Dielectric Properties of Reduced Heterogeneous Silica-Titania Glasses

摘要

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℃ and the frequency range 40-10~7Hz. 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.