Synthesis and photoluminescence enhancement of Ca_3Sr_3(VO_4)4:Eu~(3+) red phosphors by Sm~(3+) doping for white LEDs

摘要

A new type of red-emitting Eu~(3+) and Sm~(3+) co-doped Ca_3Sr_3(VO_4)_4 phosphor was synthesized by the combustion method. The photoluminescence properties and microstructure were investigated by photoluminescence spectroscopy, X-ray powder diffraction, and scanning electron microscopy. All samples were found to match perfectly with the rhombohedral structure and belong to the R3c space group. The photoluminescence emission intensity of the optimal phosphor Ca_3Sr_3(VO_4)_4:0.05Eu~(3+), 0.09Sm~(3+) at 619 nm was significantly enhanced compared with those of Ca_3Sr_3(VO_4)_4:Eu~(3+) samples and commercial Y_2O_3:Eu~(3+) at an excitation wavelength of 393 nm, as a result of the energy transfer from Sm~(3+) to Eu~(3+). The energy transfer process between Sm~(3+) and Eu~(3+) is discussed and interpreted by considering the energy level diagram. Furthermore, the CIE chromaticity coordinate of Ca_3Sr_3(VO_4)_4:0.05Eu~(3+), 0.09Sm~(3+) was closer to the standard red-emitting point (x=0.67, y = 0.33) than Y_2O_3:Eu~(3+). The luminescence performance of Ca_3Sr_3(VO_4)_4:Eu~(3+), Sm~(3+) upon excitation by near-UV radiation makes it a promising red phosphor for manufacturing white-light-emitting diodes.