On the basis of their short ultraviolet (UV) absorption edges, phosphates are ideal candidates for deep-UV nonlinear optical (NLO) applications. However, their often-weak second-harmonic generating (SHG) responses reduce their NLO applications. It has been demonstrated that the SHG response in polyphosphates or orthophosphates could be enhanced by highly polymerized P–O groups or aligned nonbonding O-2p orbitals of isolated PO4 units. Herein, we report on the design and synthesis of two pyrophosphates, K4Mg4(P2O7)3 and Rb4Mg4(P2O7)3, with potential NLO applications. Both materials exhibit relatively large SHG responses with 1064 nm radiation, 1.3× and 1.4× KH2PO4 (KDP) for K4Mg4(P2O7)3 and Rb4Mg4(P2O7)3, respectively. In addition, absorption edges below 200 nm were observed for both materials. For K4Mg4(P2O7)3, single crystal vacuum-UV transmission measurements revealed an absorption edge of 170 nm. First-principles electronic structure calculations identify that the NLO responses arise from the presence of the corner-connected [Mg4P6O21] double layers. We also investigated these compounds using hybrid density functionals, which are found to produce much better agreement with the experimental optical results. Finally, we detail the structural distortions giving rise to the NLO responses. Our results indicate that phosphates with low polymerized P–O groups, such as pyrophosphates, may exhibit large SHG responses if their structures are properly designed.

AbstractNonlinear optical (NLO) materials are of intense academic and technological interest attributable to their ability to generate coherent radiation over a range of different wavelengths. The requirements for a viable NLO material are rather strict, and their discovery has mainly been serendipitous. This study reports synthesis, characterization, and, most importantly, growth of large single crystals of a technologically viable NLO material—Rb3Ba3Li2Al4B6O20F. Through the judicious selection of cations, Rb3Ba3Li2Al4B6O20F exhibits a 3D structure that facilitates the growth of large single crystals along the optical axis direction. Measurements on these crystals indicate that Rb3Ba3Li2Al4B6O20F exhibits a moderate birefringence of 0.057 at 1064 nm enabling Type I phase-matching down to 243 nm. Theoretical calculations indicate the symmetry adapted mode displacement (SAMD) parameter scales with the second-harmonic generation intensity.

Large, centimeter size, single crystals of the UV nonlinear optical material KSrCO3F were successfully grown by a top seeded solution growth (TSSG) method. The morphology and quality of as-grown single crystals with different rotation speeds are discussed. UV-vis-NIR transmission spectra indicate an absorption edge of 195 nm. In addition, the refractive indices were measured at five different wavelengths from 450.2 to 1062.6 nm and revealed a birefringence of 0.1117 @ 532 nm and 0.1049 @ 1064 nm. The calculated phase-matching curves indicate that KSrCO3F can achieve both type I and type II phase-matching in a broad fundamental wavelength range from 400 to 1200 nm that covers technologically important 532 and 1064 nm radiation. To determine the individual non-linear optical coefficients, Maker-fringe measurements were performed. A value of d22 = 0.50 pm V−1 was measured. Finally, using a 6 ns Nd:YAG laser operating at 15 Hz, a laser damage threshold (LDT) of over 700 MW cm−2 was measured. Our results indicate that single crystal KSrCO3F is an excellent UV second-order nonlinear optical material.

Noncentrosymmetric mixed-metal carbonate fluorides are promising materials for deep-ultraviolet (DUV) nonlinear optical (NLO) applications. We report on the synthesis, characterization, structure–property relationships, and electronic structure calculations on two new DUV NLO materials: KMgCO3F and Cs9Mg6(CO3)8F5. Both materials are noncentrosymmetric (NCS). KMgCO3F crystallizes in the achiral and nonpolar NCS space group P6̅2m, whereas Cs9Mg6(CO3)8F5 is found in the polar space group Pmn21. The compounds have three-dimensional structures built up from corner-shared magnesium oxyfluoride and magnesium oxide octahedra. KMgCO3F (Cs9Mg6(CO3)8F5) exhibits second-order harmonic generation (SHG) at both 1064 and 532 nm incident radiation with efficiencies of 120 (20) × α-SiO2 and 0.33 (0.10) × β-BaB2O4, respectively. In addition, short absorption edges of <200 and 208 nm for KMgCO3F and Cs9Mg6(CO3)8F5, respectively, are observed. We compute the electron localization function and density of states of these two compounds using first-principles density functional theory, and show that the different NLO responses arise from differences in the denticity and alignment of the anionic carbonate units. Finally, an examination of the known SHG active AMCO3F (A = alkali metal, M = alkaline earth metal, Zn, Cd, or Pb) materials indicates that, on average, smaller A cations and larger M cations result in increased SHG efficiencies.

A family of six nonlinear optical (NLO) materials, A3B3CD2O14 (A = Sr, Ba, or Pb; B = Mg or Zn; C = Te or W; and D = P or V), has been synthesized and characterized. In addition to the synthesis and crystal structures, comprehensive characterization of these compounds includes second harmonic generation (SHG) measurements, theoretical calculations, infrared and diffuse reflectance spectroscopies, and thermogravimetric measurements. We find that all of the reported materials are SHG-active at 1064 nm, with responses ranging from 2.8 to 13.5 × KDP, and exhibit absorption edges in the mid- to deep-ultraviolet regime. By systematically replacing the A, B, C, and D cations, we are able to tune these properties and investigate the role of different NLO-active structural units in producing the SHG responses. Specifically, our electronic structure calculations reveal that the presence of Pb2+ on the A-site and Te6+ on the C-site is critical for generating a large SHG response. The synthesis and structure–property relationships described in this family of materials will enable the design and discovery of new NLO materials.

Deep ultraviolet (absorption edge <200 nm, band gap >6.2 eV) nonlinear optical (NLO) materials are of current interest owing to their technological applications and materials design challenges. Technologically, the materials are used in laser systems, atto-second pulse generation, semiconductor manufacturing, and photolithography. Designing and synthesizing a deep UV NLO material requires crystallographic non-centrosymmetry, a wide UV transparency range, a large second-harmonic generating coefficient (dij > 0.39 pm/V), moderate birefringence (Δn ∼ 0.07), chemical stability and resistance to laser damage, and ease in the growth of large high-quality single crystals. This review examines the known deep UV NLO materials with respect to their crystal structure, band gap, SHG efficiency, laser damage threshold, and birefringence. Finally, future directions with respect to new deep UV NLO materials are discussed.

We report on the crystal growth, linear, and nonlinear optical properties of LiNa5Mo9O30. The refractive indices were measured, and a very large birefringence of 0.2545 at 450.2 nm was determined. In addition, calculated phase-matching curves indicate that LiNa5Mo9O30 can achieve noncritical type I and type II phase-matching (NCPM) for incident 1064 nm radiation. Maker fringe measurements, to determine individual nonlinear optical coefficients, were also performed on the crystals resulting in d31 = 1.4 pm/V, d32 = 4.3 pm/V, and d33 = 1.1 pm/V. The laser damage threshold (LDT) is around 1.2 GW/cm2 at 1064 nm using a 6 ns Nd:YAG laser operating at 5 Hz. The quality of the crystals was measured by high resolution X-ray diffraction rocking curve measurements that revealed a full width at half-maximum (fwhm) of 59″ from the (001) reflection. The absorption edge was determined to be 357 nm, with transmission up to 5.26 μm. Our results indicate that single crystal LiNa5Mo9O30 is an excellent polarizer as well as second-order nonlinear optical material.

