Role of energy band structure on the luminescence performance of double perovskite La2LiMO6:Eu3+ (M=Sb, Ta, Nb) red emitting phosphors

Abstract Monoclinic double perovskite La2LiMO6:Eu3+(M = Sb, Ta, Nb) phosphors were prepared by high temperature solid state reaction method in air. The material microstructures were characterized by XRD Rietveld refinement. All La2LiMO6:Eu3+ exhibited Eu3+ - emission in the red region under excitation by ultraviolet-blue light at room temperature. In the order of M = Sb, Ta, Nb, the emission of Eu3+ in La2LiMO6:Eu phosphor declined under charge transition band (CTB) excitation in turn, while enhanced gradually under 394 nm and 465 nm excitation. The optical band gap energy was calculated through the UV–Vis reflectance spectra of La2LiMO6:Eu indicating that photoionization is the quenching scheme in La2LiMO6:Eu. Co - doped with Bi3+ ions further reduces the energy band (i.e. forbidden bandwidth) of LLN:Eu, resulting in the significant enhancement of Eu3+- emission under 465 nm excitation, which demonstrates its potential application value as the red component of a blue chip based-white LED.