High‐Temperature Dynamic Mechanical Thermal Analysis of a Lithium Zinc Silicate Glass‐Ceramic

High‐temperature dynamic mechanical thermal analysis (DMTA) has been used to study a lithium zinc silicate glassceramic. The DMTA technique was capable of measuring the glass transition temperature of the original starting glass composition, as well as being able to follow crystallization and structural changes within the glass. The greater sensitivity of DMTA compared to differential thermal analysis, or differential scanning calorimetry, enabled the detection and measurement of the glass transition temperature of the residual glass phase in a largely crystalline glassceramic. An activation energy of 542 kJ·mol ^‐1 for this glass transition was obtained from a multifrequency experiment. A second transition was found in the crystallized glassceramics, and this is thought to be due to a crystal phase transition. Some evidence was also found supporting the view that in these glasses nucleation occurs by an amorphous phase separation mechanism.