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[en] Short note. 1 ref.; 1 fig

[en] The physical and chemical properties of the zirconium tungstate Zr₂ W₂ O₈ has been studied in the United States. This compound is a ceramic with a cubic symmetry which on the contrary of most of the materials contract in a large temperature range (23 K-1023 K) when the temperature increases. Some ceramics have already shown similar behaviours but the contraction was only in one space direction. The zirconium tungstate is a more especially interesting compound as it contracts in all the space directions. The crystal structure of this compound is given. It will be used for the manufacture of electronic circuits components in nuclear spectroscopic instrumentation, nuclear instrumentation or high-energy physics instrumentation. (O.M.). 1 fig

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[en] 67 barrels from 17 deliveries of the technically significant intermediate ammonium-parawolframate have been investigated with a view to the contents of 11 tracer elements. The large number of data obtained was analyzed by means of multivariate analysis methods. A BASIC programme 'MEDIAN' for conversational processing was used. From this programme the methods 'Principal components', 'Nonlinear Mapping' and 'CLUPOT' were applied. It was possible to demonstrate the occurrence of clusters, and both sorting and judging the homogeneity were likewise possible. (author)

[en] Crystalline solubility and structural changes brought about by the replacement of V⁴⁺ by W⁴⁺ in the system VO₂-V₂WO₆ are reported. Three structurally related phases were identified between the monoclinic WO₂ and the trirutile V₂WO₆ phases. The crystalline solubility of V₂WO₆ in MO₂ or MO₂ in V₂WO₆ was found to be entirely different depending upon whether M=V or W. This difference in crystalline solubility is explained on the basis of differences in the ionic radii of the two ions. Unit cell parameters at room temperature are tabulated, and it is reported that the parameter decreases while the c parameter increases with increasing amounts of V₂WO₆ in WO₂

[en] Moessbauer spectra of FeNbsub(1-x)Wsub(x)O⁴ with 0< x<1 between 77 and 600 K are discussed. The temperature quadrupole splitting variation of FeWO⁴ is explained by an activated electron delocalization in agreement with the semiconducting behavior of this compound. Intermediate valence state for iron is observed by Moessbauer spectroscopy in FeNbsub(1-x)Wsub(x)O⁴ with 0< x<1. (Auth.)

[en] The M₂WO₄-Sc₂(WO₄)₃ (M=Li-Cs, Tl, Ag) systems are studied. Melt liquation is established in the systems, components of which are alkali metal (Na-Cs) and thallium tungstates. Boundaries of stratification are determined. Liquation runs according to the monotectic reaction with participation of the crystal phase in systems with Na₂WO₄ and Tl₂WO₄, and in systems with potassium, rubidium and cesium tungstates as one of the components - stratification begins above liquidus. In systems with lithium and silver tungstates stratification does not detected

[en] Mn²⁺ EPR spectra change is studied in the course of dehydration of hydrates of magnesium di-, para-and tetratungstates. With water molecule removing from ditungstate, the cubic symmetry of magnesium ion environment decreases and non-equivalent Mn²⁺ positions, causing two lines with g=2.0 and 4.3 in EPR spectrum appear. Such spectrum is also observed in magnesium dehydrated paratungstate. In tetratungstate the spectrum does not practically change in the course of dehydration

No abstract available