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Jul 2, 2015 - with that obtained from the Bravais−Friedel and Donnay−Harker. (BFDH) method. The crystal structure of CTW has been solved for the f...
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Top-Seeded Solution Growth, Structure, Morphology, and Functional Properties of a New Polar Crystal  Cs2TeW3O12 Peng Zhao, Hengjiang Cong, Xiangxin Tian, Youxuan Sun, Chengqian Zhang, Shengqing Xia, Zeliang Gao,* and Xutang Tao* State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100, China S Supporting Information *

ABSTRACT: Single crystals of the polar material Cs2TeW3O12 (CTW) with dimensions up to 26 × 18 × 4 mm3 were successfully grown using a top-seeded solution growth method. The morphologies of the as-grown crystals have been described and compared with that obtained from the Bravais−Friedel and Donnay−Harker (BFDH) method. The crystal structure of CTW has been solved for the first time using single-crystal X-ray diffraction: the compound crystallizes in polar hexagonal space group P63 (No. 173) with cell parameters a = b = 7.3279(3) Å, c = 12.4075(5) Å, Z = 2, and V = 577.00(4) Å3. Thermal analysis shows that CTW is thermally stable up to 820 °C, at which it melts incongruently. Further high-resolution X-ray diffraction experiments gave a full-width at half-maximum of the rocking curve of 33″, indicating a good crystalline quality for the as-grown crystals. Optical transmittance spectra of CTW show a broad transmission range from 410 to 5310 nm. Powder second-harmonic generation (SHG) measurements with a 1064 nm laser indicates that CTW exhibits a strong SHG efficiency of about 1.5 the one of KTiOPO4. Polarization measurements indicate that CTW is not ferroelectric; i.e., the polarization is not “switchable”. In addition, CTW is nonhygroscopic and resistant to diluted HNO3 aqua-solution.

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INTRODUCTION Noncentrosymmetric (NCS) crystals are of great interest owing to their technologically relevant physical properties such as second-harmonic generation (SHG), piezoelectricity, pyroelectricity, and ferroelectricity.1−4 Among the NCS crystals, some polar crystals which belong to the point groups 1, 2, 3, 4, 6, m, mm2, 3m, 4mm, or 6mm exhibit a macroscopic dipole moment.5 Concerning functional properties, second-order nonlinear optical (NLO) and piezoelectricity properties may be observed in NCS materials, but ferroelectricity and pyroelectricity can only be observed in polar materials. Recently, many design strategies have been discussed for creating new polar materials by incorporating NCS chromophores as building units. Therefore, under the guidance of the secondorder Jahn−Teller (SOJT) distortions, a novel kind of NCS and polar oxides have been synthesized by Halasyamani et al.6 SOJT distortions are often observed in two kinds of cations: (i) octahedrally coordinated d0 transition metals (Ti4+, V5+, Nb5+, Mo6+, W6+, etc.) and (ii) cations with stereoactive lone pairs (Se4+, Sb3+, Te4+, I5+, Pb2+, etc.), both of which are in asymmetric oxide coordination environments. If the energy gap between the highest occupied (HOMO) and lowest unoccupied (LUMO) orbitals is small and there is asymmetry allowed distortion permitting mixing of these two orbitals, the distortion would occur.7 Halasyamani et al. consider as “SOJT effects occur when the empty d-orbitals of the metal mix with the filled p-orbitals of the oxide ligands. In extended structures, this mixing results from a spontaneous distortion of the metal © 2015 American Chemical Society

cation that removes the near degeneracy of these two orbital sets.”6 There are three categories of metal cations displacements: toward an edge, a face, or a vertex of the octahedron.8 The situation with the stereoactive lone pair cations is somewhat more complex. Specifically, previous researchers argue that the interaction of the s- and p-orbitals of the metal cation with the oxide anion p-states is critical for lone-pair formation. Regardless of how the lone pair is created, its structural consequences are important, as the lone-pair “pushes” the oxide ligands toward one side of the cation, resulting in a highly asymmetric coordination environment.9 To date, a multitude of polar materials which contain these cations have been synthesized, including β-BaTeMo2O9,7 BaTeW2O9,7 Na2TeW2O9,10a and Cs2TeMo3O12.11a All of these compounds belong to polar materials and exhibit polar properties. In recent years, our group has paid considerable attention to crystal growth.11b,12−14 In 2008, β-BaTeMo2O9 single crystal growth was reprorted for the first time by our group, and its properties including SHG, piezoelectricity, pyroelectricity, and stimulated Raman scattering were also reported, demonstrating that β-BaTeMo2O9 is an excellent multifunctional crystal.13−15 Recently, large-sized single crystals, such as α-BaTeMo2O9,16 Na2TeW2O9,10b Cs2TeMo3O12,11b and Na2Te3Mo3O16,17 were grown by our group, the Halasyamani group, and the Shen Received: June 2, 2015 Revised: June 29, 2015 Published: July 2, 2015 4484

