The SrAl2B2O7:Dy3+ phosphor is synthesizd through a general high temperature solid-state reaction, and its luminescence properties are investigated. The emission spectrum of SrAl2B2O7:Dy3+ shows the bands at 480nm,573nm and 678nm under the 365nm excitation, corresponding to the 4F9/2→6H15/2,4F9/2→6H13/2 and 4F9/2→6H11/2 typical transitions of Dy3+ respectively. The excitation spectrum for 573nm emission has excitation bands at 295 nm,325 nm,350 nm,365 nm and 400nm. The influence of doped Dy3+ contentration on the emission spectrum and the luminescent intensity of SrAl2B2O7:Dy3+ is investigated. The result shows that the intensity ratio of yellow emission (573nm) to blue emission (483 nm), Iy/Ib, increases with the increase of Dy3+ concentration, which may be explained by the Judd-Ofelt theory. The luminescent intensity increases first with the increase of Dy3+ concentration, then decreases. The concentration self-quenching is attributed to the d-d interaction according to the Dexter theory. The introducing of charge compensation agents of Li+, Na+ and K+ ions can augment the emission intensity. It is found that Li+ ions are the best to enhance the emission intensity.

No abstract

Two green emitting phosphors, Ba3Tb(BO3)3 and Ba3Tb(BO3)3 ∶Ce3+, are synthesized by the high temperature solid-state method, and their luminescent characteristics are investigated. Ba3Tb(BO3)3 phosphor shows several emission peaks located at 439, 493, 547, 589 and 629 nm separately. The emission peaks correspond to the 5D3→7F4 and 5D4→7FJ=6. 5, 4, 3 transitions of Tb3+, respectively, and the maximal peak is 547 nm. For the 547 nm emission, the excitation spectrum consists of several bands, and the maximal peak is located at 380 nm. The Ce3+-activated Ba3Tb(BO3)3 phosphor is studied, and the result shows that the emission spectrum distribution of Ba3Tb(BO3)3 ∶Ce3+ is the same as that of Ba3Tb(BO3)3 phosphor, however, its emission intensity is higher than that of Ba3Tb(BO3)3,which is attributed to the sensitizing action of Ce3+ on Tb3+ in Ba3Tb(BO3)3. For the 547 nm emission, the excitation spectrum of Ba3Tb(BO3)3 ∶Ce3+presents a broad band, differing from that of Ba3Tb(BO3)3 phosphor. The effect of H3BO3 on the emission intensity of Ba3Tb(BO3)3 ∶Ce3+ phosphor is investigated, and the results show that the emission intensity can reach a maximum for 15 wt% excessive H3BO3. All the results show that Ba3Tb(BO3)3 ∶Ce3+ is a green emitting phosphor for white LED.

A blue emitting phosphor Ba2Ca(PO4)2:Eu2+ is synthesized by a high temperature solid state method. Effect of the conditions is inverstigated, such as preparation temperature and time, the ratio of Ba/Ca, and Eu2+ concentration, on the phase and luminescent property. Results show that Ba2Ca(PO4)2 and Ba2Ca(PO4)2:Eu2+ have been achieved by selecting the appropriate conditions, such as the temperature 900/1200 ℃ and the time 4 h. The compound Ba2Ca(PO4)2:Eu2+ produces an asymmetric emission band centered at 454 nm under 343 nm UV excitation. For the 454 nm emission, the excitation spectrum extends from 200 to 450 nm with a peak at 343 nm, and has an obvious excitation band in the range of 350–410 nm. With increasing Eu2+ concentration, there occur the concentration quenching effect and redshift phenomenon. With decreasing ratio of Ba/Ca, there has an obvious enhancement in the green region, and the emission color gradually turns from blue to cyan. It is shown that the Eu2+ ion not only can occupy the Ba2+ site but also the Ca2+ site. Therefore, different luminescence centers of Eu2+ can exist in Ba2Ca(PO4)2, and affect its luminescence.

No abstract