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New molecular salt like hybrids contain ammonia borane AB in co existence with lithium halides in single lattices. [LiI] NH 3 BH 3 and [LiI] NH 3 BH 3 2 are members of a generic [LiX] m AB n X I amp; 8722; , H 4 amp; 8722; ; m, n integer materials family which release hydrogen on decomposition and demonstrate Li ion conductivity more than two orders of magnitude higher than either LiBH 4 or LiI

Nickel nitrate diammine, Ni(NH3)2(NO3)2, can be synthesised from the thermal decomposition of nickel nitrate hexammine, Ni[(NH3)6](NO3)2. The hexammine decomposes in two distinct major stages, the first releases 4 equivalents of ammonia while the second involves the release of NOx, N2, and H2O to yield NiO. The intermediate diammine compound can be isolated following the first deammoniation step or synthesised as a single phase from the hexammine under vacuum. Powder X-ray diffraction (PXD) experiments have allowed the structure of Ni(NH3)2(NO3)2 to be solved for the first time. The compound crystallises in orthorhombic space group Pca21 (a = 11.0628 (5) &Aring, b = 6.0454 (3) &Aring, c = 9.3526 (4) &Aring, Z = 4) and contains 11 non-hydrogen atoms in the asymmetric unit. Fourier transform infrared (FTIR) spectroscopy demonstrates that the bonding in the ammine is consistent with the structure determined by PXD.

Nickel nitrate diammine, Ni(NH3)2(NO3)2, can be synthesised from the thermal decomposition of the nickel nitrate hexammine, Ni[(NH3)6](NO3)2. The hexammine decomposes in 2 distinct steps; the first releases 4 equivalents of ammonia while the second involves the release of NOx, N2 and H2O to yield NiO. The intermediate diammine compound can be isolated following the first deammoniation step or synthesised as a single phase from the hexammine under vacuum. Powder X-ray diffraction (PXD) experiments have allowed the structure of Ni(NH3)2(NO3)2 to be solved for the first time. The compound crystallises in orthorhombic space group Pca21 (a = 11.0628 (5) Å, b = 6.0454 (3) Å, c = 9.3526 (4) Å; Z = 4) and contains 11 non-hydrogen atoms in the asymmetric unit. Fourier Transform Infrared (FTIR) spectroscopy demonstrates that the bonding in the ammine is consistent with the structure determined by PXD.

A co-precipitation process using transition metal hydrates was used to prepare a mixture of M(OH) 2 and MO(OH) (M=Ni 0.5 Co 0.2 Mn 0.3 ). This powder consisted of dense, quasi-spherical particles each composed of plate-like particles of ca. 250 nm across. By increasing the temperature, M(OH) 2 was made to transform into MO(OH) at ca. 220 °C, then into M 3 O 4 at ca. 330 °C. Moreover, the M 3 O 4 phase persisted without further reaction until 700 °C. During these phase transitions, the mixed-metal (M) in M(OH) 2 , MO(OH) and M 3 O 4 retained disordered cation distributions at the same crystallographic sites of their host lattices without appearance of any phases related to Ni, Co and Mn. The MO(OH) phase appeared owing to exposure to air. M(OH) 2 at room temerature had the lattice parameters ( a = b =2.9991(2) A and c =8.5892(2) A) with space group ( P6 3 /mmc ).

Traditional techniques for the growth of crystals are typically lengthy and are based on the slow over-saturation of either solutions or melts. By contrast, the reactions of solids at moderate temperatures and pressures normally lead to the formation of powders of small crystallites. In this paper, we present a new and effective method to grow crystals of surprisingly large sizes (up to ca. 0.05 mm in the largest dimension). We use the reaction of [Ni(H 2 O) 6 ](NO 3 ) 2 with NH 3(g) at room temperature to create macro-crystals of [Ni(NH 3 ) 6 ](NO 3 ) 2 . The synthesis proceeds via simple ligand exchange and crystal growth is facilitated in-situ via the solvent effect of the released water. The nitrate ammine product was characterised by powder X-ray diffraction (PXD) and Scanning Electron Microscopy (SEM). This reaction is important since it demonstrates that aquo complexes can undergo facile ligand exchange with gaseous ammonia under realistic conditions for ammonia storage. The single crystal structure of [Ni(H 2 O) 6 ](NO 3 ) 2 was determined for the first time below ambient temperature (at 100 K). The latter result offers no evidence to support a previously postulated low temperature phase-transformation at 100≤ T / K ≤295.

The phase-pure binary aluminium carbide, Al4C3 can be synthesised in vacuo from the elements in 30 minutes via microwave heating in a multimode cavity reactor. The success of the reaction is dependent on the use of finely divided aluminium and graphite starting materials, both of which couple effectively to the microwave field. The yellow-brown powder product was characterised by powder X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy thermogravimetric-differential thermal analysis and Raman spectroscopy. Powders were composed of hexagonal single crystallites tens of microns in diameter (rhombohedral space group R[3 with combining macron]m; Z = 3; a = 3.33813(5) Å, c = 25.0021(4) Å) and were stable to 1000 °C in air, argon and nitrogen. Equivalent microwave reactions of the elements in air led to the formation of the oxycarbide phases Al2OC and Al4O4C.

