Ralph Layland

The simultaneous powder X-ray and neutron diffraction refinement of two η-carbide type nitrides, Fe3Mo3N and Co3Mo3N, prepared by ammonolysis and by plasma nitridation of oxide precursors

Abstract The intermetallic nitrides Fe3Mo3N and Co3Mo3N were synthesized by the ammonolysis of the ternary oxide precursors FeMoO4 and CoMoO4 as well as by plasma nitridation of the oxide precursors. The structures of Fe3Mo3N and Co3Mo3N were determined from the simultaneous Rietveld refinements of powder X-ray and neutron diffraction data. Both compounds were found to be isostructural with η-Fe3W3C which crystallizes with cubic symmetry in the space group Fd 3 m with Z=16. The lattice parameters were found to be a=11.0859(3) A and a=11.0270(6) A for Fe3Mo3N and Co3Mo3N, respectively. The general atomic positions that gave the best refinement for the intermetallic nitrides M3Mo3N are Mo on 48f, M on 32e and 16d and N on 16c. The structure consists of corner shared NMo6 octahedra with the metal atoms occupying the sites between the octahedra. Magnetic susceptibility data for Co3Mo3N was found not to follow the Curie law.

New manganese pyrophosphates: The syntheses, crystallographic characterizations and magnetic properties of BaMnP2O7 and CaMnP2O7

Abstract The new compound BaMnP2O7 was obtained in two crystallographic modifications, (monoclinic-1) and (triclinic-2), by heating mixtures of BaCO3, P2O5 and MnO2 to 1100°C and to 1000°C for 72 h, respectively. CaMnP2O7 (3) was obtained by heating a mixture of CaCO3, P2O5 and MnO2 to 1050°C for 48 h. Both crystallographic forms of BaMnP2O7 and CaMnP2O7 (3) were investigated by single-crystal X-ray diffraction analysis. The high-temperature monoclinic form of BaMnP2O7 could not be obtained free of the low-temperature triclinic form in the bulk form. In monoclinic-1 the manganese ions exist in a distorted MnO6 octahedron surrounded by five closely and one remotely positioned oxygen atoms. In triclinic-2 and -3 forms the manganese ions are associated in pairs by the formation of Mn2O10 units that share one edge of two adjacent octahedra. The magnetic properties of the triclinic-2 and -3 forms were also investigated. The effective magnetic moments, μeff, are 5.7 B.M. and 5.8 B.M./Mn atom for triclinic-2 and -3, respectively, and are consistent with a high-spin Mn2+ ion in an octahedral environment with five unpaired electrons. The temperature-dependent magnetic measurements of 2 and 3 have revealed a combination of short-range antiferromagnetic coupling, J, between the two Mn ions within the Mn2O10 units and a longer range weaker antiferromagnetic coupling, J′, between the neighbouring Mn2O10 units, |J′/J| = 0.18 and 0.074 for 2 and 3, respectively.

Growth of single crystals belonging to a family of one-dimensional oxides: commensurate and incommensurate structures

Abstract Mixtures of alkaline earth carbonates together with nickel or copper oxide and iridium, ruthenium, platinum or rhodium metal in a carbonate flux at 1050–1150°C leads to the formation of black crystals. These crystals, whose habit is either hexagonal plates or hexagonal rods, belong to a family of perovskite related phases of general composition [A]x[(A′,B)O3]. Preliminary diffraction experiments indicate that these crystals form with a composite structure, some commensurate and others incommensurate. The structures of the commensurate crystals were determined by single-crystal X-ray diffraction, while the structures of the incommensurate crystals are being investigated by powder diffraction. Several commensurate and incommensurate single crystals and their growth conditions are discussed in this paper.

A new mixed metal titanate: The synthesis and characterization of Ba2Fe2Ti4O13

Abstract The new mixed metal titanate Ba 2 Fe 2 Ti 4 O 13 ( 1 ) was obtained in crystalline form by heating a mixture of BaCO 3 , Fe 3 O 4 and TiO 2 at 1350°C for 48 h. Compound 1 was characterized by single-crystal X-ray diffraction methods. It is isomorphous to the related known compounds Na 2 Ti 6 O 13 and Ba 2 NiTi 5 O 13 . The X-ray diffraction and Mossbauer measurements of 1 obtained at room temperature indicate that the iron ions are unequally distributed between the three independent sites occupied by the transition metal ions.

Synthesis, characterization, and magnetic properties of a commensurate and incommensurate phase of Sr3ZnRhO6: zinc in trigonal prismatic coordination

Abstract The new compound Sr 3 ZnRhO 6 has been synthesized as both a commensurate and an incommensurate phase. The commensurate compound was structurally characterized by Rietveld refinement of powder X-ray diffraction data in the space group R 3 c (no. 167), Z =6. The lattice parameters for this compound were found to be a =9.6194(1) A and c =11.1061(1) A. It belongs to a family of pseudo one-dimensional materials and is isostructural with the K 4 CdCl 6 structure. The commensurate structure contains zinc in a highly unusual trigonal prismatic coordination environment. The structure consists of infinite one-dimensional chains of alternating face-shared RhO 6 octahedra and ZnO 6 trigonal prisms. The strontium cations are located between the chains and are coordinated in a distorted square antiprismatic environment. Magnetic measurements were made for both compounds. The data for the commensurate structure shows that the susceptibility of Sr 3 ZnRhO 6 increases rapidly below 20 K without the usual signs of long range ferromagnetic ordering. The magnetic susceptibility of the incommensurate phase of Sr 3 ZnRhO 6 , however, is quite different from the commensurate analog and does not exhibit the rapid increase in magnetization at low temperature and appears much more Curie-like.

The synthesis of [Fe(CO)3(?1-dppm) {Sn(n-Bu)2}]2 by silicon-tin exchange, its crystal structure and its use as a metallodiphosphine ligand

AbstractThe reaction of the siloxyl containing ferrate [Fe(CO)3(η1-dppm){Si(OMe)3}]−,1 (dppm = Ph2PCH2PPh2) with Sn(OAc)2(n-Bu)2 has yielded the new dimeric complex [Fe(CO)3(η1-dppm){µ-Sn(n-Bu)2}]2, 3 in 89% yield. Compound3 was characterized crystallographically and was found to be a centrosym-etrical molecule with a rhomboidal Fe2Sn2 cluster at the center. Each iron atom contains meη1-dppm ligand. Compound3 was found to react with [Pd(dmba) (µ-Cl)]2 (dmba=dimethylbenzylamine) to yield the new complexmer-[Fe(CO)3{Sn(n-Bu)2}(µ-dppm)Pd(dmba)Cl]2, 4 by attachment of a palla-dium grouping to each of the uncoordinated phosphorus atoms in 3. Crystal data for 3: space groupP

Preparation, characterization, and magnetic properties of the solid solution series: Ca4−xNixIrO6 (x = 0.1, 0.2, 0.3, 0.4)

\bar 1

A barium copper titanate. The synthesis and structural characterization of Ba8Cu2Ti22O54

,a=11.399(2) Å, 6=15.98(3) Å, c=10.869(3) Å, α=94.10(2)°.β=100.56(2)°, γ=69.35(1)°,Z=2, 3533 reflections,R=0.034.