A novel ceramic synthesis technique, combustion synthesis, was used to produce submicron-sized Y2O3:Eu3+ phosphors. This technique exploits the exothermic redox reaction of yttrium and europium nitrates (oxidizers) with urea (CH4N2O) fuel (reducing agent). Resulting powders were luminescent in the as-synthesized state. However, their luminous intensity increased with increasing postreaction annealing treatments (1000-1600 degrees C for 2 h). The low-voltage (200-1000 V) cathodoluminescence efficiency of Y2O3:Eu3+ was found to increase with increasing crystallite size, independent of the particle size. A model of low-voltage cathodoluminescence that includes the effects of the crystallite size, the probability of radiative recombination, and the effect of surface-bound electrons was developed to predict phosphor efficiency at low voltages. The efficiencies predicted by the model are in very good agreement with experimental results.