Synthesis, structure, and characterization of two new layered mixed-metal phosphates, BaTeMO4(PO4) (M = Nb5+ or Ta5+

Two new isostructural mixed-metal phosphates, BaTeMO(4)(PO(4)) (M = Nb(5+) or Ta(5+)), have been synthesized as bulk phase powders and single crystals by standard solid-state techniques using BaCO(3), TeO(2), Nb(2)O(5) (or Ta(2)O(5)), and NH(4)H(2)PO(4) as reagents. The materials have novel layered crystal structures consisting of [M(5+)O(6/2)](-) corner-sharing octahedral chains that are connected to [Te(4+)O(4/2)](0) polyhedra and [P(5+)O(2/1)O(2/2)](-) tetrahedra. The Ba(2+) cations reside between the layers and maintain charge balance. The Te(4+) cations are in asymmetric coordination environments attributable to their lone pairs. The Nb(5+) distorts along the local C(4) direction of its octahedron resulting in a "short-long-short-long" Nb-O-Nb bond motif. The Nb(5+) cation displaces away from the oxide ligands that are bonded to Te(4+) or P(5+) cations, attributable to the structural rigidity of the TeO(4) and PO(4) polyhedra. Thus, the TeO(4) and PO(4) polyhedra support and reinforce the intraoctahedral distortion observed within the NbO(6) octahedra. Infrared and Raman spectroscopy, thermogravimetric analysis, and ion-exchange experiments are also presented. Crystal data: BaTeNbO(4)(PO(4)), orthorhombic, space group Pbca (No. 61), with a = 6.7351(9) A, b = 7.5540(10) A, c = 27.455(4) A, V = 1396.8(3) A(3), and Z = 8; BaTeTaO(4)(PO(4)), orthorhombic, space group Pbca (No. 61), with a = 6.734(2) A, b = 7.565(3) A, c = 27.435(9) A, V = 1372.6(8) A(3), and Z = 8.     

Anionic templating: synthesis,structure, and characterization of novel three-dimensional mixed-metal oxychlorides Te(4)M(3)O(15).Cl (M = Nb(5+) or Ta(5+))

Two new three-dimensional oxychlorides are reported, Te(4)M(3)O(15).Cl (M = Nb(5+) or Ta(5+)). The isostructural materials were synthesized by chemical transport reactions utilizing TeO(2), M(2)O(5), and MCl(5) (M = Nb(5+) or Ta(5+)) as reagents. The compounds exhibit a three-dimensional cationic tunnel framework, with Cl(-) anions occupying the tunnels. Crystal data: monoclinic, space group C2/c, a = 18.9944(7) A, b = 7.8314(3) A, c = 21.1658(8) A, beta = 116.6400(10) degrees, Z = 8 (T = 295 K).     

Syntheses,structures, and characterization of new lead(II)-tellurium(IV)-oxide halides: Pb3Te2O6X2 and Pb3TeO4X2 (X = Cl or Br)

The syntheses, structures, and characterization of four new lead(II)-tellurium(IV)-oxide halides, Pb(3)Te(2)O(6)X(2) and Pb(3)TeO(4)X(2) (X = Cl or Br) are reported. The materials are synthesized by solid-state techniques, using Pb(3)O(2)Cl(2) or Pb(3)O(2)Br(2) and TeO(2) as reagents. The compounds have three-dimensional structural topologies consisting of lead-oxide halide polyhedra connected to tellurium oxide groups. In addition, the Pb(2+) and Te(4+) cations are in asymmetric coordination environments attributable to their stereoactive lone pair. We also demonstrate that Pb(3)Te(2)O(6)X(2) and Pb(2)TeO(4)X(2) can be interconverted reversibly through the loss or addition of TeO(2). X-ray data: Pb(3)Te(2)O(6)Cl(2), monoclinic, space group C2/m (No. 12), a = 16.4417(11) A, b = 5.6295(4) A, c = 10.8894(7) A, beta = 103.0130(10) degrees, Z = 4; Pb(3)Te(2)O(6)Br(2), monoclinic, space group C2/m (No. 12), a = 16.8911(8) A, b = 5.6804(2) A, c = 11.0418(5) A, beta = 104.253(2) degrees, Z = 4; Pb(3)TeO(4)Cl(2), orthorhombic, space group Bmmb (No. 63), a = 5.576(1) A, b = 5.559(1) A, c = 12.4929(6) A, Z = 4; Pb(3)TeO(4)Br(2), orthorhombic, space group Bmmb (No. 63), a = 5.6434(4) A, b = 5.6434(5) A, c = 12.9172(6) A, Z = 4.     

