Highly Luminous N3–-Substituted Li2MSiO4−δN2/3δ:Eu2+ (M = Ca, Sr, and Ba) for White NUV Light-Emitting Diodes

Abstract The N3–-substituted Li2MSiO4:Eu2+ (M = Ca, Sr, and Ba) phosphors were systematically prepared and analyzed. Secondary-ion mass spectroscopy measurements revealed that the average N3– contents are 0.003 for Ca, 0.009 for Sr, and 0.032 for Ba. Furthermore, the N3– incorporation in the host lattices was corroborated by infrared and X-ray photoelectron spectroscopies. From the photoluminescence spectra of Li2MSiO4:Eu2+ (M = Ca, Sr, and Ba) phosphors before and after N3– doping, it was verified that the enhanced emission intensity of the phosphors is most likely due to the N3– doping. In Li2MSiO4:Eu2+ (M = Ca, Sr, and Ba) phosphors, the maximum wavelengths of the emission band were red-shifted in the order Ca < Ba < Sr, which is not consistent with the trend of crystal field splitting: Ba < Sr < Ca. This discrepancy was clearly explained by electron–electron repulsions among polyhedr…