Effectof LaF3 admixture on thermal stability of borosilicateglasses

Oxyfluoride glass-ceramics based on the aluminosilicate glass-matrix with the nano-phase of fluoride is an interesting material for optoelectronics. A new glass from the SiO₂–B₂O₃–Na₂O–LaF₃ system in which nanocrystallization of LaF₃ could be obtained as well is presented. Thermal stability of glass and the crystalline phases formed upon heat treatment were determined by DTA/DSC and XRD methods, respectively. The effect of the glass composition on thermal stability was investigated by the SEM method. It has been found that the addition of LaF₃ increases the tendency to decomposition of the borosilicate glass. In glasses with the ratio B₂O₃/(Na₂O+3La₂F₆)<1 it is possible to obtain the immersed crystallization of LaF₃ in transparent glassy matrix. The process is preceded by LaOF formation. Glasses with the composition B₂O₃/(Na₂O+3La₂F₆)≥1 revealed the tendency to La(BSiO₅) crystallization.