Single phase nitridometallates Li3−x−yMxN (0.05 ≤ x ≤ 0.27; M = Co, Ni and Cu) with potential use as negative electrodes in lithium (Li+) ion batteries have been synthesised in

A new ternary nitride, SrTiN(2), has been synthesized by the solid-state reaction of Sr(2)N with TiN and characterized by powder X-ray diffraction. SrTiN(2) crystallizes in the tetragonal space group P4/nmm (a = 3.8799(2) Å, c = 7.6985(4) Å, Z = 2) and is isostructural with KCoO(2). Titanium is coordinated to five nitrogens in a distorted square-based pyramidal geometry, forming layers of edge-sharing pyramids which stack along the (001) direction. Strontium is situated between the Ti-N layers and is coordinated to five nitrogen atoms. The title compound is only the third example of a ternary titanium nitride.

The new ternary nitride Ca6MnN5 has been synthesized by the solid state reaction of Ca3N2 with Mn4N and characterized by powder X-ray diffraction. Ca6MnN5 crystallizes in the hexagonal space group P63/mcm (a = 6.2269(1) Å, c = 12.3122(1) Å, Z = 2) and is isostructural with Ca6FeN5 and Ca6GaN5. Manganese(III) forms trigonal planar [MnN3]6- units analogous to carbonate anions, which lie in planes parallel to the c axis, sandwiched between layers of Ca-N polyhedra. Calcium is coordinated to five nitrogens in a distorted square pyramidal geometry. Interestingly, at room temperature the material is diamagnetic. © 1995 American Chemical Society.

Samples of ternary nitride fluorides, Mg3NF3 and Mg2NF have been prepared by solid state reaction of Mg3N2 and MgF2 at 1323–1423K and investigated by powder X-ray and powder neutron diffraction techniques. Mg3NF3 is cubic (space group: Pm3m) and has a structure related to rock-salt MgO, but with one cation site vacant. Mg2NF is tetragonal (space group: I41/amd) and has an anti-LiFeO2 related structure. Both compounds are essentially ionic and form structures in which nitride and fluoride anions are crystallographically ordered. The nitride fluorides show temperature independent paramagnetic behaviour between 5 and 300K.

New ternary and quaternary nitride halides, Ba(2)N(X,X') (X = F, Cl, Br; X' = Br, I), have been synthesized from the high temperature reactions of barium subnitride with the respective barium halides under an inert atmosphere. The former include the first fully characterized barium nitride halides for X other than F, and the latter are the first examples of barium nitride mixed halides. The variation in structure with composition has been investigated by powder X-ray and powder neutron diffraction techniques. The heavier ternary and quaternary nitride halides (X, X' = Cl, Br, I) crystallize in the hexagonal space group R3m, with the anti-α-NaFeO(2) structure. Ba(2)NF forms with both an anti-α-NaFeO(2) structure, in which N(3-) and F(-) are ordered and an anion-disordered simple rock salt structure. The hexagonal polymorph of Ba(2)NF is the only example to date of a nitride fluoride adopting this layered structure. Both the ternary and the quaternary compounds display very weak, temperature independent paramagnetism.

Defect structures in the Li−Mg−N system can be tuned by control of composition and temperature. A series of compounds in the Li3N−Mg3N2 system have been synthesized via solid state reaction of the ...

The temperature-programmed reaction of Co3Mo3N under H2/Ar results in a new nitride with composition Co6Mo6N. Powder neutron diffraction (PND) studies have confirmed unequivocally that the compound possesses the η-12 carbide structure, in which N atoms are exclusively located at 8a crystallographic sites, as opposed to the 16c sites exclusively occupied in the Co3Mo3N phase. On this basis, it possible to rationalize the observation that 50% nitrogen loss occurs under the high-temperature reduction conditions employed. Reaction of the reduced η-12 phase under N2/H2 results in the regeneration of the η-6 Co3Mo3N nitride and return of nitrogen to the 16c sites (only). Although established for corresponding ternary carbide structures, the η-12 carbide structure is unprecedented in nitrides and a topotactic cycling between η-carbide structures is hitherto unknown. The ammonia synthesis activity of the η-6 nitride at ambient pressure and 400 °C is 167 μmol g−1 h−1, whereas the η-12 structure is unstable and rev...

New quaternary carbide nitrides in the V 1− x Ti x (C,N) (0 ≤ x ≤ 0.4) system have been synthesised rapidly (0.5–1.5 h) by carbothermal reduction, carburisation and ammonolysis via microwave heating using a custom-modified, multimode cavity microwave reactor. The products were structurally characterised by powder X-ray diffraction (PXD), while scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) were used to examine morphology and composition. The resulting carbonitrides crystallise with the rock salt structure and the cubic lattice parameters vary linearly with increasing titanium concentration ( x ), hence following Vegard's law. Particle sizes typically range from 250 nm to 2 μm.

