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Luminescence Properties of Ca19Ce(PO4)14:A (A = Eu3+/Tb3+/Mn2+) Phosphors with Abundant Colors: Abnormal Coexistence of Ce4+/3+-Eu3+ and Energy Transfer of Ce3+ → Tb3+/Mn2+ and Tb3+-Mn2.

A series of Eu3+/Tb3+/Mn2+-ion-doped Ca19Ce(PO4)14 (CCPO) phosphors have been prepared via the conventional high-temperature solid-state reaction process. Under UV radiation, the CCPO host presents a broad blue emission band from Ce3+ ions, which are generated during the preparation process because of the formation of deficiency. The Eu3+-doped CCPO phosphors can exhibit magenta to red-orange emission as a result of the abnormal coexistence of Ce3+/Ce4+/Eu3+ and the metal-metal charge-transfer (MMCT) effect between Ce3+ and Eu3+. When Tb3+/Mn2+ are doped into the hosts, the samples excited with 300 nm UV light present multicolor emissions due to energy transfer (ET) from the host (Ce3+) to the activators with increasing activator concentrations. The emitting colors of CCPO:Tb3+ phosphors can be tuned from blue to green, and the CCPO:Mn2+ phosphors can emit red light. The ET mechanism from the host (Ce3+) to Tb3+/Mn2+ is demonstrated to be a dipole-quadrapole interaction for Ce3+ → Tb3+ and an exchange interaction for Ce3+ → Mn2+ in CCPO:Tb3+/Mn2+. Abundant emission colors containing white emission were obtained in the Tb3+- and Mn2+-codoped CCPO phosphors through control of the levels of doped Tb3+ and Mn2+ ions. The white-emitted CCPO:Tb3+/Mn2+ phosphor exhibited excellent thermal stability. The photoluminescence properties have shown that these materials might have potential for UV-pumped white-light-emitting diodes.