Optical and structural properties of float-type soda-lime-silica (SLS) glasses doped with 0.2 mol % TiO2, ZrO2, HfO2, Nb2O5, Ta2O5, MoO3 or WO3 have been studied. Under ultraviolet excitation all d doped glasses exhibit broadband visible emission centred between 19 000 and 25 000 cm(-1) (400-525 nm) due to a transition from the 2p orbital of O2- to the metal d orbital. Dopant additions lead to shifts in the ultraviolet absorption edge to lower energies, with doped glasses having an absorption edge 2000 cm(-1) (similar to 20 nm), and in the case of MoO3, 4000 cm' (similar to 40 nm), shifted relative to the corresponding undo ped glass. Combined ultraiolet-visible absorption and X-band EPR spectroscopy analyses confirm that dopant cations occur in the studied glasses in the expected oxidation states of Ti4+, Zr4+, Hf4+, Nb5+, Ta5+ Mo6+ and W6+, although very low levels of Mo5+ are also observed, as demonstrated by the EPR resonance at g=1.92 (3.7 T). The incorporation of the studied dopants into SLS glasses may find applications as cover glasses in photovoltaic (PV) applications, providing ultraviolet protection of polymers and solar cell materials in PV units whilst enhancing solar cell efficiency through downconversion/fluorescence of absorbed ultraviolet photons with re-emission as visible photons, available for absorption and conversion by the solar cell material.

The neutron diffraction isotopic substitution technique is employed to investigate the environment of Fe3+/Fe2+ cations in a sodium borosilicate glass matrix of composition 0.210Na(2)O.0.185(11)B(2)O(3).0.605SiO(2). The neutron diffraction data were obtained using the D4c diffractometer at the Institut Laue-Langevin (ILL; Grenoble, France), and were recorded for three samples; the base glass, the base glass incorporating natural Fe2O3 (12 mol%) and a similar glass containing Fe2O3 enriched in Fe-57. The data are Fourier transformed to yield the real space total correlation function, T(r), and the first co-ordination shells of the Fe3+/Fe2+ cations are investigated via a peak fit to the isotopic difference correlation function Delta T-Fe(r). It is concluded that the iron is mainly present as Fe3+ cations, both tetrahedrally and octahedrally co-ordinated by oxygen atoms, plus a small fraction (0.07 +/- 0.01) of Fe2+ cations in octahedral co-ordination. The Fe3+ tetrahedral fraction is 0.45 +/- 0.10, and appears to exist as Fe empty set (-)(4) structural units incorporated into the network of silicate chemical groupings, with their negative charge being balanced by Na+ network modifying cations. The remaining Fe3+ cations (fraction 0.48 +/- 0.10) are thought to be predominantly octahedrally co-ordinated and associated with BO33- orthoborate anions in FeBO3 chemical groupings, which become non-stoichiometric due to the reduction of some of the Fe3+ cations to Fe2+.

Four new phases of general formula, Li11RE18M4O39-δ: REM = NdAl, NdCo, SmCo, SmFe, have been synthesised and characterised. The NdAl phase, and probably the others, is isostructural with the NdFe analogue, but some cation disorder and partial site occupancies prevent full structural refinement of powder neutron diffraction data. The NdCo phase also forms a solid solution with variable Li content (and charge compensation by either oxygen vacancies or variable transition metal oxidation state). The NdAl phase is a modest conductor of Li(+) ions whereas the other three phases are electronic conductors, attributed to mixed valence of the transition metal ions. Subsolidus phase diagrams for the systems Li2O-Nd2O3-Al2O3, 'CoO' have been determined and an additional new phase, LiCoNd4O8, which appears to have a K2NiF4-related superstructure, identified.

(57)Fe Mössbauer spectra have been recorded from the hexagonal (6H)- and trigonal (15R)- modifications of BaFeO2F and are compared with those previously recorded from the cubic form of BaFeO2F. The spectra, recorded over a temperature range from 15 to 650 K show that all of the iron in all the compounds is in the Fe(3+) state. Spectra from the 6H- and 15R-modifications were successfully fitted with components that were related to the Fe(1) and Fe(2) structural sites in the 6H variant and to the Fe(1), Fe(2) and Fe(3) structural sites in the 15R form. The magnetic ordering temperatures were determined as 597  ±  3 K for 6H-BaFeO2F and 636  ±  3 K for 15R-BaFeO2F. These values are surprisingly close to the value of 645  ±  5 K determined for the cubic form. The magnetic interactions in the three forms are compared with a view to explaining this similarity of magnetic ordering temperature.