A new d0 transition metal tellurite, Na6Te4W6O29, was synthesized by solid-state methods. The material crystallizes in monoclinic space group P21/c (No. 14) with the following values: a = 7.3297(3) Å, b = 21.9057(9) Å, c = 10.2871(3) Å, β = 133.490(2)°, and Z = 2. Additionally, large crystals of Na6Te4W6O29 (13 mm × 11 mm × 10 mm) and Na2TeW2O9 (23 mm × 5 mm × 3 mm) were grown by the top seeded solution growth method. In addition to the crystal growth, refractive indices were measured, and the Sellmeier equations were fitted by using the minimum deviation technique. Interestingly, the two reported compounds exhibit relatively large birefringences: Δn3 = nz – nx = 0.0828–0.1248 from 1062.6 to 450.2 nm for Na6Te4W6O29, and Δn3 = nz – nx = 0.1471–0.2069 from 1062.6 to 450.2 nm for Na2TeW2O9. The results indicate that Na6Te4W6O29 and Na2TeW2O9 may have uses in applications involving birefrigent materials.

Ba3(ZnB5O10)PO4 (BZBP) single crystals were grown successfully by a top-seeded solution growth method. High-resolution X-ray diffraction rocking curve measurements reveal a full width at half-maximum of 34.56″ of a BZBP single crystal grown from a [101]-oriented seed. The refractive indices from the UV to the near infrared region were measured, and revealed a birefringence of 0.04179–0.03059 in the wavelength range of 253.6–2325.4 nm. In addition the type-I and type-II phase-matching range for second and third harmonic generation were calculated based on the fitted Sellmeier equations. In order to further evaluate the potential application of Ba3(ZnB5O10)PO4, the thermal properties including specific heat, thermal diffusivity, and thermal conductivity were also measured along different crystallographic axes.

A new ultraviolet nonlinear optical (NLO) material, Pb3Mg3TeP2O14 (PMTP), has been synthesized and characterized. The chiral material exhibits a large second harmonic generation (SHG) response of 13.5 × KDP (600 × α-SiO2), and the shortest absorption edge (250 nm) of reported materials with a strong SHG response (>10 × KDP). PMTP has a three-dimensional crystal structure of corner-shared MgO4, PO4, and TeO6 polyhedra, which form a [TeMg3P2O14]∞ framework. Electronic structure calculations revealed that the stereoactive lone pair on the Pb2+ cation is critical to producing the substantial NLO response and that the NLO activity is further enhanced by the presence of triply bidentate Te6+ cations found in Te–O–O–Pb rings.

A new deep-ultraviolet nonlinear optical material, RbMgCO3F, has been synthesized and characterized. The achiral nonpolar acentric material is second harmonic generation (SHG) active at both 1064 and 532 nm, with efficiencies of 160 × α-SiO2 and 0.6 × β-BaB2O4, respectively, and exhibits a short UV cutoff, below 190 nm. RbMgCO3F possesses a three-dimensional structure of corner-shared Mg(CO3)2F2 polyhedra. Unlike other acentric carbonate fluorides, in this example, the inclusion of Mg2+ creates pentagonal channels where the Rb+ resides. Our electronic structure calculations reveal that the denticity of the carbonate linkage, monodentate or bidendate, to the divalent cation is a useful parameter for tuning the transparency window and achieving the sizable SHG response.

Polar materials are critical for a variety of functional properties including ferroelectricity, pyroelectricity, and nonlinear optical behavior. Vital to developing new polar materials is an understanding of how the polarity influences the functional property, i.e., structure–property relationships. At present, structure–property relationships on polar materials have focused on materials with similar structural motifs. Interestingly, there are limited reports on the structure–property relationships of polar polymorphs, likely attributable to the challenge of synthesizing polar polymorphic materials. In this paper, a new strategy for the synthesis of polar polymorphs is presented. By employing this strategy, we report on the synthesis and characterization of the first example of a borate with all polar polymorphs: P1 for α-Pb2Ba4Zn4B14O31 (α-PBZB), Cc for β-PBZB, and P32 for γ-PBZB. In addition, powder second-harmonic generation (PSHG) measurements indicate that the polymorphs are SHG-active and type-I phase matchable. Structure–property relationships are discussed through theoretical calculations.

A new mixed-valence iron (Fe2+/Fe3+) fluoride material with a layered perovskite-related structure has been synthesized and characterized. The material, K4Fe3F12 [K4(Fe2+)(Fe3+)2F12], was synthesized using mild hydrothermal conditions. The material exhibits a layered perovskite structure consisting of alternating sheets of apex-linked Fe2+F6 and Fe3+F6 octahedra; thus, each layer of Fe2+F6 centers is sandwiched between two layers of Fe3+F6 centers. Magnetization and neutron powder diffraction data show that, upon cooling below 120 K, K4Fe3F12 adopts a magnetically ordered state in which the Fe3+ and Fe2+ spins are aligned in an approximately antiparallel manner to each other to yield a pseudoferrimagnetic structure with a net spontaneous moment of 5.41 μB per formula unit at 10 K. Crystal data: K4Fe3F12, trigonal space group R3̅m (No. 166), a = b = 5.7649(9) Å, c = 28.086(9) Å, V = 808.36(3) Å3, Z = 3, T = 296(2) K.

We use a symmetry-based structural analysis combined with an electronic descriptor for bond covalency to explain the origin of the second-order nonlinear optical response (second harmonic generation, SHG) in noncentrosymmetric nonpolar ATeMoO6 compounds (where A = Mg, Zn, or Cd). We show that the SHG response has a complex dependence on the asymmetric geometry of the AO6 and AO4 functional units and the orbital character at the valence band edge, which we are able to distinguish using an A–O bond covalency descriptor. The degree of covalency between the divalent A-site cation and the oxygen ligands dominates over the geometric contributions to the SHG arising from the acentric polyhedra, and this can be understood from considerations of the local static charge density distribution. The use of a local dipole model for the polyhedral moieties (AO4/AO6, MoO4, and TeO4) can account for a nonzero SHG response, even though the materials exhibit nonpolar structures; however, it is insufficient to explain the change in the magnitude of the SHG response upon A-cation substitution. The atomic scale and electronic structure understanding of the macroscopic SHG behavior is then used to identify hypothetical HgTeMoO6 as a candidate telluromolybdate with an enhanced nonlinear optical response.

Two lead fluorocarbonates, RbPbCO3F and CsPbCO3F, were synthesized and characterized. The materials were synthesized through solvothermal and conventional solid-state techniques. RbPbCO3F and CsPbCO3F were structurally characterized by single-crystal X-ray diffraction and exhibit three-dimensional (3D) crystal structures consisting of corner-shared PbO6F2 polyhedra. For RbPbCO3F, infrared and ultraviolet–visible spectroscopy and thermogravimetric and differential thermal analysis measurements were performed. RbPbCO3F is a new noncentrosymmetric material and crystallizes in the achiral and nonpolar space group P6̅m2 (crystal class 6̅m2). Powder second-harmonic generation (SHG) measurements on RbPbCO3F and CsPbCO3F using 1064 nm radiation revealed an SHG efficiency of approximately 250 and 300 × α-SiO2, respectively. Charge constants d33 of approximately 72 and 94 pm/V were obtained for RbPbCO3F and CsPbCO3F, respectively, through converse piezoelectric measurements. Electronic structure calculations indicate that the nonlinear optical response originates from the distorted PbO6F2 polyhedra, because of the even–odd parity mixing of the O 2p states with the nearly spherically symmetric 6s electrons of Pb2+. The degree of inversion symmetry breaking is quantified using a mode-polarization vector analysis and is correlated with cation size mismatch, from which it is possible to deduce the acentric properties of 3D alkali-metal fluorocarbonates.

