New Insight for Luminescence Tuning Based on Interstitial sites Occupation of Eu2+ in Sr3Al2-xSixO5-xNxCl2 (x=0-0.4)

Currently, nitridation of phosphors provides an enormous inspiration for phosphor designing. In this paper, a nitridation process by means of substituting Al3+-O2- with Si4+-N3- in initial Sr3Al2O5Cl2:Eu2+ system is implemented. The phase purity is confirmed by X-ray diffraction. The corresponding photoluminescence properties are recorded and analyzed by the excitation and emission spectra. Interestingly, new blue emission bands emerge in the range of 400-500 nm and the intensity increases with the increasing of substitution concentration. It is verified that the new emission band is derived from the residence of Eu2+ ions in the interstitial sites. The crystal structure refinement, transmission electron microscopy, and solid-state nuclear magnetic resonance spectroscopy are exploited to analyze the color-tunable luminescence mechanisms induced by the structural variation. Moreover, the thermal stability is characterized by the temperature-dependent spectra. Attributed to the enhancement of lattice rigidity, the serious thermal quenching behavior is improved. Finally, the electroluminescence performance is measured for the fabricated white light-emitting diodes (LEDs). By combining 370 nm ultraviolet LED chips, CaAlSiN3:Eu2+ and Sr3Al2O5Cl2:Eu2+ phosphors, an ideal warm-white emitting LED is successfully fabricated with the color rendering index = 92, color temperature = 3476 K, and color coordinate x = 0.37, y = 0.34.