Multi-color luminescence evolution of SrGdAlO4:Ln3+ (Ln3+ = Eu3+ and/or Tb3+) nanocrystalline phosphors via a sol-gel process

Abstract

A series of rare-earth (Eu3+ and/or Tb3+) ions doped SrGdAlO4 nanocrystalline phosphors have been synthesized via a Pechini-type sol-gel process. X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and fluorescence spectrophotometer were utilized to characterize the prepared phosphors. XRD reveals that the samples begin to crystallize at 900 °C and the pure SrGdAlO4 can be obtained at 1000 °C. FE-SEM images indicate that the SrGdAlO4:Ln3+ (Ln3+ = Tb3+ and/or Eu3+) samples consist of fine and spherical grains with size around 100–200 nm in diameter. Under the excitation of the near ultraviolet light, the prepared SrGdAlO4:Ln3+ (Ln3+ = Eu3+ and/or Tb3+) phosphors show both the characteristic red emission of Eu3+ (5DJ→7FJ′ J, J′ = 0, 1, 2, 3 transitions) and characteristic green emission of Tb3+ (5D4→7F6,5,4,3 transitions). There exists energy transfers from Gd3+ to Tb3+, and Tb3+ to Eu3+ ions in SrGdAlO4:Ln3+ (Ln3+ = Eu3+ and/or Tb3+) phosphors. The luminescence color of SrGdAlO4:Ln3+ (Ln3+ = Eu3+ and/or Tb3+) phosphors can be tuned from blue to blue-green, green, white, orange, etc. by varying the doping species, concentration, and relative ration of the codoping Eu3+/Tb3+ ions in SrGdAlO4 host lattice to some extent. A single-phase white-light-emission has been realized in Tb3+/Eu3+ codoped SrGdAlO4 nanocrystalline phosphors. The obtained SrGdAlO4:Eu3+, SrGdAlO4:Tb3+, and SrGdAlO4:Eu3+,Tb3+ nanocrystalline phosphors have potential application in the areas of UV white-light-emitting diodes and other optoelectronics lighting and display devices.