Mixed-metal tellurites: synthesis, structure, and characterization of Na1.4Nb3Te4.9O18 and NaNb3Te4O16

Two new mixed-metal tellurites, Na1.4Nb3Te4.9O18 and NaNb3Te4O16, have been synthesized by standard solid-state techniques using Na2CO3, Nb2O5, and TeO2 as reagents. The structures of Na1.4Nb3Te4.9O18 and NaNb3Te4O16 were determined by single-crystal X-ray diffraction. Both of the materials exhibit three-dimensional structures composed of NbO6 octahedra, TeO4, and TeO3 polyhedra. The Nb5+ and Te4+ cations are in asymmetric coordination environments attributable to second-order Jahn-Teller (SOJT) effects. The Nb5+ cations undergo an intraoctahedral distortion toward a corner (local C4 direction), whereas the Te4+ cations are in distorted environments owing to their nonbonded electron pair. Infrared and Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, thermogravimetric analysis, and dielectric measurements were also performed on the reported materials. Crystal data: Na1.4Nb3Te4.9O18, monoclinic, space group C2/m (No. 12), with a = 32.377(5) A, b = 7.4541(11) A, c = 6.5649(9) A, beta = 95.636(5) degrees, V = 1576.7(4) A3, and Z = 4; NaNb3Te4O16, monoclinic, space group P2(1)/m (No. 11), with a = 6.6126(13) A, b = 7.4738(15) A, c = 14.034(3) A, beta = 102.98(3) degrees, V = 675.9(3) A3, and Z = 2.     

PbMSeO6 (M = Mo and W): new quaternary mixed metal selenites with asymmetric cationic coordination environments

Two new isostructural mixed metal selenites, PbMSeO(6) (M = Mo(6+) or W(6+)), that are only composed of second-order Jahn-Teller (SOJT) distortive cations have been synthesized by standard solid-state reaction techniques using PbO, SeO(2), and MoO(3) (or WO(3)) as reagents. The structures of the reported materials were determined by single-crystal and powder X-ray diffraction. The materials show a three-dimensional framework structure consisting of chains of corner-shared MO(6) octahedra connected by SeO(3) and PbO(8) polyhedra. All of the constituent cations (M(6+), Se(4+), and Pb(2+)) are in distorted environments attributable to second-order Jahn-Teller (SOJT) effects. While the Mo(6+) cations undergo a C(2)-type intraoctahedral distortion toward an edge, the Se(4+) and Pb(2+) cations are in asymmetric coordination environments attributable to their lone pairs. The SeO(3) polyhedra strongly influence the direction of the Mo(6+) intraoctahedral distortion. Infrared spectroscopy, thermogravimetric analysis, the magnitudes of out-of-center distortions, and dipole moment calculations are also presented. Crystal data: PbMoSeO(6), triclinic, space group P-1 (No. 2), with a = 6.8944(6) ?, b = 7.2219(6) ?, c = 10.8294(9) ?, α = 99.751(2)°, β = 99.996(2)°, γ = 90.041(2)°, V = 523.09(8) ?(3), and Z = 2; PbWSeO(6), triclinic, space group P-1 (No. 2), with a = 6.8689(2) ?, b = 7.2398(2) ?, c = 10.9037(3) ?, α = 99.699(4)°, β = 100.348(3)°, γ = 90.139(4)°, V = 525.50(3) ?(3), and Z = 2.     

