Crystal structure, luminescence properties, energy transfer and thermal properties of a novel color-tunable, white light-emitting phosphor Ca9−x−yCe(PO4)7:xEu2+,yMn2+

Abstract

A series of Ca_9−x−yCe(PO₄)₇:xEu²⁺,yMn²⁺ phosphors were synthesized by a high-temperature solid-state reaction method. The as-prepared samples were characterized by XRD and EDX measurements, which showed that Eu²⁺ and Mn²⁺ could be efficiently doped into the host. Ce³⁺ acts concurrently as activator and sensitizer in Ca₉Ce(PO₄)₇, and the energy transfer mechanisms between Ce³⁺/Eu²⁺ and Ce³⁺/Mn²⁺ in Ca₉Ce(PO₄)₇ were validated and proven to be a resonant type via dipole–quadrupole and dipole–dipole interactions, respectively. Besides, there is also energy transfer from Eu²⁺ to Mn²⁺ ions. The host, Ca₉Ce(PO₄)₇, emits blue-white light and Ca₉Ce(PO₄)₇:xEu²⁺,yMn²⁺ phosphors emit blue-green through white to orange-red light under near-ultraviolet radiation as a result of tuning the ratio of Eu²⁺/Mn²⁺. Ca₉Ce(PO₄)₇:0.04Eu²⁺,0.08Mn²⁺ emits white light with CIE coordinates (0.333, 0.310), a CCT of 5446 K, and a high CRI of 81. The energy transfer efficiency between Ce³⁺ and Mn²⁺ increases significantly with temperature. These results reveal that Ca₉Ce(PO₄)₇:Eu²⁺,Mn²⁺ may be a potential candidate for white light-emitting phosphors.