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Within the frame of systematic morphological studies concerning the solvothermal formation of nanoscale and microscale molybdenum oxides from the interaction of a molybdenum-based precursor such as MoO 3 ¥ 2 H 2 O with ionic additives such as alkali and earth alkali halides, we studied ± with the aim to elaborate preparative guidelines ± the influence of the precursor structure and the alkali halide upon the crystal structure of the emerging alkali polymolybdates in terms of solvothermal fields and high-throughput solvothermal techniques. The discussion of the resulting crystal structures revealed a structure-directing potential of the alkali cations that was explored for the synthesis of new mixed alkali polymolybdates.

The solid-state precursor cluster chlorides Na(4)[(Zr(6)Be)Cl(16)] and K[(Zr(6)Fe)Cl(15)] readily dissolve in Lewis-basic ionic liquids consisting of mixtures of EMIm-Br and AlBr(3) (EMIm: 1-ethyl-3-methyl-imidazolium) to give dark colored solutions. From these solutions, the cluster phases (EMIm)(4)[(Zr(6)Fe)Br(18)] (1) and (EMIm)(4)[(Zr(6)Be)Br(18)] (2) were obtained in acceptable yields. Crystallographic data of the isostructural phases are the following: monoclinic, P2(1)/c, Z = 2. The data for 1 follow: a = 10.5746(4) Angstrom, b = 22.6567(9) Angstrom, and c = 13.0260(5) Angstrom, beta = 111.279(2) degrees. The data for 2 follow: a = 10.574(2) Angstrom, b = 22.681(4) Angstrom, and c = 13.041(2) Angstrom, beta = 111.31(2) degrees. Compound 1 is the first detailed structurally characterized molecular Fe-centered zirconium bromide cluster phase. In the bromide based ionic liquid, a complete exchange of all the outer and inner chlorides by bromide takes place. Since the inverse reaction, the exchange of all bromides by chlorides, was reported before, this complete ligand exchange can be considered as reversible, with the equilibrium being largely determined by the free ligand concentration. The electronic spectra of a chloride supported cluster precursor in different ionic liquids were measured and analyzed.

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We present a magnetization study of low density YBa2Cu3O7−x ceramics carried out in magnetic fields 0.5 Oe < H < 50 kOe. It was demonstrated that superconducting links between grains may be completely suppressed either by a magnetic field H ∼ 100 Oe (at low temperatures) or by an increase of temperature above 70 K. This property of present samples allowed to evaluate the ratio between an average grain size and the magnetic field penetration depth λ. Furthermore, at temperatures T > 85 K, using low-field magnetization measurements, we could evaluate the temperature dependence of λ, which turned out to be very close to predictions of the conventional Ginzburg-Landau theory. Although present samples consisted of randomly oriented grains, specifics of magnetization measurements allowed for evaluation of λ ab (T ). Good agreement between our estimation of the grain size with the real sample structure provides evidence for the validity of this analysis of magnetization data. Measurements of equilibrium magnetization in high magnetic fields were used for evaluation of Hc2(T ). At temperatures close to Tc, the Hc2(T ) dependence turned out to be linear in agreement with the Ginzburg-Landau theory. The value of temperature, at which Hc2 vanishes, coincides with the superconducting critical temperature evaluated from lowfield measurements.

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