A series of Eu3+-doped silica sol-gels are prepared under various conditions: (1) pH values of the sols are controlled at 3.0, 5.5, and 7.5; (2) the counterions of dopants are selected from acetate, chloride, and nitrate of europium (III) compounds; (3) two chelating agents, namely ethylenediaminetetraacetic acid (EDTA) and ethylenediaminetriacetic (HEDTA) are used for complexing the europium (III) dopants; (4) a sol-gel matrix containing low O-H functionality is synthesized by using deuterated solvents (D2O and C2D5OD) and under an extremely dry N-2 environment; and (5) a mixture of 1% of aluminum or antimony alkoxide and 99% of silicon alkoxide is adopted as precursors. The conditions that these differences have on the network structures of a gel matrix are examined in order to determine the optimal conditions for the creation of structural defects in an SiO2 network, generation of electron-hole centers and utilization of them to reduce EU3+ to EU2+ during the sol-gel processing. Both differential scanning calorimetric (DSC) measurements and thermogravimetric and differential thermal analysis (TG/DTA) are employed to illustrate which gel samples are the most liquidlike and have the greatest cross-linking density. The results from thermoanalysis are then correlated to the emission intensity and lifetimes of each Eu3+-doped sample. The relative emission intensity of Eu2+/EU3+ gives the degree of conversion of EU3+ to EU2+ which is produced from the defect electron-hole pair generation. The absolute emission intensity of EU3+ and EU2+ is strongly quenched by the presence of OH groups in xerogels and is shown to be enhanced by laser irradiation due to water evaporation. The results show that a basic gel prepared by the mixed metal alkoxides most efficiently converts EU3+ to Eu2+ because or its liquidlike nature, reduced cross-linking density, and low OH quenching.