The synthesis and luminescence properties of a novel red-emitting phosphor: Eu3+-doped Ca9La(PO4)7

A series of novel red-emitting phosphors Ca9La1-x(PO4)(7): xEu(3+) were synthesized by high-temperature solid state reactions. The photoluminescence excitation and photoluminescence spectra of these phosphors were investigated in detail. O2--Eu3+ charge transfer band peaking at about 261 nm is dominant in the PLE spectra of Eu3+-doped Ca9La(PO4)(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 D-5(0) -> F-7(2) of Eu3+ in this lattice can emit bright red light. Ca9La(PO4)(7) could accommodate a large amount of Eu3+ with an optimal concentration of 60 mol%. The dipole-dipole interaction between Eu3+ is the dominant mechanism for concentration quenching of Eu3+. The calculated color coordinates lie in red region (x = 0.64, y = 0.36), which is close to Y2O3: 0.05Eu(3+) (x = 0.65, y = 0.34). The integral emission intensity of Ca9La0.4(PO4)(7): 0.6Eu(3+) is 1.9 times stronger than that of widely used commercial red phosphor Y2O3:0.05Eu(3+). All these results indicate that Eu3+-doped Ca9La(PO4)(7) is a promising red-emitting phosphor which can be used in tricolor fluorescent lamps and white light-emitting diodes.