The luminescence of Sm2+ in alkaline earth borophosphates

The temperature-dependent luminescence of Sm2+ ions in MBPO5 (M = Ca2+, Sr2+, Ba2+) was studied. At low temperature, Sm2+ in this series shows 4f(6) --> 4f(6) luminescence with only a single emission line observed for the D-5(0) --> F-7(0) transition, revealing that only one crystallographic cationic site is available for Sm2+ in all the hosts. With increasing temperature, the emission intensity of the D-5(0) --> F-7(0) transition increases whereas that of the D-5(0) --> 7F(1) transitions decreases. The D-5(1) --> F-7(0) transitions of Sm2+ were observed in BaBPO5 and its intensity increases with increasing temperature. At 450 K, a broad band of the 4f(5)5d --> 4f(6) luminescent transition of Sm2+ in SrBPO5 and BaBPO5 with maximum at similar to600 ran appears due to the thermal population. The lifetime of the D-5(0) --> F-7(0) transition Sm2+ was recorded at different temperatures, showing a single exponential decay for in SrBPO5 and BaBPO5,but a nonsingle-exponential decay in CaBPO5. (C) 2002 Elsevier Science B.V. All rights reserved