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Powder X-ray Diffraction. Powder X-ray diffraction data were collected in the 2θ range from 10° to 80° with each scan step of 0.02°/0.4 s at room temperature. The instrument we used is a BrukerAXS D8 ADVANCE X-ray diffractometer equipped with monochromated Cu Kα radiations of λ = 1.54056 Å. Single-Crystal X-ray Diffraction. A CTW crystal with dimensions of about 0.11 × 0.09 × 0.08 mm3 was first mounted on a glass fiber. Then, on a Bruker APEX-II SMART CCD diffractometer equipped with a D8 goniometer, we collected its single-crystal X-ray diffraction data at room temperature using graphite-monochromated Mo Kα radiations of λ = 0.71073 Å within the ω scan method.20 From three sets of frames, initial lattice parameters and orientation matrices were determined. Data integration and cell refinement were performed through the INTEGRATE program in the APEX-II software,20 and numerical face-indexed absorption corrections were adopted using the SCALE program for area detector.20 Thermal and Chemical Stability Analysis. The thermal stability of Cs2TeW3O12 was investigated on a TGA/DSC1/1600HT analyzer (Mettler Toledo Instruments). About 30.37 mg of Cs2TeW3O12 was placed in a platinum crucible and heated from room temperature to 900 °C at a rate of 10 °C/min under flowing nitrogen. In order to study the chemical stability of Cs2TeW3O12, two polished Cs2TeW3O12 single crystals with weights of 0.05 and 0.35 g were soaked in distilled water and diluted HNO3 solution (the volume ratio of concentrated HNO3:H2O = 1:4) for 48 h at room temperature. High-Resolution X-ray Diffraction. A Bruker-AXS D5005HR diffractometer equipped with a four-crystal Ge(220) monochromator set for Cu−Kα radiation (λ = 1.54056 Å) was used for high-resolution measurement. The generator operated with settings of 30 kV and 30 mA. The step size and step time were 0.0005° (1.8″) and 1.0 s, respectively. A polished Cs2TeW3O12 sample oriented along (0002) with dimensions 4.00 × 4.00 × 1.00 mm was used for HRXRD experiment. Linear Optical Measurements. UV−visible diffuse reflectance data for Cs2TeW3O12 was collected by a Shimadzu UV 2550 spectrophotometer equipped with an integrating sphere over the spectral

group, respectively. It is worth noting that polar hexagonal molybdenum oxide materials like Cs2TeMo3O12 have potential outstanding piezoelectric, electro-optic, and NLO properties because the dipole moments of TeO3 polyhedra align along the crystallographic c axis. Moreover, the symmetry of Cs2TeMo3O12 (P63) is higher than that of β-BaTeMo2O9 (P21) and Na2TeW2O9 (Ia), which should make the crystal processing and device design more convenient.11 However, the self-flux of Cs2TeMo3O12 exhibits high viscosity, which can lead to cracking and inclusions in the single crystal. Meanwhile, Cs2TeMo3O12 has a relatively small thermal conductivity and it may limit crystal applications. The literature shows that the viscosity of solutions containing WO3 is expected to be lower than that of MoO3 solutions.18 Therefore, Cs2TeW3O12 focused our attention since it is isostructural to Cs2TeMo3O12.19 When a supercritical hydrothermal method was used, small crystals of Cs2TeW3O12 were obtained. Unfortunately, no satisfactory structural refinements were achieved from single-crystal diffraction.19 From our former experiences on growing Cs2TeMo3O12, we believed that the flux method might be feasible and Cs2TeW3O12 would not only possess properties comparable with those of Cs2TeMo3O12 but also exhibit better thermal property. In this contribution, we report the growth of bulk Cs2TeW3O12 single crystals through a top-seeded solution growth (TSSG) method. X-ray single-crystal diffraction experiments show that the material has a polar structure of space group P63. In addition, the crystal morphologies with respect to the seed orientation, as well as their chemical and thermal stability, linear and nonlinear optical properties, polarization, and structure− property relationships, are discussed.

