Crystal structure and luminescence properties of a novel single-phase orange-red emitting phosphor Ca9La (PO4)7:Sm3+

Abstract

Ca₉La_1−x(PO₄)₇:xSm³⁺ phosphors (0.01 < x < 0.25) were synthesized via high temperature solid-state reaction. Their properties including crystal structure, decay performance, thermal stability and photoluminescence were examined in detail. Phase analysis indicated that the phosphors crystallized in a rhombohedral structure, and the emission spectra of the phosphors consisted of four peaks centered around 570, 607, 653, and 714 nm, attributed to Sm³⁺ ions transitions ⁴G_5/2 → ⁶H_J (J = 5/2, 7/2, 9/2, and 11/2, respectively). The optimal Sm³⁺ doping content was 0.12 mol and the Ca₉La(PO₄)₇:Sm³⁺ phosphor also exhibited better thermal stability compared to other phosphors. In addition, the mechanism behind the energy transfer between Sm³⁺ ions was determined to be dipole–dipole interactions as described by Dexter theory. The results indicated that as orange-red phosphors, Ca₉La (PO₄)₇:Sm³⁺ phosphors were promising candidates for being integrated into white light emitting diodes.