Relaxation dynamics of the conductive processes in BaTiO3 ceramics at high temperature

The temperature and frequency dependences of the undoped BaTiO3 ceramics dielectric properties were measured between 25 °C and 700 °C and 100 Hz to 10 MHz, respectively. A dielectric anomaly was observed at low frequencies in the temperature range of 400–700 °C. This anomaly was associated to a low frequency dispersion process taking place at high temperature. The relaxation dynamics of the conductive process in BaTiO3 ceramics was investigated. A relaxation function in the time domain (Φ(t)) was determined from the frequency dependence of the dielectric modulus, using a relaxation function in the frequency domain (F*(ω)). In BaTiO3 ceramics context, the best relaxation functions (F*(ω)), in the temperature ranges of 220–400 °C and 425 °C and 630 °C, were found to be a Cole–Cole and Davidson–Cole distribution functions, respectively. The relaxation function (f(t)) obtained by the time domain method was found to be a Kohlrausch–Williams–Watts (KWW) function type. The activation energy values (0.72 eV and 0.8 eV) reveal a mechanism correlated with the movement of single ionized oxygen vacancies and electrons of the second level of ionization, probably due to the formation of a titanium liquid phase during the sintering process.