Sol-gel synthesis of silica-based oxyfluoride glass-ceramic thin films:: Incorporation of Eu3+ activators into crystallites

Transparent oxyfluoride glass-ceramic thin films were prepared using a sol-gel method starting from rare-earth trifluoroacetate/silicon alkoxide solutions. SiO2-LaF3 and SiO2- LaOF glass-ceramics were formed by heating at temperatures of 300 degrees -500 degreesC and 600 degrees -900 degreesC, respectively. Eu3+ activators were successfully incorporated into oxyfluoride crystals, as evidenced by their luminescent properties, such as capability of a charge-transfer (O2--Eu3+) excitation, suppression of a multiphonon relaxation, and occurrence of a cross-relaxation at low Eu3+ concentrations. As a result, the films exhibited strong red emission by ultraviolet excitation. The incorporation supposedly originated from decomposition of the (La,Eu)-trifluoroacetates in the silica-gel matrix.