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Abstract: A novel long-lasting phosphorescence phosphor, Mn2+-activated Mg2SnO4, has been synthesized and its optical properties have been investigated. The Mg2SnO4:Mn2+ emits green light with high luminance, upon UV irradiation, centered at 499nm from the spin forbidden transitions of the d-electrons in Mn2+ ions. The CIE chromaticity coordinates of the Mg2SnO4:Mn2+ phosphor are and under 254nm UV excitation. The phosphorescence can be observed by the naked eyes (0.32mcd/m2) in the dark clearly for over 5h after the 5min UV irradiation. Thermoluminescence has been studied and the mechanism of the long-lasting phosphorescence has been discussed. [Copyright &y& Elsevier]

Abstract: Expanded emission spectra ranging from green to red are reported in Ca3Sc2Si3O12 (CSS):Ce3+,Mn2+ silicate garnets. Mn2+ may occupy Ca2+ site (Mn2+(I)) to generate a yellow emission band at 574nm or Sc3+ site (Mn2+(II)) with red emission band at 680nm. Efficient energy transfers from the green emitting Ce3+ to both Mn2+(I) and Mn2+(II) occur upon blue excitation into Ce3+. Concentration dependence of Mn2+ emission is analyzed based on Ce3+–Mn2+ energy transfer, steady state rate equations, and fluorescence lifetimes. Energy transfer efficiency (η T) and rate (W) are calculated with values as high as 45% and 14.01×106 s−1, respectively. [Copyright &y& Elsevier]

Abstract: BaMg2Al6Si9O30:Eu2+ phosphors are synthesized by the solid-state reaction method and their photoluminescence (PL) properties are investigated. The ultraviolet emission originates from Eu2+(I) substituting for Ba2+ sites, whereas the blue emission is attributed to Eu2+(II) substituting for Mg2+ sites. With increasing Eu2+ doping concentrations, the blue emission band shifts to long wavelength and the PL intensity ratio of blue to ultraviolet emission increases. Energy transfer between the two different Eu2+ ions is analyzed by photoluminescence excitation and emission spectra, and lifetimes. Results indicate that the emission spectra can be tuned by changing Eu2+ contents. We have also demonstrated that BaMg2Al6Si9O30:Eu2+ phosphor is a kind of potential phosphor for fluorescent lamps. [Copyright &y& Elsevier]

Abstract: The yellow-emitting phosphor [Ca3−(x+0.06)Lu x Ce0.06](Sc2−y Mg y )Si3O12 obtained from Lu3+ and Mg2+ co-modified green-emitting silicate garnet Ca3Sc2Si3O12:Ce3+ (CSS:Ce3+) exhibits promising applications for white LEDs. In this paper, we discuss the effect of charge balance on the garnet structure formation. The changes of bond length and covalence caused by the replacement of Lu3+ and Mg2+ for Ca2+ and Sc3+ are analyzed. The shift of the Ce3+ emission and excitation can be attributed to the combined results from crystal field splitting effect and centroid shift of Ce3+ 5d levels. Thermal stability is analyzed according to configurational coordinate diagram. [Copyright &y& Elsevier]

Abstract: Eu2+ and Mn2+ co-doped Ca8Zn(SiO4)4Cl2 phosphors have been synthesized by a high temperature solid state reaction. Energy transfer from Eu2+ to Mn2+ is observed. The emission spectra of the phosphors show a green band at 505nm of Eu2+ and a yellow band at 550nm of Mn2+. The excitation spectra corresponding to 4f7-4f65d transition of Eu2+ cover the spectral range of 370–470nm, well matching UV and/or blue LEDs. The shortening of fluorescent lifetimes of Eu2+ followed by simultaneous increase of fluorescent intensity of Mn2+ with increasing Mn2+ concentrations is studied based on energy transfer. Upon blue light excitation the present phosphor can emit intense green/yellow in comparison with other chlorosilicate phosphors such as Eu2+ and Mn2+ co-doped Ca8Mg(SiO4)4Cl2 and Ca3SiO4Cl2, demonstrating a potential application in phosphor converted white LEDs. [Copyright &y& Elsevier]

