Dielectric Properties of Reduced Heterogeneous Silica–Titania Glasses

We have studied the frequency and temperature dependences of the dielectric properties of a heterogeneous silica–titania (SiO ₂ –TiO ₂ ) glass by ac impedance spectroscopy measurements in the temperature range 25–700°C and the frequency range 40–10 ⁷ Hz. The heterogeneous glass was prepared by the controlled heat treatment of a homogenous SiO ₂ –TiO ₂ glass, containing ∼7.5 wt% TiO ₂ , in a reducing atmosphere to create a microstructure consisting of many discrete particles of the rutile/anatase TiO ₂ phase dispersed in a homogeneous SiO ₂ ‐rich glassy matrix. Unlike the homogeneous SiO ₂ –TiO ₂ glass, which exhibited only one electrical/dielectric dispersion, presumably due to ion hopping, the heterogeneous glass material exhibited two distinct electrical responses in the impedance formalism. We attributed these contributions to the two‐phase microstructure and explained the dielectric behavior in terms of the Maxwell–Wagner relaxation arising at the interfaces between the TiO ₂ crystals and the SiO ₂ ‐rich matrix phase.