Synthesis and luminescence properties of NaLa(MoO4)2−xAGx:Eu3+ (AG = SO42−, BO33−) red phosphors for white light emitting diodes

Abstract

NaLa(MoO4)2−x(SO4)x:Eu3+ and NaLa(MoO4)2−x(BO3)x:Eu3+ red phosphors, are prepared by a high temperature solid state reaction. These doubled molybdate phosphors have scheelite isostructure, which hardly be affected by SO42− and BO33− partial substitution for MoO42−. Infrared spectra of obtained phosphors show strong absorption peaks between 1000 and 1300cm−1 which are assigned to the vibration of O–S in SO42− groups and O–B in BO33− groups. Due to the 5D0→7F1–3 transitions of Eu3+ ions, photoluminescence spectra show a strong red emission at 618nm under excitation of near UV light at 395nm and blue light at 465nm, respectively. The luminescent intensity of NaLa(MoO4)2−x(SO4)x:Eu3+ and NaLa(MoO4)2−x(BO3)x:Eu3+ are obviously improved comparing with those of NaLa(MoO4)2:Eu3+ and commercial red phosphor Y2O3:Eu3+ by several times. And the lifetime values of NaLa(MoO4)2−xAGx:Eu3+ with SO42− and BO33− substitution are extended to 0.461ms and 0.468ms from 0.459ms of NaLa(MoO4)2:Eu3+, respectively.