Structure evolution and delayed quenching of the double perovskite NaLaMgWO6:Eu3+ phosphor for white LEDs

Abstract Eu 3+ ions activated NaLaMgWO 6 phosphors were successfully synthesized by an improved sol-gel method using citric acid and polyethylene glycol as complexing agents. Crystal structure and doping site were investigated by XRD, Rietveld refinement and Raman spectra. The phosphors had monoclinic double perovskite structure with space group C 2/ m , as well as layered ordering of A-site and rock-salt ordering of B-site. The blueshift of Raman T 2g (1) mode manifested Eu 3+ ions had entered into A-site. Thereafter, luminescence properties, such as excitation and emission spectra, CIE coordinates, concentration quenching and thermal quenching were discussed. The quenching concentration for hypersensitive electric dipole transition of Eu 3+ reached up to 50.0 mol%. The delayed concentration quenching was observed in NaLaMgWO 6 : Eu 3+ phosphor. The theoretical quenching concentration was obtained based on L. Ozawa's theory, and the quenching mechanism on Dexter's theory. Excellent thermal stability of this phosphor shows that it is a potential red phosphor for solid state lighting.