L. Trichet

Les intercalaires Ax Ti S2 et Ax Zr S2. Structure et liaisons. (A = Li, Na, K, Rb, Cs)

Abstract A general survey of alkali metals intercalation compounds with titanium and zirconium disulfides is given. A model A + x (Ti S 2 x− or A + (Zr S 2 ) x− with an electronic delocalization in the (Ti 2 S 2 ) or (Zr S 2 ) slabs, is suggested according to crystallographic and magnetic studies, N.M.R. measurements, and chemical behaviour. The alkali metal coordination is related to several factors: size of the A + ion, value of the x parameter, strength of the T.S. bonds.

Les conducteurs ioniques NaxInxZr1−xS2

Substituted and intercalated lamellar dichalcogenides have been prepared in the series Na/sub x/In/sub x/Zr/sub 1-x/S/sub 2/. According to the values of x, (0 less than x less than or equal to 1), three different phases have been characterized with trigonal prismatic or octahedral coordination of sodium and with different ways of stacking of the slabs of the host structure. Conductivity measurements have been performed and show these phases to be valuable ionic conductors, especially the trigonal prismatic compounds.

Sur les propriétés électriques et magnétiques des phases MxZrS2 (M = Fe, Co, Ni)

Abstract The M x ZrS 2 systems with M = Fe, Co, Ni have been investigated: nonstoichiometric phases are observed with M in the tetrahedral sites between ZrS 2 layers. Electric measurements characterize a semiconducting behaviour and suggest the occurrence of trigonal zirconium + III clusters. Magnetic measurements seem to confirm also MM bond formation.

Preparation and structure of alkali metal intercalation compounds

Abstract The preparation methods of intercalation compounds fall into four main groups: use of alkali metal solutions in liquid ammonia, organometallic reagents, electrochemical methods, and solid state processes. Each of these will be briefly described and a general comparison of the advantages and disadvantages will be made. Structural problems concern the positions occupied by the guest ions and their mobility from one site to one another in the host structure. The resulting ionic conductivity of the intercalation compounds depends on factors such as the ratio between available and occupied sites in the van der Waals gap, the ionicity of the bonds in the host structure, the site geometry, and the nature of the alkali metal.

Structural, electrical, magnetic and NMR study of the NaxCrxTi1−xS2 system

Abstract Two phases are characterized in the Na x Cr x Ti 1− x S 2 . The first one spans the composition range 0.34 x 2 is found in the range 0.87 x ⩽ 1, the alkali-metal ions being this time in octahedral sites. Electrical measurements performed by the complex impedance method show that the conductivity is thermally activated. Magnetic and NMR experiments indicate the existence of localized magnetic moments on the chromium ions. These moments induce a shift of the NMR line and produce the most important contribution to the relaxation. The variation of the Curie temperature seems to indicate a continuous weakening of the ferromagnetic coupling between chromium ions of the same layer as the number of chromium ions decreases. An antiferromagnetic coupling then becomes preponderant.