The induced absorption spectra were measured for equally grown CaWO₄ and CaWO₄ : La single crystals after ⁶⁰Co radioisotope irradiation by doses within 1 to 230 Gy. La doping increases considerably the radiation hardness of CaWO₄ material similarly as was observed for isostructural PbWO₄ single crystals recently. Transmission of as grown undoped CaWO₄ shows a noticeable decrease below 450 nm, which gives the evidence of deep trapping states. These trapping centres are effectively diminished by La doping as well. Induced absorption bands are discussed in the light of known and hypothesized color centers in CaWO₄ and PbWO₄single crystals, which were reported earlier in the literature.

 

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The surface of silver tungsten points would reach a molten state in the opening and closing moment because there are Joule heat and arc high temperature action among tungsten silver points and which will be solidified in the cooling process and weld after that resulting that working contacts no longer disconnected. If machinery is designed poorly or prepared improperly, which can bring about the result of silver tungsten contact bounce and short arc, and its welding problem will be very prominent at the time.

Anti-welding properties of silver tungsten points lie on the welding force of silver tungsten points. Welding force is referring to the force needed to separate the two welded silver tungsten points, and its size is connected to the tensile strength of silver tungsten points. If the toughness of contact material is better, then the tensile strength of silver tungsten points will be stronger, and the welding force will be greater, and its anti-welding properties will be worse; on the contrary, if the tensile strength of silver tungsten points is weaker, and the welding force will be smaller, and its anti-welding properties will be better.



 

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Utilization of luminescent substances in various optoelectronic devices depends on their luminescent properties and sensitivity to various excitation radiation as well as on particle size distribution and crystalline structure of luminous powders. Calcium tungstate phosphors are well excited with roentgen radiation, so that they are largely used for manufacture of x-ray intensifying screens. Being sensitive to short UV-radiation as well, they could be utilized in Plasma Display Panels or in advertising signs fluorescent tubes. In order to diversify the utilization possibilities of this tungstate class, luminescent powders based on CaWO₄:Eu³⁺ and CaWO₄:Tb³⁺ were synthesized and characterized. As compared with the starting self-activated phosphor, larger excitation wavelength domain and emission colors from blue-to-green-to- yellow-to-red were obtained. The good UV excitability and variable luminescence color recommend these phosphors for optoelectronic device manufacture.

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Acousto-optic modulators are main component of communication fibre-optic systems. From the other side the studies of the absolute piezo-optic effect (POE) are one of the important steps to estimate the acousto-optic efficiency of optical materials.The investigation results of POE in calcium tungstate crystals (CaWO4) has been represented. It is also proved that this crystal is essentially better acousto-optic material in comparison with lithium niobate (LiNbO3) widely used in acousto-optic devices.

 

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