Photoluminescent properties and site occupation preference in Bi 3+ , Eu 3+ doped CaY 4 (SiO 4 ) 3 O phosphor

Abstract Bi 3+ , Eu 3+ doped CaY 4 (SiO 4 ) 3 O phosphors were synthesized through high temperature solid state reaction. Their photoluminescent properties were investigated and site occupation preference of Bi 3+ in cationic sites was analyzed. The structure of CaY 4 (SiO 4 ) 3 O is characterized by three non-equivalent cationic sites with different coordination and cation-oxygen distances. By means of dielectric theory of the chemical bond for complex crystals, several kinds of chemical bond parameters like fractional covalence of CaY 4 (SiO 4 ) 3 O were calculated and integrated to yield environmental factor h e . According to quantitative equations between the transition energy of Bi 3+ and environmental factor h e , the excitation bands at 308 and 226 nm were assigned to 1 S 0 → 3 P 1 transition of Bi 3+ in Y(6h) and Y(4f) site, respectively. Another excitation band centered at 210 nm should be the overlap of Bi 3+ A -band in Ca site and C -band in Y(6h) site. Optical band gap of pure CYSO was calculated using Kubelka–Munk method from diffuse reflectance spectra. Red emission can be realized in CaY 4 (SiO 4 ) 3 O:Bi 3+ , Eu 3+ under UV light excitation because of efficient energy transfer from Bi 3+ to Eu 3+ and decay behaviors of Bi 3+ and Eu 3+ emission were investigated. Without optimization, the internal quantum efficiency of CYSO:2%Bi 3+ , 7%Eu 3+ at 310 and 393 nm excitations were 31.563%, 74.252%, respectively.