Elastic and mechanical properties of transparent nanocrystallized KNbGeO5 glass

Abstract

KNbGeO 5 (i.e., 25K2O-25Nb2O5-50GeO2) glass with the glass transition 622 °C and crystallization onset 668 °C temperatures shows prominent nanocrystallization, giving K3.8Nb5Ge3O20.4 nanocrystals with the size of ∼30 nm. Dielectric, elastic and mechanical properties of transparent nanocrystallized KNbGeO5 glasses are examined using some techniques such as polarizability analysis, cube resonance spectra and Vickers nanoindentation. Electronic polarizability, shear modulus, bulk modulus, Young’s modulus (E), Debye temperature (θD), Vickers hardness, and deformation energies during nanoindentation increase largely due to the nanocrystallization, e.g., E=64.1 GPa and θD=500 K for the base glass and E=85.5 GPa and θD=575 K for a transparent nanocrystallized glass. The values of Poisson’s ratio and fractal bond connectivity of nanocrystallized glasses are the same as those of the base glass, suggesting that relative arrangements of constituent ions (K+, Nb5+, Ge4+) in nanocrystallized glasses are basically similar to those in the base glass. The present study suggests that nanocrystallization in glass results in not only more compact atomic arrangements but also in an increase in interatomic strength.