Fluorescence of UV-excited single crystals of LiSmP4O12 and LiDyP4O12

Fluorescence under UV excitations with LEDs has been studied on flux-grown single crystals of lithium lanthanide tetraphosphates (LiLnP4O12) with Ln = Sm or Dy. LiSmP4O12 has been excited at 8 wavelengths, 245-370 nm and LiDyP4O12 - at 7 wavelengths, 245-325 nm. The emissions have been registered at room temperature and assigned using known energy-level differences from absorptions of the same single crystals and from fluorescence of Sm3+ in phosphate glass. More 4f-4f Stokes emissions have been observed under these UV excitations compared to previously reported studies with λexc ≥ 450 nm. The dependencies of the relative transitions on the excitation wavelengths and the efficiency of the Stokes transitions have been also discussed.