Two new quaternary sodium tungsten selenites, Na2(WO3)3(SeO3)·2H2O (P31c) and Na6(W6O19)(SeO3)2 (C2), have been synthesized and characterized. The former exhibits a hexagonal tungsten oxide layered structure, whereas the latter has a one-dimensional “ribbon” structure. The layers and “ribbons” consist of distorted WO6 and asymmetric SeO3 polyhedra. The layers in Na2(WO3)3(SeO3)·2H2O and the “ribbons” in Na6(W6O19)(SeO3)2 are separated by Na+ cations. Powder second-harmonic-generation (SHG) measurements on Na2(WO3)3(SeO3)·2H2O and Na6(W6O19)(SeO3)2 using 1064 nm radiation reveal SHG efficiencies of approximately 450× and 20× α-SiO2, respectively. Particle size versus SHG efficiency measurements indicate that the materials are type 1 non-phase-matchable. Converse piezoelectric measurements result in d33 values of approximately 23 and 12 pm/V, whereas pyroelectric measurements reveal coefficients of −0.41 and −1.10 μC/m2·K at 60 °C for Na2(WO3)3(SeO3)·2H2O and Na6(W6O19)(SeO3)2, respectively. Frequency-dependent polarization measurements confirm that the materials are nonferroelectric; i.e., the macroscopic polarization is not reversible, or “switchable”. IR and UV–vis spectroscopy, thermogravimetric and differential thermal analysis measurements, and electron localization function calculations were also done for the materials. Crystal data: Na2(WO3)3(SeO3)·2H2O, trigonal, space group P31c (No. 159), a = 7.2595(6) Å, b = 7.2595(6) Å, c = 12.4867(13) Å, V = 569.89(9) Å3, Z = 2; Na6(W6O19)(SeO3)2, monoclinic, space group C2 (No. 5), a = 42.169(8) Å, b = 7.2690(15) Å, c = 6.7494(13) Å, β = 98.48(3)°, V = 2046.2(7) Å3, Z = 4.

Two new potassium lead fluoride carbonates, KPb2(CO3)2F and K2.70Pb5.15(CO3)5F3, have been synthesized and characterized. The materials were synthesized through solvothermal and conventional solid-state techniques. KPb2(CO3)2F and K2.70Pb5.15(CO3)5F3 were structurally characterized by single crystal X-ray diffraction and exhibit two-dimensional crystal structures consisting of corner-shared PbO6F and PbO6F2 polyhedra. K2.70Pb5.15(CO3)5F3 is noncentrosymmetric, and crystallizes in the achiral and nonpolar space group P6̅m2 (crystal class −6m2). Powder second-harmonic generation (SHG) measurements using 1064 nm radiation revealed a SHG efficiency of approximately 40 × α-SiO2, whereas a charge constant, d33, of approximately 20 pm/V was obtained through converse piezoelectric measurements. For the reported materials, infrared, UV–vis, thermogravimetric, and differential thermal analysis measurements were performed.

Single crystals of polar LiCrP2O7 were grown by using a top-seeded solution growth method. In addition to the crystal structure, detailed magnetic measurements reveal anisotropic magnetic behavior with a spin-flop transition. Piezoelectric, polarization, and heat capacity measurements were also taken on the single crystals. Powder second-harmonic generating measurements, using 1064 nm radiation, revealed type 1 phase-matching behavior with an efficiency of approximately 30 × α-SiO2.

A new charge-ordered magnetically frustrated mixed-metal fluoride with a pyrochlore-related structure has been synthesized and characterized. The material, RbFe2F6 (RbFe2+Fe3+F6) was synthesized through mild hydrothermal conditions. The material exhibits a three-dimensional pyrochlore-related structure consisting of corner-shared Fe2+F6 and Fe3+F6 octahedra. In addition to single-crystal diffraction data, neutron powder diffraction and magnetometry measurements were carried out. Magnetic data clearly reveal strong antiferromagnetic interactions (a Curie–Weiss temperature of −270 K) but sufficient frustration to prevent ordering until 16 K. No structural phase transformation is detected from the variable-temperature neutron diffraction data. Infrared, UV-vis, thermogravimetric, and differential thermal analysis measurements were also performed. First-principles density functional theory (DFT) electronic structure calculations were also done. Crystal data: RbFe2F6, orthorhombic, space groupPnma (no. 62), a = 7.0177(6), b = 7.4499(6), c = 10.1765(8) Å, V = 532.04(8) Å3, Z = 4.

Five new vanadium selenites, Ca2(VO2)2(SeO3)3(H2O)2, Sr2(VO2)2(SeO3)3, Ba(V2O5)(SeO3), Sr4(VO2)2(SeO3)4(Se2O5), and Pb4(VO2)2(SeO3)4(Se2O5), have been synthesized and characterized. Their crystal structures were determined by single crystal X-ray diffraction. The compounds exhibit one- or two-dimensional structures consisting of corner- and edge-shared VO4, VO5, VO6, and SeO3 polyhedra. Of the reported materials, A4(VO2)2(SeO3)4(Se2O5) (A = Sr2+ or Pb2+) are noncentrosymmetric (NCS) and polar. Powder second-harmonic generation (SHG) measurements revealed SHG efficiencies of approximately 130 and 150 × α–SiO2 for Sr4(VO2)2(SeO3)4(Se2O5) and Pb4(VO2)2(SeO3)4(Se2O5), respectively. Piezoelectric charge constants of 43 and 53 pm/V, and pyroelectric coefficients of −27 and −42 μC/m2·K at 70 °C were obtained for Sr4(VO2)2(SeO3)4(Se2O5) and Pb4(VO2)2(SeO3)4(Se2O5), respectively. Frequency dependent polarization measurements confirmed that the materials are not ferroelectric, that is, the observed polarization cannot be reversed. In addition, the lone-pair on the Se4+ cation may be considered as stereo-active consistent with calculations. For all of the reported materials, infrared, UV–vis, thermogravimetric, and differential thermal analysis measurements were performed. Crystal data: Ca2(VO2)2(SeO3)3(H2O)2, orthorhombic, space group Pnma (No. 62), a = 7.827(4) Å, b = 16.764(5) Å, c = 9.679(5) Å, V = 1270.1(9) Å3, and Z = 4; Sr2(VO2)2(SeO3)3, monoclinic, space group P21/c (No. 12), a = 14.739(13) Å, b = 9.788(8) Å, c = 8.440(7) Å, β = 96.881(11)°, V = 1208.8(18) Å3, and Z = 4; Ba(V2O5)(SeO3), orthorhombic, space group Pnma (No. 62), a = 13.9287(7) Å, b = 5.3787(3) Å, c = 8.9853(5) Å, V = 673.16(6) Å3, and Z = 4; Sr4(VO2)2(SeO3)4(Se2O5), orthorhombic, space group Fdd2 (No. 43), a = 25.161(3) Å, b = 12.1579(15) Å, c = 12.8592(16) Å, V = 3933.7(8) Å3, and Z = 8; Pb4(VO2)2(SeO3)4(Se2O5), orthorhombic, space group Fdd2 (No. 43), a = 25.029(2) Å, b = 12.2147(10) Å, c = 13.0154(10) Å, V = 3979.1(6) Å3, and Z = 8.

