Enhancement of red emission intensity of Ca2Al2SiO7:Eu~(3+) phosphor by M0O3 doping or excess SiO2 addition for application to white LEDs

摘要

Ca_(1.86)Al2(Si_(1-x)Mo_x)O7:0.14Eu~(3+) and Ca_(1.86)Al2Si_(1+y)O_(7+2y):0.14 Eu~(3+)were synthesized by solid-state reaction. X-ray powder diffraction, excitation and emission spectra were used to investigate their structures and photoluminescence properties. The results shows that the phosphor Ca_(1.86)Al2SiO7:0.14Eu~(3+) cannot be excited efficiently by light of 393 nm. The introduced Mo ion does not change the position of the excitation peak, but increases both the absorption at 400nm and the emission intensity of Eu~(3+). The intense red emitting phosphor Ca_(1.86)Al2(Si_(0.95)Mo_(0.05))O7:0.14Eu~(3+) was obtained, which has 67% enhanced luminous intensity compared to that of the undoped sample Ca_(1.86)Al2SiO7:0.14Eu~(3+). Otherwise, SiO2 excess of non-stoichiometric phosphors Ca_(1.86)Al2Si_(1+y)O_(7+2y):0.14Eu~(3+)showed the characteristic pattern of a tetragonal structure with a small Si02 concentration. The optimal phosphor of Ca_(1.86)Al2Si_(1.1)O_(7.2):0.14Eu~(3+) has a luminous intensity about two times higher than that of the original stoichiometric phosphor Ca_(1.86)Al2SiO7:0.14Eu~(3+). We confirmed that the photoluminescence intensity of the obtained phosphors is fairly enhanced by excessive SiO2. The mechanism of this photoluminescence enhancement is discussed in this paper.