange. Br has been omitted in b for clarity.
tained at 380 K, 300 K, and 100 K to determine if Cs2SbBr6 undergoes crystallographic phase
transitions that could account for these peaks. The data collected at all three temperatures are
consistent with the original structure reported by Prassides and Day, indicating that the crystallo-
graphic structure of Cs2SbBr6 is preserved between 100 K and 380 K. Furthermore, experimental
determination of the specific heat between T = 2-150 K does not reveal any enthalpy-releasing
transitions (Fig 4).
Table 2: Comparison of crystal structure determination results from SCXRD data collected at
300 K. and 380 K and original crystal structure determination from powder neutron diffraction
data collected at 4.7 K.7 Further crystallographic details are available in Table S1.
Crystallographic Data
Temperature
Space Group
4.7 K7
100K
300 K
380 K
I41/amd
I41/amd
I41/amd
I41/amd
˚
a, A
10.7320(1) 10.7535(8) 10.842(3) 10.888(3)
21.7442(2) 21.6794(16) 21.91(15) 21.979(6)
˚
c, A
III
˚
˚
Avg Sb –Br Bond Length, A 2.733(2)
Avg Sb –Br Bond Length, A
2.7672(7) 2.7842(9) 2.7897(12)
2.5736(2) 2.5661(3) 2.5627(12)
V
2.580(5)
Based on these data, Cs2SbBr6 appears to undergo positive thermal expansion upon heating
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Figure 3: Single crystal XRD precession images collected at 380 K along the (0kl) direction show-
ing clarity and intensity of reflections. The reflections corresponding to the cubic lattice observed
for most VODPs are especially intense and those corresponding to the tetragonal superlattice occur
in between the more intense cubic reflections.
although the average bond lengths of SbV-Br contract as temperature increases. Bond length con-
traction has been reported to stem from continuous charge transfer in SrCu3Fe4O12 15 so it is likely
that the well-known charge transfer in these materials is responsible for the SbV-Br bond length
contraction. Similar behavior in the CsSnBr3 perovskite has been reported and is likely to mani-
fest due to stereochemically active lone pairs on the Sn center.16 However in Cs2SbBr6, we find
no contraction of the SbIII-Br bonds, allowing us to conclude that stereochemically active lone
pairs on the SbIII center are unlikely to be the source of the bond length contraction exhibited by
Cs2SbBr6.
Bond valence sum calculations for the Sb centers were performed to elucidate the valence of
each Sb center and to determine the degree of delocalization of charge between metal centers.17
Calculated bond valences suggest the Sb centers retain oxidation states consistent with localized
SbIII and SbV charges.
Table 3: Bond valence sums calculated from SCXRD data collected at 300 K.
Atom 300 K R0
β
SbIII 3.0
SbV
4.7
2.51 0.37
2.48 0.37
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Figure 4: Heat capacity data for Cs2SbBr6 showing a lack of phase transitions between T = 2-
150 K.
Double perovskites tend to order in a checkerboard pattern in order to minimize the energy
from electrostatic interactions.18 However, this checkerboard motif is not observed in Cs2SbBr6.
The charge ordering of Sb centers can be described as two interpenetrating diamond lattices of like-
valence antimony. Figure 2b shows that SbIII and SbV centers each form a diamond lattice to create
a charge ordering pattern in Cs2SbBr6 that resembles Cu2O elongated along one crystallographic
axis.19
Cs2SbBr6 forms shiny black crystals with a variety of habits and well defined, smooth faces as
shown in Figure 1. Usually the habit forms as a truncated octahedron and appears nearly hexagonal.
Insight into the crystal habit is provided by performing Laue diffraction on large single crystals.
Mounting crystals such that their largest faces are orthogonal to the incident beam, we readily iden-
¯
tified the (001) zone axes, as illustrated in Figure 5 and Figure S1 . The habit of Cs2SbBr6 crystals
is rationalized by considering the arrangement of octahedra in the crystal structure of this material.
The apparent zero-dimensional connectivity of Cs2SbBr6 creates natural cleavages which stabilize
crystal face formation as shown in Figure 2c. This formation yields no dangling Sb-Sb bonds and
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¯
Figure 5: Laue diffraction image showing the a (001) zone axis and b the corresponding fit with
¯
selected points indexed. c shows the crystal structure of Cs2SbBr6 with the (001) plane indicated
in pink.
can be electrostatically screened by the protic, polar solvent. Further Laue experiments suggest
that a large crystal face can also be preferentially formed along the {112} planes of Cs2SbBr6 as
shown in Figure S2. This family of planes cuts through the close-packed sublattice of bromine
atoms forming a stable plane for growth of a stable face. These planes were identified by perform-
ing Laue diffraction at a perpendicular face and using the stereographic projection to determine the
face 90◦ from the diffracted plane. It is probable that both the {112} and {001} form comparably
stable crystal faces and that individual crystals can form large faces along these planes depending
on their habit. The octahedral faces of the crystal habit are thus likely composed of the {112}
faces, comprised of the close-packed anionic planes.
Conclusions
Hydrothermal reactions in aqueous HBr are used to produce large single crystals of the defect per-
ovskite Cs2SbBr6. The solubility behavior of the compound is reported at multiple temperatures.
Specific heat measurements from 2-150 K suggest an absence of any phase transitions. When
compared with SCXRD, we conclude that the crystal structure of Cs2SbBr6 is preserved from T
= 2-380 K. Furthermore, examination of the crystal structure shows that the mixed valence Sb
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centers in Cs2SbBr6 produce a charge ordering pattern in which the Sb centers order into interpen-
etrating diamond lattices. The habit of single crystalline Cs2SbBr6 is defined by large faces along
close-packed planes of anions or between octahedra.
