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[en] Recent experiments have demonstrated that valence band dispersion may be observed on suitably prepared surfaces of quasicrystals. We present model calculations for optical transitions for one-dimensional a periodic lattices, and show that these calculations are consistent with the experimental photoemission results. We estimate the total number of bands which can be observed in such an experiment is reduced from infinite, to just two to three bands in a typical experiment

[en] The morphological and electrical properties of Ba_1-xSr_xCe_0.8Y_0.2O_3-δ with x varying from 0 to 1 prepared by a modified Pechini method were investigated as potential high temperature proton conductors. Dense microstructures were achieved for all the samples upon sintering at 1500 C for 5 h. The phase structure analysis indicated that perovskite phase was formed for 0 (le) x (le) 0.2, while for x larger than 0.5, impurity phases of Sr₂CeO₄ and Y₂O₃ appeared. The tolerance to H₂O for the samples improved with the increase in Sr content when exposed to boiling water, while the electrical conductivity decreased from x = 0 to 1. However, the resistance to CO₂ attack at elevated temperatures was not improved within the whole x range studied.

[en] The crystallographic and electronic structure of UFe2Al10 was studied as a function of pressure by combining X-ray diffraction results with the full potential linearized augmented plane wave (LAPW) calculations method. The volume-pressure reduction measured at 23.5 GPa is V/V0 = 0.87, with a B0 value of 132 ± 8 GPa. The uranium 5f electrons in this compound are located in a narrow and well-defined band above EFermi, having a very weak interaction with the iron 3d band located below EFermi. Consequently, the DOS at EFermi is close to zero, indicating a close to zero-magnetic moment of the uranium atom at low temperature up to a pressure of 23.5 GPa, as expected from the layered crystallographic structure of this compound. The above assumption is supported by preliminary neutron diffraction data, where no long-range magnetic order was detected down to 3 K.

[en] A series of crystalline Gd-W oxides, with Gd:W ratios spanning the values 0.1-3.5, has been prepared and treated with a flow of NH₃(g) in the temperature range 700-1100 C. Besides the previously reported formation of GdWO₃N and Gd₂WO₃N₂, the following new results were obtained: (i) cubic Gd_0.1WO₃ upon ammonolysis forms an (oxy)nitride Gd_0.1W(O, N)_x with an f.c.c. lattice; (ii) the previously described Gd₂WO₃N₂ exhibits a solid solubility range Gd_3-xW_1+x(O, N)_y with, approximately, 0≤x≤1; (iii) ammonolysis of Gd₁₄W₄O₃₃ yields an oxynitride, the composition of which varies with the synthesis temperature according to Gd₁₄W₄O_33-xN_y(0≤x≤17±2, 0≤y≤9±2). All strong diffraction lines, including those of the pure oxide (x=y=0), can be indexed with a body-centred monoclinic unit cell derived from that of fluorite. For Gd₁₄W₄O₃₃ the cell parameters are a=5.3592(11), b=3.7295(7), c=3.8636(8) A, β=92.170(2) and V=77.17 A³. However, strong superstructure reflections in the electron diffraction patterns indicate that the true unit cell is considerably larger. A partial structure determination of Gd₁₄W₄O_33-xN_y has been carried out by the Rietveld method. Magnetic susceptibility measurements in the temperature interval 15-300 K show a Curie-Weiss law behaviour for Gd₁₄W₄O_33-xN_y, with μ_eff=8.08±0.06 Bohr magnetons per Gd³⁺ and θ=-12.4±1.1 K for all compositions. (orig.)

[en] The Ru-Sn liquid-solid and some solid-solid equilibria have been completely revised by means of differential thermal analysis, X-ray powder diffraction and microprobe investigations. The existence of two intermetallic phases has been clearly established: Ru_0.4Sn_0.6 decomposed by a peritectic reaction at 1266(±4) C and Ru_0.3Sn_0.7 congruently melting at 1257(±2) C. (orig.)

[en] The standard enthalpies of formation of LuSi, Lu₅Sn₃ and Lu₅Ge₃ have been remeasured by direct synthesis calorimetry at 1473 ± 2 K. The following ΔH^o_f (kJ mol^-1) values of atoms are reported: LuSi -79.1±2.7; Lu₅Sn₃ -75.1±2.7; Lu₅Ge₃ -93.1±2.2. The results are compared with our previously reported values. (orig.)

[en] The magnetic properties of alkali metal uranates(V) MUO₃ (M, alkali metal) with the perovskite structure have been studied. In this study RbUO₃ (cubic perovskite structure) was prepared and its magnetic susceptibility was measured from 4.2 K to room temperature. It was found that a magnetic anomaly (magnetic transition) occurred at about 27 K. As a result of the U⁵⁺ ion in the paramagnetic state, the electron paramagnetic resonance spectrum was not observed even at 4.2 K. The magnetic susceptibility results and the optical absorption spectrum were analysed on the basis of an octahedral crystal field model. The magnetic transition temperatures and crystal field parameters determined for MUO₃ (M triple bond Li, Na, K, Rb) are compared and discussed. (orig.)

[en] The La-Ru system has been examined to search for new superconducting phases in addition to the previously known superconductor LaRu₂. Electrical resistivity measurements reveal that La₃Ru (Fe₃C structure type), La₅Ru₂ (Mn₅C₂ structure type) and La₇Ru₃ (Sr₇Pt₃ structure type) exhibit superconductive transitions at 5.55, 3.35 and 1.75 K, respectively. Magnetic susceptibility measurements give estimates of the lower and upper critical field at selected temperatures for the three phases. Pauli-like paramagnetism in the normal state for all compounds is observed. (orig.)

[en] Recently, the synthesis of a novel ferromagnetic compound with a high Curie temperature of 655 C and the approximate stoichiometry GdFe_8.4Ge_1.6, has been reported in this Journal. The work reported here shows that samples prepared with identical experimental conditions are not actually single-phase, but three-phase mixtures containing a majority substitutional solid solution of germanium in α iron (85.3% wt.), GdFe₂Ge₂ (12.3% wt.), and a small proportion of the hexagonal polymorph of Fe₃Ge (2.4% wt.), as shown by X-ray diffraction, scanning electron microscopy and thermomagnetic measurements. (orig.)