Exciton-like luminescence of Bi3+-doped yttrium niobate

Abstract Characteristics of the intrinsic and Bi3+-related luminescence of YNbO4:Bi powders with different Bi contents are studied at 4.2–500 K by steady-state and time-resolved spectroscopy methods. The emission of YNbO4:Bi is suggested to be of an exciton origin. The main Bi3+-related emission band (2.53 eV) excited at 4.09 eV is ascribed to the radiative decay of an exciton localized around a single Bi3+ ion. A weak lower-energy (2.41 eV) emission is ascribed to an exciton localized around a dimer Bi3+ center. No emission arising from the 3P1,0 → 1S0 transitions of a Bi3+ ion is found. The structure and parameters of the exciton states, responsible for the luminescence of YNbO4:Bi, as well as the radiative and nonradiative processes ongoing in these states are clarified. From the dependence of the afterglow intensity on the irradiation energy, the band gap energy of YNbO4 is estimated to be 5.3–5.4 eV.