The cathodoluminescent properties of nanocrystalline Lu3Ga5O12:Tb3+ phosphor films were investigated. Phosphor films were prepared on indium tin oxide coated glass by a screen printing method. The Lu3Ga5O12:Tb3+ phosphor is mixed with In2O3 nanoparticles to improve the luminescence and degradation properties of phosphor films under electron excitation. Cathodoluminescent spectra and luminance degradation behavior of the Lu3Ga5O12:Tb3+ phosphor films under electron bombardment were studied. Enhancement of the luminescence was observed after being mixed with In2O3 nanoparticles. Also, the In2O3 mixed Lu3Ga5O12:Tb3+ phosphor shows improvement of the resistance to the electron bombardment. The results show that the Lu3Ga5O12:Tb3+ phosphor is stable under electron bombardment and has potential for application in field emission display devices. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3392039]