Time-resolved photoluminescence and excited state structure of Bi3+ center in YAlO3

Abstract

YAlO3:Bi ceramics prepared from the nanopowders synthesized by the sol–gel (Pechini) method are studied at 8–400K by the time-resolved spectroscopy methods. An intense dominant ultraviolet luminescence of YAlO3:Bi is shown to arise from the radiative decay of the metastable and radiative minima of the triplet relaxed excited state (RES) of Bi3+ centers related to the 3P0, 3P1 levels of a free Bi3+ ion, respectively. At T<80K, the radiative transitions from the metastable minima take place. Thermally stimulated nonradiative transitions between the metastable and radiative minima of the triplet RES appear at T>80K in the temperature dependences of the emission spectrum and decay kinetics. From these dependences, the energy separation between the radiative and metastable minima, and the rates of the radiative and nonradiative transitions from these minima, are determined. The excitation bands of the ultraviolet emission, located at 4.425, around 5.6eV and at the energy higher than 6eV, are ascribed to the 1S0→3P1, 1S0→3P2, and 1S0→1P1 transitions of a free Bi3+ ion, respectively.