Luminescence properties of Sm2+-activated barium chloroborates

The luminescence properties of Sm2+-activated stoichiometric and non-stoichiometric Ba2B5O9Cl were investigated from 16 to 450 K. In stoichiometric Ba2B5O9Cl, the emission spectra of Sm2+ are composed of 4f6→4f6 transitions over the 16–450 K temperature range studied. Luminescence was observed from Sm2+ in four inequivalent cationic sites at 16 K and two inequivalent sites at room temperature. In the non-stoichiometric compound, the emission is characterized by 4f6→4f6 transitions at low temperature and 4f55d1→4f6 transitions at high temperature. The Sm2+ doped into the Ca2+ and Sr2+ analogues in the M2B5O9Cl series shows the broad band 4f55d1→4f6 luminescence in both the stoichiometric and non-stoichiometric compounds due to the increased ligand field caused by the smaller ionic radii of the metal ions.