New quaternary lithium – d0 cation – lone-pair oxides, Li6(Mo2O5)3(SeO3)6 (Pmn21) and Li2(MO3)(TeO3) (P21/n) (M = Mo6+ or W6+), have been synthesized and characterized. The former is noncentrosymmetric and polar, whereas the latter is centrosymmetric. Their crystal structures exhibit zigzag anionic layers composed of distorted MO6 and asymmetric AO3 (A = Se4+ or Te4+) polyhedra. The anionic layers stack along a 2-fold screw axis and are separated by Li+ cations. Powder SHG measurements on Li6(Mo2O5)3(SeO3)6 using 1064 nm radiation reveal a SHG efficiency of approximately 170 × α-SiO2. Particle size vs SHG efficiency measurements indicate Li6(Mo2O5)3(SeO3)6 is type 1 nonphase-matchable. Converse piezoelectric measurements result in a d33 value of ∼28 pm/V and pyroelectric measurements reveal a pyroelectric coefficient of −0.43 μC/m2K at 50 °C for Li6(Mo2O5)3(SeO3)6. Frequency-dependent polarization measurements confirm that Li6(Mo2O5)3(SeO3)6 is nonferroelectric, i.e., the macroscopic polarization is not reversible, or ‘switchable’. Infrared, UV–vis, thermogravimetric, and differential thermal analysis measurements and electron localization function calculations were also done for all materials.

Two new noncentrosymmetric (NCS) polar oxides, BaMgTe2O7 and BaZnTe2O7, have been synthesized and characterized, with their crystal structures determined by single crystal X-ray diffraction. The iso-structural materials exhibit structures consisting of layers of corner-shared MgO5 or ZnO5, Te6+O6, and Te4+O4 polyhedra that are separated by Ba2+ cations. The Te4+ cation is found in a highly asymmetric and polar coordination environment attributable to its stereoactive lone-pair. The alignment of the individual TeO4 polar polyhedra results in macroscopic polarity for BaMgTe2O7 and BaZnTe2O7. Powder second-harmonic generation (SHG) measurements revealed a moderate SHG efficiency of approximately 5 × KDP (or 200 × α-SiO2) for both materials. Piezoelectric charge constants of 70 and 57 pm/V, and pyroelectric coefficients of −18 and −10 μC·m–2·K–1 were obtained for BaMgTe2O7 and BaZnTe2O7, respectively. Although the materials are polar, frequency dependent polarization measurements indicated that the materials are not ferroelectric, that is, the observed macroscopic polarization cannot be reversed. Infrared, UV–vis diffuse spectroscopy, and thermal properties were also measured. Crystal data: BaMgTe2O7, orthorhombic, space group Ama2 (No. 40), a = 5.558(2) Å, b = 15.215(6) Å, c = 7.307(3) Å, V = 617.9(4) Å3, and Z = 4; BaZnTe2O7, orthorhombic, space group Ama2 (No. 40), a = 5.5498(4) Å, b = 15.3161(11) Å, c = 7.3098(5) Å, V = 621.34(8) Å3, and Z = 4.

Large single crystals of LiFeP2O7, a multifunctional polar material, were successfully grown by using a top-seeded solution growth (tssg) technique. The morphologies of the single crystals with different rotation speeds are described. Functional properties such as second-harmonic generation (SHG), piezoelectricity, pyroelectricity, and ferroelectricity were measured. LiFeP2O7 is SHG active, with an SHG efficiency of approximately 200 × α-SiO2 using 1064 nm radiation. The material is piezoelectric, with a d22 value of 1.2 pC/N, and pyroelectric, with pyroelectric coefficients of 9.25 μC/m2K (1 kHz) and 10.6 μC/m2K (50 Hz) at 60 °C. Although polar, LiFeP2O7 is not ferroelectric; that is, the polarization is not “switchable”. Optical spectra indicate that the absorption edge is approximately 480 nm, with transmission up to 4.3 μm.

Large, centimetre-size crystals of the polar and noncentrosymmetric K3V5O14 were successfully grown by a top-seeded solution growth (tssg) method. The morphologies of as-grown single crystals with different oriented seeds are described. The optical spectra indicate that its UV absorption edge is approximately 605 nm, and it has a transmission window to 5 μm. Piezoelectricity was also measured by the direct and converse methods. Finally, polarization properties were investigated on grown single crystals.

Crystals and polycrystalline powders of two new oxide materials, Tl4CuTeO6 and Tl6CuTe2O10, have been synthesized by hydrothermal and solid-state methods. The materials were structurally characterized by single-crystal X-ray diffraction. Tl4CuTeO6 and Tl6CuTe2O10 exhibit one dimensional anionic slabs of [CuTeO6]4− and [CuTe2O10]6−, respectively. Common to both slabs is the occurrence of Cu2+O4 distorted squares and Te6+O6 octahedra. The slabs are separated by Tl+ cations. For Tl4CuTeO6, magnetic measurements indicate a maximum at ∼8 K in the temperature dependence of the susceptibility. Low temperature neutron diffraction data confirm no long-range magnetic ordering occurs and the susceptibility was adequately accounted for by fits to a Heisenberg alternating chain model. For Tl6CuTe2O10 on the other hand, magnetic measurements revealed paramagnetism with no evidence of long-range magnetic ordering. Infrared, UV–vis spectra, thermogravimetric, and differential thermal analyses are also reported. Crystal data: Tl4CuTeO6, Triclinic, space group P-1 (No. 2), a=5.8629(8) Å, b=8.7848(11) Å, c=9.2572(12) Å, α=66.0460(10), β=74.2010(10), γ=79.254(2), V=417.70(9) Å3, and Z=2; Tl6CuTe2O10, orthorhombic, space group Pnma (No. 62), a=10.8628(6) Å, b=11.4962(7) Å, c=10.7238(6) Å, V=1339.20(13) Å3, and Z=4.Graphical AbstractTwo new oxide materials, Tl4CuTeO6 and Tl6CuTe2O10, have been synthesized and characterized. The materials exhibit one dimensional crystal structures consisting of CuO4 and TeO6 polyhedra.Highlights► Two New Tl–Te–Cu-oxides have been synthesized and structurally characterized. ► For Tl4CuTeO6, magnetic measurements indicate a maximum at ∼8 K. ► Low temperature neutron diffraction data confirm no long-range magnetic ordering. ► For Tl6CuTe2O10 magnetic measurements revealed no long-range magnetic ordering.

A new noncentrosymmetric (NCS) and polar material containing two lone-pair cations, Bi3+ and I5+, and exhibiting an Aurivillius-type (Bi2O2)2+ layer has been synthesized and structurally characterized. The material, BiO(IO3), exhibits strong second-harmonic generation (SHG), ∼12.5 × KDP (or ∼500 × α-SiO2), using 1064 nm radiation, and is found in the NCS polar orthorhombic space group Pca21 (No. 29). The structure consists of (Bi2O2)2+ cationic layers that are connected to (IO3)− anions. The macroscopic polarity, observed along the c-axis direction, may be attributed to the alignment of the IO3 polyhedra. In addition to the crystal structure and SHG measurements, polarization and piezoelectric measurements were performed, as well as electronic structure analysis.

