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Abstract: A new pyrochlore-type structure (Bi1.56Co0.44)(Sb1.48Co0.52)O7 compound has been synthesized using ceramic method in air. Rietveld refinements using X-ray powder diffraction data confirmed an overall A2B2O7 cubic pyrochlore structure with a =10.44896 (2)Å and Fd-3m symmetry. The reliability factors are R wp =3.09%; R p =2%; R exp =1.39% and R Bragg =4.38%. The magnetic susceptibility measurements achieved between 4 and 800K indicate a paramagnetic behaviour with an oxidation state “+2” of the cobalt ion. The electric resistivity measured using the complex impedance spectroscopy method evidenced an increase of the electric conductivity with the temperature, which reached 1.88×10−3 (ohmcm)−1 at 775K. [Copyright &y& Elsevier]

The results of the studies of the physical properties of organic composites obtained by direct solid–solid charge-transfer (CT) reaction between bis(ethylenedithio)tetrathiafulvalene (BEDT–TTF) and iodine or gold iodide are presented and discussed. It is shown that the analysis of experimental data of dc conductivity and thermoelectric power and the relation between morphology of composites and their electrical properties result in understanding the charge transport phenomena and allow to propose the model of electrical transport in these materials. The main factors that affect the electrical properties of composites are recognized and the ways of controlling these factors and tuning the electrical properties are proposed. To cite this article: A. Graja, M. Golub, C. R. Chimie 6 (2003). [Copyright &y& Elsevier]

In the continuing search for new physical properties and combinations of properties in molecular materials, novel phenomena and structures are identified in three categories of TTF and BEDT–TTF (bis-ethylenedithiotetrathiafulvalene) charge-transfer salts with inorganic complex anions. When the anion is a 3d complex containing NCS– and an aromatic donor, long range π–d ferrimagnetic order is established by donor-anion π–π overlap; when the anion is a tris-oxalato-metallate(III) complex, both normal state and superconducting behaviour are dramatically influenced by changing guest molecules in the lattice, while incorporating columns of crown ether and H3O+/H2O leads to metallic conductors that simultaneously transport protons. To cite this article: P. Day, C. R. Chimie 6 (2003). [Copyright &y& Elsevier]