Structure and luminescence of a novel orange-yellow-emitting Ca1.62Eu0.38Si5O3N6 phosphor for warm white LEDs, discovered by a single-particle-diagnosis approach
An orange-yellow-emitting Ca1.62Eu0.38Si5O3N6 phosphor was discovered by a single-particle-diagnosis approach. The crystal structure was analysed by single crystal X-ray diffraction, revealing that it crystallizes in a monoclinic system with the space group of Cm (No. 8), cell parameters of a = 7.0595(2) Å, b = 23.7504(6) Å, and c = 9.6345(2) Å. Both the single crystal and the powder sample show similar luminescence properties. The excitation spectrum ranges from UV to blue light regions, enabling its use in UV, or blue LED driven white-LEDs. The new phosphor exhibits a two-peak emission behavior, with a very weak blue emision band centered at about 470 nm and a strong orange-yellow emission band centred at 592– 600 nm, which correspond to the emissions of two different Eu2+ sites in the structure. Subsequently, an efficient energy transfer between two different Eu2+ sites was discussed. In addition, the new phosphor shows high thermal stability. At 150 °C, the luminescence intensity of the single crystal remains 84% of that measured at room temperature, with high activation energy for thermal quenching (0.240 eV). The results suggest that the new orange-yellow phosphor has potential application in vivid indoor lighting or displays.