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Browsing by Author "Tung, Chien-Yueh"

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    A study on the luminescence properties of CaAlBO(4): RE(3+) (RE=Ce, Tb, and Eu) phosphors
    (2008)
    Liu, Wei-Ren
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    Chiu, Yi-Chen
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    Tung, Chien-Yueh
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    Yeh, Yao-Tsung
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    Jang, Shyue-Ming
    A series of new phosphors of CaAlBO(4):RE(3+) (RE=Ce, Tb, Eu) were synthesized by conventional solid-state reactions. The X-ray diffraction data indicate that a pure phase of CaAlBO(4):RE(3+) can be successfully obtained. The photoluminescence (PL) spectra, quantum efficiency, and CIE coordinates of CaAlBO(4):RE(3+) were investigated. The PL and PL excitation spectra indicate that the emission wavelengths of CaAlBO(4):Ce(3+) are 372 and 398 nm (with full width at half maximum of 33 nm) attributed to the 4f(6)5d-4f(7) transition of the Ce(3+) activator, respectively. CaAlBO(4):Tb(3+) displays green emission at 483, 543, 584, and 620 nm, while CaAlBO(4):Eu(3+) shows a dominating emission peak at 621 nm, which is attributed to the Eu(3+) (5)D(0)-(7)F(2) transition. The quantum efficiencies of optimized CaAlBO(4):Ce(3+), CaAlBO(4):Tb(3+), and CaAlBO(4):Eu(3+) were found to be 43, 21, and 19%, respectively. The phosphors may provide a new kind of luminescent material under UV excitation. (C) 2008 The Electrochemical Society.
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    Visible quantum cutting through downconversion in green-emitting K2GdF5 : Tb3+ phosphors
    (2006-09-25)
    Lee, Te-Ju
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    Luo, Li-Yang
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    Diau, Eric Wei-Guang
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    Chen, Teng-Ming
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    Cheng, Bing-Ming
    Visible quantum cutting under excitations at 212 and 172 nm in a green-emitting phosphor K2GdF5:Tb3+ (11%) via a downconversion mechanism is investigated. The authors measured the vacuum ultraviolet (VUV) excitation and emission spectra and proposed mechanisms to rationalize the quantum-cutting effect. One short-UV or one VUV photon absorbed by Tb3+ is split into multiple visible photons emitted by Tb3+ through cross relaxation and direct energy transfer. Calculations indicate an optimal quantum efficiency as great as 189% for this phosphor. (c) 2006 American Institute of Physics.