Temperature Dependence of Complex Dielectric Constant of TGS Powders

The real part ε ' and the imaginary part ε '' of the complex dielectric constant of TGS powders have been measured precisely at 1 kHz as functions of temperature from 40°C to 58°C. Powders separated into different particle sizes using sieves ranging from 25 µm to 210 µm in mesh size were used as specimens. A well defined peak of ε ' at 49°C ( T c ), indicating ferroelectric phase transition, was observed on the specimen with particle size less than 25 µm, as well as on the specimens with larger particle sizes. The thickness of the nonferroelectric surface layer should be far smaller than 20 µm, the thickness reported by Mansingh and Bawa. Both components of the complex dielectric constant showed remarkable particle size dependence. Behaviors of ε ' and ε '' below T c are explained by considering the domain wall motion, and the origin of ε '' above T c is attributed to the ionic conduction.