RESUMEN
Phosphors of KZnF3 : Ce3+, KZnF3 : Tb3+ and KZnF3 : Ce3+, Tb3+ nanoparticles were synthesized in a cetyltrimethylammonium bromide (CTAB)/2-octanol/water microemulsion system. X-ray diffraction (XRD) pattern was used to identify the formation of KZnF3 phase without detectable impurity. Environment scanning electron microscopy (ESEM) image showed that the average sizes of the KZnF3 : Ce3+ , Tb3+ nanocrystals were 30 nm in diameter. Photoluminescence characteristics of the rare earth ions doped nanoparticles were investigated and compared with that of the sample prepared by solid state reaction at a high temperature. The emission peak of the KZnF3 : Ce3+ nanoparticles showed an obvious red shift as compared to that of polycrystalline powder. In a co-doped system of KZnF3 nanoparticles, the emission band of Ce3+ even could hardly be observed and the luminescence intensity of Tb3+ was increased much compared with that Tb-doped singly. This showed that the emission of the Tb3+ was sensitized by Ce3+. The experimental results indicated that there was an effective energy transfer from Ce3+ to Tb3+ in KZnF3 nanoparticles.
RESUMEN
The line emission peak of Eu2+ ion in crystal KMgF3 is at 360 nm. The probability of stimulated emission on 4f7 (6 P7/2 )-->4f7 (8 S7/2 ) transition was predicted with a four-level decay model of Eu2+ 6P7/2 excited states proposed by the authors. Optic gain and net gain coefficient (g=11. 4+/-3. 2)cm(-1) of 360 nm emission in crystal KMgF3 : Eu2+ were measured by ASE method, and the predication was proved by experiment. The net gain coefficient can be increased by annealing or doping crystal KMgF3 : Eu2+ with Gd3+ or Ce+.
RESUMEN
The concentration dependence of luminescence under different excitations in Y2O2S:Sm3+ phosphor has been studied. The optimum activator concentration was found to be a function of the number of excited activator ions as well as the excitation wavelength. The concentration dependence curve of Y2O2S:Sm3+ phosphor under 413 nm excitation was different from the curve obtained with 263 nm excitation. For excitation radiation having longer wavelength (413 nm), the concentration quenching of Y2O2S:Sm3+ phosphor occurred at about 2%, which is ten times the result with shorter wavelength (263 nm) excitation (-0.2%). Fitting the concentration dependence curve and the result shows that the cross-relaxation caused by the dipole-quadrupole interaction of neighboring Sm3+ ions results in the concentration quenching.