Optical transition and luminescence properties of Sm3+-doped YNbO4 powder phosphors

A series of YNbO4: Sm3+ powder phosphors with different doping concentrations were synthesized by a traditional high-temperature solid-state reaction method. The crystal structure of the obtained samples was characterized by means of X-ray diffraction. Concentration quenching, energy-transfer mechanism, and luminescence thermal stability of YNbO4: Sm3+ samples were studied through the fluorescence spectra and decays. It was concluded that electric dipole-dipole interaction was the dominant energy-transfer mechanism between Sm3+ ions according to both Van Uitert's model and Dexter's model. Using the Arrhenius model, crossover process was proven to be responsible for the luminescence thermal quenching of Sm3+. Moreover, a novel approach for evaluating the optical transition properties of Sm3+ ion in YNbO4 powders using the diffuse-diffraction spectrum and fluorescence decay was examined in the framework of Judd-Ofelt (J-O) theory. It was confirmed that the J-O parameters omega(lambda) (lambda = 2, 4, 6) of Sm3+ in YNbO4 powder were reliable by comparing the radiation transition rate with the measured emission results.