Bi³⁺ and Eu³⁺ Activated Luminescent Behaviors in Non-Stoichiometric LaO_0.65F_1.7 Structure

Optical materials composed of La_1--BiEuO_0.65F_1.7 (p = 0.001-0.05, q = 0-0.1) were prepared via a solid-state reaction using La(Bi,Eu)₂O₃ and NH₄F precursors at 1050 °C for two hours. X-ray diffraction patterns of the phosphors were obtained permitting the calculation of unit-cell parameters. The two La³⁺ cation sites were clearly distinguished by exploiting the photoluminescence excitation and emission spectra through Bi³⁺ and Eu³⁺ transitions in the non-stoichiometric host lattice. Energy transfer from Bi³⁺ to Eu³⁺ upon excitation with 286 nm radiation and its mechanism in the Bi³⁺- and Eu³⁺-doped host structures is discussed. The desired Commission Internationale de l'Eclairage values, including emissions in blue-green, white, and red wavelength regions, were obtained from the Bi³⁺- and Eu³⁺-doped LaO_0.65F_1.7 phosphors.