C. de la Calle

Swelling and structural organization of saponite

AbstractThe structural formula of Kozfikov saponite (Czechoslovakia) is as follows:

Non-one-dimensional behavior in charge-ordered structurally quasi-one-dimensional Sr6Co5O15

N{a_{0.005}}C{a_{0.22}}{K_{0.01}}[S{i_{3.30}}A{l_{0.68}}F{e^{3 + }}{}_{0.02}][M{g_{2.50}}F{e^{2 + }}{}_{0.26}F{e^{3 + }}{}_{0.24}]{O_{10}}{(OH)_2}.

STACKING ORDER IN A K/Mg INTERSTRATIFIED VERMICULITE FROM MALAWI

Saturated with 6 different cations (Li, Na, K, Ca, Mg, Ba) its swelling in ethylene glycol, glycerol and water and its homogeneous hydration extents according to the relative humidity have been studied. Our results were compared with those found for montmorillonites, beidellites and vermiculites in order to estimate the respective influence of the surface charge density and the charge localization on the swelling properties. The three-dimensional organization of the saponite is more or less affected by random stacking faults and by multiple b/3 translations according to the exchangeable cation, the swelling state and the nature of the solvation liquid. Our experimental results indicate that the three-dimensional order met in the hydrated saponites can be explained by an anchoring of the layers towards each other by chains made up of cation -dipole interactions and of hydrogen bonds between negatively charged surface oxygens and the interlayer water. This type of interlayer link is relatively weak. It is therefore easy to introduce stacking faults in these edifices in particular by grinding of the samples.

Transition from Pauli-paramagnetism to ferromagnetism in CaCu3(Ru4−xMnx)O12 (0 ≤ x ≤ 3) perovskites

RCoO3 perovskites (R = Pr, Tb, Dy, Ho, Er, Tm, Yb, Lu) have been prepared in a polycrystalline form by thermal treatment in air (R = Pr, Tb, Dy), under O2 pressure (200 bar) (R = Ho, Er) or moderate hydrostatic pressures (20 kbar) (R = Tm, Yb, Lu). The samples have been studied at room temperature by high-resolution neutron powder diffraction to follow the evolution of the crystal structures along the series. In all cases, the structure is orthorhombic, space group Pbnm. The spontaneous orthorhombic strain and the tilting angle of the CO6 octahedra progressively increase from Pr to Lu due to simple steric factors. The CoO6 octahedra also undergo a progressive axial deformation along the series, which cannot be ascribed to electronic factors, given the low-spin configuration exhibited at room temperature by Co3+ (t62ge0g) cations for R = Tb…Lu. The stability of the crystal structure is discussed in the light of bond-valence arguments.

The Ho2MnRuO7 pyrochlore oxide: Magnetic structure versus magnetic frustration

We have synthesized Sr

Evolution of benzylammonium-vermiculite and ornithine-vermiculite intercalates

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Electronic structure analysis of the quasi-one-dimensional oxide Sr6Co5O15 within the LDA+U method

Co

Effect of Texture on Vermiculite Structure : Lithium Minerals

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