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Acknowledgments
This work was supported by Grant DE-SC0016083 funded by the U.S. Department of Energy,
Office of Science. J.R.N. and V.E.C. acknowledge support from Research Corporation for Science
Advancement through a Cottrell Scholar Award, and J.R.N. thanks the A.P. Sloan Foundation for
assistance provided from a Sloan Research Fellowship. V.E.C. thanks Dr. A.E. Maughan, D.R.
Yahne, and Dr. K.A. Ross for assistance.
Additional Information
Supporting Info
Crystallographic information files (CIFs) Laue diffraction images and fits for (001) and (112)
planes Crystallographic details for Cs2SbBr6 at 100 K, 300 K, and 380 K. Powder X-ray diffraction
of Cs2SbBr6
Author Information
Corresponding Author
james.neilson@colostate.edu
Notes
The authors declare no competing financial interest.
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References
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(1) Coey, J.; Viret, M.; Von Molnar, S. Mixed-valence manganites. Adv. Phys. 1999, 48, 167–293.
8
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(2) Cava, R.; Batlogg, B.; Krajewski, J.; Farrow, R.; Rupp Jr, L.; White, A.; Short, K.; Peck, W.;
Kometani, T. Superconductivity near 30 K without copper: the Ba0.6K0.4BiO3 perovskite.
Nature 1988, 332, 814.
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42
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44
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(3) Zhao, D.; Wang, C.; Song, Z.; Yu, Y.; Chen, C.; Zhao, X.; Zhu, K.; Yan, Y. Four-terminal all-
perovskite tandem solar cells achieving power conversion efficiencies exceeding 23%. ACS
Energy Lett. 2018, 3, 305–306.
(4) Maughan, A. E.; Ganose, A. M.; Bordelon, M. M.; Miller, E. M.; Scanlon, D. O.; Neil-
son, J. R. Defect tolerance to intolerance in the vacancy-ordered double perovskite semicon-
ductors Cs2SnI6 and Cs2TeI6. J. Am. Chem. Soc. 2016, 138, 8453–8464.
(5) Prassides, K.; Day, P.; Cheetham, A. K. Anion ordering in mixed valence dicesium hex-
achloroantimonate (Cs2SbCl6) and related salts. J. Am. Chem. Soc. 1983, 105, 3366–3368.
(6) Maughan, A. E.; Ganose, A. M.; Scanlon, D. O.; Neilson, J. R. Perspectives and Design Prin-
ciples of Vacancy-Ordered Double Perovskite Halide Semiconductors. Chem. Mater. 2019,
(7) Prassides, K.; Day, P.; Cheetham, A. K. Crystal structures of mixed-valency and mixed-metal
salts A2MI0I.I5SbV0.5X6 (A= Rb, Cs; M= Sb, Bi, In, Tl, Fe, Rh; X= Cl, Br). A powder neutron
diffraction study. Inorg. Chem. 1985, 24, 545–552.
(8) Day, P. Molecules Into Materials: Case Studies in Materials Chemistry—Mixed Valency,
Magnetism and Superconductivity; World Scientific, 2007; pp 120–124.
(9) Atkinson, L.; Day, P. Charge transfer in mixed-valence solids. Part IV. Electronic spectra of
hexachloroantimonates (III, V). J. Chem. Soc. 1969, 2423–2431.
(10) Clark, H.; Swanson, B. I. Effects of outer-sphere electron transfer on the vibrational spectrum
of dicesium antimony hexachloride. J. Am. Chem. Soc. 1981, 103, 2928–2933.
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(11) Toby, B. H. EXPGUI, a graphical user interface for GSAS. J. Appl. Crystallogr. 2001, 34,
5
6
210–213.
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8
9
(12) Sheldrick, G. M. A short history of SHELX. Acta Crystallogr. A. 2008, 64, 112–122.
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(13) Bruker, S. Version 6.02 (includes XPREP and SADABS). Bruker AXS Inc., Madison, Wis-
consin, USA 1999,
(14) Momma, K.; Izumi, F. VESTA: a three-dimensional visualization system for electronic and
structural analysis. J. Appl. Crystallogr. 2008, 41, 653–658.
(15) Tilley, R. J. Perovskites: structure-property relationships; John Wiley & Sons, 2016.
(16) Fabini, D. H.; Laurita, G.; Bechtel, J. S.; Stoumpos, C. C.; Evans, H. A.; Kontos, A. G.;
Raptis, Y. S.; Falaras, P.; Van der Ven, A.; Kanatzidis, M. G.; Seshadri, R. Dynamic Stere-
ochemical Activity of the Sn2+ Lone Pair in Perovskite CsSnBr3. J. Am. Chem. Soc. 2016,
138, 11820–11832.
(17) Brown, I. D. Bond Valences; Springer, 2013; pp 11–58.
(18) Howard, C. J.; Kennedy, B. J.; Woodward, P. M. Ordered double perovskites–a group-
theoretical analysis. Acta Crystallogr. B. 2003, 59, 463–471.
(19) Niggli, P. XII. Die Kristallstruktur einiger Oxyde I. Z. Kristallogr. Cryst. Mater. 1922, 57,
253–299.
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Crystal Growth & Design
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For Table of Contents Use Only
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Hydrothermal Crystal Growth of Mixed Valence Cs2SbBr6
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Victoria E. Combs, Iain W. H. Oswald, James R. Neilson
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Synopsis
The preparation of high-quality single crystals of the mixed valence compound Cs2SbBr6 via hy-
drothermal synthesis is reported. Single crystal X-ray diffraction in conjunction with heat capacity
measurements suggest an absence of any phase transitions between T = 2 to 380 K. Laue diffraction
shows that Cs2SbBr6 crystals form large faces along the (001) and (112) planes.
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