Highlighting of LaF3 Reactivity with SiO2 and GeO2 at High Temperature

Abstract

LaF3 is commonly added to oxide glass, in particular to silica, to form oxyfluoride glass. After appropriate thermal treatment at a temperature lower than 800 °C, usually, glass ceramics are obtained. Recently, LaF3 nanoparticles have been used as precursors to obtain amorphous nanoparticles of undefined composition in optical fiber. However, fiber fabrication necessitates temperature much higher (typically up to 2000 °C) than the one required for bulk glass. In this article, we report on the reactivity of fluoride ions in LaF3 with SiO2 and GeO2 (a common dopant used to dope optical fiber) powders at high temperature. TGA, EDX-SEM, XRD and Raman analyses were performed. Above 1000 °C, LaF3 starts to react, preferentially with SiO2, to form SiF4 gaseous species. The remaining lanthanum ions form La2Si2O7 and La2Ge2O7 phases. These results could contribute to improve material development for the fiber optics community.