Calcium lanthanide oxyborate doped with rare-earth ions LnCa
4O(BO
3)
3:RE
3+ (LnCOB:RE, Ln=Y, La, Gd, RE=Eu, Tb, Dy, Ce) was synthesized by the method of solid-state reaction at high temperature. Their fluorescent spectra were measured from vacuum ultraviolet (VUV) to visible region at room temperature. Their excitation spectra all have a broadband center at about 188 nm, which is ascribed to host absorption. Using Dorenbos’ and Jφrgensen's work [P. Dorenbos, J. Lumin. 91 (2000) 91, R. Resfeld, C.K. Jφrgensen, Lasers and Excite States of Rare Earth [M], Springer, Berlin, 1977, p. 45], the position of the lowest 5d levels
E(Ln,A) and charge transfer band
Ect were calculated and compared with their excitation spectra.Eu
3+ and Tb
3+ ions doped into LnCOB show efficient luminescence under VUV and UV irradiation. In this system, Ce
3+ ions do not show efficient luminescence and quench the luminescence of Tb
3+ ions when Tb
3+ and Ce
3+ ions are co-doped into LnCOB. GdCOB doped with Dy
3+ shows yellowish white light under irradiation of 254 nm light for the reason that Gd
3+ ions transfer the energy from itself to Dy
3+. Because of the existence of Gd
3+, the samples of GdCOB:RE
3+ show higher excitation efficiency than LaCOB:RE
3+ and YCOB:RE
3+, around 188 nm, which indicates that the Gd
3+ ions have an effect on the host absorption and can transfer the excitation energy to the luminescent center such as Tb
3+, Dy
3+ and Eu
3+.
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