A series of new phases in the alkali metal-Nb(V)/Ta(V)-Se(IV)/Te(IV)-O systems

Six new phases in the alkali metal-Nb(V)/Ta(V)-Se(IV)/Te(IV)-O systems have been prepared by solid-state reactions at high-temperatures. Their structures were determined by single-crystal X-ray diffraction studies. AM(3)O(6)(QO(3))(2) (A = K, Rb, M = Nb, Ta, Q = Te; A = K, M = Nb, Q = Se) are isomorphous and their structures feature a 3D network with 1D 4- and 6-MRs tunnels along the a-axis which is composed of 2D layers of corner-sharing MO(6) octahedra bridged by QO(3) groups. The alkali metal ions are located at the above 1D tunnels of 6-MRs. The structure of Cs(3)Nb(9)O(18)(TeO(3))(2)(TeO(4))(2) features a thick Nb-Te-O layer built of corner-sharing NbO(6) octahedra, TeO(3) and TeO(4) groups. The 2D layer of the NbO(6) octahedra with 1D tunnels of 6-MRs along the c-axis are formed by 1D chains of NbO(6) chains along the c-axis and linear Nb(4)O(21) tetramers by corner-sharing. The TeO(3) and TeO(4) groups are grafted on both sides of the niobium-oxide layer via Nb-O-Te or/and Te-O-Te bridges. The caesium(i) ions are located at the above 1D tunnels of 6-MRs. TGA, UV-vis and infrared spectral measurements as well as electronic structure calculations have also been performed.     

Two new noncentrosymmetric (NCS) polar oxides: syntheses, characterization, and structure-property relationships in BaMTe2O7 (M = Mg2+ or Zn2+)

Two new noncentrosymmetric (NCS) polar oxides, BaMgTe(2)O(7) and BaZnTe(2)O(7), 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 MgO(5) or ZnO(5), Te(6+)O(6), and Te(4+)O(4) polyhedra that are separated by Ba(2+) cations. The Te(4+) cation is found in a highly asymmetric and polar coordination environment attributable to its stereoactive lone-pair. The alignment of the individual TeO(4) polar polyhedra results in macroscopic polarity for BaMgTe(2)O(7) and BaZnTe(2)O(7). Powder second-harmonic generation (SHG) measurements revealed a moderate SHG efficiency of approximately 5 × KDP (or 200 × α-SiO(2)) 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 BaMgTe(2)O(7) and BaZnTe(2)O(7), 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: BaMgTe(2)O(7), orthorhombic, space group Ama2 (No. 40), a = 5.558(2) ?, b = 15.215(6) ?, c = 7.307(3) ?, V = 617.9(4) ?(3), and Z = 4; BaZnTe(2)O(7), orthorhombic, space group Ama2 (No. 40), a = 5.5498(4) ?, b = 15.3161(11) ?, c = 7.3098(5) ?, V = 621.34(8) ?(3), and Z = 4.     

Synthesis and structure of A4V6[Te2(4+)Te6+]O24 (A = K, Rb)-two new quaternary mixed-valent tellurium oxides

Two new mixed-valent tellurium oxides with vanadium(V), A(4)V(6)[Te(2)(4+)Te(6+)]O(24) (A = K and Rb), have been synthesized by hydrothermal and conventional solid state techniques. Their structures were determined by single-crystal X-ray diffraction analysis. These two iso-structural compounds exhibit layered structural topologies consisting of [V(6)Te(3)O(24)](4-) anionic units. In these anionic structural units, a Te(6+)O(6) octahedron is connected to six VO(4) tetrahedra by corner-sharing to generate a [V(6)TeO(24)] unit, and each of these [V(6)TeO(24)] units are interconnected by sharing two Te(4+)O(3) polyhedra to complete the infinite [V(6)Te(3)O(24)](4-) sheets. Infrared spectroscopy, UV-Visible diffuse reflectance spectroscopy, and thermogravimetric analysis were also performed on these two compounds. Crystal data: K(4)V(6)Te(3)O(24), trigonal, space group R ?3c (No. 167) with a = b = 9.7075(6) ?, c = 42.701(3) ?, V = 3484.9(4) ?(3), and Z = 6; Rb(4)V(6)Te(3)O(24), trigonal, space group R ?3c (No. 167) with a = b = 9.8399(9) ?, c = 43.012(4) ?, V = 3606.6(6) ?(3), and Z = 6.     

