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[en] Within this work new attempts have been done to prepare unknown compounds in the field of quaternary tetrahedral compounds. Therefore it was tried to synthesize compounds of the composition A"I_2M"I"IM"I"VS_4 with A = Ag, Li, M"I"I = Fe, Co, Mn, Hg, Cd, Zn, Pb, MIV = Si, Ge, Sn, which are not known in the literature so far. For these compositions the known copper compounds were used as a model. Using this route, the new compounds Ag_2MnSnS_4, Ag_2FeGeS_4, Li_2MnSnS_4 and Li_2FeSnS_4 were synthesized. All of the mentioned compounds except Ag_2FeGeS_4, that crystallizes tetragonal, crystallize in the wurtzite-type. The predicted anti-ferromagnetism for Ag_2MnSnS_4 mentioned in the literature could not be confirmed. Furthermore it was attempted to synthesize new compounds containing titanium, zirconium and hafnium as tetravalent cation that resulted in the compound Cu_2ZrS_3 which was not known in the literature before. Additionally, the compounds Cu_1_0Cd_2As_4S_1_3 and Cu_1_0Mn_2As_4S_1_3 were prepared, which could be derived from Cu_1_2As_4S_1_3.
[en] The rare earth molybdenum sulfides REsub(x)Mo6S8(RE-=rare earth) have been synthesized and are found to be superconducting with a few exceptions. This result, which is surprising in view of the high concentration of magnetic ions, is correlated with the particular structure of these compounds based on units of Mo6S8. (author)
[en] A simple principle of lanthanide thermochemistry is used to estimate the standard free energy change for the semiconductor-metal transition in the lanthanide monosulfides at 298.15 K. The results are in satisfactory agreement with the distribution of semiconducting and metallic monosulfides within the lanthanide series, and with the observed transition pressure regions in SmS, EuS, and YbS. In cases where experimental values of the standard enthalpies of formation are currently unavailable, estimated values for both semiconducting and metallic monosulfides are also obtained. (author)
[en] Madelung (UM) and experimental lattice (UP) energies have been determined for the series of lanthanide monosulphides (LnS, Ln=Ce-Lu, excluding Pm). Comparative crystal-field (CF) analysis has been performed for the same series in the point-charge model with inclusion of the ground 4fn and the excited 4fn-15d configurations. It has been found that the variations of both UM/UP and the CF parameters for the 4fn-15d configuration across the lanthanide series exhibit minima for the magnetic semiconductors SmS, EuS, and YbS.
[en] The results of a crystallographic analysis of the structures of CsFe2S3, Tl2PbZrS4, and Tl2PbGeS4 with a 1:1 cation-anion ratio are used to identify a joint F sublattice for Cs and S in the first compound and two separate F sublattices for cations and anions in the second compound (the PbS structural type). The substitution of the small Ge4+ (with its tetrahedral coordination by sulfur) for Zr4+ in the composition results in an increase in the unit cell volume, i.e., a decrease in the packing density for both cations and anions in the structure of the third compound. In the absence of regular F sublattices, there are ''two-dimensional'' orderings, typical of the PbS type, for the atomic positions in the projections of this structure.
[en] Several analytical techniques were employed to characterize oxidation-resistant metal-sulfide species that have recently been suggested to be present in oxic waters. Sulfide in synthetic Cd-, Zn-, Pb-, Cu-sulfide solutions was found to persist in oxic waters for a prolonged period of time (2 to more than 10 weeks) whereas it was oxidized rapidly in Fe-, Mn- and Ni-sulfide solutions. Multiple lines of evidence did not support the presence of soluble molecular metal-sulfide clusters in these solutions as suggested previously. Instead, the metal-sulfide species resistant to oxidation in oxic waters were more likely a mixture of truly dissolved metal-sulfide complexes and dynamic metal-sulfide colloids. The morphology and size of the colloids, as monitored by transmission electron microscopy (TEM), changed significantly with time. Nanomolar to sub-micromolar levels of acid-volatile sulfide (AVS) and chromous-volatile sulfide (CVS) were measured in oxic surface waters of six lakes located on the Canadian Shield and in the nearby areas. Thermodynamic calculations indicated that at the AVS levels measured, the dissolved metal-sulfide complexes play a minor role in the speciation of Class B metal ions such as Pb, Cd, Cu, Hg. The relative importance of metal-sulfide colloids in these natural oxic waters remains unknown
[en] The M/sub x/Pb/sub 1plus-or-minusx/Mo/sub 6+y/S8 thin films (where x=0.1 and 0.2; y=0 and 0.35; M=La, Nd, Pr, Gd, Y, or U) were prepared by a dc getter sputtering method. The influence of dopind elements ion critical transition temperature T/sub c/, initial slope [dH/sub c/2/dT]/sub T/c-italic, and critical current density J/sub c/ was studied. The critical current was determined as a function of external magnetic field and heat treatment. It was found that in some cases the soping elements increase the critical transition temperatures and initial slope. Between 4 and 14T they also make the critical current of the PbMo6S8 phase less dependent on external field
[en] Heat capacity measurements between 2 and 200K were made on a series of nearly stoichiometric rare earth sesquisulfides RS/sub 1.5/ with R = La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, or Lu. No magnetic ordering was observed. Extra heat capacity contributions beyond those due to the lattice and conduction electrons occur in all cases except in the La and Lu compounds. Such contributions are mostly of the Schottky type associated with crystal field effects
[en] The compounds of the K2Tm23.33S36 type are known with Tm, Yb, Lu. They have same crystal structure as Yb18In7.33S36. The two structures are analyzed; they only differ by the different contents of some sites
[fr]Les composes de type K2Tm23,33S36 sont connus avec les terres rares: Tm, Yb, Lu. Ils possedent la meme structure cristalline que Yb18In7,33S36. Les deux sttructures sont analysees; elles ne different que par les remplissages de certains sites
[en] The reaction of UOS was tested on various sulfides. It was only positive in the case of the R2S3 sulfides at very high temperature (1500-19000C) with formation of the title compounds. The crystal structure was solved in the case of (UO)2ErS3: tetragonal cell, space group I4/m mm, a = 3.785, c = 20.83 A, Z = 2. A sheet structure is formed by alternating (UO) and (ErS3) sheets. The apparent oxydation state of U is 3.5, and there is only one serie of positions for this element. But it is presently impossible to choose between mixed valencies or intermediate valency to represent the electronic state of U. (author)