Optical, mechanical and thermal properties in HfO2-doped TiO2-LaO3/2 glasses fabricated by aerodynamic levitation

Abstract

70.21TiO2-(29.79-x)LaO3/2-xHfO2 (x=0, 1.5, 3, 4.5, 6) glasses were fabricated by aerodynamic levitation technique. XRD shows the amorphous state of these synthesized glasses. DSC indicates that the glass transition temperature (Tg) and onset crystallization temperature (Tx) decreases while ΔT (=Tx - Tg) decreases and then increases with the increase of HfO2. Density increases from 4.931 to 5.147 gcm−3 with the addition of HfO2, while hardness increases from 8.587 to 9.058 GPa. Raman spectra indicate that the maximum phonon energy is 720 cm−1. The transmittance region of glasses is wide from 386nm to 6.5 μm, and the largest transmittance can reach 72%. Furthermore, Abbe number decreases from 17.797 to 16.969 with the addition of HfO2, which is attributed to the increase in the inherent absorption wavelength (λ0). Finally, the refractive index increases from 2.293 to 2.324 with the addition of HfO2, which is attributed to the increase in oxygen packing density (OPD), decrease in molar volume (Vm). The reason for the relatively small increase in the refractive index is that the oxygen polarizability has a certain decrease, which offsets a part of the effects of Vm and OPD. These results are useful for designing new optical glass with excellent properties.