Vacuum ultraviolet and ultraviolet (VUV–UV) spectroscopy and relaxation dynamics of Eu3+ ions doped in Ca3Gd2(BO3)4 phosphor

• The luminescence properties of Ca3Gd2(BO3)4:Eu3+ are investigated.
• The host exciton band and the O2−–Eu3+ charge transfer band are observed at 185 and 250 nm, respectively.
• Energy transfer from Gd3+ to Eu3+ depends strongly on Eu3+-concentration.

The Ca3Gd2(BO3)4:Eu3+ phosphors were synthesized by high temperature solid-state reaction. Luminescence properties of Ca3Gd2(BO3)4:Eu3+ are investigated by using the VUV–UV excitation and emission spectra together with decay curves. The phosphors could be efficiently excited giving the strong emission at 612 nm under the VUV–UV excitations of the strong host-related band at 188 nm and CTB of Eu3+–O2− at 250 nm. The analysis of the decay curves of the 5D0 → 7F2 emission reveals that the weak energy transfer occurs between Eu3+ pairs in Ca3Gd2(BO3)4:Eu3+ . Under UV excitation the concentration quenching of the 5D0 → 7FJ emission depends on excitation wavelengths. The energy transfer mechanism among host, Gd3+ and Eu3+ ions is discussed in relation to the luminescence decays and Eu3+ concentrations.

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