Polymer-salt synthesis and study on structure of vanadium-doped yttrium-aluminum garnet

Nanoscaled YAG:V powders were synthesized using low-temperature polymer-salt method. A comparison of their structure with monocrystals structure was performed. Structure, morphology and chemical composition of materials were studied using XRD, SEM and energy-dispersive X-ray spectroscopy. Estimation of average sizes of nanocrystals and crystal cell parameters was performed based on XRD data. The results were compared with the results obtained earlier for YAG:V monocrystals. Nanopowders synthesized at 1000 °C consist from microscopic aggregates of YAG:V nanocrystals with average size of 43 nm and crystal structure characteristic for YAG monocrystals. It was found that V3+ incorporation and their substitution of aluminum ions leads to distortion of crystal cell. It was shown that this phenomenon is observed both in YAG:V monocrystals and nanopowders synthesized using low-temperature polymer-salt method. The infrared spectroscopy data shows the similarity of the monocrystal and nanopowders structure. Obtained powders can be applied for fabrication of light-absorbing optical ceramics and organo-inorganic composites

INFLUENCE OF QUARTZ CERAMICS SINGLE-STAGE PROCESSING BY GEL-FORMING WATER SOLUTIONS ON ITS STRENGTH

The main research results of the influence of quartz ceramics processing by silicon- and aluminum-containing gel- forming water solutions on its durability and porosity are given. Aqueous-alcoholic solutions based on tetraethoxysilane (TEOS, Si(C2H5O)4) with additives of aluminum nitrate are proposed for impregnation of porous quartz ceramics samples. Ceramic samples are being impregnated with solutions at the room temperature for 12 minutes. After impregnation they are being exposed to drying at the room temperature for 24 hours and heat treatment in the electric muffle furnace. The made experiments show that impregnation of quartz ceramics porous samples by gel-forming solutions leads to durability growth of not burned samples by 6-7 times even without additional heat treatment. High-temperature heat treatment of previously impregnated ceramic samples leads to decomposition of aluminum nitrate and removal of fossils, and also to hardening of the formed additional bonds between material particles. It considerably improves strength characteristics of quartz ceramics as well. Thus, the possibility of considerable hardening of porous quartz ceramics and stability growth of its strength properties by preliminary impregnation of silicon- and aluminum-bearing gel-forming solutions even without additional heat treatment is experimentally shown. It is revealed that impregnation of porous quartz ceramic samples by these solutions leads only to insignificant reduction of porosity of samples. Subsequent heat treatment of the impregnated porous ceramic samples at the temperatures, equal to 900-1200oC, results in additional significant increase in their mechanical durability

Mobilita lithných iontů ve sklech systému B2O3-GeO2-P2O5

Effect of the structural changes, electrical conductivity, and dielectric properties on the addition of a third glass-former, GeO2, to the borophosphate glasses, 40Li2O−10B2O3−(50−x)P2O5−xGeO2, x = 0−25 mol %, has been studied.Byl studován vliv přídavku GeO2, jako třetího sklotvorného oxidu, na strukturu, elektrickou vodivost a dielektrické vlastnosti lithných borofosforečnanových skel, připravených v kompoziční řadě 40Li2O−10B2O3−(50−x)P2O5−xGeO2 (x = 0−25 mol %)