Abstract
Oxyfluoride glasses are the basic materials for obtaining transparent glass–ceramic (TGC) which can be used in a wide range of optoelectronics devices such as: amplifiers, up-conversion, telescopes, laser sources. Oxyfluoride TGC is obtained by the control heat treatment of the parent glass due to low phonon nanocrystalline phases. The oxyfluoride glasses from the sodium–lead–silica system were the object of investigation. The influence of fluoride content on the thermal properties of glasses was analyzed. Thermal characteristics of glasses like the transition temperature T g, the temperature for the crystallization onset T x, and the maximum crystallization temperature T c, thermal stability parameter were determined by DTA/DSC method. The linear expansion coefficients of oxyfluoride glasses as a function of temperature were measured using a thermo-mechanical analyzer (TMA 7 Perkin-Elmer). The effect of crystallization on the thermal expansion coefficient and softening temperature T s was found.
Highlights
Transparent oxyfluoride nano-glass–ceramics (GC), made photo-luminescent by doping with rare-earth ions, haveM
Fluorine content has been shown to have a strong effect on the reduction of the glass transition temperature in a variety of glass systems such as fluoro-alumino-silicate, calcium-fluoro-aluminate, phosphor-fluoro-alumino-silicate, phosphorfluoro calcium-alumino-silicate, phosphor-fluoro-silicate, and fluoro-silicate glasses [13, 14]
The formation of b-PbF2 phase is observed at the first stage of crystallization and a-PbF2 at the second stage; increasing amount of fluorine in the glass structure causes the break of lead–silicate glass matrix crystallization
Summary
Transparent oxyfluoride nano-glass–ceramics (GC), made photo-luminescent by doping with rare-earth ions, haveM. The introduction of fluorine ions, replacing the oxygen ions in the glass structure, increases the tendency of glass to undergo PbF2 crystallization. Increase of fluorine content causes a slight decrease of the temperature of the second crystallization event, as well as a gradual disappearance of the effect. The formation of b-PbF2 phase is observed at the first stage of crystallization and a-PbF2 at the second stage; increasing amount of fluorine in the glass structure causes the break of lead–silicate glass matrix crystallization. This can be explained by the fact that crystallization process usually starts in those components whose bonds can be broken
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