Hydrothermal synthesis is described of layered lithium iron selenide hydroxides Li(1-x)Fe(x)(OH)Fe(1-y)Se (x ∼ 0.2; 0.02 < y < 0.15) with a wide range of iron site vacancy concentrations in the iron selenide layers. This iron vacancy concentration is revealed as the only significant compositional variable and as the key parameter controlling the crystal structure and the electronic properties. Single crystal X-ray diffraction, neutron powder diffraction, and X-ray absorption spectroscopy measurements are used to demonstrate that superconductivity at temperatures as high as 40 K is observed in the hydrothermally synthesized samples when the iron vacancy concentration is low (y < 0.05) and when the iron oxidation state is reduced slightly below +2, while samples with a higher vacancy concentration and a correspondingly higher iron oxidation state are not superconducting. The importance of combining a low iron oxidation state with a low vacancy concentration in the iron selenide layers is emphasized by the demonstration that reductive postsynthetic lithiation of the samples turns on superconductivity with critical temperatures exceeding 40 K by displacing iron atoms from the Li(1-x)Fe(x)(OH) reservoir layer to fill vacancies in the selenide layer.

Near-phase-pure nanoparticle iron carbides (Fe3C and Fe5C2) were synthesised. Debye model calculations were used with hyperfine parameters gathered by Fe-57 Mossbauer spectroscopy within a temperature range of 10 K to 293 K, with analysis providing Debye temperatures of 422 K and 364 K for two Fe sites in Fe5C2 and 355 K for ferromagnetic Fe3C. The intrinsic isomer shifts were calculated as 0.45 mm s(-1) and 0.43 mm s(-1) for iron sites 1 and 2 respectively in Fe5C2 and 0.42 mm s(-1) for Fe3C. Recoil-free fractions for the two iron sites were also calculated at f(300) 0.785 and 0.726 for site 1 and 2 respectively.

Hydrothermal synthesis is described of layered lithium iron selenide hydroxides Li1-xFex(OH)Fe1-ySe (x ~ 0.2; 0.02 < y < 0.15) with a wide range of iron site vacancy concentrations in the iron selenide layers. This iron vacancy concentration is revealed as the only significant compositional variable and as the key parameter controlling the crystal structure and the electronic properties. Single crystal X-ray diffraction, neutron powder diffraction and X-ray absorption spectroscopy measurements are used to demonstrate that superconductivity at temperatures as high as 40 K is observed in the hydrothermally synthesised samples when the iron vacancy concentration is low (y < 0.05) and when the iron oxidation state is reduced slightly below +2, while samples with a higher vacancy concentration and a correspondingly higher iron oxidation state are not superconducting. The importance of combining a low iron oxidation state with a low vacancy concentration in the iron selenide layers is emphasised by the demonstration that reductive post-synthetic lithiation of the samples turns on superconductivity with critical temperatures exceeding 40 K by displacing iron atoms from the Li1-xFex(OH) reservoir layer to fill vacancies in the selenide layer

Reaction of the appropriate Sr3(M(0.5)Ru(0.5))2O7 (M = Ti, Mn, Fe), n = 2, Ruddlesden-Popper oxide with CuF2 under flowing oxygen results in formation of the oxide-fluoride phases Sr3(Ti(0.5)Ru(0.5))2O7F2, Sr3(Mn(0.5)Ru(0.5))2O7F2, and Sr3(Fe(0.5)Ru(0.5))2O(5.5)F(3.5) via a topochemical anion insertion/substitution process. Analysis indicates the titanium and manganese phases have Ti(4+), Ru(6+) and Mn(4+), Ru(6+) oxidation state combinations, respectively, while Mössbauer spectra indicate an Fe(3+), Ru(5.5+) combination for the iron phase. Thus, it can be seen that the soft fluorination conditions employed lead to formation of highly oxidized Ru(6+) centers in all three oxide-fluoride phases, while oxidation states of the other transition metal M cations remain unchanged. Fluorination of Sr3(Ti(0.5)Ru(0.5))2O7 to Sr3(Ti(0.5)Ru(0.5))2O7F2 leads to suppression of magnetic order as the fluorinated material approaches metallic behavior. In contrast, fluorination of Sr3(Mn(0.5)Ru(0.5))2O7 and Sr3(Fe(0.5)Ru(0.5))2O7 lifts the magnetic frustration present in the oxide phases, resulting in observation of long-range antiferromagnetic order at low temperature in Sr3(Mn(0.5)Ru(0.5))2O7F2 and Sr3(Fe(0.5)Ru(0.5))2O(5.5)F(3.5). The influence of the topochemical fluorination on the magnetic behavior of the Sr3(M(0.5)Ru(0.5))2O(x)F(y) phases is discussed on the basis of changes to the ruthenium oxidation state and structural distortions.

