Nanoindentation Analysis of Elastic/Mechanical Behaviour of Surface of Transparent Glass Ceramics with Fresnoite Ba2TiSi2O8 Nanocrystals

Transparent glass-ceramics containing Ba2TiSi2O8 (BTS) nanocrystals with sizes of ∼200 nm were obtained by heat treatment of 40BaO-20TiO2-40SiO2 glass. Their elastic/mechanical properties were evaluated using the cube-resonance method and the Berkovich nanoindentation technique under standard and 'continuous stiffness measurement' (CSM) modes, and the relation between these properties and the volume fraction (f) of BTS nanocrystals was clarified. The glass-ceramics were obtained by 1-h heat treatments at 760-790 deg. C of the precursor glass, resulting in the formation of BTS nanocrystals with f=2.7-54.5%, with a corresponding Young's modulus of 84-107 GPa. The CSM nanoindentation measurements gave an indentation modulus of 90 GPa for the glass and 110 GPa for the glass-ceramic heat-treated at 790 deg. C, for indentation depths of 200-1500 nm. The results suggest that the BTS nanocrystals confer a high resistance to deformation during indenter loading.