Photoluminescence properties of near ultraviolet excited Ca8La2(PO4)6O2:Sm3+ red orange phosphor

Novel Ca8La2(PO4)6O2:Sm3+ phosphors are successfully synthesized in air by the high temperature solid state reaction method. The X-ray diffraction patterns, morphology, energy spectrum diagram, elemental mapping, luminescence properties, concentration-dependent emission spectra, thermal stability, and decay curves are investigated. The excitation spectrum of Ca8La2(PO4)6O2:8%Sm3+ phosphor monitored at 604 nm extends the region from 220 nm to 520 nm with many excitation spectral bands because of the O2−–Sm3+ charge transfer band and the f–f transitions of Sm3+ ion. Ca8La2(PO4)6O2:Sm3+ phosphor with excitation at 402 nm emits red orange light in the range of 550–770 nm with many emission spectral bands derived from the 4G5/2 → 6H5/2 (550–570 nm), 4G5/2 → 6H7/2 (570–630 nm), 4G5/2 → 6H9/2 (630–690 nm), and 4G5/2 → 6H11/2 (690–760 nm) transitions of Sm3+ ion, and the optimal Sm3+ concentration is ~ 8 mol%. The lifetime of Ca8La2(PO4)6O2:Sm3+ phosphor decreases from 1.39 to 1.11 ms with increasing Sm3+ concentration from 2 to 12 mol%. Ca8La2(PO4)6O2:Sm3+ phosphor has the good thermal stability and emission color stability. The luminous mechanism, concentration quenching, and thermal quenching are explained, respectively. The experimental results indicate that Ca8La2(PO4)6O2:Sm3+ phosphor as red orange component has a potential application in white LED based on near ultraviolet LED chip.