Luminescence properties and energy transfer of a red-emitting Ca₃ (PO₄)₂:Sm³⁺, Eu³⁺ phosphor

Abstract

A series of Sm³⁺, Eu³⁺ and Sm³⁺–Eu³⁺ doped Ca₃(PO₄)₂ were prepared by a high temperature solid-state method. Their luminescent properties were studied by photoluminescence emission, excitation spectra and decay curves. Under excitation with a wavelength at 403 nm, Ca₃(PO₄)₂:Sm³⁺ emits red–orange light, and the dominated peak situates at 602 nm which is due to the ⁴G_5/2 → ⁶H_7/2 transition of Sm³⁺. Ca₃(PO₄)₂:Eu³⁺ produces red light under the 394 nm excitation, and the strongest peak centers at 613 nm, which is assigned to ⁵D₀ → ⁷F₂ transition of Eu³⁺. The energy transfer from Sm³⁺ to Eu³⁺ in Ca₃(PO₄)₂ host has been studied and demonstrated to be a resonant type via a dipole–quadrupole interaction mechanism. The critical distance of Sm³⁺–Eu³⁺ in Ca₃(PO₄)₂ is calculated to be 13.5 Å. With the increase of Eu³⁺ doping content, the energy transfer efficiency (Sm³⁺ → Eu³⁺) obtained from decay curves gradually increases to 30.7 %. Moreover, the emitting color of Ca₃(PO₄)₂:Sm³⁺, Eu³⁺ can be tuned by appropriately adjusting the relative doping composition of Sm³⁺/Eu³⁺.