The perovskite-type oxynitride LaTiO 2 N was prepared by heating an oxide precursor at 950 °C for 5 hours under NH 3 atmosphere at a flow rate of 1 dm 3 /min. The precursor was prepared by the polymerized complex method. The oxynitride obtained was almost stoichiometric, LaTi(O 0.68 N 0.32 ) 2.9 , with a reddish orange color. The oxynitride was successively annealed at 950 °C for 3 hours under a NH 3 atmosphere at flow rates of 50 cm 3 /min, 30 cm 3 /min and 10 cm 3 /min, respectively. The color and composition varied from yellow LaTi(O 0.89 N 0.11 ) 2.8 through green-yellow LaTi(O 0.93 N 0.07 ) 2.9 to light-blue LaTi(O 0.98 N 0.02 ) 2.9 in accordance with the decreased flow rate. The absorption edges varied from 2.28 eV for the reddish orange, 2.56 eV for the yellow, 3.17 eV for the green-yellow, to 3.44 eV for the light-blue oxynitrides. Annealing under NH 3 is therefore effective in color tuning, mainly resulting in a blue-shift of the absorption edge. DV-Xα calculations support the conclusion that the lower flow rate of NH 3 led to a lower amount of nitrogen and higher oxygen levels in the oxynitrides.
In order to understand the solution chemistry of electrolyte solutions at concentrations far from infinite dilution, the solution density, viscosity and ionic conductivity of Li- and Na-TFSI dissolved in GBL and PC were measured at 0.1 ⩽ C/mol · dm− 3 ⩽ 2.0 and 278 ⩽ T/K ⩽ 328, where TFSI = bis(trifluoromethanesulfonyl)imide, GBL = γ-butyrolactone and PC = propylene carbonate. The results are compared to those of previously determined perchlorate salts. The partial molar volume of the solute, derived from the density, confirmed that the Na-systems occupy more volume in the solution than the Li-systems. On the other hand, the viscosity and ionic conductivity suggested that the Na-systems are more fluid and conductive than the Li-systems. The relative viscosity vs. the molarity follows a modified empirical Jones-Dole equation. The molar conductivity linearly decreased with respect to the cube-root of the molarity, which was analyzed by the pseudolattice model. The Raman spectroscopy revealed that, while the solvation number is comparable at 1-2 for either the Li- or Na-systems, Li+ is more tightly bound to the solvent molecules than Na+. The higher fluidity and conductivity of the Na-systems than those of the Li-systems result from the less occurrence of the solvent-shared ion pairs in the former than in the latter.
Effects of hydrogen plasma treatment on the 1.54 μm luminescence of erbium-doped porous silicon Mechanism of the visible electroluminescence from metal/porous silicon/ n -Si devices
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