The refractive indices of 509 oxides and 55 fluorides were analyzed using two forms of a one-term Sellmeier equation: ͑1͒ 1/(n 2 Ϫ1)ϭϪA/ 2 ϩB, where A, the slope of the plot of (n 2 Ϫ1) Ϫ1 versus Ϫ2 in units of 10 Ϫ16 m 2 , gives a measure of dispersion and B, the intercept of the plot at ϭϱ, gives n ϱ ϭ(1ϩ1/B) 1/2 and ͑2͒ n 2 Ϫ1ϭE d E o /(E o 2 Ϫ(ប) 2), where បϭthe photon energy, E o ϭthe average single oscillator ͑Sellmeier͒ energy gap, and E d ϭthe average oscillator strength, which measures the strength of interband optical transitions. Form ͑1͒ was used to calculate n at ϭ589.3 nm (n D) and n at ϭϱ (n ϱ), and the dispersion constant A. The total mean polarizabilility for each compound was calculated using the Lorenz-Lorentz equation: ␣ e ϭ3/4 ͓(V m) (n ϱ 2 Ϫ1)/(n ϱ 2 ϩ2)], where V m is the molar volume in Å 3. Provided for each compound are: n D , n ϱ , V m , ͗␣ e ͘, ͗A͘, ͗B͘, ͗E d ͘, ͗E o ͘, the literature reference, the method of measurement of n and estimated errors in n. Results obtained by prism, infrared reflectivity, ellipsometry, and interference methods are compared. Consistency of dispersion values among like compounds and structural families is used to evaluate the accuracy of refractive index data. Dispersion values range from 40 to 260ϫ10 Ϫ16 m 2 with the majority of values in the range of 60-100ϫ10 Ϫ16 m 2. High dispersion is associated with s 2 , p 6 , d 10 , and transition metal ions, H 2 O, and crystalline hydrates, whereas normal dispersion values are found in borates, aluminates, gallates, silicates, germanates, phosphates, and sulfates not containing H 2 O or any of the above ions. Exceptionally high dispersion is observed in liquid H

X-ray precession photographs and optical investigations of TPA-ZSM-5 (silicalite) and TEA-ZSM-8 zeolites reveal that ZSM-8 consists of two interpenetrating species rotated by 90° round the crystallographic c axis similarly to ZSM-5. The c axis of ZSM-5 coincides with refractive index n_x, the c axis of ZSM-8 coincides with n_y. The intergrowth species are differently shaped in ZSM-5 and ZSM-8. ZSM-5 consists of an orthorhombic prism penetrated by two pyramidal fragments. The ZSM-8 crystals studied here consist of species with two-dimensional hourglass-like shapes embedded in orthorhombic prisms. The orientations of the optical indicatrices of ZSM-5 and ZSM-8 are identical after calcination, Le., after removing or decomposing the template. This confirms recent work which showed that the framework structures of ZSM-5 and ZSM-8 are essentially identical

Abstract:This article reports about nanocomposites, which refractive index is tuned by adding TiO 2 nanoparticles. We compare in situ/ex situ preparation of nanocomposites. Preparation procedure is described, properties of nanocomposites are compared, and especially we examine the applicability of two-photon polymerization (2PP) of synthesized nanocomposites. All prepared samples exhibit suitable optical transparency at specific laser wavelengths. Three-dimensional structures were generated by means of two-photon polymerization effect induced by a femtosecond laser.

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Henritermierite, space group I4 1 /acd, at 293 K a = 12.489(1), c = 11.909(1) Å, Z = 8, with close to end-member composition (Ca 2.98 Na 0.01 Mg 0.01 ) VIII (Mn 1.95 Fe 0.01 Al 0.04 ) VI [SiO 4 ] 2.07 [H 4 O 4 ] 0.93 from the N'Chwaning II mine at the Kalahari manganese fields, Republic of South Africa, has been studied by single-crystal X-ray diffraction at 100 and 293 K at ambient pressure and up to 8.7 GPa in a diamond-anvil cell at 293 K. Polarized FTIR spectroscopy at 80 and 293 K was also performed. The Mn 3+ O 6 octahedra display a tetragonally elongated type of Jahn-Teller distortion where the oxygen atoms of the elongated O-Mn-O axis (Mn-O: 2.2 Å) are moderately hydrogen bonded (O-H … O: 2.76 Å) to the H 4 O 4 tetrahedra, which replace 1/3 of SiO 4 tetrahedra in an ordered fashion. Thus Jahn-Teller distortion and H 4 O 4 arrangement are coupled and both are responsible for the tetragonal bulk symmetry. The H 4 O 4 tetrahedra have a center-to-O distance of 1.98 Å and the H atoms are slightly above the tetrahedral faces as similarly observed in the synthetic katoite end-member, Ca 3 Al 2 [H 4 O 4 ] 3 . However, in henritermierite the O-H … O hydrogen bond is considerably bent (ca.131°) and gives rise to an OH stretching mode at 3432(5) cm -1 . Additional, though weak, IR absorptions at 3508(2) and 3553(2) cm -1 may be due to more remote hydrogen-bond acceptors (O-H … O: 3.29 Å) within the H 4 O 4 tetrahedra.Compressibility data for a third-order Birch-Murnaghan equation of state yield a bulk modulus of K 0 = 97.9(9) GPa with a pressure derivative of K' = 5.3(3). The axial compressibilities indicate a pronounced compressional anisotropy which is explained by the orientation of the elongated axes of the Jahn-Teller distorted MnO 6 octahedra along the slightly more compressible [100] tetr directions compared to the c-axis. The crystal structure was refined at a pressure of 8.6 GPa. The MnO 6 octahedra were observed to show anisotropic compression towards a more isometric shape. Calculated spontaneous strain reveals a trend towards a weaker tetragonal distortion.If henritermierite is heated above 800 K in air it dehydrates and Mn 3+ is partially oxidized to Mn 4+ . This topotactic transformation leads to a new garnet-like phase of Ia3d symmetry with a = 12.12 Å and of Ca 3 Mn 2.26 O 2.32 [SiO 4 ] 2.42 composition in which instead of H 4 O 4 tetrahedra a new disordered octahedral site is occupied by Mn. Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 7/23/15 8:52 AM 3Fe 3+ 2Si3O12 "skiagite" garnet and Fe2SiO4-Fe3O4 spinel solid