Two new rare-earth oxyborates Ba4BiTbO(BO3)4 and Ba1.54Sr2.46BiTbO(BO3)4 and luminescence properties of the Ba4BiTb1-xEuxO(BO3)4 phosphors.

Single crystals of two new terbium oxyborates Ba4BiTbO(BO3)4 and Ba1.54Sr2.46BiTbO(BO3)4 were obtained by the high-temperature solution method. They crystallize in the hexagonal P63/mmc group (Z = 2) with lattice parameters of a = 5.41865(9) Å, c = 26.3535(5) Å, V = 670.12(3) Å3 and a = 5.36534(19) Å, c = 26.0661(10) Å, V = 649.83(5) Å3, respectively. Their crystal structures feature two kinds of layers: [Tb(BO3)2]n3n- formed by corner-sharing TbO6 octahedra and BO3 triangles, as well as [Bi(BO3)2O]n5n- consisting of Bi2O13 dimers and BO3 groups, with alkali-earth cations sitting inside and between the layers. In addition, solid solutions of Ba4BiTb1-xEuxO(BO3)4 (0 ≤ x ≤ 0.2) were prepared via the solid-state reaction method. The obtained products were characterized by powder XRD, SEM, IR/Raman, XPS, DRS, and luminescence spectroscopy. It was found that as the Eu3+ doped content varies from x = 0 to 0.2, the emission color of the Ba4BiTb1-xEuxO(BO3)4 phosphors can be adjusted from cyan to near-white and then to orange-red or from green to orange and then to red under the excitation of 349 and 377 nm, respectively. Furthermore, the emission intensities and chromaticity coordinates were found to be sensitive to the temperature for the phosphor Ba4BiTb0.999Eu0.001O(BO3)4 upon 377 nm excitation. The above results demonstrate that Ba4BiTb1-xEuxO(BO3)4 phosphors have potential as multifunctional materials for solid-state lighting and temperature sensing applications.

A new melilite-type rare-earth borate CdTbGaB2O7 and multicolor tunable emission in the CdTb1-xSmxGaB2O7 (0 ≤ x ≤ 0.2) phosphors.

A new mixed metal borate, CdTbGaB2O7, was successfully synthesized using the high-temperature solution method and its crystal structure was determined by single-crystal X-ray diffraction with the following unit-cell data: P4̄21m, a = b = 7.3487(1) Å, c = 4.7247(1) Å, V = 255.150(9) Å3, and Z = 2. It belongs to a new member of the melilite family, which features a 3D framework consisting of alternately stacked [Ga(B2O7)]n5n- tetrahedral layers and (Cd2+/Tb3+) cationic layers that are interconnected via B(Ga)-O-(Cd/Tb) bridges. In addition, the solid solutions of CdTb1-xSmxGaB2O7 (0 ≤ x ≤ 0.2) were prepared via the solid-state reaction method. The combined techniques of XRD, SEM, IR/Raman, XPS and PLE/PL were employed to characterize the products. It was found that the CdTb1-xSmxGaB2O7 phosphors simultaneously showed green emission of Tb3+ at 545 nm and orange emission of Sm3+ at 603 nm under excitation at 370 nm. The emission color can be adjusted from green to orange-red by varying the Sm3+ doped content via an energy transfer mechanism. For CdTb0.995Sm0.005GaB2O7, a QY of 13.22% was obtained, and its emission intensity at 423 K was 94% of that at 303 K. These results show that the prepared materials can act as potential color-tunable phosphors for UV w-LEDs.

Synthesis, Characterization, and Polishing Properties of a Lanthanum Cerium Fluoride Abrasive.

One kind of lanthanum cerium fluoride abrasive was prepared using the raw materials Ce2(CO3)3, La·Ce(CO3)3, and NH4F at temperatures of 400-1050 °C. The combined techniques of X-ray diffraction with Rietveld refinements, scanning electron microscopy, and X-ray photoelectron spectroscopy were employed to characterize the products. It was found that the materials are all made up of agglomerated irregular block-shaped particles with particle sizes in micrometer ranges. Below 850 °C, the product is a mixture of cubic CeO2 and trigonal LaF3, while above 900 °C, it is a mixture of cubic CeO2 and tetragonal LaOF. A higher calcination temperature suppresses the formation of the LaF3 phase but enhances the LaOF phase. The Ce in the prepared material is present in mixed states of Ce3+ and Ce4+, and the Ce4+/Ce3+ ratio increases with increasing calcination temperature. When the material prepared at 900 °C was used in the polishing test on K9 glass, the obtained polishing surface is very clean and flat, and the thickness difference before and after grinding is moderate, indicating its potential as an abrasive for polishing the surface of optical glass.

