Synthesis and characterization of CaLu(GaO)(BO):Ce,Tb phosphors: tunable-color emissions, energy transfer, and thermal stability.

Blue-green dual-emitting phosphors CaLu(GaO)(BO):Ce,Tb (CLGB:Ce,Tb) were synthesized a traditional solid-state reaction method. The phase of the phosphors was characterized by X-ray diffraction and the luminescence properties were investigated using the excitation and emission spectra, decay curves, temperature-dependent emission spectra, CIE chromaticity coordinates, and the internal quantum efficiency. Under 345 nm UV light excitation, Ce singly doped CLGB phosphors presented intense blue light in the 350-550 nm wavelength region with a maximum peak at 400 nm. In sharp contrast, CLGB:Ce,Tb phosphors showed both the blue and green emission wavelengths of Ce and Tb ions, respectively. The overall emission colors can be tuned from blue (0.164, 0.042) to green (0.331, 0.485) increasing the concentration of Tb ions, due to the energy transfer (ET) from Ce ions to Tb ions. The optimal doping concentration of Tb ions in CLGB:Ce,Tb phosphors was found to be 40 mol%. The mechanism of the ET from the Ce to Tb ions was demonstrated to be electric quadrupole-quadrupole interaction. The CLGB:0.04Ce,0.40Tb sample possessed a high IQE of 54.2% and excellent thermal stability with an activation energy of 0.3142 eV when excited at 345 nm. The integrated emission intensity of CLGB:0.04Ce,0.40Tb at 423 K was found to be about 74% of that at 303 K. Finally, under 300 mA driven current, the fabricated prototype white light-emitting diode showed CIE chromaticity coordinates of (0.3996, 0.3856) and high color rending index of 81.2. Considering all the above characteristics, the obtained CLGB:Ce,Tb phosphors can be a type of multicolor emitting phosphor for application in white light-emitting diodes.