The synthesis of powders of the calcium nitride carbodiimides, Ca4N2(CN2) (1) and Ca11N6(CN2)2 (2) has been studied and the products characterised initially by powder X-ray diffraction. The latter phase (2) is unobtainable in pure bulk form and is always accompanied by the former compound. Nevertheless, definitive structures of the compounds were obtained from Rietveld refinements against time-of-flight powder neutron diffraction data. Each of the nitride carbodiimides are composed of Ca–N three dimensional networks built from edge- and vertex-sharing NCa6 octahedra arranged to create one-dimensional channels. The size of the channels is dependent on the Ca:C (host:guest) ratio and the larger channels in (1) are occupied by twice as many guest species as those in (2). Importantly, neutron diffraction data confirm that the identity of these guest species is carbodiimide (as opposed to isoelectronic azide), that neither the framework nor the channels therefore contain excess electrons and that the compounds are hence not “nitride electrides” as per the parent subnitride, Ca2N.

Zn{sub 3}N{sub 2} powders were prepared by ammonolysis reactions at 600 deg. C and examined by thermogravimetric analysis, powder X-ray and neutron diffraction. The powders obtained in this way are unstable in an oxygen atmosphere above 450 deg. C. In an argon atmosphere, the powders are stable up to their decomposition point at around 700 deg. C. Structural models obtained from Rietveld refinements against the powder neutron diffraction data indicate that the Zn{sub 3}N{sub 2} powders so-prepared have the anti-bixbyite structure and are almost certainly stoichiometric with no compelling evidence of nitrogen vacancies. Further, no evidence was found for aliovalent oxygen substitution at the nitrogen sites. The calculated bond valence sums imply that Zn{sub 3}N{sub 2} cannot be described as a 100% ionic compound. The structural findings are supported by photoluminescence measurements that reveal a band gap of approximately 0.9 eV. - Graphical abstract: Zn{sub 3}N{sub 2} powders prepared by careful ammonolysis reactions form with the anti-bixbyite structure and are almost certainly stoichiometric with no evidence for aliovalent oxygen substitution at the nitrogen sites. Zn{sub 3}N{sub 2} cannot be described as a 100% ionic compound and PL measurements reveal a narrow band gap of approximately 0.9 eV.

Powder samples of Cu3N prepared from a CuF2 precursor using ammonolysis reactions have been examined by powder X-ray and neutron diffraction, and scanning electron microscopy (SEM). Rietveld refinements against the powder diffraction data confirm that this compound is cubic, space group P m 3 ¯ m , with nitrogen atoms located at the corners of the unit cell and the copper atoms occupying the centres of the unit cell edges. The neutron diffraction data confirmed that both nitrogen and copper sites are fully occupied and showed no evidence for nitrogen non-stoichiometry or the presence of interstitial copper atoms at the centre of the unit cell. The SEM study reveals that the Cu3N powders are composed of plate-shaped particles of sub-micron size. The overall results indicate that the synthetic procedure reported here can be used to prepare reproducibly large amounts of stoichiometric Cu3N powders of high purity.

Four copper(II) oxime complexes, [Cu(HPPK)(PPK)X] (HPPK = phenyl-2-pyridylketoxime and X = CI− (I), CF3COO− (II), C3F7COO− (III), and [Cu(PPK)2]2 (IV)), were synthesized and characterized by elemental analysis, infrared spectroscopy (IR), and single-crystal X-ray diffraction (XRD). XRD analysis revealed that I–III contain copper(II) coordinated by four nitrogen atoms from two oxime molecules in the basal plane and one monodentate anion X in the apical position of a distorted square pyramid. Complex IV is dimeric and it is formed by two Cu(PPK)2 units. Bridges between these units are formed by the two oxygen atoms of the deprotonated oxime groups. Thermal stability of I–IV was investigated by thermogravimetric analysis (TGA) in air and in nitrogen atmosphere, respectively. Evolved gaseous decomposition products were characterized by IR. I–IV decompose via multistep processes. Fluorocarbons and CO2 were observed to be the most abundant gaseous species evolved. Preliminary ammonolysis experiments were performed to examine the possibility of using II and IV as precursors for the synthesis of copper nitride. Moreover, solutions of IV were spin-coated onto silicon substrates. Surface structure and morphology of the resulting films were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) and layers with island-like distribution of material were observed.

A number of new, layered nitride mixed halides have been synthesised in the quaternary phase systems Sr–N–Cl–Br and Sr–N–Br–I. The variation in structure with composition has been investigated by powder X-ray and powder neutron diffraction techniques and the structure of strontium nitride iodide, Sr2NI, has been determined for the first time (rhombohedral space group R-3m, a = 4.0103 ( 1 ) A , c = 23.1138 ( 2 ) A , Z = 3 ). A continuous solid solution exists between Sr2NCl and Sr2NBr with intermediate compounds adopting the same anti-α-NaFeO2 structure (rhombohedral space group R-3m) as the ternary end members. A similar smooth and linear relationship between structure and composition is seen from Sr2NBr to Sr2NI and hence cubic close packing of metal–nitrogen layers is adopted regardless of halide, X (X′). While nitride and halide anions occupy distinct crystallographic sites, there is no ordering of the halides in the quaternary materials irrespective of stoichiometry or temperature (between 3 and 673 K).

