Abstract
A novel phosphor, ZnB4O7:Eu3+, with urchin-like structure consisting of radially arranged high density nanorods was successfully synthesized by hydrothermal process at 150°C for 24 h. The nanorods were measured from 200 to 400 nm in diameter and severalµm in length. The urchins were fewµm to 40 µm in diameter. The ZnB4O7:Eu3+phosphors were efficiently excited by ultraviolet (UV ~ 254 nm) to visible light of ~ 220 to 450 nm and exhibited intense orange-red emission consisting of main peaks at 590, 615, and 695 nm due to the charge transfer in the host andf→ftransitions (5D0to7F1,2,4) of the Eu3+ions. Effect of the Eu3+ions concentration on the photoluminescence (PL) emission intensity was investigated and it was found that 5 at% Eu3+is the optimum concentration. Meanwhile, the concentration quenching mechanism was discussed. The key parameters, such as temperature dependent PL and CIE values of ZnB4O7:Eu3+phosphors, were studied. The ZnB4O7:Eu3+phosphor exhibited good thermal stability and better absorption cross section compared to the commercial Y2O2S:Eu3+phosphor. All these characteristics indicate that the phosphor will be a potential candidate for the UV based white LEDs.
Highlights
Phosphors based on borates have attracted much attention due to their high stability, low synthetic temperatures, and high ultraviolet and optical damage threshold [1,2,3,4]
Rare earth orthoborates like LaBO3 and YBO3 have been proved to be very useful host lattices for the luminescence of Eu3+ and Tb3+
The photoluminescence efficiency in the soft UV to blue excitation range can be increased through associated host absorption and energy transfer or forced direct f → f transitions by manipulating/selecting the suitable host materials with low band gap or constructing the crystal lattice having low symmetry so that the forced electric dipole f-f transition of the Eu3+ ions will be pronounced
Summary
Phosphors based on borates have attracted much attention due to their high stability, low synthetic temperatures, and high ultraviolet and optical damage threshold [1,2,3,4]. Rare earth orthoborates like LaBO3 and YBO3 have been proved to be very useful host lattices for the luminescence of Eu3+ and Tb3+. They found wide applications in various optical devices such as field emission displays, plasma display panels, and new generation Hg-free fluorescent lamps [7, 8]. The photoluminescence efficiency in the soft UV to blue excitation range can be increased through associated host absorption and energy transfer or forced direct f → f transitions by manipulating/selecting the suitable host materials with low band gap or constructing the crystal lattice having low symmetry so that the forced electric dipole f-f transition of the Eu3+ ions will be pronounced. Controlled morphology and enhanced optical properties have been discussed in detail
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