Structure dependent luminescence characterization of greenyellow emitting Sr2SiO4:Eu2 phosphors for near UV LEDs

摘要

This paper reports on the luminescence properties of mixtures of α- and β-(Sr_(0.97)Eu_(0.03))_2SiO_4 phosphors. These phosphors were prepared by 3 different synthesis techniques: a modified solgel/Pechini method, a co-precipitation method and a combustion method. The structural and optical properties of these phosphors were compared to those of solid state synthesized powders. The emission spectra consist of a weak broad blue band centered near 460 nm and a strong broad greenyellow band centered between 543 and 573 nm depending on the crystal structure. The greenyellow emission peak blue-shifts as the amount of β phase increases and the photoluminescence emission intensity and quantum efficiency of the mixed phase powders is greater than those of predominant α-phase powders when excited between 370 and 410 nm. Thus, (Sr_(1-x)Eu_x)_2SiO_4 with larger proportion of the β phase are more promising candidates than single α-phase powders for use as a greenyellow emitting phosphor for near UV LED applications. Finally the phosphors prepared by the solgel/Pechini method, which have larger amount of β phase, have a higher emission intensity and quantum efficiency than those prepared by co-precipitation or combustion synthesis.