A comprehensive study of the system Li3-x-yNixN has investigated systematically the way in which synthesis parameters can be utilized to control stoichiometry and structure. Powder neutron diffraction and SQUID magnetometry have been used to characterize several representative compounds (with 0 < x < 1) in the ternary phase system. The results show that processing conditions such as reaction time and temperature have profound effects on the levels of lithium vacancies (y) that, in a manner similar to lithium nitride (Li3N) itself, are randomly distributed across lithium sites within the hexagonal [Li2-yN] planes. Nickel occupies the interplanar site with lithium irrespective of the doping level, x, or the synthesis conditions applied. The magnetic behavior evolves from localized Curie−Weiss-type to delocalized Pauli paramagnetic with increased nickel substitution levels. The concentration of lithium vacancies, however, appears to have no profound effect on the magnetic and electronic properties. The resul...

Blue-color emitting material, CaMgSi 2 O 6 :Eu 2+ (CMS:Eu 2+ ), was synthesized by a normal solid state reaction using CaCO 3 , MgO, SiO 2 and EuF 3 as starting materials. The Rietveld method was employed to quantitatively determine the structural parameters of synthesized CMS:Eu 2+ . The structural parameters for CMS:Eu 2+ were successfully determined by Rietveld refinement using X-ray powder diffraction data. The final weighted R -factor, R wp , was 9.22% and the goodness-of-fit indicator, S ( = R wp / R e ) , was 1.45. The synthesized sample consisted of CMS:Eu 2+ and SiO 2 (cristobalite) phases with refined phase fractions of 89.18(1)% and 10.82(2)%, respectively. Doped Eu 2+ ions occupied the Ca sites (4 e ) and replaced 1.0% of the Ca 2+ ions. The refined model of CMS:Eu 2+ describes a structure in monoclinic space group C 2/ c with Z = 4 , a = 9.7474 (2) A, b = 8.9384 (2) A, c = 5.2490 (1) A and β = 105.87 (1)°.

Both structural refinement using neutron powder diffraction data and Raman scattering were carried out to determine the site preference of La atoms and the cation distribution in Bi3.75La0.25Ti3O12 compound. Of three possible cation-disorder models, the best structural refinement result was obtained from a model that La atoms substitute only for Bi atoms outside of the TiO6 octahedra in the Bi2Ti3O10 unit. The model proposed by the structural refinement was corroborated by the Raman spectroscopic study. The final weighted R-factor, Rwp, and the goodness-of-fit indicator, S (= Rwp/Re), based on the neutron diffraction and the Raman scattering were 4.12% and 1.43, respectively. The occupancy of La atoms for two Bi sites in the perovskite-like unit was 0.082 and 0.074, respectively. The refined model described a structure in monoclinic space group B1a1 with Z = 4, a = 5.4387(1) A, b = 5.4129(1) A, c = 32.8441(1) A and β = 90.03(1)∘.

Novel Nb3Te4 nanowires have been successfully synthesized through the direct reaction and annealing of the elemental powders, by means of a vapor transport mechanism. This is the first instance of the production of group 5 transition metal telluride nanowires. Synthesis involved the initial formation of NbTe2 crystallites which were subsequently annealed to generate crystalline Nb3Te4 nanowires. Characterization using powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, and X-ray photoelectron spectroscopy (XPS) confirmed the wires to be single crystalline, with their longitudinal axes coincident with the crystallographic c-direction of Nb3Te4. The nanowires ranged in dimension from 50 nm to ∼1 μm in diameter and from 1 to 30 μm in length.

The quaternary systems Ca–N–Cl–Br and Ca–N–Br–I have been investigated resulting in the synthesis of a number of new layered nitride mixed halides. The evolution of structure with composition has been investigated by powder X-ray and powder neutron diffraction techniques. A continuous solid solution exists between Ca2NCl and Ca2NBr with intermediate compounds adopting the same anti- α-NaFeO2 structure (rhombohedral space group R 3 ¯ m ) as the ternary end members. A phase transition occurs in the Ca2NBr1−yIy system between y = 0.7 and y = 0.8 corresponding to a switch from cubic close packing to hexagonal close packing of metal–nitrogen layers and corresponding adoption of the anti-β-RbScO2 (filled anti-CdI2) structure (hexagonal space group P 6 3 / mmc ). While nitride and halide anions occupy distinct crystallographic sites, there is no ordering of halides in quaternary materials irrespective of stoichiometry or structure type. All the nitride halides show temperature independent paramagnetic behaviour between 2 and 300 K.

Crystalline boron nitride nanotubes (BNNTs) with an average outer diameter of about 40 nm and several micrometres in length were synthesized by chemical vapour deposition from boron and magnesium oxide. Rietveld refinement and 11B solid-state nuclear magnetic resonance (NMR) spectroscopy were employed to quantitatively determine the phase of synthesized BNNTs. The structural parameters for the BNNTs were determined by Rietveld refinement against powder x-ray diffraction data with a model based on the results of NMR analysis. The final weighted R-factor, Rwp, was 6.08% and the goodness-of-fit indicator, S (= Rwp/Re), was 1.52. The BNNTs consisted of hexagonal BN, rhombohedral BN and MgO with refined weight fractions of 76.3%, 21.2% and 2.5%, respectively.

