Vickers nanoindentation hardness and deformation energy of transparent erbium tellurite nanocrystallized glasses

Transparent nanocrystallized glasses consisting of Er2Te5O13 nanocrystals (∼100 nm size) have been prepared in 10BaO · 10Er2O3 · 80TeO2, and load/unload displacement curves at room temperature (humidity 53%) have been measured in the penetration depth of ht=200–600 nm using a Vickers nanoindentation technique. The values (4.0–9.4±0.1 GPa) of universal (dynamic) hardness (Hu) in the nanocrystallized glasses are larger than those (Hu=2.7–6.5±0.1 GPa) in the precursor glass and are slightly smaller than those (Hu=4.4–9.7±0.1 GPa) in the opaque crystallized glass consisting of Er2TeO6 crystals. The elastic recoveries during unloading are 0.53–0.61, being almost the same as those in the precursor and opaque crystallized glasses. The elastic Ue and plastic Up deformation energies at ht=500 nm in the nanocrystallized glasses are estimated to be Ue=106 and Up=91±3 kJ mol−1, respectively. These values are larger than those of the precursor glass (Ue=83 and Up=57±3 kJ mol−1), suggesting that the deformation energy during loading in TeO2-based glasses is largely increased due to nanocrystallization. The main origin of plastic deformation at ht<600 nm is considered to be densification.