Expanding the remarkable structural diversity of uranyl tellurites: hydrothermal preparation and structures of K[UO(2)Te(2)O(5)(OH)], Tl(3)[(UO(2))(2)[Te(2)O(5)(OH)](Te(2)O(6))].2H(2)O,beta-Tl(2)[UO(2)(TeO(3))(2)], and Sr(3)[UO(2)(TeO(3))(2)](TeO(3))(2)

The reactions of UO(2)(C(2)H(3)O(2))(2).2H(2)O with K(2)TeO(3).H(2)O, Na(2)TeO(3) and TlCl, or Na(2)TeO(3) and Sr(OH)(2).8H(2)O under mild hydrothermal conditions yield K[UO(2)Te(2)O(5)(OH)] (1), Tl(3)[(UO(2))(2)[Te(2)O(5)(OH)](Te(2)O(6))].2H(2)O (2) and beta-Tl(2)[UO(2)(TeO(3))(2)] (3), or Sr(3)[UO(2)(TeO(3))(2)](TeO(3))(2) (4), respectively. The structure of 1 consists of tetragonal bipyramidal U(VI) centers that are bound by terminal oxo groups and tellurite anions. These UO(6) units span between one-dimensional chains of corner-sharing, square pyramidal TeO(4) polyhedra to create two-dimensional layers. Alternating corner-shared oxygen atoms in the tellurium oxide chains are protonated to create short/long bonding patterns. The one-dimensional chains of corner-sharing TeO(4) units found in 1 are also present in 2. However, in 2 there are two distinct chains present, one where alternating corner-shared oxygen atoms are protonated, and one where the chains are unprotonated. The uranyl moieties in 2 are bound by five oxygen atoms from the tellurite chains to create seven-coordinate pentagonal bipyramidal U(VI). The structures of 3 and 4 both contain one-dimensional [UO(2)(TeO(3))(2)](2-) chains constructed from tetragonal bipyramidal U(VI) centers that are bridged by tellurite anions. The chains differ between 3 and 4 in that all of the pyramidal tellurite anions in 3 have the same orientation, whereas the tellurite anions in 4 have opposite orientations on each side of the chain. In 4, there are also additional isolated TeO(3)(2-) anions present. Crystallographic data: 1, orthorhombic, space group Cmcm, a = 7.9993(5) A, b = 8.7416(6) A, c = 11.4413(8) A, Z = 4; 2, orthorhombic, space group Pbam, a = 10.0623(8) A, b = 23.024(2) A, c = 7.9389(6) A, Z = 4; 3, monoclinic, space group P2(1)/n, a = 5.4766(4) A, b = 8.2348(6) A, c = 20.849(3) A, beta = 92.329(1) degrees, Z = 4; 4, monoclinic, space group C2/c, a = 20.546(1) A, b = 5.6571(3) A, c = 13.0979(8) A, beta = 94.416(1) degrees, Z = 4.     

