Synthesis and luminescence properties of Li+, Bi3+ ions co-doped CaSiO3:Eu3+ red emitting phosphors

Abstract

Li+, Bi3+ ions co-doped CaSiO3:Eu3+ red emitting phosphors were synthesized by a sol–gel method. The crystal structure and luminescence properties of Li0.04Ca0.95−xSiO3:Eu0.01,Bix (x = 0.00–0.04) phosphors calcined at different temperature were investigated by X-ray diffraction and photoluminescence spectra. The results show that the phosphors exhibit β-CaSiO3 phase belonging to monoclinic structure with space group P21/a when calcined at temperature below 1200 °C, however, when calcination temperature is over 1200 °C, α-CaSiO3 phase is obtained, which has triclinic crystal structure with space group P-1(2). Li0.04Ca0.95−xSiO3:Eu0.01,Bix phosphors can be excited at a wavelength of 220–310 nm and exhibit the strongest red emission at 612 nm upon 276 nm excitation, which corresponds to 5D0→7F2 of Eu3+ ions. It is proved that addition of Bi3+ ions increase the luminescence intensity of Li0.04Ca0.95−xSiO3:Eu0.01,Bix phosphors due to energy transfer from Bi3+ to Eu3+ ions and co-doping Li+ ions as charge compensator can further enhance the luminescence intensity due to the charge compensation effect. With increasing Bi3+ ions up to 0.02 mol, the luminescence intensity reaches a maximum value and then decrease with further increasing Bi3+ ions concentration. The concentration quenching behavior of Bi3+ ions and charge compensation effect has been discussed.