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EXPERIMENTAL SECTION

Polycrystalline Synthesis. Polycrystalline Cs2TeW3O12 were synthesized by standard solid-state reaction techniques. Stoichiometric amounts of Cs2CO3, (Alfa Aesar, 99.9%), TeO2 (Sinopharm Chemical Reagent Co., Ltd., 99.99%), and WO3 (Alfa Aesar, 99.8%) were ground and packed into columns. The columns were heated under air at 400 °C for 24 h and then sintered at 600 °C for 48 h with several intermittent regrindings. The power X-ray diffraction results show that the light yellow powder was pure Cs2TeW3O12. Crystal Growth of Cs2TeW3O12. The Cs2TeW3O12 single crystals were grown by a flux method employing TeO2 as a self-flux. The temperature of the furnace was heated up to 750 °C and held for 1 day to melt the mixture. Then, a Pt crucible containing Cs2CO3, TeO2, and WO3 (a molar ratio of 1:3:3) was placed in the furnace. A platinum stirrer was dipped into the solution and mechanically stirred for 1 day to melt the mixture to a homogeneous solution. Then, the platinum stirrer was substituted by a platinum wire to obtain the spontaneous nucleation of crystals. The melt was then allowed to cool at a rate of 0.5 °C/h, from 750 to 650 °C. This resulted in high-quality Cs2TeW3O12 crystals grown by spontaneous nucleation along the platinum wire during the slow-cooling process. Some hand-picked crystals were used as seeds to grow large-sized single crystals through a TSSG method. The temperature of saturation was determined by a tentative seed crystal method. A regular shaped seed crystal of Cs2TeW3O12 was attached with a platinum wire to an alumina rod, and slightly introduced into the surface of the solution surface at 5 °C above the temperature of saturation. The temperature was held for 1 h to dissolve the impurities on the seed crystal surface, and the solution was then quickly (within in 30 min) cooled to the saturation temperature. From the temperature of saturation, the solution was cooled at a rate of 0.5−1.0 °C/day until a large-sized single crystal was obtained. The crystal was pulled out of the solution and then cooled to room temperature at a rate of 5−10 °C/h.

Figure 1. Calculated and experimental powder X-ray diffraction patterns for Cs2TeW3O12.

Figure 2. Polished crystal was soaked in distilled water and in diluted HNO3 solution. 4485

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function.21 The transmission spectra of Cs2TeW3O12 were collected using a Hitachi U-4100 UV/vis/IR spectrometer from 350 to 2400 nm and a Nicolet NEXUS 670 FTIR spectrometer in the range of 2400− 5600 nm, respectively. The crystal sample for determining HRXRD was also used for optical measurements. Second-Harmonic Generation (SHG). Powder SHG measurements were performed on a modified Kurtz-NLO22 system. As the powder SHG efficiency has been shown to depend strongly on particle size, polycrystalline samples of Cs2TeW3O12 and KTiOPO4 were ground and sieved into distinct particle size ranges (28−48, 48−75, 75−109, 109−150, 150−250, 250−350 μm). The sieved KTiOPO4 powders were used as a reference. The samples were pressed between glass microscope cover slides and secured with tape in 1 mm thick aluminum holders containing a 8 mm diameter hole. The pumped laser is a Q-switched Nd:YAG laser operating at 2100 nm with a pulse width and pulse energy of 10 ns and 10 mJ at 1 Hz. An interference filter (530 ± 10 nm) and photomultiplier tube attached to a RIGOL DS1052E 50-MHz oscilloscope was used to select and detect the second-harmonic signal. No index-matching fluid was used in any of the experiments. Polarization Measurement. A (0002)-faced plate of Cs2TeW3O12 single crystal coated with silver electrode was used to measure polarization reversibility. The polarization was performed on a Radiant Technologies Precision Premier II Ferroelectric Test System with a TREK high voltage amplifier. The polarization measurements were carried out at room temperature, and the static electric field was set at 5 and 9 kV/cm, with frequencies at 1, 50, 100, 200, and 500 Hz.