Two new noncentrosymmetric (NCS) polar oxide materials, Zn2(MoO4)(AO3) (A = Se4+ or Te4+), have been synthesized by hydrothermal and solid-state techniques. Their crystal structures have been determined, and characterization of their functional properties (second-harmonic generation, piezoelectricity, and polarization) has been performed. The isostructural materials exhibit a three-dimensional network consisting of ZnO4, ZnO6, MoO4, and AO3 polyhedra that share edges and corners. Powder second-harmonic generation (SHG) measurements using 1064 nm radiation indicate the materials exhibit moderate SHG efficiencies of 100 × and 80 × α-SiO2 for Zn2(MoO4)(SeO3) and Zn2(MoO4)(TeO3), respectively. Particle size vs SHG efficiency measurements indicate the materials are type 1 non-phase-matchable. Converse piezoelectric measurements resulted in d33 values of ∼14 and ∼30 pm/V for Zn2(MoO4)(SeO3) and Zn2(MoO4)(TeO3), respectively, whereas pyroelectric measurements revealed coefficients of −0.31 and −0.64 μC/m2 K at 55 °C for Zn2(MoO4)(SeO3) and Zn2(MoO4)(TeO3), respectively. Frequency-dependent polarization measurements confirmed that all of the materials are nonferroelectric; that is, the macroscopic polarization is not reversible, or “switchable”. Infrared, UV–vis, thermogravimetric, and differential thermal analysis measurements were also performed. First-principles density functional theory (DFT) electronic structure calculations were also done. Crystal data: Zn2(MoO4)(SeO3), monoclinic, space group P21 (No. 4), a = 5.1809(4) Å, b = 8.3238(7) Å, c = 7.1541(6) Å, β = 99.413(1)°, V = 305.2(1) Å3, Z = 2; Zn2(MoO4)(TeO3), monoclinic, space group P21 (No. 4), a = 5.178(4) Å, b = 8.409(6) Å, c = 7.241(5) Å, β = 99.351(8)°, V = 311.1(4) Å3, Z = 2.

The synthesis and characterization of ACuTe2O7 (A = Sr2+, Ba2+, or Pb2+) have been carried out. Interestingly, SrCuTe2O7 and PbCuTe2O7 are centrosymmetric and isostructural, whereas BaCuTe2O7 is noncentrosymmetric and polar. All of the materials contain [CuTe2O7]2– layers stacked along the b-axis direction that are separated by the “A” cations. The layers are composed of corner-shared CuO5, TeO6, and TeO4 polyhedra. The influence of the “A” cation on the polarity is described by bond valence concepts, including the bond strain index and global instability index. Infrared, UV–vis, thermogravimetric, differential thermal analysis, and magnetic measurements were performed on all three materials. For BaCuTe2O7, second-harmonic generation (SHG), piezoelectric, and polarization measurements were performed. A moderate SHG efficiency of approximately 70 × α-SiO2 was measured. In addition, we determined that BaCuTe2O7 is not ferroelectric; that is, the macroscopic polarization is not reversible. For BaCuTe2O7, a pyroelectric coefficient of −9.5 μC/m2·K at 90 °C and a piezoelectric charge coefficient of 49 pm/V were determined. Crystal data are the following: SrCuTe2O7, orthorhombic, space group Pbcm (No. 57), a = 7.1464(7) Å, b = 15.0609(15) Å, c = 5.4380(5) Å, V = 585.30(10) Å3, and Z = 4; PbCuTe2O7, orthorhombic, space group Pbcm (No. 57), a = 7.2033(5) Å, b = 15.0468(10) Å, c = 5.4691(4) Å, V = 592.78(7) Å3, and Z = 4.

Centimeter size crystals of the second-order nonlinear optical and polar oxide Na2TeW2O9 (NTW) have been grown by the top-seeded solution growth method. The specific heat, anisotropic thermal expansion, and thermal diffusivity have been measured. In addition, the average principal thermal expansion coefficients have been calculated on the basis of measurements between 23 and 500 °C. NTW exhibits strongly anisotropic thermal expansion that can be attributed to its low symmetry, monoclinic, in space group Ia. The relationships between the structure and thermal properties are discussed.

Single crystals of two new niobium and tantalum oxides, Sr3LiNbO6 and Sr3LiTaO6 were grown out of a Sr(OH)2/LiOH·H2O/KOH flux and characterized by single-crystal X-ray diffraction. The materials crystallize in the trigonal R-3c space group with a = 9.8029(14) Å (9.8111(11) Å), b = 9.8029(14) Å (9.8111(11) Å), c = 11.200(2) Å (11.2056(12) Å), α = β = 90°, γ = 120° for Sr3LiNbO6 (Sr3LiTaO6). The oxides exhibit the K4CdCl6 structure-type, and consist of alternating face-shared BO6 octahedra (B = Nb5+ or Ta5+) and LiO6 trigonal prisms.

A new quinternary oxide, NaTl3Cu4Te2O12, has been synthesized and characterized by single crystal X-ray diffraction. The reported material was synthesized by hydrothermal techniques using TlNO3, CuO, TeO2, and NaOH as reagents. The material exhibits a two-dimensional layered structure consisting of edge-shared CuO6 and TeO6 polyhedra separated by Na+ and Tl+ cations. NaTl3Cu4Te2O12 crystallizes in space group C2/m with a = 12.9800(17) Å, b = 9.3455(12) Å, c = 5.2335(7) Å, β = 104.276(2)°, V = 615.24(14) Å3, and Z = 2.

A low temperature, high yield hydrothermal route has been discovered for the phase-pure synthesis of the multiferroic BaMF4 (M = Mg, Mn, Co, Ni, and Zn) family. The synthesis involves the use of CF3COOH instead of HF in an aqueous medium and, under the correct conditions, produces pure and polycrystalline BaMF4. In addition to the synthetic description, second-harmonic generation, thermogravimetric, and differential scanning calorimetry data are presented.

We have re-examined the crystal structure and the physical properties of VOSe2O5 by performing single crystal X-ray and powder neutron diffraction, alternating current (AC) and direct current (DC) magnetization measurements, heat capacity, dielectric properties, and second-harmonic generation (SHG) measurements. From these studies, we observed that the compound undergoes three magnetic transitions near 4, 5.5, and 8 K. In addition, we observed ferrimagnetic behavior as the magnetic ground state, confirmed by the isothermal magnetization measured below 8 K that reveals a saturated magnetic moment of 0.5 μB per formula unit, consistent with density functional calculations of the magnetically ordered ground state. We propose a ferrimagnetic spin arrangement that is consistent with neutron diffraction measurements as well. Frequency dependence in the AC magnetic susceptibility, observed at 5.5 K, is considered as short-range magnetic ordering and may be associated with the competition between nearest neighbor and next nearest neighbor interactions of the V4+ cations. A dielectric anomaly near 240 K and non-centrosymmetric functional properties, notably, second harmonic generation and electric polarization, are also discussed.

A new acentric ferromagnetic material, VO(SeO2OH)2, has been synthesized and characterized by single crystal X-ray diffraction, second harmonic generation (SHG), and magnetization measurements. The crystal structure of VO(SeO2OH)2 consists of linear chains of corner-shared V4+O6 octahedra that are connected by SeO2OH groups. The material exhibits a weak SHG efficiency, comparable to α-SiO2, and a ferromagnetic transition (TC) at ∼2.5 K with a saturated magnetic moment of 1.09 μB per formula unit (μB/FU). The origin of the ferromagnetism is explained by the suppression of the antiferromagnetic superexchange (SE) and supersuper-exchange (SSE) interactions in the intra-chain and inter-chain magnetic interactions, respectively. In addition, using first principles density functional theory (DFT) calculations, we show that the SSE interactions depend on the O(2)−Se4+−O(3) angle. As we demonstrate, the stereoactive lone-pair on Se4+ is the driving force for the inter-chain ferromagnetic interactions.