The structures, magnetism and ion transport properties of the ternary nitrides Li(3-x-y)M(x)N (M = Co, Ni, Cu; y= lithium vacancy) were examined by powder X-ray diffraction, solid-state NMR and SQUID magnetometry. Doping levels are achieved up to x approximately = 0.4 for M = Cu and Co, but much higher substitution levels (x approximately =1) are obtained in the Li-Ni-N system. Transition metals substitute for Li at the Li(1) interplanar site and the ensuing lithium vacancies are disordered within the [Li(2)N] planes. High substitution levels in the Li-Ni-N system lead to the formation of ordered phases. Diffusion parameters, including activation energies, correlation times and diffusion coefficients, were obtained from variable-temperature solid-state NMR measurements in several ternary compounds. SQUID magnetometry shows significant variations of the electronic properties with dopant and x. The properties of the ternary nitrides can be rationalised in terms of the identity of the dopant and the structural modifications arising from the substitution process.

The crystal chemistry and electronic structure of the layered nitride SrTiN2 have been studied by powder neutron diffraction (PND) and density functional methods, respectively. PND investigations at room temperature, 80 K, and 2 K show that the tetragonal KCoO2 structure (space group P4/nmm (No. 129), a = 3.8823(1) A, c = 7.7008(1) A, V = 116.068(1) A3, Z = 2 at 298 K) is retained across the temperature range and confirm the structural model from previous room-temperature powder X-ray diffraction (PXD) studies. Furthermore, and importantly, PND data demonstrate that neither nitrogen nonstoichiometry nor substitution of O2- for N3- within the anion sublattice is a plausible mechanism for hole generation. Density functional calculations show that strong covalent bonding occurs within the TiN2 layers and that Sr−N interactions are pivotal in determining the band structure at the Fermi level. Calculations predict metallic and paramagnetic behavior for SrTiN2. These findings are confirmed by experimental measu...

New molybdenum(VI) and tungsten(VI) nitrides were synthesised by the reaction of barium nitride and calcium nitride with either molybdenum or tungsten foils at high temperature in sealed stainless steel crucibles. The reactions yielded single crystalline products determined by X-ray diffraction to form orthorhombic structures in the space group Pbca (no. 61). The compounds are isostructural with the low temperature (LT) form of Ba3Mo(W)N4. The structures contain isolated [Mo(W)N4]6− tetrahedra and partially disordered alkaline earth cations whose distribution across three crystallographic sites is dependent on cationic radius.

The ternary nitridotantalate, Sr 2 TaN 3 has been synthesised via the solid state reaction of strontium subnitride, Sr 2 N, with either of the tantalum nitrides TaN or Ta 3 N 5 in a sealed system under argon at elevated temperatures. The structure of Sr 2 TaN 3 was determined for the first time by Rietveld refinement against powder X-ray diffraction data. The compound crystallises with the Ba 2 ZnO 3 structure [monoclinic space group C 2/ c (No.15), a = 5.9835(1) A, b =11.2832(2) A, c =12.5814(2) A, β = 92.26(1)°, V =848.75(2) A 3 , Z =8] and is isostructural with other A II 2 M V N 3 nitrides, Ba 2 TaN 3 , Sr(Ba) 2 NbN 3 and Sr 2 VN 3 . The nitride contains infinite chains of corner-sharing TaN 4 tetrahedral anions, 1 ∞ [TaN 2 N 2/2 ] 4− , with Ta–N distances of 1.83–1.97 A. Magnetic measurements are consistent with a nitridotantalate(V).

Separated reactant metathesis methods using ternary oxide precursors and yttrium chalcogenides have been used to prepare powders and crystals of alkali metal niobium dichalcogenides, AyNbX2 (X = S, Se). The structure of Na0.5NbSe2 has been solved unambiguously for the first time from single crystal X-ray data (hexagonal space group P63/mmc (no. 194), a = 3.4762(7), c = 15.342(2) A, U = 160.55(5) A3, Z = 2). Similarly, the structure of Na0.5NbS2 has also been determined (hexagonal space group P63/mmc, a = 3.3533(4), c = 14.547(3) A, U = 141.66(4) A3, Z = 2). Products have been characterised further by powder X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. Magnetic measurements describe temperature-independent paramagnetic behaviour for both dichalcogenides, with no superconducting transitions above 1.8 K.

Two new families of nitrides containing molybdenum(VI) and tungsten(VI) were synthesised by the reaction of barium and strontium nitride with either molybdenum or tungsten foils at high temperature in sealed stainless steel crucibles. The reactions yielded single crystalline products determined by X-ray diffraction to form orthorhombic structures in the space group Pbca (no. 61). The compounds are isostructural with the “low temperature” polymorph of Ba3MoN4 and form solid solutions within the limits investigated. The structures contain isolated [Mo(W)N4]6− tetrahedra and alkaline-earth cations distributed across three crystallographic sites dependent on cationic radius. The title compounds are the first examples of mixed strontium–barium transition metal nitrides.