The spectroscopic properties of Er(3+)-doped TeO(2)-Nb(2)O(5) glasses with high mechanical strength performance

(100-x)TeO(2)-xNb(2)O(5) (x=5-20) niobic tellurite glasses doped with 0.5 mol.% Er(2)O(3) were synthesized, and their thermal, mechanical, and spectroscopic properties were measured and compared to the properties of the typical 75TeO(2)-20ZnO-5Na(2)O (TZN) tellurite glass. The refractive index (n(d)), density (rho), and glass transition temperature (T(g)) of bulk glasses increase with the Nb(2)O(5) content. The Vickers microhardness (H(v)) of bulk glass in niobic tellurite glasses also increases with the Nb(2)O(5) content. The values (2.5-3.2GPa) of H(v) in the niobic tellurite glasses are 47-88% larger than that (1.7GPa) in TZN glass. The effect of Nb(2)O(5) content on absorption spectra, the Judd-Ofelt parameters Omega(t) (t=2, 4, 6), fluorescence spectra and the lifetimes of Er(3+):I(13/2) level were also investigated, and the stimulated emission cross-section was calculated from McCumber theory. With increasing Nb(2)O(5) content in the glass composition, the Omega(t) (t=2, 4, 6) parameters, fluorescence full width at half maximum (FWHM) of I(13/2) of Er(3+) increase, while the (4)I(13/2) lifetimes of Er(3+) decreases. Compared with TZN glass, the gain bandwidth properties of Er(3+)-doped TeO(2)-Nb(2)O(5) glass is much larger than in tellurite glass based TeO(2)-ZnO-Na(2)O system, bismush-based glass, germanate, and silicate glasses, which indicates that TeO(2)-Nb(2)O(5) glasses are better choice as a practical available host material for broadband Er(3+)-doped amplifier.     

New luminescent solids in the Ln-W(Mo)-Te-O-(Cl) systems

Solid-state reactions of lanthanide(III) oxide (and/or lanthanide(III) oxychloride), MoO3 (or WO3), and TeO2 at high temperature lead to eight new luminescent compounds with four different types of structures, namely, Ln2(MoO4)(Te4O10) (Ln = Pr, Nd), La2(WO4)(Te3O7)2, Nd2W2Te2O13, and Ln5(MO4)(Te5O13)(TeO3)2Cl3 (Ln = Pr, Nd; M = Mo, W). The structures of Ln2(MoO4)(Te4O10) (Ln = Pr, Nd) feature a 3D network in which the MoO4 tetrahedra serve as bridges between two lanthanide(III) tellurite layers. La2(WO4)(Te3O7)2 features a triple-layer structure built of a [La2WO4]4+ layer sandwiched between two Te3O72- anionic layers. The structure of Nd2W2Te2O13 is a 3D network in which the W2O108- dimers were inserted in the large tunnels of the neodymium(III) tellurites. The structures of Ln5(MO4)(Te5O13)(TeO3)2Cl3 (Ln = Pr, Nd; M = Mo, W) feature a 3D network structure built of lanthanide(III) ions interconnected by bridging TeO32-, Te5O136-, and Cl- anions with the MO4 (M = Mo, W) tetrahedra capping on both sides of the Ln4 (Ln = Pr, Nd) clusters and the isolated Cl- anions occupying the large apertures of the structure. Luminescent studies indicate that Pr2(MoO4)(Te4O10) and Pr5(MO4)(Te5O13)(TeO3)2Cl3 (M = Mo, W) are able to emit blue, green, and red light, whereas Nd2(MoO4)(Te4O10), Nd2W2Te2O13, and Nd5(MO4)(Te5O13)(TeO3)2Cl3 (M = Mo, W) exhibit strong emission bands in the near-IR region.     

窄带隙IV-VI族半导体PbTe(111)的表面氧化及氧的热脱附机理

利用X射线光电子能谱(XPS)、扫描隧道显微镜(STM)以及低能电子衍射(LEED),对PbTe(111)薄膜的表面氧化及氧的热脱附机理进行了研究.结果表明:PbTe(111)薄膜经500VAr+轰击加上250℃高温退火循环处理,可得到呈(1×1)周期性排列的清洁表面.将此清洁表面暴露于大气两天后,表面被氧化形成了PbO2、PbO和TeO2,氧化层的厚度大于2个单原子层(ML),与清洁PbTe(111)表面相比,被氧化的PbTe(111)表面的Te3d5/2与Pb4f7/2芯态谱峰的面积比明显减小,表明被氧化的PbTe(111)表面是富Pb的.在热脱附处理过程中,PbO2和TeO2的芯态峰消失,且O1s芯态峰的强度迅速减弱,表明加热处理不仅使PbO2和TeO2发生了分解,同时也使氧发生了脱附,但PbO即使在350℃退火仍吸附于PbTe(111)表面.     

