Paul C. Donohue

Novel perovskites M2IILnIIIRuVO6 as emission control catalysts

New perovskites, M/sub 2//sup II/Ln/sup III/Ru/sup V/O/sub 6/, where M/sup II/ = Ba and Sr, Ln/sup III/ = rare earths, Y and Bi, were prepared. The Ba series exhibits cubic cells for Ln/sup III/ = La to Dy and hexagonal cells for Ln/sup III/ = Yb and Y. The Sr series exhibits superlattices for Ln = La through Nd and orthorhombic distortions for Ln = Sm through Yb. Ba/sub 2/LaRuO/sub 6/ showed catalytic activity and thermal stability for the reactions: 2NO + 2CO ..-->.. N/sub 2/ + 2CO/sub 2/ and 2CO + O/sub 2/ ..-->.. 2CO/sub 2/. The combustion of three basic cations per Ru and the perovskite structure stabilizes Ru in these catalysts.

The preparation and properties of BaTa0.8S3, BaNb0.8S3, and BaTa0.8Se3

Abstract Compounds of the formulas BaTa 0.8 S 3 , BaNb 0.8 S 3 , and BaTa 0.8 Se 3 were prepared by two methods: reaction of the elements in evacuated silica tubes and reaction of H 2 S over mixtures of BaCO 3 and 0.4Ta(Nb) 2 O 5 . They have the hexagonal BaNiO 3 -type structure and are diamagnetic semiconductors. From the stoichiometries and properties we conclude that Nb and Ta are pentavalent.

Preparation and properties of LnMX3, where Ln = rare earths, Bi; M = Ta, Nb, Ti, V, and X = S, Se

Abstract Compounds were prepared of the general formula LnMX 3 (where Ln = all rare earths or Bi, X = S, and M = Ta or Nb; Ln = La through Tb, X = S, and M = Ti or V; Ln = La through Gd, X = Se, and M = Ta or Nb; Ln = La, X = Se, and M = Ti or V). They were prepared by reaction of the elements in evacuated silica tubes with iodine as a mineralizing agent. They form as black shiny lamella crystals which exhibit plastic deformation, good thermal and hydrolytic stability, low coefficients of friction, and metallic conductivity. The crystal structures have subcells like PbNbS 3 but the actual cells are larger and more complex. LaTiS 3 is isotypic with LaCrS 3 .

Synthesis, structure, and superconductivity of new high pressure phases in the systems GeP and GeAs

Abstract Reactions of Ge with P and As were run in a tetrahedral anvil press at conditions ranging from 600–1300C and 15–65 kbars. Three new phases were found in the GeP system. Two phases of approximate formulas GeP 5 and GeP 3 have rhombohedral crystal structures related to the A7 arsenic type. The cell dimensions of GeP 5 are a = 3.467 (3)A, c = 10.04 (1)A and of GeP 3 a = 7.050 (1)A, c = 9.932 (3)A. The cell dimensions vary for different preparations indicating ranges of stoichiometry. A new tetragonal form of GeP was prepared by the reaction of Ge + 1.0–1.7 P at 600–800C, 45–65 kbars. The cell dimensions are a = 3.544 (2)A, c = 5.581 (1)A and space group is 14 mm. A similar tetragonal phase was formed in the GeAs system. The cell dimensions are: a = 3.715 (1)A, c = 5.832 (1)A. The tetragonal crystal structures were solved by least-squares refinement of the powder-diffraction intensity data. Bond distances and angles were calculated. Electrical measurements on single crystals show metallic behavior. Meissner effect measurements show that GeP is superconducting below 1.8–4.2K and GeAs below 3–3.5K.

High-pressure spinel type Al2S3 and MnAl2S4

Abstract New spinel type forms of Al2S3 and MnAl2S4 were prepared at pressures from 2 to 65 kb. The Al2S3 was shown to exhibit a structure similar to β-In2S3 in which ordered vacancies result in a super lattice with a tetragonal cell. The cell dimensions are a = 7.026 ± 0.001 A, c = 29.819 ± 0.001 A. Electrical measurements show semiconducting behavior with ϱ 298° K = 10 9 Ω cm , Ea = 0.3 eV . The spinel form of MnAl2S4 exhibits a range of stoichiometry as indicated by a range of cell dimension from a = 10.092 ± 0.001 A to a = 10.010 ± 0.001 A. Resistivity and magnetic measurements indicate semiconducting and paramagnetic behavior.

Palladium and platinum phosphochalcogenides—Synthesis and properties

Abstract Three new PdPyS2−y (0 P 3 m1 ) was also obtained at autogenous pressure. The crystal structure of this semiconductor was solved by refinement of X-ray powder intensity data using trial and error methods. Reactivity was much lower in the related Pt systems and only substitution of small amounts of S for P in pyrite-type PtP2 was observed.

Mixed-cation transition metal pyrite dichalcogenides—High pressure synthesis and properties

Abstract Ternary, pyrite-type dichalcogenides Zn y Mn 1− y X 2 , Cd y Mn 1− y X 2 , Zn y Cd 1− y X 2 , Zn y Cu 1− y X 2 , Cd y Cu 1− y X 2 , Mn y Cu 1− y X 2 , Cu ∼0.75 Fe ∼0.25 S 2 , and Ni 0.4–0.6 Fe 0.6-0.4 X 2 (0 y 2 was elevated upon substitution with less than 20 a/o of Zn or Cd. A noncolinear spin structure is proposed to explain the ferromagnetism observed in the Mn y Cu 1− y X 2 compounds.

The preparation of Ln2MX5 where Ln = rare earths, M = Zr and Hf, and X = S, Se

Compounds of the title formula were prepared by reactions of the elements in evacuated silica tubes in the presence of iodine. The compounds formed for the following combinations: When M = Zr or Hf and X = S, all rare earths except Eu and Yb. When M = Zr and X = Se, rare earths between La and Tb, except Eu. When M = Hf and X = Se, rare earths La and Ce. X-Ray powder patterns were indexed on the basis of orthorhombic cells analogous to that of U3S5. Electrical measurements show high-resistivity semiconduction for La2ZrS5 and Ce2HfS5 but lower resistivity for Sm2HfS5, perhaps indicative of the presence of some Sm+2.

High-pressure syntheses and properties of CoP2 and MnCoP4

Arsenopyrite-type CoP2 and marcasite-type MnCoP4 were prepared at a pressure of 65 kb. CoP2 is a diamagnetic semiconductor while MnCoP4 is antiferromagnetic and a poor metallic conductor.

The syntheses of Hg2P3X where X = Cl and Br

Two new mercury halophosphides Hg2P3Cl and Hg2P3Br, have been prepared. Hg2P3Cl has the monoclinic Cd2P3Cl structure a = 7.840 A, b = 8.849 A, c = 7.593 A, β = 98.63°. Hg2P3Br has a related orthorhombic structure a = 8.014 A, b = 8.901 A, c = 7.822 A. Both are black semiconductors stable in HCl and HNO3.