RESUMO
The effects of Dy(3+) doping concentration and calcinations on the fluorescence properties of La(3)Ga(5.5)Nb(0.5)O(14) (Dy:LGN) nanocrystals were examined for the first time. High quality Dy:LGN nanocrystals were synthesized by the sol-gel method. The room temperature fluorescence spectra were measured; they showed a yellow emission, which can be attributed to the (4)F(9/2)-(6)H(13/2) transition. The relationship between the relative emission intensity and the doping concentration of the specimens, sintered at different temperatures, is consistent with a Gaussian distribution according a fitted and modified formula. The optimum value of the Dy(3+) doping concentration in LGN nanocrystals is in the range 2.0-2.5%. Moreover, in LGN bulk crystal for laser use, the optimum value, calculated through the obtained formula, is presumed in the range 1.5-2.0%. The fluorescent lifetime of a 2.0% Dy:LGN nanocrystal is quite short, only about 8.5 ns.
RESUMO
In the title complex, ¿[MnHg(SCN)(4)(H(2)O)(2)].2C(4)H(9)NO¿(n), each Mn atom is octahedrally coordinated to four equatorial thiocyanate N atoms and two axial water O atoms. The Mn atom and two O atoms lie on a twofold axis. Two kinds of crystallographically independent Hg atoms (denoted Hg1 and Hg2) are tetrahedrally coordinated with four thiocyanate S atoms and each Hg atom lies on a -4 axis. N,N-Dimethylacetamide molecules are connected to coordinated water molecules through hydrogen bonds. Each pair of Mn and Hg atoms is bridged via one thiocyanate ion. An Mn(2)Hg1Hg2(SCN)(4) 16-membered ring is formed as a unit and the four metal atoms are in a chair-form tetrahedral arrangement. The units are linked with one another and form infinite two-dimensional networks.