Self-Reduction Mechanism and Luminescence Properties of Eu 2+ -Eu 3+ Doped Ca(PO 3 ) 2 Phosphor

A series of Ca(PO 3 ) 2 phosphors mono-doped with Eu 3+ were successfully synthesized by the conventional high-temperature solid-phase method. Rietveld correction of the X-ray diffraction shows that Eu 3+ ions occupy Ca 2+ positions in the Ca(PO 3 ) 2 lattice and have no effect on the matrix structure. In this work, the self-reduction of Eu 3+ was observed and verified by photoluminescence (PL), excitation spectroscopy (PLE) and X-ray photoelectron spectroscopy (XPS). Under excitation at 238 nm, Ca(PO 3 ) 2 : Eu exhibits a broad blue Eu 2+ emission band in addition to the usual orange-red emission of Eu 3+ . The fact that europium ions exist in divalent and trivalent forms was further confirmed, and the corresponding mechanism of the anomalous reduction of Eu 3+ to Eu 2+ is discussed. On this basis, the effect of Eu concentration on the structure and luminescence properties of Ca(PO 3 ) 2 phosphor was investigated in detail. The luminescence of the phosphor exhibited bright tunable emission in the blue region and the red region. These results indicate that the Ca(PO 3 ) 2 : Eu phosphors have potential applications as a n-UV convertible phosphor for light-emitting diodes.