Figure 3. DSC and TGA data for Cs2TeW3O12.

Figure 4. High-quality Cs2TeW3O12 crystals grown by spontaneous nucleation along the platinum wire and calculated morphology of Cs2TeW3O12 crystal.

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RESULTS AND DISCUSSION Synthesis of Polycrystalline Cs2TeW3O12. Polycrystalline Cs2TeW3O12 was obtained by the traditional solid-state reaction. The resultant light yellow solid was examined by XRD analysis. The polycrystalline phases are in good agreement with the calculated pattern. The experimental and calculated powder XRD patterns of the polycrystalline Cs2TeW3O12 are shown in Figure 1. Chemical and Thermal Stability. The weight of this polished crystal soaked in distilled water did not change when it was taken out (Figure 2). In addition, only a tiny weight loss (0.02 g) was observed for the crystal that was soaked in diluted HNO3 solution (Figure 2). It is obvious that the Cs2TeW3O12 crystal is not only nonhygroscopic but also resistant to diluted HNO3 solution. The thermal behavior of Cs2TeW3O12 was also characterized (shown in Figure 3). From the DSC and TGA curves, only one clear endothermic peak and mass loss is observed at about 820 °C. These results indicate that Cs2TeW3O12 melts incongruently. In addition, powder X-ray diffraction data

Figure 5. Simulated (a and b) and experimental (c and d) morphologies of Cs2TeW3O12 single crystals along the [211̅ ̅0] and [01̅10] directions. range of 200−800 nm. BaSO4 was used as a reference material. Reflectance spectra were converted to absorbance with the Kubelka−Munk

Figure 6. Ball-and-stick diagram of Cs2TeW3O12 crystal structure. 4486

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been grown by spontaneous nucleation during the slow-cooling process. Then, seed-crystal oriented [21̅1̅0] and [01̅10] were cut, and the well-developed and transparent single crystals with dimensions up to 25 × 10 × 5 mm3 and 26 × 18 × 4 mm3 were grown successfully by the TSSG method. The theoretical morphology of the Cs2TeW3O12 crystal is established by using the Materials Studio Modeling program23 with its structural parameters, according to the Bravais−Friedel and Donnay− Harker (BFDH) method.24 Both the bulk single crystals and predicted morphology are shown in Figure 5. As shown in Figure 5a,b, the predicted morphology exhibits (101̅0), (11̅00), (01̅10), (1̅010), (1̅100), (011̅0), and (0002) facets. The crystalline quality of the as-grown Cs2TeW3O12 crystal was checked by HRXRD and indicates that the full-width at half-maximum (FWHM) of the rocking curve is 33″ (Figure 7). Crystal Structure Determination. Cs2TeW3O12 crystallizes in the hexagonal system, space group P63 with cell parameters a = b = 7.3279(3) Å, c = 12.4075(5) Å, Z = 2, and V = 577.00(4) Å3 (Table 1). The analysis of the crystal structure shows that the (TeW3O12)2− anions form a two-dimensional layered structure with Cs+ cations between the layers for charge balance. The asymmetric unit contains two crystallographically independent Cs atoms, one independent Te atom, one independent W atom, and four independent O atoms. Both the W6+ and the Te4+ cations are in asymmetric coordination environments attributable to SOJT distortions.7 The Te4+ cations exhibit pyramidal TeO3 coordination environments with three equal Te−O bonds of 1.8866 Å (Figure 6). It is worth noting that all of the TeO 3 polyhedra “cap” one side of the

Figure 7. Rocking curve of the Cs2TeW3O12 single crystal.

