Dielectric permittivity of kaolinite heated to high temperatures

Heating of kaolinite from the room temperature to 600 °C results in a gradual decrease in the dielectric permittivity. However, when the temperature rises to 1000 °C the high frequency permittivity of kaolinite increases surprisingly. We suppose that the decomposition of the material produces imperfections, which liberate a small distance movement of polar groups. Positron annihilation experiments performed in this material confirm the appearance of empty volumes after kaolinite calcination.