Andrew L. Hector

Germanium(II) dications stabilized by azamacrocycles and crown ethers.

A crown for germanium: Neutral aza- and oxamacrocycles enable stabilization of halide-free germanium(II) dications (see structure, Ge teal, N blue, C gray). The resulting structures show a marked dependence upon the denticity, donor type, and ring size of the macrocycle.

Performance of nanocrystalline Ni3N as a negative electrode for sodium-ion batteries

Nickel nitride is synthesised by high temperature ammonolysis of nickel(II) hexamine and tris(ethylenediamine) salts. Its electrochemical characteristics are examined in half-cells vs. lithium and sodium. Samples with high surface area are found to have significant reversible charge storage capacity in sodium cells and hence to be a promising negative electrode material for sodium-ion batteries.

Synthesis and applications of nanocrystalline nitride materials

Most current applications of nitride materials are based on films deposited from the vapour phase. However, a series of other potential uses of nitrides have been envisaged based on properties such as higher conductivity than oxides, hardness, inertness and catalytic or electrochemical activity. Many current applications use nanocrystalline nitrides and increasingly the size and shape dependent properties are of interest. This feature article reviews synthesis methods to make nanocrystalline and nanoparticulate nitride materials, plus it discusses the current applications and several potential ones.

Materials synthesis using oxide free sol–gel systems

This tutorial review highlights some active areas of research into non-oxide sol-gel chemistry. These aim to capture some of the advantages of methods developed mainly with oxides for a new generation of functional materials based on main group and metal nitrides, and semiconducting chalcogenides. Sol-gel processing has a long track record in producing useful materials for optical, magnetic, electrical, catalytic and structural applications. Controlled morphologies can be produced on all lengths scales, from ordered mesoporous arrays to thin films, fibres and monoliths. Hence there is an opportunity to produce new morphologies in non-oxides and hence new applications of these materials.

Rapid, low energy synthesis of lanthanide nitrides

Abstract Thermal initiation (400°C) of the reaction between lithium nitride and anhydrous lanthanide halides produces lanthanide nitrides LnN (Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) via a rapid exothermic solid state metathesis reaction. Mixed lanthanide nitrides LnLn′N (LnLn′ = PrNd; DyHo; TbDy) are made by reaction of ground powders of LnCl 3 with Li 3 N. The lanthanide nitrides were characterized by X-ray powder diffraction, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), FTIR, magnetic moment measurement and microanalysis.

Atomic displacements in the charge ice pyrochlore Bi_{2}Ti_{2}O_{6}O^{?} studied by neutron total scattering

The oxide pyrochlore Bi2Ti2O6O? is known to be associated with large displacements of Bi and O? atoms from their ideal crystallographic positions. Neutron total scattering, analyzed in both reciprocal and real space, is employed here to understand the nature of these displacements. Rietveld analysis and maximum entropy methods are used to produce an average picture of the structural nonideality. Local structure is modeled via large-box reverse Monte Carlo simulations constrained simultaneously by the Bragg profile and real-space pair distribution function. Direct visualization and statistical analyses of these models show the precise nature of the static Bi and O? displacements. Correlations between neighboring Bi displacements are analyzed using coordinates from the large-box simulations. The framework of continuous symmetry measures has been applied to distributions of O?Bi4 tetrahedra to examine deviations from ideality. Bi displacements from ideal positions appear correlated over local length scales. The results are consistent with the idea that these nonmagnetic lone-pair containing pyrochlore compounds can be regarded as highly structurally frustrated systems.

Hydrothermal Synthesis of Rare Earth Iodates from the Corresponding Periodates: Structures of Sc(IO3)3, Y(IO3)3 · 2 H2O, La(IO3)3 · 1/2 H2O and Lu(IO3)3 · 2 H2O

Hydrothermal syntheses of single crystals of rare earth iodates, by decomposition of the corresponding periodate, are presented. This appears to be a generic method for making rare earth iodate crystals in a short period of time. Single crystal X-ray diffraction structures of the four title compounds are presented. Sc(IO3)(3): Space group R(3), Z = 6, lattice dimensions at 100 K; a = b = 9.738(1), c = 13.938(1) A; R-1 = 0.0383. Y(IO3)(3) · 2H(2)O: Space group P(1), Z = 2, lattice dimensions at 100 K: a = 7.3529(2), b = 10.5112(4), c = 7.0282(2) A, ? = 105.177(1)°, ? = 109.814(1)°, ? = 95.179(1)°; R-1 = 0.0421. La(IO3)(3) · o H(2)O: Space group Pn, Z = 2, lattice dimensions at 100 K: a = 7.219(2), b = 11.139(4), c = 10.708(3) A, ? = 91.86(1)°; R-1 = 0.0733. Lu(IO3)(3) · 2H(2)O: Space group P(1), Z = 2, lattice dimensions at 120 K: a = 7.2652(9), b = 7.4458(2), c = 9.3030(3) A, ? = 79.504(1)°, ? = 84.755(1)°; ? = 71.676(2)°; R-1 = 0.0349.

Syntheses, powder neutron diffraction structures and Mössbauer studies of some complex iron oxyfluorides: Sr3Fe2O6F0.87, Sr2FeO3F and Ba2InFeO5F0.68

Sr2FeO3F and the novel phases Sr3Fe2O6F0.87 and Ba2InFeO5F0.68 have been prepared and their structures investigated by powder neutron diffraction methods. Sr2FeO3F crystallises with the T* modification of the K2NiF4 structure owing to oxide/fluoride ordering. Sr3Fe2O6F0.87 and Ba2InFeO5F0.68 are mixed valent phases prepared by reaction of anion deficient iron(III) materials with gaseous fluorine. Sr3Fe2O6F0.87 is a Ruddlesden–Popper type material which has been shown by Mossbauer spectroscopy to contain iron(III) and iron(V). Ba2InFeO5F0.68 is the first example of an iron oxyfluoride with a perovskite-type structure.

Sodium azide as a reagent for solid state metathesis preparations of refractory metal nitrides

Abstract Thermal initiation (∼ 300°C) of a reaction between sodium azide and anhydrous metal chlorides (LaCl3, SmCl3, TiCl3, ZrCl4, HfCl4, VCl3, TaCl5, CrCl2, WCl6 and MnCl2) in sealed evacuated ampoules rapidly produces binary metal nitrides, dinitrogen and sodium chloride. The metal nitrides were purified by trituration with methanol and characterized by powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and FT-IR.

Electrodeposition from supercritical fluids

Recent studies have shown that it is possible to electrodeposit a range of materials, such as Cu, Ag and Ge, from various supercritical fluids, including hydrofluorocarbons and mixtures of CO2 with suitable co-solvents. In this perspective we discuss the relatively new field of electrodeposition from supercritical fluids. The perspective focuses on some of the underlying physical chemistry and covers both practical and scientific aspects of electrodeposition from supercritical fluids. We also discuss possible applications for supercritical fluid electrodeposition and suggest some key developments that are required to take the field to the next stage.