Preparation and photoluminescence of novel La8Ca2(Si4P2O22N2)O2 oxynitride phosphors containing Eu2+/Ce3+/Tb3+ ions

Abstract

A series of novel Eu²⁺/Ce³⁺/Tb³⁺ ion doped La₈Ca₂(Si₄P₂O₂₂N₂)O₂-based apatite structure oxynitride phosphors have been synthesized by a solid-state method. The phase purity has been checked by X-ray diffraction (XRD) and the Rietveld method. The photoluminescence excitation (PLE) spectra indicate that the obtained phosphors have broad excitation bands in the n-UV range, which is a favourable property for application as n-UV-WLED phosphors. The concentration quenching has been investigated in detail. The temperature-dependent luminescence and efficiency study shows that the as-prepared phosphors have a good thermal stability and high quantum efficiency. Moreover, a warm white LED device with a low color temperature of 4288 K and a high color rendering index (R_a) of 80.8 has been obtained by coating a La₈Ca_1.99(Si₄P₂O₂₂N₂)O₂:0.01Eu²⁺ phosphor with a (Sr,Ca)AlSiN₃:Eu²⁺ red phosphor on a n-UV chip. Our results reveal that the La₈Ca₂(Si₄P₂O₂₂N₂)O₂:Eu²⁺ phosphor is a promising bluish-green phosphor for WLEDs.