[1] Chlorine speciation in silicate melts affects volatile exsolution, rheology, and thermodynamic properties of the melt but is poorly known. X-Ray Absorption Near Edge Structure (XANES) spectra have been used to investigate Cl speciation in 26 silicate glasses and to test the hypothesis that Cl in silicate melts is hosted by species that combine Cl and network-modifying cations such as Ca and Mg. Results indicate that Cl in CMAS (CaO-MgO-Al 2 O 3 -SiO 2 ) plus Na 2 O, K 2 O, or MnO silicate glasses exists as a combination of CaCl x and Mg-Cl x species or, possibly, as mixed Ca-Mg y -Cl x species. The geometry and stoichiometry of the proposed species is unknown, but there are similarities between spectra from Ca-bearing melts and the spectra of hydrated CaCl 2 .2H 2 O, suggesting that the Ca-Cl x species could have a salt-like atomic arrangement and ionic bonding. Further investigations using XANES, alternative spectroscopic techniques, and forward modeling approaches are required to distinguish between these possibilities.

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We have carried out Ce L- and Mn K-edge x-ray absorption near edge structure (XANES) measurements to experimentally determine the oxidation states of both Ce and Mn in (Sr(1 - x)Ce(x))MnO(3) (x = 0.1-0.4). It was found that although Ce is predominantly 4 + at low doping levels (x = 0.1 and 0.15), the Ce valency decreases with increasing Ce doping (reaching a value of around 3.5 + at x = 0.4). The average Mn oxidation state decreases with the increase of Ce content, with the percentage of Jahn-Teller active Mn(3+) ions increasing from 26% (x = 0.1) to 57% (x = 0.4). Precise structural parameters were also obtained from high resolution neutron diffraction studies for samples with x = 0.1-0.3. The crystal structure remains tetragonal in I4/mcm for x ≤ 0.3. The octahedral tilt angle increases with increasing Ce content, but the distortion of the MnO(6) octahedra is reduced significantly at x ≥ 0.2 due to a transition from long-range ordered Jahn-Teller distortions to incoherent static distortions.

This paper reports on an experimental study of the effects induced by the substitution of Co for Ru in CaRuO 3 , a prototypical oxide close to a magnetic instability. The L 2,3 x-ray absorption spectroscopy (XAS) spectra of Ru and Co in CaRu 1−x Co x O 3 reveal that Co is in a divalent state for low x values, while the Ru valence increases upon increasing the Co content. The dc and ac magnetic susceptibilities demonstrate that the CaRu 1−x Co x O 3 compounds can be classified as spin glasses. The origin of this behaviour and its implications are discussed. The effect of Co is also compared with the literature about substitutions by other cations in the magnetic sublattice of CaRuO 3 .

The electronic structure of quasi-one-dimensional (quasi-1D) blue bronze, K0.3MoO3, was investigated by angle-dependent x-ray absorption near-edge structure (XANES) spectroscopy at O and K K and Mo L3 edges along the quasi-1D MoO6 octahedron-chain direction, i.e., the b axis, and the octahedron-in-plane direction, i.e., the d axis, well below its Peierls phase transition temperature (180K). The O K-edge XANES spectra indicate that the angle dependence of O 2p–Mo 4d hybridization, especially those with the π* character, is more significant along the b axis than along the d axis. Similar trend is also observed in the Mo L3-edge XANES spectra. The K K-edge XANES spectra reveal anisotropic effect of hybridization of K 4p states with O 2p states on the MoO6 octahedron.