A new rare-earth oxyborate Ba3BiPbEuO(BO3)4 and the luminescence properties of the Ba3BiPbY1-xEuxO(BO3)4 phosphors.

A new rare-earth oxyborate Ba3BiPbEuO(BO3)4 was prepared, and its crystal structure was established by the single-crystal X-ray diffraction method with the following structural data: P63/mmc, a = 5.4305(1) Å, c = 26.3501(3) Å, V = 672.96(3) Å3 and Z = 2. This is a layered material containing two types of layers: one is formed by corner-sharing EuO6 octahedra and BO3 triangles and the other is composed of corner- or edge-sharing (Bi/Pb)O7 hexagonal pyramids and BO3 triangles. These layers and their equivalent partners are alternately stacked along the c-axis, with Ba2+ cations situated in between and within the layers. Furthermore, the phase composition, morphology, and IR, Raman, XPS, and UV-vis absorption spectra of this compound were studied. In addition, solid solutions of Ba3BiPbY1-xEuxO(BO3)4 (0 ≤ x ≤ 1) were prepared via the solid-state reaction method and their photoluminescence properties were investigated. Ba3BiPbYO(BO3)4 and Ba3BiPbEuO(BO3)4 showed blue and reddish-orange luminescence when excited at 242 and 394 nm, respectively. By doping Eu3+ into the Ba3BiPbYO(BO3)4 matrix and changing the Eu3+ doping concentration, luminescence color tunability from blue to orange-red was realized in Ba3BiPbY1-xEuxO(BO3)4 phosphors under excitation at 331 nm. This kind of material with color variability may have potential application in field-emission displays.

Two new rare-earth borates Sr2Tb3B27-δO46 and Ba2Eu3B27-δO46 (δ = 2/3): syntheses, crystal structures, and luminescence properties.

Two new alkali-earth and rare-earth metal borates, Sr2Tb3B27-δO46 and Ba2Eu3B27-δO46 (δ = 2/3), have been prepared by high-temperature solution reactions at 950 °C. The single-crystal XRD analysis showed that the borates crystallize in the rhombohedral space group R3 with the cell parameters a = 7.7468(1) Å, c = 46.3657(5) Å, V = 2409.75(3) Å3, Z = 3 and a = 7.7964(1) Å, c = 46.5086(6) Å, V = 2448.23(7) Å3, Z = 3, respectively, which further confirms that "LnMB9O16" has the right formula of M2Ln3B27-δO46 (δ = 2/3). Their crystal structures consist of 3D networks constructed by Tb(Eu)O6 trigonal prisms, BO3 planar triangles, and BO4 tetrahedra, with large cavities accommodating Sr2+ (Ba2+) cations. Furthermore, the phase composition, morphology, IR, Raman, and XPS spectra as well as photoluminescence properties of these two compounds were studied. Upon excitation by ultraviolet radiation, Sr2Tb3B27-δO46 exhibits the characteristic emission lines originating from Tb3+ corresponding to 5D4-7F6,5,4,3,2,1,0 transitions, whereas Ba2Eu3B27-δO46 displays bright red emission from Eu3+ with four groups of emission bands associated with 5D0 → 7F1,2,3,4 transitions. Both phosphors show stable luminescence and color purity at elevated temperatures. As it may be expected, Sr2Tb3B27-δO46 and Ba2Eu3B27-δO46 (δ = 2/3) are promising green (Tb) and red (Eu) components for use in WLEDs.

Crystal structures of the solid solutions Na3Zn0.912Cd0.088B5O10 and Na3Zn0.845Mg0.155B5O10.

Two new penta-borates, tris-odium zinc cadmium penta-borate, Na3Zn0.912Cd0.088B5O10, and tris-odium zinc magnesium penta-borate, Na3Zn0.845Mg0.155B5O10, have been synthesized by high-temperature solution reactions at 1023 K. Their crystal structures were determined by single-crystal X-ray diffraction. Both solid solutions crystallize in the ortho-rhom-bic form of the parent compound Na3ZnB5O10 (space group type Pbca, Z = 8) and contain the double ring [B5O10]5- anion composed of one BO4 tetra-hedron and four BO3 triangles as the basic structural motif. The anions are bridged by tetra-hedrally coordinated and occupationally disordered M2+ (M = Zn/Cd, Zn/Mg) cations via common O atoms to form [MB5O10] n3n- layers. The intra-layer inter-secting channels and the inter-layer voids are occupied by Na+ cations to balance the charge.

Linear and nonlinear optical susceptibilities and the hyperpolarizability of borate LiBaB9O15 single-crystal: theory and experiment.

