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A series of NaLaTiO: Eu red phosphors with different Eu ion concentrations were prepared via a high-temperature solid-state reaction technique. The effects of Eu ion concentration and temperature on the fluorescent properties of NaLaTiO: Eu phosphors were investigated. The XRD patterns revealed that the as-synthesized samples were single-phase NaLaTiO. Eu ion concentration-dependent excitation and emission spectra showed that there was an efficient energy transfer from NaLaTiO host to Eu ions. Concentration quenching was observed and can be ascribed to exchange interaction between Eu ions based on Van Uitert's model. According to the temperature-dependent emission spectra and the fluorescence decay curves, crossover process was confirmed to be the main mechanism for the temperature-dependent fluorescence quenching behavior of D level of Eu ions in NaLaTiO phosphors. The activation energy was obtained to be 0.30 eV by Arrhenius model. Based on the emission spectra and Judd-Ofelt theory, the optical transition properties of Eu ions in NaLaTiO phosphors were studied. [ABSTRACT FROM AUTHOR]

A series of new green-emitting BaSiO:xEu, yGd, yR (R = Li, Na or K) phosphors were synthesized by the solid-reaction method. X-ray diffraction (XRD) and fluorescence spectrophotometer are utilized to characterize the crystal structure and luminescence properties of the as-synthesized phosphors, respectively. The XRD patterns reveal that the doping of Gd, Eu and R ions have no significant influence on the BaSiO phase. The green emission of Eu ion associated with 4f5d → 4f can be obtained by 396 nm UV excitation source, which match well with the emission wavelength of UV-LEDs chip (380-420 nm). Moreover, the effect of charge compensator ions (Li, Na or K) on the luminescence intensity of (Ba, Gd)SiO:Eu phosphors were also investigated. When introducing the Li ions into the (Ba, Gd)SiO host lattices, the as-prepared phosphors show the strongest emission. The emission intensity of BaSiO:0.04Eu, 0.005Gd, 0.005Li is about 1.39 times than that of BaSiO:0.04Eu. Furthermore, the mechanism of energy transfer and concentration quenching of BaSiO:xEu, 0.009Gd, 0.009Li phosphors are also discussed. [ABSTRACT FROM AUTHOR]

Novel single-phased phosphors CaNaMg-VO:xSm that exhibit efficient white-light photoluminescence properties have been successfully synthesized by the solid-state reaction method. The formation of a single CaNaMgVO phase has been confirmed by X-ray powder diffraction (XRD). The wavelength-tunable white light is realized by coupling of the broad emission band at 500 nm due to a V−O charge-transfer state transition and the sharp emission peaks at 564, 616, 650 and 708 nm assigned to G→H (J = 5/2, 7/2, 9/2, 11/2) transitions of the Sm ion. The luminescence color can be tuned from green to white by adjusting the doping concentration of Sm. When the doping concentration of Smis increased from x = 0 to x = 0.20, the color rendering index of the CaNaMgVO:xSm phosphors increased from 55 to 83. The present white phosphors show a great potential for white LEDs. [ABSTRACT FROM AUTHOR]

Sm 3+ single-doped and Sm 3+ , Dy 3+ co-doped NaGdTiO 4 phosphors were synthesized via a traditional high temperature solid-state reaction method. The crystal structure was characterized by means of x-ray diffraction. The luminescence properties and energy transfer in Sm 3+ single-doped and Sm 3+ , Dy 3+ co-doped NaGdTiO 4 phosphors were systematically studied. The electric dipole-dipole interaction between Sm 3+ ions was identified as the main mechanism for the concentration dependent fluorescence quenching in Sm 3+ single-doped samples. It is confirmed that there is almost no energy transfer between Sm 3+ and Dy 3+ in Sm 3+ , Dy 3+ co-doped samples. The introduction of Sm 3+ can compensate the red emission component and adjust the colorimetric performance of Dy 3+ -doped NaGdTiO 4 phosphors. Moreover, different emitting colors can be obtained from Sm 3+ , Dy 3+ co-doped NaGdTiO 4 phosphor by changing the excitation pathway. [ABSTRACT FROM AUTHOR]

Usually, Er 3+ doping concentration effect on the temperature sensing properties of Er 3+ containing materials is ignored. In this work, we demonstrated the influence of Er 3+ concentration and excitation path on the spectral and temperature sensing properties in Er 3+ , Yb 3+ co-doped NaGdTiO 4 system. The NaGdTiO 4 : Er 3+ /Yb 3+ phosphors were prepared by a high temperature solid state reaction method. Different spectral patterns for down- and up-conversion processes were observed and ascribed to the different excitation and population routes. The concentration quenching behaviors for down- and up-conversion processes were explained via cross relaxations between Er 3+ ions. Most importantly, the Er 3+ concentration dependent optical temperature sensing performance was observed and experimentally explained as a fact that the optical transition rate of Er 3+ in different samples was changed with various Er 3+ doping concentration. [ABSTRACT FROM AUTHOR]