The ligand bis(2-pyridylmethyl)sulfide L′ and the complexes it formed were used as simple probes for the complexes of 2,5-bis(2-pyridylmethylsufanylmethyl)pyrazine L. L′ and L were reacted in 1 ∶ 1 and 1 ∶ 2 molar ratios, respectively, with both CuCl2 and CuI. Crystal structures of all four complexes were determined, CuCl2L′·H2O (1), Cu2Cl4L (2), Cu2I2L′2 (3) and [Cu2I2L]∞ (4). The Cu(II) ions in 1 and 2 were square pyramidal. For 2 crystal structures of the anti (2a) and the syn (2b) isomers were determined and both were found to form proto-polymeric chains. Complex 3 was dimeric and contained Cu2I2 bridges. The structure of 4 revealed one-dimensional polymeric chains in which the ligands were joined by Cu2I2 bridges. This work demonstrated the successful use of the complexes of L′ as probes for 4 and to a lesser extent for 2a and 2b.

Two-dimensional structures are an emerging class of materials within nitride chemistry. We report here our systematic studies of two groups of these layered compounds: 1 Lithium transition metal compounds, Li3-x-y□yMxN (M = Co, Ni, Cu, □ = Li vacancy) and 2 ternary transition metal nitrides of general formulation AMN2 (A = alkaline earth metal, M = Ti, Zr, Hf). Compounds in class 1 are based on the hexagonal Li3N structure, unique to nitrides. Compounds in group 2, by contrast, crystallise with oxide structures (α-NaFeO2 or KCoO2). Specific and unusual synthetic methods have been developed to reproducibly prepare these compounds. Compounds in series 1 contain ordered or disordered Li vacancies at increased levels relative to the parent Li3N, itself a Li+ fast ion conductor. Nitrides in series 2 should be nominally diamagnetic (S = 0), yet magnetic measurements reveal behaviour seemingly inconsistent with this assumption. © 2001 Elsevier Science B.V.

The quaternary scandium cuprate Ba3Cu3Sc4O12 has been prepared via the high temperature solid state reaction of the respective binary oxides and BaCO3 in air at 950 °C. The cuprate was characterised by powder X-ray diffraction (PXD) and its structure determined for the first time by Rietveld refinement of powder data. Crystallite morphology and metal stoichiometry were examined by SEM/EDAX. Oxygen stoichiometry and thermal behaviour were evaluated by TG/DTA and TPR. Ba3Cu3Sc4O12 crystallises with a tetragonal, perovskite-derived structure in space group I4/mcm (a = 11.9021(6) A, c = 8.3962(4) A, V = 1189.41(10) A3, Z = 4, c/a = 0.71), isostructural with Ba3Cu3In4O12. Ba3Cu3Sc4O12 is paramagnetic at room temperature consistent with Cu(II). In readily substitutes for Sc to form Ba3Cu3Sc4 − xInxO12 334-phases continuously to Ba3Cu3In4O12 (x = 4). Structures of selected members have been determined from PXD data and correlated to the trivalent cation substituent level, x.

C60(CO2)x, where x = 0.2 or 0.95, has been synthesized from solutions of C60 in conventional organic solvents using antisolvent precipitation with supercritical CO2. The technique requires much lower pressures and temperatures than current routes to C60(CO2)x and, for small quantities, is quicker. Products were characterized by SEM, IR, 13C solid-state NMR, and powder XRD. Reitveld refinement of the powder XRD shows CO2 to be located in the octahedral interstitial sites of the C60 lattice. The cell lattice parameter is observed to increase for higher occupancies of CO2. Experimental conditions can be varied to generate radically different morphologies of C60(CO2)x. Using rapid antisolvent precipitation, irregular aggregates of ca. 200 nm particles are formed, where x = 0.2. With slower, diffusion-controlled precipitation, regular, highly crystalline, octahedral-shaped particles (1−70 μm) can be formed, where x = 0.95. All products were precipitated completely free from the original organic solvent, and we...

The new ternary nitride oxide Sr4[MoN4]O was synthesised by the reaction of strontium nitride with molybdenum nitride under a low partial pressure of oxygen in a sealed stainless steel crucible. Structure determination from single crystal X-ray data showed the structure to be monoclinic in the space group P21/m (no. 11). The crystal morphology and strontium/molybdenum ratios were investigated using scanning electron microscopy and energy dispersive analysis by X-rays. The structure contains isolated [MoN4]6− tetrahedra. Oxygen is ordered in the anion sublattice and is found only in the co-ordination sphere of the alkaline earth metal.

The subnitride Ca2N has been prepared via several synthetic routes described for the first time, including reduction of Ca3N2 and reaction of Ca metal dissolved in liquid sodium with nitrogen gas. Products have been characterised by powder X-ray and powder neutron diffraction. Crystallite morphology and compound stoichiometry have been examined by SEM/EDAX. Ca2N crystallises with a hexagonal layered structure in space group Rtext-decoration:overline3m (a = 3.62872(3) A, c = 19.0921(4) A, V = 217.72(1) A3, Z = 3, c/a = 5.26). [NCa2]+ layers composed of compressed, edge-sharing NCa6 octahedra stack along the c-axis and are separated by large 'van der Waals' gaps. The material is metallic and paramagnetic at room temperature. The c-parameter, [NCa2]+ layer thickness and interlayer gap are larger than previously reported and there is no evidence of hydride or other anion intercalation between layers.