The single-crystal borate LiBaB9O15 was synthesized by a high-temperature solution reaction and structurally determined by the single-crystal X-ray diffraction technique. It crystallizes in the noncentrosymmetric space group R3c and features a three-dimensional ∞3[B9O15]3­ anionic framework, with infinite channels in which the Li+ and Ba2+ cations are located. The linear optical properties were investigated experimentally in terms of the absorption spectrum, which reveals an optical gap of 5.17 eV. In addition we have calculated the linear optical properties using state-of-the-art all-electron full potential linearized augmented plane wave method. The nonlinear optical susceptibilities, namely, the second harmonic generation and the hyperpolarizability of the single-crystal borate LiBaB9O15 are calculated and evaluated at a static limit and at λ = 1064 nm. The calculation shows there exists three second-order nonlinear optical susceptiblities tensors components. We present measurements of the IR spectra in the range 500­2000 cm­1, and the second harmonic generation was performed using a Quantel 15 ns Nd:YAG laser operating at 1064 nm.

X-ray diffraction, X-ray photoelectron spectra, crystal structure, and optical properties of centrosymmetric strontium borate Sr2B16O26.

We report results of X-ray diffraction (XRD) and valence band X- ray photoelectron (VB-XPS) spectra for strontium borate Sr(2)B(16)O(26). The X-ray structural analysis shows that the single crystals of Sr(2)B(16)O(26) crystallize in the monoclinic space group P2(1)/c with a = 8.408(1) A, b = 16.672(1) A, c = 13.901(2) A, beta = 106.33(1) degrees , and Z = 4. The crystal structure consists of a 3D network of the complex borate anion [B(16)O(20)O(12/2)](4-), formed by 12 BO(3) triangles and four BO(4) tetrahedra, which can be viewed as three linked [B(3)O(3)O(4/2)](-) triborate groups bonded to one pentaborate [B(5)O(6)O(4/2)](-) group and two BO(3) triangles. Using this structure, we have performed theoretical calculations using the all-electron full potential linearized augmented plane wave (FP-LAPW) method for the band structure, density of states, electron charge density, and the frequency-dependent optical properties. Our experimental VB-XPS of Sr(2)B(16)O(26) is compared with results of our FP-LAPW calculations. Our calculations show that the valence band maximum (VBM) and conduction band minimum (CBM) are located at Gamma of the Brillouin zone (BZ) resulting in a direct energy gap of about 5.31 eV. Our measured VB-XPS show reasonable agreement with our calculated total density of states for the valence band that is attributed to the use of the full potential method.

X-ray diffraction, crystal structure, and spectral features of the optical susceptibilities of single crystals of the ternary borate oxide lead bismuth tetraoxide, PbBiBO4.

The all-electron full-potential linearized augmented plane-wave method has been used for an ab initio theoretical study of the band structure, the spectral features of the optical susceptibilities, the density of states, and the electron charge density for PbBiBO4. Our calculations show that the valence-band maximum (VBM) and conduction-band minimum (CBM) are located at the center of the Brillouin zone, resulting in a direct energy gap of about 3.2 eV. We have synthesized the PbBiBO4 crystal by employing a conventional solid-state reaction method. The theoretical calculations in this work are based on the structure built from our measured atomic parameters. We should emphasize that the observed experimental X-ray diffraction (XRD) pattern is in good agreement with the theoretical one, confirming that our structural model is valid. Our calculated bond lengths show excellent agreement with the experimental data. This agreement is attributed to our use of full-potential calculations. The spectral features of the optical susceptibilities show a small positive uniaxial anisotropy.

Synthesis, IR, UV-vis spectra, x-ray diffraction and band structure of a non-centrosymmetric borate single-crystal CaBiGaB(2)O(7).

A non-centrosymmetric borate, CaBiGaB(2)O(7), has been grown by a solid-state reaction method at a temperature below 700 °C. The single-crystal x-ray structural analysis has shown that it crystallizes in the tetragonal space group [Formula: see text] with a = 0.7457(1) nm, c = 0.4834(1) nm, Z = 2. It has a three-dimensional (3D) structure in which [B(2)O(7)](8-) groups are bridged by [GaO(4)](5-) tetrahedra through shared O atoms to form 2D [Formula: see text] layers that are further linked by Bi(3+)/Ca(2+) cations giving rise to the final 3D framework. The IR spectrum confirms the presence of [BO(4)](5-) groups and the UV-vis diffuse reflectance spectrum shows that the optical band gap is about 2.9 eV. This value is compared with our band structure calculations using the full potential linearized augmented plane wave approach within the framework of the Engel-Vosko GGA formalism.

X-ray diffraction and optical properties of a noncentrosymmetric borate CaBiGaB(2)O(7).

