SiO2-Gd2O3 : Eu3+ nanocomposite thin films were successfully synthesized by a sol-gel method. Precursor solutions were prepared by mixing aqueous rare-earth acetate solutions and ethanolic tetraethylorthosilicate solutions containing trifluoroacetic acid and N,N-dimethylformamide, respectively. The solutions were then spin-coated on silica glass substrates and heat-treated. Two kinds of heat-treatment processes were adopted; one involved heating the coated substrates immediately at temperatures of 700-1000degreesC, and the other involved preheating them at 300 degreesC, followed by heating at 700-1000 degreesC. In the latter process, denoted a two-step process, SiO2-GdF3 composite films formed at 300 degreesC were pyrolytically converted into SiO2-Gd2O3 nanocomposite films at the higher heating temperatures. This process was effective in enhancing the crystallinity of Gd2O3. Observations of the structure and luminescent properties of the films revealed that Eu3+ ions were incorporated into cubic-type Gd2O3 nanocrystals that were surrounded by the silica matrix. As a result, efficient red emissions at approximately 610 nm were produced from Eu3+ in response to a UV light excitation at 256 nm. (C) 2004 The Electrochemical Society.