of the residue after DSC and TGA unambiguously demonstrate that Cs2TeW3O12 decomposed to Cs3W6O11 as well as some unknown phase (Figure S1, Supporting Information). Therefore, large Cs2TeW3O12 single crystals must be grown by the flux method and below the decomposition temperature. Growth and Morphology of the Cs2TeW3O12 Crystals. Self-fluxes such as TeO2, WO3, and a TeO2−WO3 mixture were first examined to grow the Cs2TeW3O12 crystals. The crystals through spontaneous nucleation were physically separated from the platinum wire and verified using powder X-ray diffraction. After a great amount of attempts, the TeO2 flux was adopted to grow large crystals. As shown in Figure 4, high-quality Cs2TeW3O12 crystals with a whole calculated morphology have Table 1. Crystal Data and Structure Refinement for CTW

Cs2TeW3O12a −1

formula weight (g·mol ) temperature (K) wavelength (Å) crystal system space group unit cell dimensions (Å)

1136.97 296(2) 0.71073 hexagonal P63 (No. 173) a = 7.3279(3) b = 7.3279(3) c = 12.4075(5) 577.00(4) 2 6.544 38.583 960 0.11 × 0.09 × 0.08 3.21−26.99 −9 ≤ h ≤ 9, −9 ≤ k ≤ 9, −15 ≤ l ≤ 15 9290/838 [R(int) = 0.03 100.0% numerical 0.1400 and 0.0974 full-matrix least-squares on F2 838/1/56 1.178 R1 = 0.0124, wR2 = 0.0247 R1 = 0.0129, wR2 = 0.0248 0.003(8) 0.0159(3) 0.790 and −0.629

volume (Å3) Z calculated density (Mg·m3) absorption coefficient (mm−1) F(000) crystal size (mm3) θ range for data collection (deg) limiting indices reflections collected/unique completeness to θ = 26.99° absorption correction max. and min. transmission refinement method data/restraints/parameters goodness-of-fit on F2 final R indices [I > 2σ(I)] R indices (all data) absolute structure parameter extinction coefficient largest diff. peak and hole (e·A−3) a

Empirical formula. 4487

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Figure 8. UV−visible diffuse reflectance spectroscopy data for polycrystalline Cs2TeW3O12. The upper-right inset shows the (αhν)2−(hν) curve.

Figure 10. SHG intensity vs particle size curve for Cs2TeW3O12. The red curve drawn is to guide the eye and is not a fit to the data, and the inset is the comparative SHG signals for the powder (250−350 μm) of KTP and Cs2TeW3O12.

Figure 9. Transmission spectra of the Cs2TeW3O12 crystal: (a)UV− vis−NIR, (b) mid-IR.

(TeW3O12)2−anionic layers, which result in a large net dipole moment along the c axis. The WO6 octahedral is also distorted. Specifically, the W6+ cations are displaced toward a face of the WO6 octahedron (local C3 direction), which results in three short (1.7469(50), 1.8302(30), and 1.8467(38) Å), and three long (2.0288(35), 2.0442(29), and 2.1096(38) Å) W−O bond distances (Figure 6). The arrows in Figure 6 indicate the approximate directions of the local dipole moments on each kind of polyhedron. However, as seen in Figure 6, there are two TeO3 and six WO6 polyhedra, and their dipole moments along a and b axes totally overlapped. However, every dipole moment has components along the c axis, which results in a large dipole moment in Cs2TeW3O12 along the c axis. Linear Optical Properties. As shown in Figure 8, near the cutoff of the optical transmission, the band gap, the absorption, and the wave frequency obey the following equation

Figure 11. Polarization versus electric field plots for a (0002) faced wafer of the Cs2TeW3O12 single crystal at 4 and 9 kV/cm and at different frequencies.

to ref 19, the (αhν)2−(hν) curve was drawn in the upper-right inset of Figure 8. The calculated band gap is 2.89 eV (by fixing the tangent line of the curve and the (hν) axis). The UV− vis−NIR spectrum and mid-IR spectrum of the Cs2TeW3O12 crystal are shown in Figure 9. The UV absorption edge of Cs2TeW3O12 is located at 410 nm. In the range of 450− 5000 nm, the Cs2TeW3O12 crystal is highly transparent. The results is comparable to those of previously reported molybdate/ tungstate tellurites, such as α-BaTeMo2O9 (380 nm−5.5 μm),26a β-BaTeMo2O9 (400 nm−5.4 μm),12 Cs2TeMo3O12 (430 nm− 5.38 μm),11 Na 2TeW2O 9 (360 nm−5 μm),10 MgTeMoO6

