The non-isothermal devitrification of glasses in the CaO·4GeO2–SrO·4GeO2 composition range

The effect of replacing CaO by SrO on the glass transition temperature and on devitrification behaviour in a series of glasses in the calcium tetragermanate–strontium tetragermanate composition range has been studied by differential thermal analysis (DTA), X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectra. A similar GeO4/GeO6 molar ratio was found in all the glasses of the series. The progressive replacing of CaO by SrO caused a decrease of the glass transition temperature. All glasses studied exhibited internal crystal nucleation. The crystallizing phases were identified as CaGe4O9 and SrGe4O9. No solid solutions occur in glass containing both CaO and SrO. The effect of the specific surface of the glass samples on devitrification processes has been studied.