Two new polar noncentrosymmetric (NCS) oxides, Rb2(MoO3)3(SeO3) and Tl2(MoO3)3(SeO3), have been synthesized and characterized. The materials exhibit the layered hexagonal tungsten oxide (HTO) structural topology—Class 2, i.e., the MoO6 layers are “capped” on one side by the SeO3 polyhedra. The Rb+ and Tl+ cations are found between the layers. The Mo6+ and Se4+ cations are present in asymmetric coordination environments that are attributable to second-order Jahn−Teller (SOJT) effects. In addition to structural characterization, the materials were characterized by second-harmonic generation (SHG), piezoelectric, and polarization measurements. SHG measurements using 1064-nm radiation revealed doubling efficiencies of 300 and 400 × α-SiO2 for the Rb- and Tl-phases, respectively. Piezoelectric experiments revealed d33 values of ∼9−13 pm/V. Polarization measurements indicate that the materials are not ferroelectric, i.e., the polarization is not “switchable”. The materials are pyroelectric, with total pyroelectric coefficients (p), at 45 °C, of −1.1 μC m−2 K−1 for Rb2(MoO3)3(SeO3) and −2.1 μC m−2 K−1 for Tl2(MoO3)3(SeO3). Thermogravimetry, differential scanning calorimetry, UV−vis, and infrared spectroscopy measurements were also performed. We also examine all of the known polar HTO-type materials to gain a better understanding of the functional properties and structure−property relationships. Crystal data for Rb2(MoO3)3(SeO3): hexagonal, space group P63 (No. 173), a = b = 7.2992(14) Å, c = 11.978(5) Å, V = 552.7(3) Å3, and Z = 2; crystal data for Tl2(MoO3)3(SeO3): trigonal, space group P31c (No. 159), a = b = 7.2867(10) Å, c = 11.794(3) Å, V = 542.33(18) Å3, and Z = 2.

Three polar noncentrosymmetric (NCS) oxide materials, A3V5O14 (A = K+, Rb+, or Tl+), have been synthesized by hydrothermal and conventional solid state techniques. Their crystal structures and functional properties (second-harmonic generation, piezoelectricity, and polarization) have been determined. The iso-structural materials exhibit a layered structural topology that consists of corner-sharing VO4 tetrahedra and VO5 square pyramids. The layers stack parallel to the c-axis direction and are separated by the K+, Rb+, or Tl+ cations. Powder second-harmonic generation (SHG) measurements using 1064 nm radiation indicate the materials exhibit moderate SHG efficiencies of ∼100 × α-SiO2. Additional SHG measurements, that is, particle size versus SHG efficiency, indicate the materials are type-I phase-matchable. Converse piezoelectric measurements for K3V5O14, Rb3V5O14, and Tl3V5O14 revealed d33 values of 28, 22, and 26 pm/V, respectively. Pyroelectric measurements, that is, temperature-dependent polarization measurements, resulted in pyroelectric coefficients of −2.2, −2.9, and −2.8 μC/m2·K at 65 °C, for K3V5O14, Rb3V5O14, and Tl3V5O14 respectively. Frequency-dependent polarization measurements confirmed that all of the materials are nonferroelectric, consistent with our first principle density functional theory (DFT) electronic structure calculations. Infrared, UV−vis, thermogravimetric, and differential scanning calorimetry measurements were also performed. Crystal data: K3V5O14, trigonal, space group P31m (No. 157), a = 8.6970(16) Å, c = 4.9434(19) Å, V = 323.81(15), and Z = 1; Rb3V5O14, trigonal, space group P31m (No. 157), a = 8.7092(5) Å, c = 5.2772(7) Å, V = 346.65(5), and Z = 1; Tl3V5O14, trigonal, space group P31m (No. 157), a = 8.7397(8) Å, c = 5.0846(10) Å, V = 336.34(8), and Z = 1.

Centimeter-size single crystals of the noncentrosymmetric and polar material Na2TeW2O9 were successfully grown through a top-seeded solution growth (TSSG) method. Differently oriented seeds, along the [100], [010], and [001] directions, were used to grow large single crystals. The morphologies of the grown crystals with different oriented seeds are described. Na2TeW2O9 crystallizes in the noncentrosymmetric and polar monoclinic space group Ia (No. 9). Functional properties including piezoelectricity and polarization were also measured. The d11 and d33 piezoelectric coefficients are 4.0 pC/N and 13.9 pC/N, respectively. Polarization measurements indicate that although Na2TeW2O9 is polar, the material is not ferroelectric; that is, the polarization is not switchable. In addition, optical measurements indicate a UV absorption edge near 360 nm, with a transmission window up to 5 μm.

We have synthesized a series of new alkali-metal or Tl+ titanium iodates, A2Ti(IO3)6 (A = Li, Na, K, Rb, Cs, Tl). Interestingly the Li and Na phases are noncentrosymmetric (NCS) and polar, whereas the K, Rb, Cs, and Tl analogues are centrosymmetric (CS) and nonpolar. We are able to explain the change from NCS polar to CS nonpolar using cation-size arguments, coordination requirements, and bond valence concepts. The six materials are topologically similar, consisting of TiO6 octahedra, each of which is bonded to six IO3 polyhedra. These polyhedral groups are separated by the A+ cations. Our calculations on Na2Ti(IO3)6 indicate that polarization reversal is energetically very unfavorable, rendering the material polar but not ferroelectric. For all of the materials, synthesis, structural characterization, electronic structure analysis, infrared spectra, UV−vis and thermogravimetric measurements, and ion-exchange reactions are reported. For the polar materials, second-harmonic generation, piezoelectricity, and polarization measurements were performed. Crystal data: Li2Ti(IO3)6: hexagonal, space group P63 (No. 173), a = b = 9.3834(11) Å, c = 5.1183(6) Å, Z = 1. Na2Ti(IO3)6: hexagonal, space group P63 (No. 173), a = b = 9.649(3) Å, c = 5.198(3) Å, Z = 1. K2Ti(IO3)6: trigonal, space group R3̅ (No. 148), a = b = 11.2703(6) Å, c = 11.3514(11) Å, Z = 3. Rb2Ti(IO3)6: trigonal, space group R3̅ (No. 148), a = b = 11.3757(16) Å, c = 11.426(3) Å, Z = 3. Cs2Ti(IO3)6: trigonal, space group R3̅ (No. 148), a = b = 11.6726(5) Å, c = 11.6399(10) Å, Z = 3. Tl2Ti(IO3)6: trigonal, space group R3̅ (No. 148), a = b = 11.4167(6) Å, c = 11.3953(11) Å, Z = 3.