Hexa-ammine complexes, Mn(NH3)6X2 (X = Cl, Br), have been synthesized by ammoniation of the corresponding transition metal halide and characterized by Powder X-ray diffraction (PXRD) and Raman spectroscopy. The hexa-ammine complexes are isostructural (Cubic, Fm-3m, Z = 4, a = 10.2742(6) Å and 10.527(1) Å for X = Cl, Br respectively). Temperature programmed desorption (TPD) demonstrated that ammonia release from Mn(NH3)6X2 complexes occurred in three stages corresponding to the release of 4, 1 and 1 NH3 equivalents respectively. The chloride and bromide both exhibit a deammoniation onset temperature below 323 K. The di-ammoniates from the first desorption step were isolated during TPD measurements and their crystal structures determined by Rietveld refinement against PXRD data (X = Cl: orthorhombic Cmmm, a = 8.1991(9) Å, b = 8.2498(7) Å, c = 3.8212(4) Å, Z = 2, X = Br: orthorhombic Pbam, a = 6.0109(5) Å, b = 12.022(1) Å, c = 4.0230(2) Å, Z = 2).

The hydrogen sorption properties of Li3N under reactive milling conditions have been investigated in- and ex-situ as a function of polytype structure (alpha vs. beta), focusing on the influence of the micro-structure and/or the crystal structure upon hydrogen uptake. LiNH2 and LiH were synthesized by reactive milling of Li3N at 20 bar hydrogen pressure for 4 h. Reactive milling represents a quick and effective technique to produce LiNH2 by hydrogenation of Li3N at low hydrogen pressure and without any need for heating. As to our knowledge, we present a full hydrogenation of Li3N under the aforementioned conditions for the first time. The (de)hydrogenation and rehydrogenation behaviour of milled amides was evaluated using a combination of powder X-ray diffraction, differential scanning calorimetry, thermogravimetry and in situ Raman spectroscopy. In situ Raman spectroscopy showed a shift in the lithium amide stretching modes upon hydrogenation supporting a non-stoichiometric storage mechanism consistent with the literature. The microstructure and polytype composition of the Li3N dehydrogenated materials had no effect on the hydrogenation products and only minor effects on the hydrogen uptake profile during milling.

Members of the series Ba2M2–xCuxO4+δ(M = ln, x= 0.5, 1; M = Sc, x= 1) have been synthesized by solid-state reaction methods and characterised by powder neutron diffraction. Selected compositions were annealed under oxygen at 1 atm and 160 atm. The evolution of the structure with oxygen stoichiometry δ was studied. The materials form ‘doubled perovskite’ phases, A2BB′O6–x crystallising in tetragonal space group P4/mmm. The structures essentially consist of two ABO3–x cubes stacked along the c axis in which the B cations are ordered on two crystallographically different sites. The divalent Ba cation is on average nine-coordinate and the trivalent M cation octahedrally coordinated to oxygen. The copper oxidation state and coordination varies with the oxygen level of the structure.

Lithium niobium disulfide, Li(0.63)NbS(2), has been prepared by a metathesis reaction between physically separated solid reactants, i.e. separated reactant metathesis (SRM). Single-crystal data were collected at reduced temperature [150 (2) K], yielding a refined Li content of y = 0.63 (6). The Li content in the crystalline samples was also determined analytically by flame photometry. The compound crystallizes in hexagonal space group P6(3)/mmc (No. 194), with Li(+) ions situated in octahedral sites between NbS(2) layers.

A combined NMR and neutron diffraction study has been carried out on three Li(3-x-y)Cu(x)N materials with x=0.17, x=0.29 and x=0.36. Neutron diffraction indicates that the samples retain the P6/mmm space group of the parent Li(3)N with Cu located only on Li(1) sites. The lattice parameters vary smoothly with x in a similar fashion to Li(3-x-y)Ni(x)N, but the Li(2) vacancy concentration for the Cu-substituted materials is negligible. This structural model is confirmed by wideline (7)Li NMR spectra at 193 K which show three different local environments for the Li(1) site, resulting from the substitution of neighbouring Li atoms in the Li(1) layer by Cu. Since the Cu-substituted materials are only very weakly paramagnetic, variable temperature (7)Li wideline NMR spectra can be used to measure diffusion coefficients and activation energies. These indicate anisotropic Li(+) diffusion similar to the parent Li(3)N with transport confined to the [Li(2)N] plane at low temperature and exchange between Li(1) and Li(2) sites dominant at high temperature. For the intra-layer process the diffusion coefficients at room temperature are comparable to Li(3)N and Li(3-x-y) Ni(x)N, while E(a) decreases as x increases in contrast to the opposite trend in Ni-substituted materials. For the inter-layer process E(a) decreases only slightly as x increases, but the diffusion coefficients at room temperature increase rapidly with x.

