Self-Reduction Mechanism and Luminescence Properties of Eu2+-Eu3+Doped Ca(PO3)2 Phosphor

Abstract

A series of Ca(PO3)2 phosphors mono-doped with Eu3+ were successfully synthesized by the conventional high-temperature solid-phase method. Rietveld correction of the X-ray diffraction shows that Eu3+ ions occupy Ca2+ positions in the Ca(PO3)2 lattice and have no effect on the matrix structure. In this work, the self-reduction of Eu3+ was observed and verified by photoluminescence (PL), excitation spectroscopy (PLE) and X-ray photoelectron spectroscopy (XPS). Under excitation at 238 nm, Ca(PO3)2: Eu exhibits a broad blue Eu2+ emission band in addition to the usual orange-red emission of Eu3+. The fact that europium ions exist in divalent and trivalent forms was further confirmed, and the corresponding mechanism of the anomalous reduction of Eu3+ to Eu2+ is discussed. On this basis, the effect of Eu concentration on the structure and luminescence properties of Ca(PO3)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(PO3)2: Eu phosphors have potential applications as a n-UV convertible phosphor for light-emitting diodes.