Explorations of new types of second-order nonlinear optical materials in Cd(Zn)-VV-TeIV-O Systems

Solid-state reactions of zinc(II) or cadmium(II) oxide, V(2)O(5), and TeO(2) at high temperature led to two novel quaternary compounds, namely, Zn(3)V(2)TeO(10) and Cd(4)V(2)Te(3)O(15). The structure of Zn(3)V(2)TeO(10) is a complicated three-dimensional (3D) network constructed by the interconnection of ZnO(5), ZnO(6), VO(4), and TeO(4) polyhedra via corner- and edge-sharing. Cd(4)V(2)Te(3)O(15) with an acentric structure features a 3D network in which the cadmium tellurite layers are further interconnected by both "isolated" VO(4) tetrahedra and one-dimensional (1D) vanadium oxide helical chains. Cd(4)V(2)Te(3)O(15) displays a second harmonic generation (SHG) efficiency of about 1.4 times that of KH(2)PO(4) (KDP). Both compounds are direct band-gap semiconductors and are transparent in the range of 0.6-10.0 mum. Measurements of luminescence indicate that both compounds exhibit broad emission bands in the blue-light region.     

Structure and properties of the thorium vanadyl tellurate, Th(VO2)2(TeO6)(H2O)2

The hydrothermal reaction of Th(NO3)4.xH2O with V2O5 and H6TeO6 at 200 degrees C under autogenously generated pressure results in the formation of Th(VO2)2(TeO6)(H2O)2 as a pure phase. The single-crystal X-ray data indicate that Th(VO2)2(TeO6)(H2O)2 possesses a three-dimensional structure constructed from ThO9 tricapped trigonal prisms, VO5 distorted square pyramids, VO4 distorted tetrahedra, and TeO6 distorted octahedra. Both of the vanadium polyhedra contain VO2+ vanadyl units with two short V=O bond distances. The tellurate octahedron is tetragonally distorted and utilizes all of its oxygen atoms to bond to adjacent metal centers, sharing edges with ThO9 and VO5 units, and corners with two ThO9, one VO5, and two VO4 polyhedra. Crystallographic data: Th(VO2)2(TeO6)(H2O)2, orthorhombic, space group Pbca, a = 12.6921(7), b = 11.5593(7), c = 13.0950(8) A, Z = 8 (T = 193 K). The UV-vis diffuse reflectance spectrum of Th(VO2)2(TeO6)(H2O)2 shows vanadyl-based charge-transfer absorption features. Th(VO2)2(TeO6)(H2O)2 decomposes primarily to Th(VO3)4 when heated at 600 degrees C in air.     

Syntheses and structural characterization of new mixed-valent tellurium oxides, a4[te5(6+)te(3)4+]o23 (a=rb and k)

Two new isostructural mixed-valent tellurium oxides, A4[Te(5)6+Te3(4+)]O23 [A=Rb and K], have been synthesized by solid-state reactions and characterized by X-ray diffraction and infrared spectroscopy. Compound could be prepared by hydrothermal reaction as well. These compounds, as determined from the single-crystal X-ray structure of, consist of corrugated [Te6O23] layers, built from corner-connected TeO6 octahedra and TeO5 square pyramids. These layers are connected to one another by tetravalent telluriums, having square-pyramidal and disphenoid geometries. Both compounds crystallize in the orthorhombic space group Pna2(1) (33) with Z=4 and have the following unit cell parameters: For 1, a=19.793(4), b=14.664(4), and c=7.292(4) A. For 2, a=19.573(3), b=14.448(2), and c=7.273(8) A.     

