Synthesis, structure and photoluminescence properties of europium-, terbium-, and thulium-doped Ca3Bi(PO4)3 phosphors

Abstract

A series of Eu(3+), Tb(3+), Tm(3+) singly and triply doped Ca3Bi(PO4)3 (CBP) phosphors were synthesized by solid-state reaction. Their structure and photoluminescence (PL) properties were first investigated in detail. Rietveld refinement analysis confirmed that the CBP has a cubic unit cell. Its space group was determined to be I4[combining macron]3d with cell parameters a = b = c = 9.941 Å and Z = 4. In addition, the Ca3Bi(PO4)3 shows both cation disorder and oxygen sublattice disorder. For the CBP:Eu(3+) phosphor, the charge transfer bands in the PLE spectra were different at 293 K and 4.3 K, and a model was presented to give a possible explanation for this phenomenon. CBP:Eu(3+) shows intense red emission due to (5)D0-(7)F2 transition and its integral emission intensity and quantum efficiency are higher than the commercial Y2O3:Eu(3+) phosphor under irradiation of 397 nm, indicating that the CBP:Eu(3+) phosphor might have potential application in the NUV range for solid-state lighting. The CBP:Tb(3+) and CBP:Tm(3+) phosphors show intense green and blue emission due to (5)D4-(7)F2 transition of the Tb(3+) ions and the (1)D2-(3)F4 transition of the Tm(3+) ions, respectively. The energy transfer from the Tb(3+) to Eu(3+) ions was also validated by the spectra and decay curves of the Tb(3+) ions. Tunable emission colors were obtained by triply doping Eu(3+), Tb(3+) and Tm(3+) activators in a single host and adjusting their relative ratio.