Two new polar noncentrosymmetric oxides, RbSe2V3O12 and TlSe2V3O12, have been synthesized and characterized. The oxides are isostructural, as Tl+ exhibits an inert rather than a stereoactive lone pair. The reported materials were structurally characterized by single-crystal X-ray diffraction. The materials exhibit a two-dimensional hexagonal tungsten oxide (HTO) type topology with layers of corner-shared VO6 octahedra. The layers are capped, above and below, by SeO3 polyhedra. The Rb+ and Tl+ cations are found between the layers. The V5+ and Se4+ cations are in asymmetric coordination environments attributable to second-order Jahn−Teller (SOJT) effects. In addition to structural characterization, second-harmonic generation (SHG), piezoelectric, and polarization measurements were performed. SHG measurements using 1064 nm radiation revealed doubling efficiencies ranging from ∼40−50 × α-SiO2. Piezoelectric experiments revealed d33 values of ∼6−12 pm V−1. Polarization measurements indicate the materials are not ferroelectric, i.e., the polarization is not “switchable”. The materials are pyroelectric, with a total pyroelectric coefficient, p, at 45 °C, of −4.4 and −2.6 μC m−2 K−1 for RbSe2V3O12 and TlSe2V3O12, respectively. Thermogravimetric measurements, UV−vis, and infrared spectroscopy were also performed, as were electronic structure calculations. Crystal data: RbSe2V3O12, hexagonal, space group P63 (No. 173), a = b = 7.1364(4) Å, c = 11.4687(13) Å, V = 505.83(7) Å3, and Z = 2; TlSe2V3O12, hexagonal, space group P63 (No. 173), a = b = 7.1248(3) Å, c = 11.4287(11) Å, V = 502.43(6) Å3, and Z = 2.

Two new thallium iodates have been synthesized, Tl(IO3)3 and Tl4(IO3)6 [Tl+3Tl3+(IO3)6], and characterized by single-crystal X-ray diffraction. Both materials were synthesized as phase-pure compounds through hydrothermal techniques using Tl2CO3 and HIO3 as reagents. The materials crystallize in space groups R-3 (Tl(IO3)3) and P-1 (Tl4(IO3)6). Although lone-pairs are observed for both I5+ and Tl+, electronic structure calculations indicate the lone-pair on I5+ is stereo-active, whereas the lone-pair on Tl+ is inert.Visualization of the stereo-active lone-pair (purple) through ELFs for Tl4(IO3)6. The spherical nature of the ELFs around the Tl+ cation indicates the lone-pair is inert.

The synthesis, crystal structures, second-harmonic generation (SHG), piezoelectric, pyroelectric, and ferroelectric properties of three polar noncentrosymmetric (NCS) hexagonal tungsten bronze-type oxides are reported. The materials KNbW2O9, RbNbW2O9, and KTaW2O9 were synthesized by standard solid-state techniques and structurally characterized by laboratory powder X-ray diffraction. The compounds are isostructural, crystallizing in the polar NCS space group Cmm2. The materials exhibit a corner-shared MO6 (M = Nb5+/W6+ or Ta5+/W6+) octahedral framework, with K+ or Rb+ occupying the “hexagonal” tunnels. The d0 transition metals, Nb5+, Ta5+, and W6+, are displaced from the center of their oxide octahedra attributable to second-order Jahn−Teller effects. SHG measurements using 1064 nm radiation revealed frequency-doubling efficiencies ranging from 180 to 220 × α-SiO2. Converse piezoelectric measurements resulted in d33 values ranging from 10 to 41 pm V−1. The total pyroelectric coefficient, p, at 50 °C ranged from −6.5 to −34.5 μC K−1 m−2. The reported materials are also ferroelectric, as demonstrated by hysteresis loops (polarization vs electric field). Spontaneous polarization values, Ps, ranging from 2.1 to 8.4 μC cm−2 were measured. The magnitudes of the SHG efficiency, piezoelectric response, pyroelectric coefficient, and ferroelectric polarization are strongly dependent on the out-of-center distortion of the d0 transition metals. Structure−property relationships are discussed and explored. Crystal data: KNbW2O9, orthorhombic, space group Cmm2 (No. 35), a = 21.9554(2) Å, b = 12.60725(15) Å, c = 3.87748(3) Å, V = 1073.273(13) Å3, and Z = 6; RbNbW2O9, orthorhombic, space group Cmm2 (No. 35), a = 22.00985(12) Å, b = 12.66916(7) Å, c = 3.8989(2) Å, V = 1086.182(10) Å3, and Z = 6; KTaW2O9, orthorhombic, space group Cmm2 (No. 35), a = 22.0025(2) Å, b = 12.68532(14) Å, c = 3.84456(4) Å, V = 1073.05(2) Å3, and Z = 6.

Colorless, polyhedral single crystals of Na3Ga3Te2O12 have been synthesized for the first time by supercritical hydrothermal techniques using NaOH, Ga2O3, TlNO3 and TeO2 as reagents. Na3Ga3Te2O12 was characterized by single-crystal and powder X-ray diffractions, IR, Raman, UV–vis diffuse reflectance spectroscopies and thermogravimetric analysis. Na3Te2Ga3O12 crystallizes in the cubic space group Ia-3d (No. 230) with a = 12.3604(14) Å, V = 1888.4(4) Å3, and Z = 8. Na3Ga3Te2O12 exhibits a garnet structure-type with the Te6+ and Ga3+ cations occupying the octahedral and tetrahedral sites, respectively.

Two new tellurites, NH4RbTe4O9·2H2O and NH4CsTe4O9·2H2O have been synthesized and characterized. The compounds were synthesized hydrothermally, in near quantitative yields, using the alkali metal halide, TeO2, and NH4OH as reagents. The iso-structural materials exhibit layered, two-dimensional structural topologies consisting of TeOx (x=3, 4, or 5) polyhedra separated by NH4+, H2O, Rb+ or Cs+ cations. Unique to these materials is the presence of TeO3, TeO4, and TeO5 polyhedra. Thermogravimetric and infrared spectroscopic data are also presented. Crystal data: NH4RbTe4O9·2H2O: Monoclinic I2/a (no. 15), a=18.917(3) Å, b=6.7002(11) Å, c=21.106(5) Å, β=101.813(2)°, V=2618.5(9) Å3, Z=8; NH4CsTe4O9·2H2O: Monoclinic I2/a (no. 15), a=18.9880(12) Å, b=6.7633(4) Å, c=21.476(2) Å, β=102.3460(10)°, V=2694.2(3) Å3, Z=8.Two unprecedented tellurites, NH4ATe4O9·2H2O (A=Rb or Cs) have been synthesized and characterized. The materials represent rare examples of tellurites that contain TeO3, TeO4, and TeO5 polyhedra in the same compound. All of the polyhedra are in asymmetric polar coordination environments attributable to their stereo-active lone-pair.

A new two-dimensional lead(II) vanadate, Ba3PbV4O14 has been synthesized by standard solid state techniques using BaCO3, PbO, and V2O5 as reagents. The structure of Ba3PbV4O14 was determined by single-crystal X-ray diffraction. Ba3PbV4O14 crystallizes in the triclinic space group P-1 (no. 2), with a = 7.2997(15) (Å), b = 7.2932(15) (Å), c = 13.379(3) (Å), α = 93.68(3)°, β = 99.68(3)°, γ = 91.49(3)°, V = 700.2(2) (Å3) and Z = 2. Ba3PbV4O14 exhibits a novel two-dimensional layered structure consisting of corner shared VO4 tetrahedra that are linked by edge shared PbO7 polyhedra, in which the Ba2+ cations occupy the interlayer region. The Pb2+ cations are in asymmetric coordination environments attributable to its lone pair. Infrared, Raman, and UV–vis diffuse reflectance spectroscopy, thermogravimetric analysis, and dipole moment calculations are also presented.

