Luminescence and energy transfer of Sm3+ and Eu3+ in Ca2PO4Cl

Sm3+, Eu3+, and Sm3+-Eu3+ doped Ca2PO4Cl phosphors are synthesized by a solid-state method. Ca2PO4Cl:Sm3+ can produce red emission under the 400 nm radiation excitation, and the emission peak is located at 601 nm, which is assigned to the 4G5/2→6H7/2 transition of Sm3+. Ca2PO4Cl:Eu3+ can create red emission under the 392 nm radiation excitation, and the strongest peak is located at 620 nm, which is attributed to the 5D0→7F2 transition of Eu3+. The energy transfer from Sm3+ to Eu3+ in Ca2PO4Cl has been validated and the critical distance (Rc) of Sm3+ to Eu3+ in Ca2PO4Cl is calculated to be 1.14 nm. With increasing Eu3+ doping concentration, the energy transfer efficiency (Sm3+→Eu3+) gradually increases to 53.7%. The luminescence property of Ca2PO4Cl:Sm3+, Eu3+ can be tuned by properly tuning the relative ratio of Sm3+-Eu3+, and the emission intensity of Ca2PO4Cl:Eu3+ can be greatly enhanced by codoped Sm3+.