Incorporation of Mn2+ and Eu2+ ions in β-Al2O3-like host crystals has been studied. Under ultraviolet excitation, both BaO·6Al2O3: Eu, Mn and La2O3·11Al2O3: Eu, Mn show intense green fluorescence caused by the energy transfer from Eu2+ to Mn2+. The efficiency of the luminescence is comparable to that of Zn2SiO4: Mn when excited by 254 nm light.
Emission and excitation spectra of the phosphors were compared with those of K β-Al2O3. The difference in the atomic packing in the mirror plane of these aluminates appears to be reflected in the emission spectra of Mn2+. The quenching temperature for the sensitized fluorescence of Mn2+ is governed by the Eu2+ ions, replacing mono-, di-, or tri-valent large cations in these compounds.
The amount of electric charge induced on a sample powder surface by contact with another reference powder has been measured by using a blow-off method. Samples are three binary inorganic compound systems, consisting of 36 oxides, 15 fluorides, or 13 sulfides of various metal elements. Though the blow-off charge Qc, depends considerably on particle size, charging tendency observed among samples is essentially unvaried even when they contact with different reference materials. Therefore, a series of materials, arranged according to the magnitude of Q,~ values, is governed by their chemical compositions, and can be adopted as a quantitative contact electrification series. The Q0 value for each system is found to shift linearly to a negative direction with an increase in the generalized electronegativity X~ for constituent metal cations. This is understood in terms of the acid-base properties either in an aqueous or in a gaseous phase, which are correlated with Xi. The charging tendency is also affected by anions, and shifts toward the negative direction in the order of oxides, fluorides, and sulfides. This order agrees with their acid strength order in a gaseous phase, but not with that in an aqueous phase. Extension of the results to more general systems, including materials with more complex chemical compositions, is discussed. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 157.182.150.22 Downloaded on 2015-03-11 to IP
Monoclinic Y2O3 phosphors doped with Eu3+ or Pr3+ are obtained for the first time by treatments in inductively-coupled thermal plasma. This paper reports the luminescence properties of these phosphor materials. The assumption proposed earlier by the authors, that the emitting levels of Pr3+ in Gd2O3 are determined by the distance between the Pr3+ ion and the surrounding oxygen ligands, is found consistent even when the monoclinic Y2O3:Pr and other oxides are included.
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