Abstract
Abstract Eu 3+ -doped and -undoped Ca 4 Gd(BO 3 ) 3 O phosphors were synthesized by high temperature solid-state reaction. Single phase formation of Ca 4 Gd(BO 3 ) 3 O was confirmed by X-ray powder diffraction analysis. The vacuum ultraviolet (VUV)–ultraviolet (UV) excitation and emission spectra together with decay curves at different temperatures are investigated. The excitation spectra exhibit that Ca 4 Gd(BO 3 ) 3 O:Eu 3+ is effectively excited by VUV and UV irradiations. Emission lines of Gd 3+ at around 314 nm due to the 6 P 7/2 → 8 S 7/2 transitions are observed under the VUV and UV excitations in which the line intensity depends strongly on Eu 3+ concentration in Ca 4 Gd(BO 3 ) 3 O:Eu 3+ . It is found that the energy transfer occurs from host absorption band to Gd 3+ and Eu 3+ ions in Ca 4 Gd(BO 3 ) 3 O:Eu 3+ . The energy transfer efficiency from Gd 3+ to Eu 3+ is calculated in terms of the concentration dependent decay curves. The temperature dependent lifetimes of 5 D 1 (Eu 3+ ) are investigated to calculate the radiative transition rate of 5 D 1 → 7 F J and the multiphonon relaxation rate of 5 D 1 → 5 D 0 . Cross relaxation rates among Eu 3+ ions for different Eu 3+ -doped samples are also calculated based on the concentration and temperature dependent decay curves. It is found that the cross relaxation rates are sensitive to the Eu 3+ concentration in Ca 4 Gd(BO 3 ) 3 O.
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