Influence of annealing on the giant dielectric properties of CuO ceramics prepared by a simple PVA sol-gel

Abstract

In this research, the giant dielectric constant CuO ceramics were successfully prepared by a simple PVA
sol-gel method. Phase composition and microstructure were characterized by X-ray diffraction and scanning electron
microscopy, respectively. The electrical and dielectric properties of the prepared CuO samples were investigated
as functions of frequency (103 to 6.3×106 Hz) and temperature (-50 to 80 °C). The XRD results revealed that only
the pure phase of CuO was obtained with the crystallite sizes of 21.93±6.53 nm. The sintered CuO ceramics exhibited
a giant dielectric response (εʹ ~ 104) with weak temperature dependence over the measured temperature.
Interestingly, it was found that the giant dielectric constant of the CuO ceramic at low frequency was reduced by
annealing in Ar, and could be enhanced up to the initial value by annealing in O2. The reversibility of the dielectric
constant can be explained by the interfacial polarization at the sample-electrode interface and at the outmost
surface layer-inner part interface, resulting from a non-Ohmic contact