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The chemical bonding of Mn atoms in (Na1-xBix)(Nb1-yMny)O3 ceramics were analysed using the X-ray Absorption Near Edge Structure (XANES) measurement at the Mn L3,2–edge. In all the compounds coexistence of the covalent bonding MnCV state and ionic Mn+k states was found. The increase in the Bi and Mn content caused the marked dispersion and increased the values of electric conductivity and dielectric permittivity of the ceramics. [ABSTRACT FROM PUBLISHER]

Abstract: Natural ilmenites are used all over the world as raw materials in white pigment (TiO2) production. Besides the FeTiO3 in the raw material many other compounds are present. The chemical compounds based on the minority elements influence quality of the final product and are difficult to identify. The knowledge about chemical bonding of the minor elements enables to properly adjust chemical reactions during production processes and to improve quality of the final product. In this paper the X-ray absorption spectroscopy (XAS) identification of the chemical compounds formed by Mg, Mn and Cr in natural ilmenites originating from different places is presented. [ABSTRACT FROM AUTHOR]

Abstract: The interesting chemical and physical properties of Mn-oxide-based nanomaterials offer a variety of technological applications. The novel Mn-oxide properties reached through synthetic design have the potential to be of tremendous contribution to modern, environmental friendly chemistry. A problem of Mn oxide crystal chemistry is that, even within a single mineral, Mn atoms can exhibit multiple valence states. An average oxidation state for Mn atoms can be easily and quite reasonably measured, however, determining the individual proportions/(“weights”) of Mn(IV), Mn(III), and Mn(II) in a non-destructive way is considerably more difficult. We applied X-ray absorption near edge spectroscopy (XANES) to investigate the Mn environment and to improve fundamental understanding of the structural chemistry and morphology of nanostructured Mn-oxides to produce desirable chemical and physical properties. [Copyright &y& Elsevier]

In spite of great interest of industry in titanium composites based on the cubic boron nitride (c-BN), there is a lack of information about the chemical binding of Ti in these materials. The reason for that are difficulties in characterizing the multiphase materials with high hardness using conventional methods.In the present paper, to estimate the content of different compounds of Ti formed during the technological processes we used element selective-spectroscopy. The X-ray absorption near-edge spectroscopy (XANES) and X-ray photoelectron spectroscopy (XPS) were chosen to estimate the amount and kind of compounds formed. The performed analysis proved the existence of several Ti compounds (TiC, TiB2, TiSi2, TiO2, Ti3SiC2, TiC0.7N0.3, TiC0.3N0.7) and allowed to evaluate the percent of Ti bounded to each compound. Additionally, the X-ray diffraction (XRD) measurements were performed on the same samples. Due to the existence of several compounds with similar crystal structures and the high hardness of samples, the quantitative-phase analysis was not possible by XRD. Therefore, XANES and XPS appear to be the perfect tools for the investigation of micro-chemical processes occurring in composites. [Copyright &y& Elsevier]

We report on the use of X-ray absorption spectroscopy as a tool for the identification of the phases formed in the technological process of composite preparation. A composite is a mixture of several compounds and, in many cases, the use of traditional X-ray diffraction to determine the phases can be difficult because of the small amount of phases present. X-ray absorption studies (XANES and EXAFS) of the c-BN Ti/TiN layered system are presented. These materials are models of the powdered composites used in industry for tool production. XANES and EXAFS analyses showed that, after annealing up to 1300 °C, a TiB2 phase is formed, but the chemical bonding of the Ti atoms differs slightly from that of standard TiB2 powder, showing the presence of defects in site occupancy. Assuming that the X-ray absorption spectral shape is a linear combination of the spectra of all the components, we estimated the kind and limits of other phase inclusions. [Copyright &y& Elsevier]

Theoretical and experimental studies of cubic BN mixed with Ti and TiN in the molar ratio 1:1 are reported and compared with the properties of Ti and TiN films grown by the arc plasma deposition method on cBN substrate. Theoretical calculations show that Ti and TiN react with cubic BN forming new phases at 1000 and 1400 °C. The cBN composites were prepared by high pressure hot pressing and the samples were subsequently annealed at 1000 and 1400 °C. The samples after heat treatment were characterized using transmission electron microscopy (TEM). The X-ray absorption technique and X-ray photoelectron spectroscopy (XPS) were used to study the content of new phases formed in the cBN–Ti/TiN samples. The measurements of micro-hardness showed the significant differences in mechanical properties of samples. The amount and distribution of TiB2 phase in cBN–Ti/TiN composites are shown to be determining factors for the micro-hardness. [Copyright &y& Elsevier]

Abstract: The electronic structure of InGaN epitaxial layers grown on sapphire substrates was studied using X-ray absorption at the In L 3 and N K edges, as well as N K α X-ray emission. Knowing that the InGaN crystallizes in an anisotropic wurtzite structure, the linear polarization of synchrotron radiation was exploited to estimate the influence of the crystal structure anisotropy on the distribution of the local density of states at the site of In and N. The calculated partial density of states describes the observed anisotropy in the measured spectra. Influence of the core–hole effect on the analyzed absorption spectra was verified and reveal that a core hole potential is effectively screened by the surface mobile electrons for the sample with maximum indium content. The bandgap values were provided for the investigated InGaN alloys and were found to vary preudo-lineary with indium content. [Copyright &y& Elsevier]

Abstract: We present X-ray absorption spectroscopy (XAS) and resonance inelastic X-ray scattering (RIXS) measurements of CdO thin film. The observed differences between bulk and surface XAS signals suggest the presence of a surface electron accumulation layer in CdO film. The native defects (oxygen vacancies) strongly influence on the electronic structure of CdO resulting in the absorption threshold position/onset and spectral profile changes. To interpret the obtained data ab initio theoretical calculations, using the FEFF code, were performed and compared to the experimental results. The calculated angular-momentum-projected local density of states (PDOS) describes well the experimental data. The direct and indirect gaps of CdO were estimated to be ∼2.4eV and ∼0.9eV, respectively, by overlapping the XAS spectrum with RIXS. These results are consistent with our optical absorption measurements as well as theoretical and experimental band gap values of CdO reported in the literature. [Copyright &y& Elsevier]