Synthesis, Structure, and Characterization of New Li(+) - d(0) -Lone-Pair - Oxides: Noncentrosymmetric Polar Li(6)(Mo(2)O(5))(3)(SeO(3))(6) and Centrosymmetric Li(2)(MO(3))(TeO(3)) (M = Mo(6+) or W(6+))

New quaternary lithium - d(0) cation - lone-pair oxides, Li(6)(Mo(2)O(5))(3)(SeO(3))(6) (Pmn2(1)) and Li(2)(MO(3))(TeO(3)) (P2(1)/n) (M = Mo(6+) or W(6+)), 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 MO(6) and asymmetric AO(3) (A = Se(4+) or Te(4+)) polyhedra. The anionic layers stack along a 2-fold screw axis and are separated by Li(+) cations. Powder SHG measurements on Li(6)(Mo(2)O(5))(3)(SeO(3))(6) using 1064 nm radiation reveal a SHG efficiency of approximately 170 × α-SiO(2). Particle size vs SHG efficiency measurements indicate Li(6)(Mo(2)O(5))(3)(SeO(3))(6) is type 1 nonphase-matchable. Converse piezoelectric measurements result in a d(33) value of ～28 pm/V and pyroelectric measurements reveal a pyroelectric coefficient of -0.43 μC/m(2)K at 50 °C for Li(6)(Mo(2)O(5))(3)(SeO(3))(6). Frequency-dependent polarization measurements confirm that Li(6)(Mo(2)O(5))(3)(SeO(3))(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.     

Cd2(Te6O13)][Cd2Cl6] and Cd7Cl8(Te7O17): novel tellurium(IV) oxide slabs and unusual cadmium chloride architectures

Initial attempts to prepare new Ln-Cd-Te-O-Cl compounds led to the isolation of two novel cadmium tellurium(IV) oxychlorides with two different types of structures, namely, [Cd(2)(Te(6)O(13))][Cd(2)Cl(6)] and Cd(7)Cl(8)(Te(7)O(17)). Both compounds feature novel polymeric tellurium(IV) oxide anions and unusual cadmium chloride substructures. The structure of [Cd(2)(Te(6)O(13))][Cd(2)Cl(6)] is composed of 1D [Cd(2)Cl(6)](2)(-) double chains and (002) [Cd(2)(Te(6)O(13))](2+) layers. The 1D Te(6)O(13)(2)(-) slab of the [Cd(2)(Te(6)O(13))](2+) layer is formed by TeO(3), TeO(4), and TeO(5) groups via corner- and edge-sharing, and it contains six- and seven-membered tellurium(IV) polyhedral rings. The structure of Cd(7)Cl(8)(Te(7)O(17)) features a 3D network with long-narrow tunnels along the b axis. The two types of structural building blocks are 1D [Te(7)O(17)](6)(-) anions and unusual corrugated [Cd(7)Cl(8)](6+) layers based on "cyclohexane-like" Cd(3)Cl(3) rings.     

Syntheses and crystal structures of a series of alkaline earth vanadium selenites and tellurites