A new one-dimensional tellurite phosphate, Ba2TeO(PO4)2 has been synthesized by standard solid-state reaction techniques using BaCO3, TeO2, and (NH4)H2PO4 as reagents. The structure of Ba2TeO(PO4)2 was determined by single-crystal X-ray diffraction. Ba2TeO(PO4)2 crystallizes in the triclinic space group P  -1 (No. 2), with a=6.9461(16)Å, b=7.3970(17)Å, c=8.887(2)Å, α=76.843(4)°α=76.843(4)°, β=79.933(4)°β=79.933(4)°, γ=75.688(4)°γ=75.688(4)°, V=427.40(17)Å3, and Z=2Z=2. Ba2TeO(PO4)2 has a novel one-dimensional chain structure that is composed of PO4 tetrahedra and TeO5 polyhedra. Te4+ cations are in asymmetric coordination environments attributable to their lone pairs. The lone pairs on the Te4+ cations point in the [100] and [−100] direction and interact with the Ba2+ cations. Infrared, Raman, and UV–Vis diffuse reflectance spectroscopy, thermogravimetric analysis, and dipole moment calculations are also presented.Ball-and-stick diagram showing one-dimensional structure of Ba2TeO(PO4)2 in the bc-plane. Note the chains run along the b-axis.

Two new lanthanum antimony oxides, LaSb3O9 and LaSb5O12, have been synthesized as bulk phase powders and single crystals by solid state reactions using La2O3 (or La(NO3)3·xH2O), Sb2O3 and Sb2O5 as reagents. The structures of LaSb3O9 and LaSb5O12 were determined by single crystal X-ray diffraction. LaSb3O9 contains exclusively Sb5+ cations, whereas LaSb5O12 contains both Sb3+ and Sb5+ cations. LaSb3O9 has a novel three-dimensional framework consisting of edge- and corner-shared Sb5+O6 octahedra. LaSb5O12 exhibits a layered crystal structure consisting of corner-shared Sb5+O6 octahedra. The Sb3+O3 groups cap the SbO6 layers from above and below. The Sb3+ cations are in asymmetric coordination environments attributable to their stereo-active lone-pair. We also report on the reaction of three-dimensional LaSb3O9 with Sb2O3 to form the two-dimensional LaSb5O12. Infrared, thermogravimetric and dielectric analyses are also presented.

Single crystals of KGaTeO5·H2O and K3GaTe2O8(OH)2·H2O have been synthesized by supercritical hydrothermal techniques using Te(OH)6, Ga2O3 and KOH as reagents, and characterized by single crystal X-ray diffraction, thermal analysis, IR and Raman spectroscopy. Ion-exchange studies revealed KGaTeO5·H2O, with its open-framework structure, is capable of exchanging both smaller (Na+) and larger (Rb+) ions. In addition, higher thermal stability and reversible hydration properties were observed for KGaTeO5·H2O.

The syntheses, structures, and characterization of a new family of quaternary alkali tungsten tellurites, A2TeW3O12 (A=K, Rb, or Cs), are reported. Crystals of the materials were synthesized by supercritical hydrothermal methods using 1 M AOH (A=K, Rb, or Cs), TeO2, and WO3 as reagents. Bulk, polycrystalline phases were synthesized by standard solid-state methods combining stoichiometric amounts of A2CO3, TeO2, and WO3. Although the three materials are not iso-structural, each exhibits a hexagonal tungsten oxide layer comprised of corner-sharing W6+O6 octahedra. Te4+O3 groups connect the WO6 layers in K2TeW3O12, whereas the same groups cap the WO6 layers in Rb2TeW3O12 and Cs2TeW3O12. This capping results in non-centrosymmetric structures for Rb2TeW3O12 and Cs2TeW3O12. Powder second-harmonic generation measurements on Rb2TeW3O12 and Cs2TeW3O12 revealed strong SHG efficiencies of 200 and 400×SiO2, respectively. These values indicate an average non-linear optical susceptibility, 〈deff〉exp of 16 and 23 pm/V for Rb2TeW3O12 and Cs2TeW3O12, respectively. Crystallographic information: K2TeW3O12, monoclinic, space group P21/n (No. 14), a=7.3224(13) Å, b=11.669(2) Å, c=12.708(2) Å, β=90.421(3)°, Z=4; Rb2TeW3O12, trigonal, space group P31c (No. 159), a=b=7.2980(2) Å, c=12.0640(2) Å, Z=2.

Three new tellurites, LaTeNbO6 and La4Te6M2O23 (M=Nb or Ta) have been synthesized, as bulk phase powders and crystals, by using La2O3, Nb2O5 (or Ta2O5), and TeO2 as reagents. The structures of LaTeNbO6 and La4Te6Ta2O23 were determined by single crystal X-ray diffraction. LaTeNbO6 consists of one-dimensional corner-linked chains of NbO6 octahedra that are connected by TeO3 polyhedra. La4Te6M2O23 (M=Nb or Ta) is composed of corner-linked chains of MO6 octahedra that are also connected by TeO4 and two TeO3 polyhedra. In all of the reported materials, Te4+ is in an asymmetric coordination environment attributable to its stereo-active lone-pair. Infrared, thermogravimetric, and dielectric analyses are also presented. Crystallographic information: LaTeNbO6, triclinic, space group P−1, a=6.7842(6) Å, b=7.4473(6) Å, c=10.7519(9) Å, α=79.6490(10)°, β=76.920(2)°, γ=89.923(2)°, Z=4; La4Te6Ta2O23, monoclinic, space group C2/c, a=23.4676(17) Å, b=12.1291(9) Å, c=7.6416(6) Å, β=101.2580(10)°, Z=4.

Three new quaternary selenites, A2SeMoO6 (A=Na+, K+, or Rb+), were synthesized through the solid-state reaction of A2MoO4 with SeO2 at 400°C. Although the reported materials are ‘stoichiometrically equivalent’, the compounds exhibit strikingly different crystal structures. Whereas Na2SeMoO6 has a three-dimensional crystal structure, K2SeMoO6 and Rb2SeMoO6 are molecular and uni-dimensional, respectively. However, all of the new materials have structures containing Mo6+ octahedra linked to Se4+ trigonal pyramids. Although the Mo6+ and Se4+ cations are in local asymmetric environments in all three materials, only Na2SeMoO6 is non-centrosymmetric. Single crystal X-ray data: Na2SeMoO6, cubic, space group, P213 (no. 198), a=8.375(5) Å, Z=4, R(F)=0.0143; K2SeMoO6, monoclinic, space group, P21/c (no. 14), a=6.118(8) Å, b=15.395(2) Å, c=7.580(9) Å, β=112.39(4)°, Z=4, R(F)=0.0281; Rb2SeMoO6, orthorhombic, space group, Pnma (no. 62), a=7.805(9) Å, b=6.188(7) Å, c=14.405(4) Å, Z=4, R(F)=0.0443.

A new charge-ordered magnetically frustrated mixed-metal fluoride with a pyrochlore-related structure has been synthesized and characterized. The material, RbFe2F6 (RbFe2+Fe3+F6) was synthesized through mild hydrothermal conditions. The material exhibits a three-dimensional pyrochlore-related structure consisting of corner-shared Fe2+F6 and Fe3+F6 octahedra. In addition to single-crystal diffraction data, neutron powder diffraction and magnetometry measurements were carried out. Magnetic data clearly reveal strong antiferromagnetic interactions (a Curie–Weiss temperature of −270 K) but sufficient frustration to prevent ordering until 16 K. No structural phase transformation is detected from the variable-temperature neutron diffraction data. Infrared, UV-vis, thermogravimetric, and differential thermal analysis measurements were also performed. First-principles density functional theory (DFT) electronic structure calculations were also done. Crystal data: RbFe2F6, orthorhombic, space groupPnma (no. 62), a = 7.0177(6), b = 7.4499(6), c = 10.1765(8) Å, V = 532.04(8) Å3, Z = 4.