Effect of heat-treatment on the electrical and dielectric properties of a TiO2-containing lithia–calcia–silica glass and glass ceramics

The glass 65 SiO2, 20 CaO, 15 Li2O (mol%) containing 4 g TiO2/100 g glass was prepared. Samples of this glass were heat treated at temperatures pre-determined by DTA to produce crystalline samples which were characterized by IR, XRD and SEM. The dielectric constant (ɛ′), dielectric loss (ɛ″) and conductivity σac over a wide range of frequency and temperatures were measured. Optical absorption and values of the absorption edge were also determined for the transparent samples. Li–calcium silicate was found to crystallize at 964 °C as the main phase with lithium disilicate and quartz as minor phases. An enhancement in conductivity of about 1–3 orders of magnitude was obtained in the heat treated samples as compared to parent glass. Conduction takes place through an electronic mechanism in the low temperature region. In crystalline samples, the electronic conduction is extended to high temperature regions. Crystallized samples show high ɛ′ values, particularly at low frequencies. The values of (ɛ′) reached 60–300 at 300 °C. The capacitance results indicated that these materials can be used in capacitors. Dielectric loss bands appeared in the range 0.32–5 MHz and the conduction relaxation times were calculated.