BiCaIrO Pyrochlore Phases: Structure and Properties with Varied Ir Oxidation State from 3.9+ to 4.3.

Pyrochlore phases BiCaIrOO with x from 0.0 to 1.0 have been evaluated based on Rietveld analysis of neutron diffraction data, electrical resistivity and thermopower data from 3 to 756 K, and magnetic susceptibility data from 3 to 298 K.

From Serendipity to Rational Design: Tuning the Blue Trigonal Bipyramidal Mn Chromophore to Violet and Purple through Application of Chemical Pressure.

We recently reported that an allowed d-d transition of trigonal bipyramidal (TBP) Mn is responsible for the bright blue color in the YInMnO solid solution. The crystal field splitting between a'(d) and e'(d, d) energy levels is very sensitive to the apical Mn-O distance. We therefore applied chemical pressure to compress the apical Mn-O distance in YInMnO, move the allowed d-d transition to higher energy, and thereby tune the color from blue to violet/purple.

Influence of Structural Disorder on Hollandites A(x)Ru4O8 (A(+) = K, Rb, Rb(1-x)Na(x)).

Structural disorder can play an important role in the electrical properties of correlated materials. In this work we examine the average and local disorder in hollandites A(x)Ru4O8 (A(+) = K, Rb, Rb(1-x)Na(x)) through neutron total scattering techniques. Samples with A(+) = Rb, Rb(1-x)Na(x) exhibit the largest amount of local disorder as evidenced by higher atomic displacement parameters, and as a result, a weakened temperature dependence of the resistivity is observed upon cooling as compared to K(x)Ru4O8.

Structure and Properties of Ir-Containing Oxides with Large Spin-Orbit Coupling: Ba2In(2-x)Ir(x)O(5+δ).

In this work, the solid solution series Ba2In(2-x)Ir(x)O5+δ (x = 0-1.4, 2) was synthesized, and its structural, magnetic, and charge-transport properties were measured. With increasing Ir content, three transitions in the room-temperature structure were observed: orthorhombic to tetragonal to cubic to a monoclinic distortion of a hexagonal BaTiO3 structure.

True composition and structure of hexagonal "YAlO3", actually Y3Al3O8CO3.

The discovery of a brilliant-blue color upon the introduction of Mn(3+) to the trigonal-bipyramidal (TBP) sites in YInO(3) has led to a search for other hosts for Mn(3+) in TBP coordination. An obvious choice would be YAlO(3). This compound, which has only been prepared through a citrate precursor route, has long been considered isostructural with YInO(3).

Intense turquoise and green colors in brownmillerite-type oxides based on Mn5+ in Ba2In(2-x)Mn(x)O(5+x).

Brownmillerite-type oxides Ba(2)In(2-x)Mn(x)O(5+x) (x = 0.1-0.7) have been prepared and characterized.

Undulating layers in a new rhodate network: structure of Bi(1.4)CuORh5O10.

A new rhodate, Bi(1.4)CuRh(5)O(11), with an hitherto unknown channel structure containing undulating layers of RhO(6) octahedra sharing corners and edges has been discovered and its structure refined from single crystal X-ray diffraction data. The channels contain Bi(3+), Cu(2+), and some O strongly bound to Cu.

CsTe2O(6-x): novel mixed-valence tellurium oxides with framework-deficient pyrochlore-related structure.

Structures of CsTe₂O(6-x) phases were investigated by single-crystal X-ray diffraction and neutron powder diffraction. Stoichiometric CsTe₂O₆ is a mixed-valence Cs₂Te⁴⁺Te₃⁶⁺O₁₂ compound with a rhombohedral pyrochlore-type structure where there is complete order of Te⁴⁺ and Te⁶⁺. On heating, this compound develops significant electrical conductivity.

New oxides showing an intense orange color based on Fe3+ in trigonal-bipyramidal coordination.

Hexagonal YIn(1-x)Fe(x)O(3) phases have been prepared and characterized. The coordination for the In/Fe site in this structure is trigonal-bipyramidal. The colors of the phases change from yellow to orange to dark red with increasing Fe content.

Structural studies and electrical properties of Cs/Al/Te/O phases with the pyrochlore structure.

A series of polycrystalline and single crystal cesium aluminum tellurates with the pyrochlore structure have been prepared and characterized. The variations in cell edge for the Cs/Al/Te/O phases range from 10.06 Å for the Al rich limit to 10.

New oxides showing an intense blue color based on Mn3+ in trigonal-bipyramidal coordination.

Substitution of Mn(3+) into the trigonal-bipyramidal sites of oxides with YbFe(2)O(4)-related structures produces an intense blue color because of an allowed d-d transition. This has been demonstrated utilizing a variety of hosts including ScAlMgO(4), ScGaMgO(4), LuGaMgO(4), ScGaZnO(4), LuGaZnO(4), and LuGaO(3)(ZnO)(2). The hue of the blue color can be controlled by the choice of the host.

Mn3+ in trigonal bipyramidal coordination: a new blue chromophore.

We show that trivalent manganese, Mn(3+), imparts an intense blue color to oxides when it is introduced at dilution in trigonal bipyramidal coordination. Our optical measurements and first-principles density functional theory calculations indicate that the blue color results from an intense absorption in the red/green region. This absorption is due in turn to a symmetry-allowed optical transition between the valence-band maximum, composed of Mn 3d(x(2)-y(2),xy) states strongly hybridized with O 2p(x,y) states, and the narrow Mn 3d(z(2))-based conduction-band minimum.