Spinel samples of Li1.33xCo2-2xTi1+0.67xO4 crystallize in two space groups: Fd- 3 m for 0≤x≤0.40 and x=1, and P4332 for 0.50≤x≤0.875. In S.G. P4332 magnetic Co2+ ions occupy 8c sites (for x=0.75 and 0.875), or 8c, 4b and 12d sites (for x=0.50). In x=0.25 and 0.40 samples Co2+ occupy both 8a and 16d cation sites of the S.G. Fd- 3 m [1]. Observed differences in magnetic behaviour of the samples are induced by crystallographic distribution of Co2+. Possible paths for exchange interactions in S.G. P4332 were analysed. It was found that the superexchange is the dominant exchange mechanism where Co2+
(8c)-O(24e)-Co2+(12d) path was the most important
one. On the basis of the results on crystallographic distribution we suggest x=0.50 sample as potential electrode material in Li ion rechargeable batteries.
Poster Sessions C323 subjects with various parameters of their microstructure (sizes of microparticles, specific surface) and substructure (sizes of nanoparticles and crystallites) governing their working properties.The purpose of the work is to find correlations between synthesis conditions of samples with nanosized η-TiO 2 , their characteristics and structural, sorption, catalytic and photocatalytic properties.The determination of η-TiO 2 cell parameters (a~3.8Å, c~19Å) has been made using sources of electrons, X-rays and synchrotron scattering. These parameters are associated with ones of anatase modification (a 0~3 .8Å, c 0~9 .5Å) by the relationship a~a 0 , c~2c 0 . Optimization of the sulfate method allowed increasing the yield of η-TiO 2 up to 95%. The samples were characterized by a set of methods showing variations in sizes of microparticles/ agglomerates (200/3000 nm; SEM, BET), nanoparticles (8÷24 nm, rarely 28÷55 nm; small angle X-ray scattering), crystallites, or coherent scattering regions (L=3÷6 nm; large angle X-ray scattering), as well as in sizes (~17 nm; BET) and capacities (0.02 cm 3 /g; BET) of pores and specific surface (4.5÷16 m 2 /g; BET). Dependence of some parameters (in particular, value L) on synthetic conditions (the initial concentration of TiOSO 4 • xH 2 SO 4 •yH 2 O reagent, the temperature and duration of hydrolysis, the heating speed of reaction mixture and so on) was found.Photocatalitic activity (in model reactions of decomposing methyl-orange, methylene-blue and xylenol-orange indicators under UV radiation), sorption properties (extraction of various ions from aqueous media) and catalytic properties (oxidation of CO to CO 2 in air at room temperature) depend on sample characteristics. Efficiency of CO conversion to CO 2 correlates with specific surface. For bismuth, arsenic and vanadium ions, degree of sorption equal to maximal permissible concentration was achieved. A relation between the degree of metal-ion sorption and the coherent scattering regions (value L) has been established. Degree of metal-ion sorption and rate constant for photocatalytic reactions are maximal for L ~ 4.5 nm. Photocatalytic activity (pH < 3) for the samples with η-TiO 2 is considerably higher than for commercial photocatalysts Degussa P25 (anatase-rutile mixture) tested in comparable conditions. The photocatalytic and catalytic activities obtained confirm unique surface properties of η-TiO 2 .From the X-ray diffraction study data by means of crystallochemical approach, the structure of η-TiO 2 was proposed. The quasi-layered structure model provides a very fit to the experimental data (in particular, the sorption properties). Details of structure and microstructure changes of ferrite nanoparticles are assessed using synchrotron X-ray and TOF neutron diffraction data by combining Rietveld method in reciprocal space with the atomic pair distribution function (PDF) method in direct space. Such obtained (micro)structural parameters were correlated with physical properties revealed by HRTEM, Mössbauer ...
Herein a comparative study of five nanocrystalline cerium oxides (CeO(2-delta)) synthesised by different methods and calcined at 500 degrees C is reported. XRPD analysis showed that stoichiometry parameter delta, crystallite size/strain and lattice constant were only slightly affected by the method utilized. All ceria nanoparticles are nearly spherical in shape with faceted morphology, free of defects and with a relatively uniform size distribution. The average microstrain was found to be approximately 10 times higher than that of bulk counterpart. The absorption edge of nanocrystalline materials was shifted towards a higher wavelengths (red shift) in comparison with bulk counterpart, and band gap values were in the range 2.7-3.24 eV (3.33 eV for bulk counterpart).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.