Efficient blue luminescence in Ce3+-activated borates, A6MM′(BO3)6

Photoluminescence studies on the Ce3+-activated borates of the type Sr6MGa(BO3)6 [A = Sr; M = La, Gd, Lu; M′ = Ga; Ce3+ at the M-site], Sr6YAl(BO3)6 [A = Sr; M = Y; M′ = Al; Ce3+ at the Y-site], LaSr5YMg(BO3)6 [A = La, Sr; M = Y; M′ = Mg and Ce3+ at the La3+-site] have been carried out for the first time and the results are presented here. All these compounds have been synthesized by the solid state reaction under reducing atmosphere and characterized by powder XRD, TG/DT, density, particle size, SEM, FT-IR and photoluminescence techniques. The photoluminescence of Sr6LaGa(BO3)6 activated with low and high Ce3+ concentrations has been studied. The luminescence of Ce3+ ions substituted at the larger (Gd3+) and smaller (Lu3+) ionic sites have been discussed. Two new compounds Sr6CeGa(BO3)6 and CeSr5YMg(BO3)6 have also been synthesized and studied. The photoluminescence studies show that under excitation with 254 and 355 nm, all these compounds display efficient blue emission in the region around 400–420 nm. The luminescence properties of these hexaborates under 254 nm excitation are similar to the known blue lamp phosphors Ca5(PO4)3F:Sb3+, Sr2P2O7:Eu2+, Sr5(PO4)3Cl:Eu2+ and the luminescence under 355 nm excitation are similar to the known blue TV phosphor ZnS:Ag+. Thus, the borate phosphors can be used as blue components in low pressure mercury vapor (lpmv) lamps and in television tubes.

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