Reaction of the Ruddlesden-Popper phases Sr2Fe(0.5)Ru(0.5)O4 and Sr3(Fe(0.5)Ru(0.5))2O7 with CaH2 results in the topochemical deintercalation of oxide ions from these materials and the formation of samples with average compositions of Sr2Fe(0.5)Ru(0.5)O(3.35) and Sr3(Fe(0.5)Ru(0.5))2O(5.68), respectively. Diffraction data reveal that both the n = 1 and n = 2 samples consist of two-phase mixtures of reduced phases with subtly different oxygen contents. The separation of samples into two phases upon reduction is discussed on the basis of a short-range inhomogeneous distribution of iron and ruthenium in the starting materials. X-ray absorption data and Mössbauer spectra reveal the reduced samples contain an Fe(3+) and Ru(2+/3+) oxidation state combination, which is unexpected considering the Fe(3+)/Fe(2+) and Ru(3+)/Ru(2+) redox potentials, suggesting that the local coordination geometry of the transition metal sites helps to stabilize the Ru(2+) centers. Fitted Mössbauer spectra of both the n = 1 and n = 2 samples are consistent with the presence of Fe(3+) cations in square planar coordination sites. Magnetization data of both materials are consistent with spin glass-like behavior.

Sr3 (Ti0.5Ru0.5)2O7F2 (I), Sr3 (Mn0.5Ru0.5)2O7F2 (II), and Sr3 (Fe0.5Ru0.5)2O5.5F3.5 (III) are obtained from Sr3(M0.5Ru0.5)2O7 (M: Ti, Mn, Fe) by a solid state topochemical anion insertion/substitution process using CuF2 under flowing O2 (250 °C, 3 times 8 h).

AbstractThe title compound is prepared by solid state reaction of pressed pellets of Li2CO3, Nd2O3, and Fe(C2O4) covered with a powder of the same composition to avoid Li loss (700 °C, 12 h and 950 °C, 12—24 h).

Li(11)Nd(18)Fe(4)O(39-δ) has been synthesized by the solid-state reaction of pellets, covered with powder of the same composition to avoid lithium loss, with a final reaction temperature of 950 °C. This phase has been reported previously to have various stoichiometries: Li(5)Nd(4)FeO(10), Li(8)Nd(18)Fe(5)O(39), and Li(1.746)Nd(4.494)FeO(9.493). The crystal structure of Li(11)Nd(18)Fe(4)O(39-δ) is closely related to that reported previously for two of the other three compositions but contains extra Li and differences in Li/Fe site occupancies. Fe is present in a mixture of 3+ and 4+ oxidation states, as confirmed by Mössbauer spectroscopy. The oxygen content of 39 - δ is variable, depending on the processing conditions. Samples slow-cooled in air from 800 °C are semiconducting, attributed to the presence of Fe(4+) ions, whereas samples quenched from 950 °C in N(2) are insulating.

A statistical approach has been utilised to characterise the structural and chemical properties of vitrified model sewage sludge combustion ashes. A d-optimal design has been applied to determine the effects of the compositional variability of vitrified wastes on iron redox and coordination as measured by 57Fe Mossbauer spectroscopy. Several Fe sites have been observed through the deconvolution of Mossbauer spectra, representing the Fe2+ oxidation state and tetrahedrally and octahedrally coordinated Fe3+ ions. The interdependency of iron redox and iron coordination is demonstrated, and suggests that conversion of tetrahedral Fe3+ to octahedral Fe2+ preferentially occurs upon increasing Fe2+/ΣFe. For Fe2+/ΣFe=0·30-0·89, the abundance of octahedrally coordinated Fe3+ remains approximately constant whilst tetrahedrally coordinated Fe3+ exhibits a linear decrease in its abundance with increasing Fe2+/ΣFe ratio.

The reaction of 4-ferrocenyl-1,3-dithiole-2-thione with diiodine affords an unprecedented "double" charge-transfer complex; the highly ordered ferrocenium units are held by a supramolecular polyiodide chain, and the material shows evidence of the formation of zigzag magnetic chains below 2 K.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.