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 4f6→4f6 luminescence with only a single emission line observed for the 5D0→7F0 transition, revealing that only one crystallographic cationic site is available for Sm2+ in all the hosts. With increasing temperature, the emission intensity of the 5D0→7F0 transition increases whereas that of the 5D0→7F1 transitions decreases. The 5D1→7F0 transitions of Sm2+ were observed in BaBPO5 and its intensity increases with increasing temperature. At 450 K, a broad band of the 4f55d→4f6 luminescent transition of Sm2+ in SrBPO5 and BaBPO5 with maximum at ∼600 nm appears due to the thermal population. The lifetime of the 5D0→7F0 transition was recorded at different temperatures, showing a single exponential decay for Sm2+ in SrBPO5 and BaBPO5 but a non-single-exponential decay in CaBPO5.