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Composite Crystal (composite + crystal)
Selected AbstractsLaser properties of continuous-grown GdVO4/Nd:GdVO4 composite crystalLASER PHYSICS LETTERS, Issue 9 2009X.D. Li Abstract Effective CW and A-O Q-switched laser operations were demonstrated firstly using a continuous-grown GdVO4/Nd:GdVO4 composite rod. A maximum CW output power of 19.2Wwas obtained with the slope efficiency of 79.6% and the maximum optical-optical efficiency of 73.0% to absorbed pump power. In A-O Q-switched operation, the pulse width of 15.0 ns, 10.6 ns, and 6.9 ns, the peak power of about 11.3 kW, 29.6 kW, and 130.4 kW were achieved at the repetition rate of 100 kHz, 50 kHz, and 10 kHz, respectively. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Eu3Si15,,,xAl1,+,xOxN23,,,x (x, 5/3) as a commensurate composite crystalACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2009Yuichi Michiue A new Eu-SiAlON crystal, Eu3Si15,,,xAl1,+,xOxN23,,,x (x, 5/3), was found and the structure was determined by an X-ray diffraction technique using a twinned sample. The structure consists of a host framework, which is constructed by the connection of MX4 tetrahedra (M: Si or Al; X: O or N), and Eu ions as the guest ions. The structure is considered to be a commensurate composite crystal. The basic vectors are a1 = a/3, b and c for the first substructure, and a2 = a/5, b and c for the second substructure. The first substructure consists of part of the host framework and the Eu ions, while the remainder of the host structure is taken as the second substructure. Possible phases belonging to the series are proposed using the composite crystal model in (3,+,1)-dimensional superspace. Chemical composition, possible space groups, cell parameters, and the basic model for those phases are presented. [source] Structural characterization of YV4O8: simultaneous analysis of coexisting polytypes and simulation of diffuse scattering for a stacking disorder modelACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2003Mitsuko Onoda The structure of a crystal of newly synthesized YV4O8 was refined on the assumption that two polytypes and their respective twin forms intergrow. The model was expressed as a commensurate composite crystal with two types of subsystem: one is a V4O8 framework with rather large tunnels and the other consists of Y ions. In the tunnels, Y ions and vacancies are located at every second site in an ordered manner that is characteristic of each polytype. Refinement was performed using a high-dimensional formalism and all reflections from all domains. Diffuse streaks observed in the X-ray and electron diffraction patterns were simulated using the matrix method that has been used for one-dimensional disorder such as stacking faults. The unusual diffraction phenomena that occur in a crystal of YV4O8 are explained as arising from a multiple-domain structure of coexisting polytypes. [source] 5-Oxatricyclo[5.1.0.01,3]octan-4-one, containing an enantiomorph and a racemate and not two polymorphs, is another example of a composite crystalACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2003Frank H. Herbstein This new example of a composite crystal adds to the small number previously reported among inorganic and molecular materials. Revision of the nomenclature used allows more fruitful comparison with the precedents. [source] A five-dimensional structural investigation of the misfit layer compound [Bi0.87SrO2]2[CoO2]1.82ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2000H. Leligny The structure of the misfit layer compound [BiSrO][CoO], bismuth strontium cobaltite, was determined by single-crystal X-ray diffraction using the five-dimensional superspace-group formalism. This composite crystal, of monoclinic symmetry, is composed of two subsystems exhibiting incommensurate periodicities along b, the binary axis direction. The first composite part [BiSrO] displays an intrinsic modulation of planar monoclinic type characterized by the wavevector . The second composite part [CoO] shows two different centered lattice variants. The structure of the misfit layer crystal can be described as an alternation along c of distorted rock-salt-type slabs, formed from [BiO] and [SrO] layers (first subsystem), and of [CoO] layers (second subsystem) displaying a distorted CdI -type structure. Two main structural results are obtained. First, as a consequence of the intrinsic modulation, disordered zones, characterized by Bi vacancies, are regularly distributed in the [BiO] layers. Second, strong chemical bonds are implied between the strontium atoms of the first subsystem and the oxygen atoms of the second one. [source] Refinement of modulated structures against X-ray powder diffraction data with JANA2000JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2001M. Du JANA is a computer program for the refinement and analysis of periodic and aperiodic (incommensurately modulated structures and composite crystals) crystal structures. Here a new module is introduced that allows Rietveld refinements against powder diffraction data. It is shown that JANA2000 provides a state-of-the-art description of the peak profiles. A re-analysis of the low-temperature structure of (CO)xC60 showed that the application of icosahedral symmetry restrictions to the C60 molecule leads to a better description of the electron density and to a corrected position of the CO molecule as compared with a rigid-body refinement. The incommensurately modulated structure of NbTe4 has been successfully refined against X-ray powder diffraction data. The structural parameters are equal to, but less accurate, than the parameters obtained from a single-crystal study. [source] Intersubsystem chemical bonds in the misfit layer compounds (LaS)1.13TaS2 and (LaS)1.14NbS2ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2002Andreas Jobst The modulated structures of incommensurate composite crystals (La0.912S)1.13TaS2 at room temperature and of (La0.949S)1.14NbS2 at T = 115,K are refined against high-resolution X-ray data. The compounds are isostructural with superspace group F,m2m(,,0,0)00s. For (LaS)1.13TaS2, lattice parameters of the first subsystem TaS2 were obtained as a = 3.2922,(1), b = 5.7776,(2) and c = 23.013,(2),Å. For the second subsystem LaS, the same b and c parameters were found, but a = 5.8090,(8),Å. Refinements led to a final structure model with R = 0.036 for 4767 observed unique reflections (R = 0.023 for 2147 main reflections, R = 0.099 for 1554 first-order satellites and R = 0.112 for 1042 second-order satellites). The final model includes modulation parameters up to the second-order harmonics for the displacements of the atoms, for the occupational parameters and for the temperature parameters. A clear correlation is found between the relative positions of the subsystems, the displacement modulation, the occupational modulation and the modulation of the temperature parameters. The analysis shows that the variations in environments are resolved by correlated variations in the temperature factors. For (LaS)1.14NbS2, lattice parameters at T = 115,K of the NbS2 subsystem were obtained as a = 3.3065,(4), b = 5.7960,(5) and c = 22.956,(3),Å. For the LaS subsystem, the same values for b and c were obtained, but a = 5.7983,(7),Å. Refinements led to a final structure model with R = 0.048 for 5909 observed unique reflections (R = 0.034 for 2528 main reflections, R = 0.092 for 2171 first-order satellites and R = 0.113 for 1103 second-order satellites). The final structure model is similar to that of (LaS)1.13TaS2. In particular, it is found that the values of the modulation parameters are almost equal and it is concluded that the modulations are independent of the temperature and the replacement of Ta with Nb, and thus represent a general mechanism of resolving the strain between the mutually incommensurate layers. [source] | ||||||||||