Abstract: Tm3+ and Dy3+ co-doped YAl3(BO3)4 phosphors were synthesized by the solid state reaction method. The phosphors show blue emission band centered at 450nm originated from the transition of Tm3+ ions and yellow band of 573nm ascribed to Dy3+ ions excited by UV light. The emission colors are tuned from blue to white and ultimately to yellow through concentration variation of luminescent centers of Tm3+ and Dy3+ in YAl3(BO3)4 phosphors. A white light can be achieved from YAl3(BO3)4:0.03Tm3+, 0.09Dy3+ phosphor with chromaticity coordinates of (0.310, 0.331) under excitation at 365nm. The results show that the single-phased YAl3(BO3)4:Tm3+, Dy3+ phosphors are a potential phosphors for current illuminated light source. [Copyright &y& Elsevier]

Abstract: A series of NaSrBO3:xEu3+ and NaSr1−2x BO3:xEu3+, xM+ (M=Li, Na, K) phosphors were synthesized by the solid state reaction. The crystal structure, photoluminescence properties and concentration quenching of NaSrBO3:Eu3+ phosphors were systematically investigated. The excitation spectra indicate that the phosphors can be efficiently excited by 394nm, which is matched well with the emission wavelength of near-UV LED chip. All the samples show the characteristic red emission of Eu3+ ions (5D0→7F J , J=0, 1, 2, 3 and 4). The maximum intensity of luminescence is observed at the Eu3+ concentration around x=0.11. The concentration quenching of Eu3+ in NaSrBO3:Eu3+ phosphor can be mainly attributed to quadrupole–quadrupole interaction. The relative emission intensities of Eu3+ (5D0→7F2) in NaSrBO3:Eu3+ phosphors with Li+, Na+ or K+ introduced as charge compensator are significantly enhanced, and the phosphors added with K+ ions show the strongest emission. The emission intensities of NaSr1−2x BO3:xEu3+, xM+ (M=Li, Na, K) are about 1.47, 1.64 and 2.08 times than that of commercial red phosphor Y2O2S:Eu3+. These results indicate that NaSr1−2x BO3:xEu3+, xM+ (M=Li, Na, K) phosphors exhibit potential applications in the field of near-UV LED as an efficient red-emitting phosphors. [Copyright &y& Elsevier]

Abstract: Eu3+-activated Ca2BO3Cl with different charge compensation approaches were synthesized by the solid state reaction method, and systematically characterized by photoluminescence excitation and emission spectra, concentration quenching and CIE 1931 chromaticity coordinates at room temperature. All the samples show the characteristic red emission of Eu3+ ions with good CIE chromaticity coordinates. The relative emission intensities of Eu3+ (5D0→7F2) in Ca2BO3Cl:Eu3+ phosphors with Li, Na, K introduced as charge compensators are enhanced about 2.1, 1.6 and 1.5 times than that of direct charge balanced. Such difference is considered to be due to the different ion radii effect on the spin–orbit couplings and crystal field of Eu3+ ions. These results show that Ca2−1.5x BO3Cl: and Ca2−2x BO3Cl, , (x=0.04, M=Li, Na, K) phosphors exhibit potential applications in the field of solid state illumination. [Copyright &y& Elsevier]

Abstract: A novel green phosphor NaSrBO3:Tb3+, Li+ was synthesized by the solid state reaction. The crystal structure, photoluminescence properties and concentration quenching of NaSrBO3:Tb3+, Li+ phosphor were systematically investigated. The phosphor shows monoclinic structure and the optimal Tb3+ concentration in NaSrBO3:Tb3+, Li+ is 6mol%. The phosphor presents bright green emission centered at 542nm corresponding to 5D4 → 7F5 transition of Tb3+ ions under the ultraviolet excitation of 378nm. The concentration quenching mechanism can be mainly attributed to the quadrupole–quadrupole interaction. The present work suggests that NaSrBO3:Tb3+, Li+ phosphor is a potential green-emitting phosphor for UV LEDs. [Copyright &y& Elsevier]

Thermal luminescence quenching behavior was observed from the temperature-dependent emission spectra under 383 nm excitation. The emission intensity of Er3+ at 423 K still remained about 67.0% of the initial value at 303 K, revealing that this kind of phosphor possessed superior thermal luminescence stability. The activation energy was determined to be about 0.188 eV. It was found that the temperature sensitivity of Er3+ was sensitive to the doping concentration of Er3+. The lower the concentration of Er3+ was, the higher the temperature sensitivity was. Thermal luminescence property is one of the important factors to evaluate the performance of the phosphors. In this work, a series of Er3+-doped K 2 La 2 Ti 3 O 10 phosphors were synthesized by a sol-gel auto-combustion method. The crystal structure, surface morphology, luminescence performance, thermal stability, and temperature sensing properties were investigated in detail. All samples exhibited green emissions around 530 and 564 nm due to the 2H 11/2 , 4S 3/2 →4I 15/2 transitions of Er3+ upon 383 nm excitation. The optimal doping concentration of Er3+ was about 3 mol%. Electric dipole-dipole interaction was determined to be the main mechanism for the concentration quenching of Er3+ and possible cross-relaxation routes were proposed. Thermal luminescence quenching behavior was observed from the temperature-dependent emission spectra, and the results showed that K 2 La 2 Ti 3 O 10 : Er3+ phosphors had superior thermal luminescence stability. The activation energy was determined to be about 0.188 eV. Moreover, it was found that the temperature sensitivity of Er3+ in K 2 La 2 Ti 3 O 10 : Er3+ phosphors was sensitive to the doping concentration of Er3+. The lower the concentration of Er3+ was, the higher the temperature sensitivity was. [ABSTRACT FROM AUTHOR]