Near UV excited multi-color photoluminescence in RE3+ (RE=Tb, Sm, Dy and Eu) doped Ca2Pb3(PO4)3Cl phosphors

Abstract

The Ca2Pb3(PO4)3Cl: RE3+ (RE = Tb, Sm, Dy and Eu) phosphor materials were prepared by wet chemical method. The synthesized phosphors were analyzed by using XRD, SEM and photoluminescence (PL) characterization techniques. The excitation spectrum of the Ca2Pb3(PO4)3Cl:Tb3+ phosphor consists of several bands in the 300–400 nm region by monitoring emission at 545 nm, which are assigned due to electronic transitions from 7F6 to the upper levels of Tb3+ ion. The Ca2Pb3(PO4)3Cl:Tb3+ phosphor emits efficient narrow green emission at 545 nm due to 5D4 → 7F5 transition upon 371 nm excitation. The PL excitation spectrum of the Ca2Pb3(PO4)3Cl:Sm3+ phosphor exhibits narrow bands in the near ultraviolet (NUV) region due to Sm3+ ion. The Ca2Pb3(PO4)3Cl: Sm3+ phosphor shows orange red emission centered at 598 nm, which is attributed to the 4G5/2 → 6H7/2 transition of Sm3+ ion. The concentration quenching has been studied in both the cases and the critical distance was calculated as 38.5 Å. The blue (482 nm) and yellow (576 nm) emissions are obtained in the Ca2Pb3(PO4)3Cl:Dy3+ phosphor under 352 nm and 455 nm excitations, which are attributed to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ion, respectively. However, the Ca2Pb3(PO4)3Cl:Eu3+ phosphor emits strong orangish red emission centered at 594 nm, which is attributed to the 5D0 → 7F1 transition of Eu3+ ion on excitation with 396 nm. The CIE diagram shows green and orange red photoluminescence for the Ca2Pb3(PO4)3Cl:Tb3+ and Ca2Pb3(PO4)3Cl:Sm3+ phosphors, respectively whereas the bluish-yellow and orangish red photoluminescence for the Ca2Pb3(PO4)3Cl:Dy3+ and Ca2Pb3(PO4)3Cl:Eu3+ phosphors, respectively. The CIE coordinates indicate that the present phosphors have high color purity. These phosphors may act as good candidates for phosphor converted LEDs for solid state lighting technology.