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

Abstract

A series of Eu³⁺, Tb³⁺, Tm³⁺ 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 I3d 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:Eu³⁺ 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:Eu³⁺ shows intense red emission due to ⁵D₀–⁷F₂ transition and its integral emission intensity and quantum efficiency are higher than the commercial Y₂O₃:Eu³⁺ phosphor under irradiation of 397 nm, indicating that the CBP:Eu³⁺ phosphor might have potential application in the NUV range for solid-state lighting. The CBP:Tb³⁺ and CBP:Tm³⁺ phosphors show intense green and blue emission due to ⁵D₄–⁷F₂ transition of the Tb³⁺ ions and the ¹D₂–³F₄ transition of the Tm³⁺ ions, respectively. The energy transfer from the Tb³⁺ to Eu³⁺ ions was also validated by the spectra and decay curves of the Tb³⁺ ions. Tunable emission colors were obtained by triply doping Eu³⁺, Tb³⁺ and Tm³⁺ activators in a single host and adjusting their relative ratio.