Low-Temperature Crystallization and Highly Enhanced Photoluminescence of Gd_2-xY_xO₃:Eu³⁺ by Li Doping

The influence of Li doping on the crystallization behavior, morphology, and enhancement in photoemission intensity of Gd 2 - x Y x O 3:Eu 3+ solid−solution was investigated. To maximize an effect of the Li component which is volatile at elevated temperature, the citrate route was adopted for the synthesis at low temperature (650−850 °C). Firing the metal citrate precursor at 650 °C for 5 h was sufficient for the formation of 100 nm sized, nonaggregated, and spherical Li-doped Gd 2 - x Y x O 3:Eu 3+ particles, whose photoluminescence (PL) emission intensity is comparable with that of commercial red phosphor Y 2 O 3:Eu 3+ . Such a temperature is much lower than the typical solid-state reaction or spray pyrolysis temperature (>1400 °C). Additional heat treatment up to 850 °C resulted in well-developed 500 nm sized pseudospherical particles whose PL brightness is close to ∼150% in comparison with that of commercial red phosphor. Li-doped Gd 2 - x Y x O 3:Eu 3+ appears to be a very promising red phosphor because the particle size and shape can be controlled at low temperature (650−850 °C) by the change of Y or Li contents without significant loss of brightness.