Members of the series Ba 2 M 2- x ,Cu x O 4+δ , M = In, Sc (0 ≤ x ≤ 1), have been synthesised by solid-state reaction methods and products characterized by powder X-ray diffraction (PXD). Selected compounds have been annealed under oxygen at 1 atm and oxygen stoichiometries for unannealed and oxygen annealed samples have been calculated following thermogravimetric analysis (TGA). Structures for M = In, x = 0, 0.5, 1 and M = Sc, x = 1 were determined by Rietveld analysis of PXD data. Ba 2 In 2 O 5 has been shown to crystallize in the orthorhombic space group Ibm 2 (Brownmillerite structure) with a = 6.0956(1) A, b = 16.7112(3) A c = 5.9601(1) A. The copper-containing phases adopt a tetragonal "doubled perovskite" structure built up of copper-substituted BaInO 2.5 cubes. The copper coordination and oxidation state can be controlled by varying the oxygen level of the structure.

Two new ternary nitrides, Sr3CrN3 and Ba3CrN3, were synthesised from the appropriate alkaline-earth-metal nitride and chromium metal or the chromium nitride, Cr2N, at high temperatures in sealed stainless-steel capsules. Structure determination from single-crystal X-ray data showed them to be isostructural in the hexagonal space group P63/m, Z= 2, with lattice constants a= 7.724(2), c= 5.249(1)A for Sr3CrN3 and a= 8.201(2), c= 5.497(1)A for Ba3CrN3. The structures contain trigonal-planar [CrN3]6– anions and either Sr2+ or Ba2+ cations.

The new ternary nitrides SrZrN2 and SrHfN2 have been synthesized by the solid state reactions of Sr2N with ZrN and HfN and characterized by powder X-ray diffraction. Both nitrides form structures in the hexagonal space group R3m (SrZrN2, a = 3.37302(5) A, c = 17.6756(3) A, Z = 3; SrHfN2, a = 3.34481(3) A, c = 17.6779(2) A, Z = 3) and are isostructural with α-NaFeO2. The structures are constructed of alternating layers of strontium−nitrogen edge-sharing octahedra and either zirconium−nitrogen or hafnium−nitrogen edge-sharing octahedra stacked along the c axis. Alternatively, Sr2+ can be regarded as occupying octahedral holes between Zr(Hf)N2 octahedral layers. The title nitrides are essentially diamagnetic at room temperature, consistent with the chemical composition. These compounds are the first alkaline earth ternary nitrides observed to have the α-NaFeO2 layered structure.

A new ternary nitride, SrTiN2, has been synthesized by the solid-state reaction of Sr2N with TiN and characterized by powder X-ray diffraction. SrTiN2 crystallizes in the tetragonal space group P4/nmm (a = 3.8799(2) A, c = 7.6985(4) A, Z = 2) and is isostructural with KCoO2. Titanium is coordinated to five nitrogens in a distorted square-based pyramidal geometry, forming layers of edge-sharing pyramids which stack along the (001) direction. Strontium is situated between the Ti−N layers and is coordinated to five nitrogen atoms. The title compound is only the third example of a ternary titanium nitride.

Structures of lithium nitride (α-Li3N) and ternary nitridometalates Li3-x-yMxN (M = Ni, Cu) have been refined from time-of-flight powder neutron diffraction data using the Rietveld method. The parent binary nitride was synthesized by reaction of lithium metal with nitrogen using liquid sodium as a solvent. The ternary nitrides were prepared by reaction of Li3N with the respective transition metals under nitrogen. Refined data confirm the hexagonal structure previously reported by single-crystal X-ray diffraction for lithium nitride (P6/mmm, a = 3.6576(1) A, c = 3.8735(1) A, Z = 1) and show that the α-Li3N phase contains close to 3% Li vacancies at room temperature. The substituted nitridometalates, Li1.36Ni0.79N and Li2.21Cu0.40N, both form structures analogous to α-Li3N (P6/mmm, a = 3.7697(1) A, c = 3.5270(1) A and a = 3.6791(1) A, c = 3.7725(1) A, respectively) in which the transition metal is disordered with Li between [Li2-yN] planes and Li vacancies are disordered within these planes. The nickel and ...

Compounds in the system La 2−x Ba x SrCu 2 O 6± δ have been synthesised by conventional solid state methods and characterised in terms of oxygen stoichiometry and distribution. Thermogravimetric analysis of these materials has shown copper oxidation states as high as Cu 2.35+ for materials annealed in oxygen; a.c. susceptibility measurements, however, have shown that superconductivity is not present. The structures of four compounds in this system have been determined by powder neutron diffraction profile refinement. These have indicated a significant occupancy of the oxygen site situated between the copper-oxygen planes. The occupancy of this site disrupts the square pyramidal coordination of the copper ion and may be at least partially responsible for the absence of superconductivity in these materials which are structurally very similar to the superconducting compounds YBa 2 Cu 3 O 7− δ and La 2−x Sr x CuO 4− δ . The high anisotropic temperature factors (B 11 and B 22 ) observed for the interlayer oxygen site may indicate a static disordering in the unannealed materials.