Cooperative Energy Transfer and Frequency Upconversion in Yb3+–Tb3+ and Nd3+–Yb3+–Tb3+ Codoped GdAl3(BO3)4 Phosphors
ABSTRACT Polycrystalline GdAl3(BO3)4 phosphors codoped with Yb3+/Tb3+ and/or Nd3+/Yb3+/Tb3+ have been synthesized by combustion method. Upon excitation with a 980 nm laser diode, an intense green upconversion luminescence has been observed in GdAl3(BO3)4:Yb,Tb phosphor. The quadratic dependence of the luminescence on the pump-laser power indicating a cooperative energy transfer process. Meanwhile, it is noticed that upon excitation with 808 nm laser diode, intense luminescence has clearly been detected in GdAl3(BO3)4:Nd,Yb,Tb phosphor. The luminescence intensity exhibits also a quadratic dependence on incident pump-laser power. However, no green-emission has been observed in GdAl3(BO3)4 phosphors codoped with Yb3+/Tb3+ or Nd3+/Tb3+ respectively upon excited at 808 nm laser diode. A proposed upconversion mechanism involving energy transfer from Nd3+ to Yb3+, and then a cooperative energy transfer process from two excited Yb3+ to Tb3+ has been presented.
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ABSTRACT: Upon 980nm diode laser excitation visible upconversion emission from the Tb(3+) ions has been observed in combustion synthesized Tb(3+)-Yb(3+) codoped Y2O3 phosphor. The intensity of upconversion as well as downconversion emission bands has been increased by codoping of Li(+) ions into Tb(3+)-Yb(3+):Y2O3 phosphor and the reason behind this increment is discussed. The pump power dependence of upconversion emission bands has shown two-photon absorption process. The cooperative energy transfer from Yb(3+) to Tb(3+) ions is supposed to be responsible for the upconversion emission from the Tb(3+) ions on near infrared excitation. The calculated colour coordinates indicate the purity of intense green emission from present phosphor which is suitable for various photonic applications.Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 09/2013; 118C:619-623. · 1.98 Impact Factor
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ABSTRACT: The codoping effect of Zn(2+) ions on luminescence emission in visible and near infrared (NIR) regions of Y2O3:Ho(3+)-Yb(3+) phosphor prepared by low temperature combustion process have been investigated under 980 nm and 448 nm excitations. The phase and crystallite size of the prepared phosphor were determined by X-ray diffraction analysis and processes involved in the upconversion mechanism have been discussed in detail via pump power dependence, decay curve analysis and a suitable energy level diagram. The temperature sensing performance of the developed material has also been investigated by measuring the fluorescence intensity ratio of the blue upconversion emission bands centred at 465 nm and 491 nm up to 673 K. It is found that by using fluorescence intensity ratio technique, appreciable sensitivity for temperature measurement can be achieved from the present phosphor material, which indicates its applicability as a high temperature sensing probe. The fabrication of green LEDs using the developed phosphor material has also been suggested.Dalton Transactions 06/2013; · 4.10 Impact Factor
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ABSTRACT: In this work the energy transfer between Nd3+ and Yb3+ ions in oxyfluoride silicate glass at room temperature was analyzed. In order to match energy transfer (Nd3+ -> Yb3+), absorption cross-section of glass doped with various Yb3+ ions concentration and emission cross-section of glass doped with Nd3+ were calculated. The percentage efficiency of energy transfer calculated according to the Dextera-Forster model for the glass doped with 0.15Nd3+ : 0.75Yb3+ amounts to 60%. The emission spectrum with 100 nm bandwidth of the Nd3+/Yb3+ co-doped glass samples under excitation at 808 nm was measured.Proc SPIE 06/2009;