Structural characterization of quaternary selenites of tungsten(VI), A 2W3SeO12 (A = NH4, Cs, Rb, K or Tl)

The quaternary A 2W3SeO12 (A = NH4, Cs, Rb, K or Tl) selenites have been prepared in the form of single crystals by hydrothermal and novel solid-state reactions. They were characterized by X-ray diffraction, thermal and spectroscopic studies. All of them have a hexagonal tungsten oxide (HTO) related [W3SeO12]2− anionic framework with pyramidally coordinated Se4+ ions. The known A 2W3SeO12 (A = NH4, Cs or Rb) compounds are isostructural with the Cs2W3TeO12 compound and have a non-centrosymmetric layered structure containing intra-layer Se—O bonds. The new compound K2W3SeO12(α) is isostructural with the K2W3TeO12 compound and has a centrosymmetric three-dimensional structure containing interlayer Se—O bonds. It is inferred that the new Tl2W3SeO12 compound has the same three-dimensional structure as K2W3SeO12(α).

Thermal and spectroscopic studies of polymer protective coatings used in optical fibers technology

<p>An important factor determining the quality of optical fibers is their mechanical reliability. The control of the mechanical reliability allows define the lifetime of a fiber, which was under the stress during the work. Decisive influences on the mechanical and optical properties of the optical fibers have the protective coatings. Optical fiber technology requires that the coatings were applied on them on-line, directly after they have been drawn. So far, little attention has been paid to optimizing the conditions of coatings curing. In this work, the comparison of a thermoanalytical and spectroscopic analysis of coatings that were cured in an UV oven in which the power of the UV lamps was changed will be shown. As part of the research tasks, completed mechanical strength measurements were made with a silica fiber of 0.125 mm diameter.</p>