Impedance Spectroscopy and Structural Characterization of Nanostructured ZnO and Hf- Doped ZnO Ceramics

Abstract Nanostructured zinc oxide (ZnO) and hafnium-doped zinc oxide ceramic samples were prepared by the sol-gel technique. ZnO and %0.5 hafnium-doped ZnO (HZO) nanostructures and their surface morphologies were studied by X-ray diffraction and field-emission scanning electron microscopy. AC electrical properties (capacitance, conductance, and complex impedance) of ZnO and HZO were studied by impedance analyzer with the frequency range from 20 Hz to 1.5 MHz and temperature range from 300 to 500 K. General analysis of AC electrical measurements showed that both samples had different equivalent circuit diagrams. The best-fitted equivalent circuit diagram for ZnO was "R(RC)(RC)" at all temperatures. The circuit diagram for HZO was "R(RCPE)" at 300, 350, and 400 K temperatures and "R(RCPE)(RCPE)" at 450 and 500 K temperatures. Negative temperature coefficient of resistance (NTCR), non-Debye behavior, and multiple relaxation times were observed.