Preparation of rare earth (europium(3+), terbium(3+), thulium(3+), and ytterbium(3+)) doped yttrium oxide luminescent ceramics by the use of reverse micelles

Nanophosphors of Y2O3:Eu, Y2O3:Tb, and Y2O3:Tm,Yb were prepared by reverse microemulsions. The prepared nanophosphors were then characterized using a variety of techniques and annealed to obtain a particular phase and improve crystallinity. Monoclinic and cubic phases of Y2O3 were obtainable with crystallite sizes of 5 nm--50 nm, with the monoclinic phase present at the lower crystallite sizes. Defects such as chemical species were present in annealed samples, but in minute quantities. The red and green luminescence properties of nanocrystalline Y2O3:Eu and Y2O3:Tb were evaluated. The peak intensity of both nanophosphors increased as annealing temperature and time increased. Therefore, larger crystallite size and elimination of impurities produced a higher luminescence. This was not shown in the case of the blue Y2O3:Tm,Yb nanophosphors. In this case, as heat treatment temperature increased the luminescence decreased. This was attributed to a change in phase between the monoclinic phase and the cubic phase.