Vol. 33, Issue 1, pp. 161-166
Keywords
nanocrystallization, oxyfluoride glasses, nanotechnology
Abstract
Crystallization of LaF3 in glasses from the SiO2–Al2O3–Na2O–LaF3 system has been investigated. The structure of this compound makes it a good host for the rare earths. It has been found that the range of chemical compositions of glasses from which ultra-transparent glass-ceramics with LaF3 nanocrystallites can be obtained is very limited. It is determined by crystalochemical factors, in particular by the position of Al and La in the glass structure. The optical proportions between Al2O3, Na2O and LaF3, leading to the effect of nanocrystallization of this fluoride, as well as the temperature and time of ceramization, have been determined. If these proportions are not maintained, the undesirable crystals of nepheline (NaAlSiO4) and LaAl2O3 are formed. It has been found that the crystallization of LaF3 is essentially affected by the kind of the compounds used to introduce La and F into the glass. In the obtained material the dimensions of LaF3 crystallites varied from 20 to 100 nm.