αhν = A(hν − Eg )n /2

The band structure calculation indicates that Cs2TeW3O12 has a direct band gap, so here, n = 1 for Cs2TeW3O12.25 According 4488

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(360 nm−5.2 μm),26b Na2Te3Mo3O16 (420 nm−5.4 μm),17 and BaTeW2O9 (360 nm−5.0 μm).26c Second-Harmonic Generation. As shown in Figure 10, the second-harmonic intensity increases with particle size and exhibits a plateau from 150 μm, which means that the material can support Type I phase-match. Under the same experimental conditions, the second-harmonic signal of Cs2TeW3O12 is about 1.5 × KTP. Polarization Measurements. As Cs2TeW3O12 is a polar oxide, ferroelectric measurements were performed to investigate whether there is any polarization reversibility. As shown in Figure 11, a linear relationship between polarization and electric field was observed, which signifies that the polarization cannot be switched under an external electric field and Cs2TeW3O12 is not ferroelectric. The structure data show that the W−O bonds in Cs2TeW3O12 are strong, which makes the switching of a W6+ cation from one face to the opposite difficult. Meanwhile, the TeO3 polyhedra are also stable and are hard to invert unless in the case of bond breaking. In a word, polarization reversal in Cs2TeW3O12 is unpractical.

also extended to Dr. Romain Gautier for his help in revising the manuscript.

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(1) Lang, S. B. Phys. Today 2005, 58, 31−36. (2) Ok, K. M.; Chi, E. O.; Halasyamani, P. S. Chem. Soc. Rev. 2006, 35, 710−717. (3) Khomskii, D. I. Physics 2009, 2, 20. (4) Lang, S. B.; Das-Gupta, D. K. In Handbook of Advanced Electronic and Photonic Materials and Devices; Hari Singh, N., Ed.; Academic Press: Burlington, MA, 2001; p 1. (5) Hahn, Th., Ed. International Tables for Crystallography; Kluwer Academic: Dordrecht, The Netherlands, 2006; Vol. A (Space-Group Symmetry). (6) (a) Ok, K. M.; Halasyamani, P. S.; Casanova, D.; Llunell, M.; Alemany, P.; Alvarez, S. Chem. Mater. 2006, 18, 3176−3183. (b) Bersuker, I. B. Chem. Rev. 2001, 101, 1067−1114. (c) Halasyamani, P. S.; Poeppelmeier, K. R. Chem. Mater. 1998, 10, 2753−2769. (7) Ra, H. S.; Ok, K. M.; Halasyamani, P. S. J. Am. Chem. Soc. 2003, 125, 7764−7765. (8) Goodenough, J. B. Annu. Rev. Mater. Sci. 1998, 28, 1−27. (9) Halasyamani, P. S. Chem. Mater. 2004, 16, 3586−3592. (10) (a) Goodey, J.; Broussard, J.; Halasyamani, P. S. Chem. Mater. 2002, 14, 3174−3180. (b) Zhang, W. G.; Li, F.; Kim, S.-H.; Halasyamani, P. S. Cryst. Growth Des. 2010, 10, 4091−4095. (11) (a) Balraj; Vidyasagar, K. Inorg. Chem. 1998, 37, 4764−4774. (b) Zhang, J. J.; Tao, X. T.; Sun, Y. X.; Zhang, Z. H.; Zhang, C. Q.; Gao, Z. L.; Xia, H. B.; Xia, S. Q. Cryst. Growth Des. 2011, 11, 1863− 1868. (12) Zhang, W. G.; Tao, X. T.; Zhang, C. Q.; Gao, Z. L.; Zhang, Y. Z.; Yu, W. T.; Cheng, X. F.; Liu, X. S.; Jiang, M. H. Cryst. Growth Des. 2008, 8, 304−307. (13) Gao, Z.; Tao, X.; Yin, X.; Zhang, W.; Jiang, M. Appl. Phys. Lett. 2008, 93, 252906. (14) Gao, Z. L.; Liu, S. D.; Zhang, S. J.; Zhang, W. G.; He, J. L.; Tao, X. T. Appl. Phys. Lett. 2012, 100, 261905. (15) (a) Zhang, W. G.; Tao, X. T.; Zhang, C. Q.; Zhang, H. J.; Jiang, M. H. Cryst. Growth Des. 2009, 9, 2633−2636. (b) Yu, Q. X.; Gao, Z. L.; Zhang, S. J.; Zhang, W. G.; Wang, S. P.; Tao, X. T. J. Appl. Phys. 2012, 111, 013506. (16) Zhang, J. J.; Zhang, Z. H.; Zhang, W. G.; Zheng, Q. X.; Sun, Y. X.; Zhang, C. Q.; Tao, X. T. Chem. Mater. 2011, 23, 3752−3761. (17) Zhang, W. L.; Sun, J. F.; Wang, X. Q.; Shen, G. Q.; Shen, D. Z. CrystEngComm 2012, 14, 3490−3494. (18) Iliev, K.; Peshev, P.; Nikolov, V.; Koseva, I. J. Cryst. Growth 1990, 100, 225−232. (19) Goodey, J.; Ok, K. M.; Broussard, J.; Hofmann, C.; Escobedo, F. V.; Halasyamani, P. S. J. Solid State Chem. 2003, 175, 3−12. (20) Bruker APEX2; Bruker Analytical X-ray Instruments, Inc.: Madison, WI, 2005. (21) Kubelka, P.; Munk, F. Z. Z. Tech. Phys. 1931, 12, 593−601. (22) Kurtz, S. K.; Perry, T. T. J. Appl. Phys. 1968, 39, 3798. (23) Accelrys MS Modeling Getting Started; Accelrys Software Inc.: San Diego, CA, 2006. (24) (a) Bravais, A. Etudes Crystallographiques; Academie des Sciences: Paris, 1913. (b) Donnay, J. D. H.; Harker, D. Am. Mineral. 1937, 22, 463. (25) Butler, M. A. J. Appl. Phys. 1977, 48, 1914−1920. (26) (a) Zhang, J. J.; Zhang, Z. H.; Sun, Y. X.; Zhang, C. Q.; Tao, X. T. CrystEngComm 2011, 13, 6985−6990. (b) Zhang, J. J.; Zhang, Z. H.; Sun, Y. X.; Zhang, C. Q.; Zhang, S. J.; Liu, Y.; Tao, X. T. J. Mater. Chem. 2012, 22, 9921−9927. (c) Zhang, Z. H.; Tao, X. T.; Zhang, J. J.; Sun, Y. X.; Zhang, C. Q.; Li, B. CrystEngComm 2013, 15, 10197− 10204.

