Influence of heat treatment for electrical response and a Raman spectroscopic investigation in CaO - TiO^sub 2^-xSiO^sub 2^ glasses

The heat treatment-dependent Raman spectra and complex electrical impedance for the CaO-⊕TiO2x-SiO2 (CTSO; x = 0.5, 1 and 2) glasses were measured. We investigate the influence of different compositions in CTSO systems on the dielectric and electrical properties with respect to the oxygen-vacancy-related frequencies of 600 Hz ≤ ω ≤ 100 MHz and from room temperature to 600 °C. The observed Raman spectra of as-quenched CTSO glasses are almost identical with these 6 cycles heat-treated samples in the whole range of bands. Impedance measurement shows that the oxygen vacancies remain during the heat treatment for these glasses. We discuss the origin of oxygen vacancy and its role for the electrical conductivity. The dc electrical activation energies Edc for all CTSO glasses are found to be the same as ~0.83 eV, indicating that dc electrical conduction in bulk does not dependent on changes in glass structure. The dielectric relaxation time for CTSO (x = 0.5) glass is short compared to that of CTSO (x = 1 and 2) glasses.