Luminescence spectroscopy and crystallographic sites of Sm2+ doped in Sr6BP5O20

Sm2+-doped strontium borophosphate, Sr6BP5O20, was prepared by high-temperature solid-state reaction method. The photoluminescence excitation and emission spectra together with the decay curves of Sm2+ ions were investigated from 10 to 300 K. The emission arises from the 5D0 level of Sm2+ ions. The investigations were focused mainly on the distribution of Sm2+ sites in Sr6BP5O20 crystal, which exhibits different spectroscopic features. There exist two isolated Sm2+ crystallographic sites in Sr6BP5O20 at low temperature (10 K), where no energy transfer could be detected. Only one Sm2+ site could be detected at high temperature above 100 K. Luminescence and microstructure of Sm2+ ions were discussed based on the structure of Sr6BP5O20 crystal.