Gehlenite:Eu3+ phosphors from a silicone resin and nano-sized fillers

Gehlenite (Ca2Al2SiO7) ceramics have been successfully prepared by a novel approach, consisting of the heat treatment of a silicone resin embedding CaO and Al2O3 precursors, in the form of nano-sized particles that act as reactive fillers. Luminescence was due to the use of nano-sized Eu2O3 as secondary additive, particularly adopting a charge compensation formulation, i.e. Ca2−2xEu2xAl(Al1+2xSi1−2xO7), with x = 0.07. The phase development and the emission characteristics could be adjusted by simply changing the thermal treatment applied to powders of silicone/fillers mixtures. While conventional firing at 1300 °C (for 1 h) led to practically phase-pure crystalline Eu-doped gehlenite, exhibiting a strong red luminescence, flame synthesis yielded amorphous powders, exhibiting an emission in a much broader range. When excited at 394 nm both gehlenite glass and polycrystalline gehlenite emitted light, which CIE chromaticity coordinates were found to be (x = 0.65, y = 0.35), indicating that both systems are good candidates for red light emitting phosphors.