Six new novel alkaline-earth metal vanadium(V) or vanadium(IV) selenites and tellurites, namely, Sr(2)(VO)(3)(SeO(3))(5), Sr(V(2)O(5))(TeO(3)), Sr(2)(V(2)O(5))(2)(TeO(3))(2)(H(2)O), Ba(3)(VO(2))(2)(SeO(3))(4), Ba(2)(VO(3))Te(4)O(9)(OH), and Ba(2)V(2)O(5)(Te(2)O(6)), have been prepared and structurally characterized by single crystal X-ray diffraction analyses. These compounds exhibit six different anionic structures ranging from zero-dimensional (0D) cluster to three-dimensional (3D) network. Sr(2)(VO)(3)(SeO(3))(5) features a 3D anionic framework composed of VO(6) octahedra that are bridged by SeO(3) polyhedra. The oxidation state of the vanadium cation is +4 because of the partial reduction of V(2)O(5) by SeO(2) at high temperature. Ba(3)(VO(2))(2)(SeO(3))(4) features a 0D [(VO(2))(SeO(3))(2)](3-) anion. Sr(V(2)O(5))(TeO(3)) displays a unique 1D vanadium(V) tellurite chain composed of V(2)O(8) and V(2)O(7) units connected by tellurite groups, forming 4- and 10-MRs, whereas Sr(2)(V(2)O(5))(2)(TeO(3))(2)(H(2)O) exhibits a 2D layer consisting of [V(4)O(14)] tetramers interconnected by bridging TeO(3)(2-) anions with the Sr(2+) and water molecules located at the interlayer space. Ba(2)(VO(3))Te(4)O(9)(OH) exhibits a one-dimensional (1D) vanadium tellurite chain composed of a novel 1D [Te(4)O(9)(OH)](3-) chain further decorated by VO(4) tetrahedra. Ba(2)V(2)O(5)(Te(2)O(6)) also features a 1D vanadium(V) tellurites chain in which neighboring VO(4) tetrahedra are bridged by [Te(2)O(6)](4-) dimers. The existence of V(4+) ions in Sr(2)(VO)(3)(SeO(3))(5) is also confirmed by magnetic measurements. The results of optical diffuse-reflectance spectrum measurements and electronic structure calculations based on density functional theory (DFT) methods indicate that all six compounds are wide-band gap semiconductors.     

New members in the Ni(n+1)(QO3)nX2 family: unusual 3D network based on Ni4ClO3 cubane-like clusters in Ni7(TeO3)6Cl2

Three new members in the family of nickel(II) tellurium(IV)/selenium(IV) oxyhalides generally formulated as Ni(n+1)(QO3)nX2 (Q = Te, X = Cl, n = 6, 10; Q = Se, X = Br, n = 4) have been synthesized by solid-state reactions of NiX2, QO2, and NiO (or Ni2O3) at high temperature. The structure of Ni7(TeO3)6Cl2 features a novel 3D network based on Ni4ClO3 cubane-like clusters with Te atoms located at the cavities of the network. Ni4ClO3 clusters are interconnected into a hexagonal layer through additional O...O edges. The neighboring two layers are further interconnected, via sharing of common Ni(II) atoms, into a novel 3D network. The 3D open framework of Ni5(SeO3)4Br2 is built from 2D nickel(II) oxybromide layers bridged by Se and additional Ni atoms. The structure of Ni11(TeO3)10Cl2 features a condensed 3D network based on NiO5Cl, NiO6, and NiO5 polyhedra interconnected via corner and edge sharing, as well as O-Te-O bridges. The results of magnetic property measurements indicate that all three compounds display antiferromagnetic interactions between nickel(II) centers.     

Synthesis, structure, and characterization of novel two- and three-dimensional vanadates: Ba2.5(VO2)3(SeO3)4.H2O and La(VO2)3(TeO6).3H2O

Two new vanadates, Ba(2.5)(VO2)3(SeO3)4.H2O and La(VO2)3(TeO6).3H2O, have been synthesized by hydrothermal methods using BaCO3, Ba(OH)2.H2O, La(NO3)3.6H2O, V2O5, TeO2, and H2SeO3 as reagents. The structures were determined by single-crystal X-ray diffraction. Ba(2.5)(VO2)3(SeO3)4.H2O exhibits a two-dimensional layered structure consisting of VO(5) square pyramids and SeO3 polyhedra, whereas La(VO2)3(TeO6).3H2O has a three-dimensional framework structure composed of VO(4) tetrahedra and TeO6 octahedra. Infrared and Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, and thermogravimetric analysis are also presented. Crystal data: Ba(2.5)(VO2)3(SeO3)4.H2O, trigonal, space group P (No. 147) with a = b = 12.8279(15) A, c = 7.2631(9) A, V = 1035.1(2) A(3), and Z = 2; La(VO2)3(TeO6).3H2O, trigonal, space group R3c (No. 161) with a = b = 9.4577(16) A, c = 23.455(7) A, V = 1816.9(7) A3, and Z = 6.