The synthesis and luminescence properties of a novel red-emitting phosphor: Eu~(3+)-doped Ca_9La(PO_4)_7

摘要

A series of novel red-emitting phosphors Ca_(9_) La_(1-x)(PO_4))7: xEu~(3+) were synthesized by high-temperature solid state reactions. The photoluminescence excitation and photoluminescence spectra of these phosphors were investigated in detail. O~(2-)-Eu~(3+) charge transfer band peaking at about 261 nm is dominant in the PLE spectra of Eu~(3+)-doped Ca_9La(PO_4)_7, indicating that the phosphors are suitable for tricolor fluorescent lamps. The phosphors also show a good absorption in near ultraviolet (around 395 nm) and blue (around 465 nm) spectral region, which indicates that it can be pumped with NUV and blue chips for white light-emitting diodes. The transition of ~5D_0 → ~7F_2 of Eu~(3+) in this lattice can emit bright red light. Ca_9La(PO_4)_7 could accommodate a large amount of Eu~(3+) with an optimal concentration of 60 mol%. The dipole-dipole interaction between Eu~(3+) is the dominant mechanism for concentration quenching of Eu~(3+). The calculated color coordinates lie in red region (x = 0.64, y = 0.36), which is close to Y_2O_3: 0.05Eu~(3+) (x = 0.65, y = 0.34). The integral emission intensity of Ca_9La_(0.4)(PO_4)_7: 0.6Eu~(3+) is 1.9 times stronger than that of widely used commercial red phosphor Y_2O_3: 0.05Eu~(3+). All these results indicate that Eu~(3+)-doped Ca_9La(PO_4)_7 is a promising red-emitting phosphor which can be used in tricolor fluorescent lamps and white light-emitting diodes .