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I. Rammo M. Kerikmyaé M. Lepist L. Matizen L. Pung K. Ritslaid A. Haav 《Journal of Applied Spectroscopy》1997,64(2):182-187
It is found that the shape of luminescence spectra of SrS−Ce phosphors is independent of both the species and concentration
of a cofactor F, Cl, Br, or 1 introduced in the form of ammonium halide at least up to 6.5 at.%. The only exception is F,
which, when added as a coactivator with a concentration of 2.4 at.% and above, gives rise to new longwave luminescence bands,
part from the luminescence of the Ce3+ ion. Analysis has shown that this additional luminescence spectrum is similar to the Ce3+ spectrum but is shifted towards the longwave region by about 0.14 eV. The luminescence decay time constant (τ=57 nsec) is
very close to Br, I, and small concentrations of F, a model is valid according to which the halogen that substitutes for sulfur
and the Ce3+ that substitutes for Sr are the closest neighbors not to each other, but to a probable compensator of the charge of Sr vacancies.
At high concentrations of fluorine some of the F ions are located at interstitial lattice sites in the immediate neighborhood
of Ce3+, providing compensation for the charge of Ce3+ ions and having a marked effect on them.
Tartu University, 18, Ulikooli St., Tartu EE2400, Estonian Republic. Translated from Zhurnal Prikladnoi Spektroskopii, Vol.
64, No. 2, pp. 173–178, March–April, 1997. 相似文献
2.
Jaan Aarik Aleks Aidla Arvo Kikas Tanel Kmbre Raul Rammula Peeter Ritslaid Teet Uustare Vino Sammelselg 《Applied Surface Science》2004,230(1-4):292-300
Atomic layer deposition of hafnium dioxide (HfO2) on silicon substrates was studied. It was revealed that due to low adsorption probability of HfCl4 on silicon substrates at higher temperatures (450–600 °C) the growth was non-uniform and markedly hindered in the initial stage of the HfCl4–H2O process. In the HfI4–H2O and HfI4–O2 processes, uniform growth with acceptable rate was obtained from the beginning of deposition. As a result, the HfI4–H2O and HfI4–O2 processes allowed deposition of smoother, more homogeneous and denser films than the HfCl4–H2O process did. The crystal structure developed, however, faster at the beginning of the HfCl4–H2O process. 相似文献
3.
HfO2 films were grown by atomic layer deposition from HfCl4 and H2O on Si(1 0 0), Si(1 1 1) and amorphous SiO2 substrates at 180-750 °C and the effect of deposition temperature and film thickness on the growth rate and optical properties of the film material was studied. Crystallization, texture development and surface roughening were demonstrated to result in a noticeable growth rate increase with increasing film thickness. Highest surface roughness values were determined for the films deposited at 350-450 °C on all substrates used. The density of the film material increased with the concentration of crystalline phase but, within experimental uncertainty, was independent of orientation and sizes of crystallites in polycrystalline films. Refractive index increased with the material density. In addition, the refractive index values that were calculated from the transmission spectra depended on the surface roughness and crystallite sizes because the light scattering, which directly influenced the extinction coefficient, caused also a decrease of the refractive index determined in this way. 相似文献
4.
Rammo I. Kerikmyaé M. Lepist M. Matizen L. Pung L. Ritslaid K. 《Journal of Applied Spectroscopy》1997,64(4):560-562
We investigate the impurity absorption of SrS−Ce phosphors. For this purpose, we measure the spectra of diffuse reflection
of powder phosphors. It is established that the introduction of Ce simultaneously with a coactivator gives rise to a strong
absorption band at 2.88 eV, and the introduction of a coactivator (NH4F, NH4Cl, NH4Br, NH4I, LiCl, NaCl or KCl), to an absorption band at about 2.36 eV. We assume that the absorption band at 2.88 eV is caused by
that portion of Ce introduced that forms the center of luminescence of Ce3+.
Tartu University, Estonian, Republic, 18, Yulikooli St., Tartu, EE2400, Estonia. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 64, No. 4, pp. 542–544, July–August, 1997. 相似文献
5.
N. Alexeyeva V. Sammelselg P. Ritslaid K. Tammeveski 《Applied Surface Science》2010,256(10):3040-1312
A novel type of gold nanoparticle/multi-walled carbon nanotube (AuNP/MWCNT) composite electrodes is presented. The electrochemical reduction of oxygen on these hybrid electrodes was studied using the rotating disk electrode (RDE) method. The AuNP/MWCNT nanocomposites were prepared by sputter deposition of gold in argon atmosphere on MWCNTs followed by heat-treatment of the catalyst at different temperatures. High-resolution scanning electron microscopy (HR-SEM), glancing incidence angle X-ray powder diffraction (GIXRD) and small-angle X-ray scattering (SAXS) techniques were employed to characterise the surface structure and morphology of catalyst materials. Au nanoparticles with diameter around 20 nm were dispersed at the tips and on the sidewalls of nanotubes. Electrochemical measurements were performed to demonstrate the electrocatalytic properties of the composite catalysts towards O2 reduction in acid media. The successful preparation of AuNP/MWCNT nanocomposites by magnetron sputtering opens up the possibility of making an efficient dispersion of nanoparticles for electrocatalyst design. 相似文献
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