AC electrical conduction mechanisms and dielectrical studies of DD3 kaolin sintered at high temperature

Abstract In this study, DD3 kaolin, as a raw material, was thermally treated at a temperature ranging from 1000 °C to 1600 °C. The X-ray diffraction (XRD) patterns show the appearance of cristobalite and mullite phases at sintered temperature less than 1300 °C. Moreover, they revealed the formation of mullite at a higher temperature (1600 °C). The surface of mullite sample (DD3 at 1600 °C) is showed roughly with prismatic grains having an average size in the range of 32–42 nm. The FTIR spectrum is dominated by the stretching Si-O modes and Al-O at the wave number ranging from 443 to 1257 cm −1 . The dielectric and electrical properties were investigated in a wide frequency (0.1–10 MHz) and at a temperature ranging from 0 to 200 °C. A strong dispersion of permittivity constants was observed at a low frequency, which can be attributed to interfacial Maxwell–Wagner–Sillar (MWS) relaxation. It is found that the ac conductivity depends on frequency and temperature with the Joncher power law A(T) ω s . Temperature analysis showed that the electron conductivity is controlled by both the small polaron tunneling (SPT) and the hopping correlated barrier (CBH) models.