Reduction of Eu3+ to Eu2+ in α-Y2Si2O7 and X1-Y2SiO5 and their luminescent properties

Due to its bright tunable emission, Eu-doped yttrium silicates are very interesting materials for LED applications. The microparticles of α-Y1.98 Eu0.02 Si2O7 and the low-temperature phase of Y1.98 Eu0.02 SiO5 (X1) were prepared by sol gel technique. Then, the samples were reduced at high temperatures using pure hydrogen as reduction agent. The materials obtained were characterized by X-Ray diffraction, Scanning Electron Microscopy, Energy Dispersive X-Ray and Photoluminescence spectroscopy. The presence of Eu2+ in the materials after the reduction was confirmed by the blue-green band emission and the wide absorption band, observed only in the excitation spectra of the reduced samples. These bands are congruent with the information previously reported in the literature. A red shift of the broadband emission of Eu2+ doped α-Y2Si2O7 system was observed compared to previously reported results. Also, the luminescent properties of Eu2+ host in X1-Y2SiO5 are presented for first time. The relative contribution of Eu2+ and Eu3+ depends on the excitation wavelength leading to a tunable emission phosphor with potential application in white LEDs. Summarizing, the reduction of Eu ions in yttrium silicates is presented in this work, leading to a tunable emission phosphor with potential application in white LEDs.