Spectral properties and emission efficiencies of GdVO4 phosphors |
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Authors: | M Anitha P Ramakrishnan A Chatterjee G Alexander H Singh |
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Institution: | (1) Rare Earth Development Section, S-30A, South Site, BARC, Trombay, Mumbai 400 085, India, IN |
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Abstract: | GdVO4 with activators Eu, Dy, Sm and Bi has been synthesised by a solid-state reaction. GdVO4:Eu3+ (3%) yielded the highest quantum efficiency of 95%. Interesting energy-transfer properties have been revealed in the mixed-activator
phosphor (GdVO4:Eu3+, Sm3+) when excited in the 4f shell of Sm3+ at 408 nm. Bismuth-activated GdVO4 gives rise to a broad-band emission peaking at 525 nm in comparison to YVO4:Bi3+, which gives an emission peak at 570 nm under UV excitation. The quantum efficiency of GdVO4:Bi3+ increases gradually with bismuth concentration and reaches a maximum of 80% for a bismuth concentration of ≈0.5%. There is
a shift in the excitation band of GdVO4:Bi3+ towards longer wavelengths with increasing concentration of bismuth, which can lead to energy transfer from bismuth to europium
in a phosphor with both these activators. Heat treatment of GdVO4:Bi3+ at 1500 °C for 3–3.5 h resulted in a large percentage of bismuth being lost from the lattice as evaluated by X-ray fluorescence.
However, if a large percentage of bismuth (of the order of 3% or more) is initially added, a sufficient quantity of bismuth
can still be retained after heat treatment, which can lead to the development of ceramic scintillators for X-ray tomographic
applications. Addition of 3–5% boron gives a white GdVO4 phosphor without any chemical treatment.
Received: 27 Feruary 2001 / Accepted: 1 August 2001 / Published online: 30 October 2001 |
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Keywords: | PACS: 78 55 K |
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