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CONCLUSIONS We have grown for the first time large-sized single crystals of Cs2TeW3O12 with dimensions up to 26 × 18 × 4 mm3 using a TSSG method. X-ray single-crystal diffraction results show that Cs2TeW3O12 crystallizes in the noncentrosymmetric and polar hexagonal space group P63 (No. 173) with cell parameters a = b = 7.3279(3) Å, c = 12.4075(5) Å, Z = 2, and V = 577.00(4) Å3. The morphologies with respect to different seed orientations are discussed and compared with that simulated from the Bravais−Friedel and Donnay−Harker (BFDH) method. The result of the high-resolution X-ray diffraction indicates a good quality of the as-grown crystals, which has a full-width at half-maximum (FWHM) of the rocking curve of 33″. Optical transmittance spectra of CTW show a broad transmission range from 410 to 5310 nm. Its strong powder second-harmonic generation makes the Cs2TeW3O12 crystal an excellent candidate for mid-IR NLO.

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ASSOCIATED CONTENT

S Supporting Information *

X-ray crystallographic files (in CIF format) for the Cs2TeW3O12 single crystal, crystallographic data, powder XRD pattern, and a photo of the seed crystal. The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.cgd.5b00753.

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REFERENCES

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (X.T.). *E-mail: [email protected] (Z.G.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We gratefully acknowledge the financial support from the State National Natural Science Foundation of China (Grant Nos. 51321091, 51272129, 50802054, and 51227002) and the Program of Introducing Talents of Disciplines to Universities in China (111 program no. b06015). We also thank the Shandong Provincial Natural Science Foundation, China (ZR2010EQ010). Thanks are 4489

DOI: 10.1021/acs.cgd.5b00753 Cryst. Growth Des. 2015, 15, 4484−4489