Abstract: CePO4:Tb nanorods were synthesized via a simple wet-chemical route. The as-synthesized CePO4:Tb nanorods present high photoluminescence efficiency due to an efficient energy transfer form Ce3+ to Tb3+. However, heat treatment at 150°C in air leads to a significant decrease of photoluminescence. X-ray photoelectron spectroscopy and excitation spectra revealed the oxidation of Ce3+ to Ce4+ in the heat-treatment process, which should be responsible for significant photoluminescence degradation due to the breakage of Ce3+→Tb3+ energy transfer. This conclusion is further supported by atmosphere and size effects of photoluminescence of CePO4:Tb under the heat treatment. [Copyright &y& Elsevier]

Abstract: With the help of the Dexter''s theory, the energy transfer mechanism from Pr3+ 1S0 to Cr3+ is investigated theoretically in SrAl12O19:Pr3+, Cr3+ quantum cutting phosphors. The electron spin resonance (ESR) spectra of Pr3+ and Cr3+-doped SrAl12O19 with magnetoplumbite structure have been studied. The Cr3+ ion is found to enter the Al4(4f) site, which is very close to the Sr(2d) site replaced by the Pr3+ ions in the host. The theoretical results indicate that the efficient Pr3+ 1S0→Cr3+ energy transfer can only take place in the intermediate mirror planes, in which for the nearest and next-nearest Pr3+–Cr3+ pairs, both dipole–dipole and dipole–quadrupole interactions can play their parts in the transfer. Finally, an overview is given about the research on the energy transfer from Pr3+ 1S0 to codopants in their co-doped materials. [Copyright &y& Elsevier]

Abstract: Intense photoluminescence at room temperature was observed in amorphous cadmium aluminum silicate doped with europium prepared by the sol–gel method. The structure of the 3CdO–Al2O3–3SiO2:Eu3+ system (CAS:Eu3+) has been determined by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The excitation and the emission spectra indicated that the red characteristic emission (611nm) of CAS:Eu3+ under UV excitation due to 5D0→7F2 electric dipole transition is the strongest. Both XRD data and the emission ratio of (5D0→7F2)/(5D0→7F1) reveal that the Eu3+ is in a site without inversion symmetry. The maximum photoluminescence intensity has been obtained for 25mol% concentration of Eu3+ in CAS, and the intensity enhancement and lifetime increase of Eu3+ with increasing sintering temperature were observed due to the less OH-content in the samples. [Copyright &y& Elsevier]

Abstract: Sm3+- and Eu3+-doped rare-earth borate glasses (Li2O–BaO–La2O3–B2O3) have been fabricated and characterized optically. The density, refractive index, optical absorption, Judd-Ofelt parameters, and spontaneous transition probabilities have been measured, calculated and analyzed. Sm3+ and Eu3+ emit intense reddish-orange and red lights under blue and UV light excitations, respectively. In Sm3+ and Eu3+ co-doped glasses, the excitation wavelength range of Eu3+ emission is broadened owing to the energy transfer from Sm3+ to Eu3+. This broadening makes the Ar+ 488nm wavelength laser a powerful excitation source for Eu3+ fluorescence. The rare-earth doped glasses with various visible emissions are useful for developing new color light sources, fluorescent display devices, UV-sensor and tunable visible lasers. [Copyright &y& Elsevier]

Abstract: Novel red long persistent phosphors of BaMg2Si2O7:Mn2+, Eu2+, Dy3+ have been synthesized at high temperature and weak reductive atmosphere. There are a deep blue emission with peak wavelength of 400nm and a broader emission band centered at 680nm when excited by 340nm. The broad emission band is attributed to the spin-forbidden transitions of the d-orbital electrons associated with the Mn2+ ions (4T1(4G)–6A1(6S)). The excitation and emission spectra of the samples with different dopants and doping concentrations show that the Mn2+ emission is dominantly due to the persistent energy transfer from Eu2+. Red long persistent phosphors have been observed in the system for over 2h. [Copyright &y& Elsevier]