Single crystals of the noncentrosymmetric borate CaBiGaB(2)O(7) were synthesized by conventional solid state reaction. The purity of the crystal was checked by x-ray powder diffraction. The optical properties were measured by analyzing the diffuse reflectance data obtained with a Shimadzu UV-3101PC double-beam, double-monochromator spectrophotometer. We find a steep absorption edge confirming its semiconducting nature. The optical band gap obtained by extrapolation of a linearlike absorption edge was roughly 2.9 eV consistent with the observed pale yellow color of the sample. Theoretical calculations based on the structural model built from our measured atomic parameters have been performed using the all-electron full potential linearized augmented plane wave method. The generalized gradient approximation (GGA) of the exchange correlation potential as given by Engel-Vosko GGA is used. The frequency-dependent complex dielectric function was calculated and the origin of some of the spectral peaks is discussed. The linear optical properties show strong uniaxial anisotropy and birefringence that favors large second order susceptibility. Our calculations show that the complex second order nonlinear optical susceptibility tensor chi(322) ((2))(omega) is the dominant component having the largest total Re chi(322) ((2))(0) value of about 1.8 pm/V.

A new polymorph of magnesium oxalate dihydrate.

In the asymmetric unit of the title compound, catena-poly[[diaqua-magnesium(II)]-µ-oxalato], [Mg(C(2)O(4))(H(2)O)(2)](n), there is one Mg atom in an octa-hedral coordination with site symmetry 222, a unique C atom of the oxalate anion lying on a twofold axis, an O atom of the anion in a general position and a water O atom at a site with imposed twofold rotation symmetry. The Mg(2+) ions are ligated by water mol-ecules and bridged by the anions to form chains that are held together by O-H⋯O hydrogen bonds. The structure of the title compound has already been reported in a different space group [Lagier, Pezerat & Dubernat (1969 ▶). Rev. Chim. Miner.6, 1081-1093; Levy, Perrotey & Visser (1971 ▶). Bull. Soc. Chim. Fr. pp. 757-761].

Poly[disodium [diaqua-tri-µ(2)-oxalato-dimagnesium(II)]].

The title compound, {Na(2)[Mg(2)(C(2)O(4))(3)(H(2)O)(2)]}(n), is isotypic with its Co analogue. There are two crystallographically independent oxalate groups in the asymmetric unit, one lying on an inversion center and the other on a general position. Mg(2+) ions are ligated by H(2)O mol-ecules and bridged by tri- and tetra-dentate oxalate ligands, forming ladder-like double chains that are held together via O-H⋯O hydrogen bonds, with Na(+) cations located between the chains to balance the charge.

Lithium dioxobis[trioxoiodato(V)]vanadate, Li[VO2(IO3)2].

The title compound represents a new structure type, in which distorted VO6 octahedra are bridged by iodate groups to form infinite two-dimensional [VO2(IO3)2]- layers that are separated by octahedrally coordinated Li+ cations.

Gallium tris(iodate), Ga(IO3)3.

Ga(IO(3))(3) crystallizes in the space group P6(3), with the Ga atom at a site with imposed threefold symmetry. The crystal structure consists of slightly distorted GaO(6) octahedra that are bridged by I atoms of IO(3)(-) groups, giving rise to a three-dimensional polar network. The framework contains unoccupied hexagonal channels running parallel to the hexagonal [001] direction. The iodate groups have their stereochemically active non-bonded electron pairs pointing in the same direction along [001], which creates the polarity in the structure. The I-O bond distances and O-I-O angles are normal, being in the ranges 1.783 (3)-1.847 (2) A and 94.68 (11)-99.61 (12) degrees , respectively.

APdCu(Se2)(Se3) (A = K and Rb): new quaternary copper palladium polyselenides with unusual metal-selenium coordination.

Two novel metal polyselenides, KPdCu(Se(2))(Se(3)) (I) and RbPdCu(Se(2))(Se(3)) (II), have been synthesized from solvothermal reactions in superheated ethylenediamine at 160 degrees C. The isostructural compounds crystallize in the monoclinic space group P2(1)/m, Z = 2, with a = 6.145(1) A, b = 7.268(1) A, c = 8.865(2) A, beta = 102.41(3) degrees for I, and a = 6.253(1) A, b = 7.267(1) A, c = 8.993(2) A, beta = 102.28(3) degrees for II. Their crystal structures are two-dimensional networks with [PdCu(Se(2))(Se(3))](-) anionic layers built from one-dimensional [Pd(Se(2))(Se(3))](2)(-) "chains" that are "stitched" together by tetrahedrally coordinated Cu atoms. The DSC data show that I and II are stable up to 400 degrees C and decompose at ca. 436 and 424 degrees C, respectively. Both compounds are narrow band-gap semiconductors with estimated band gaps of about 0.7 eV (I) and 0.8 eV (II), respectively. They are the first structurally characterized quaternary copper palladium polychalcogenides with a (Se(2))(2)(-) and a (Se(3))(2)(-) fragment, both exhibiting interesting and unusual metal-selenium coordination.