Non-isothermal crystallization of LiNaGe4O9 glass

The glass of lithium-sodium tetragermanate LiNaGe4O9 is crystallized on heating under the control of differential scanning calorimetry and thermal gravimetric analysis. The measurements were prepared in the temperature range 300-870 K and showed the relatively weak endothermic DSC anomaly and 40-50 K above the single exothermic peak. The endothermic anomaly observed at Tg testified to softening the glass structure whereas the exothermic peak at TC manifested crystallization of the amorphous phase. Studying of TGA demonstrated smooth nearly linear dependences without any visible anomalies. Varying the heating rate from 1.2 up to 40 K/min resulted in noticeable increase of the characteristic temperatures Tg and TC. Lower limit of the glass transition temperature Tg0 was estimated with the help of the existing model. The mechanism of the LiNaGe4O9 glass crystallization is discussed.

Physico-chemical properties and structural transformations in the synthesis of boroalumosilicate glass-crystal materials

The aim of this work is to study the areas of glass formation and metastable liquation of the pseudo-ternary system (MgO·Al2O3)-B2O3-SiO2, and study of the crystallization process of glasses of cordierite composition. The crystallization process of glasses of cordierite composition containing B2O3 by a single-stage heat treatment at 1000 oC and 1200 oC, the nature of crystallization, the thermal properties of glasses and glass crystalline materials of the system (MgO·Al2O3)-B2O3-SiO2 were studied. It revealed that during the isolation of a boron-containing solid solution, the residual glassy phase enriched with oxides of MgO and Al2O3, which lead to an increase in the thermal expansion coefficient of the glass phase. The research results provide possibility to synthesize glass-ceramics with certain thermophysical parameters by stopping further glass crystallization at the stage of formation of a certain amount and ratio of the required crystalline and glassy phases.