Impedance Spectroscopy of Sodium Excess Ta-Modified (K_0.5Na_0.5)NbO₃ Ceramics Prepared by Reactive Templated Grain Growth

Abstract

Polycrystalline, sodium excess Ta-modified (K_0.470Na_0.545)(Nb_0.55Ta_0.45)O₃ ceramics were synthesized by reactive templated grain growth method. The crystal structure and microstructure of the synthesized (K_0.470Na_0.545)(Nb_0.55Ta_0.45)O₃ ceramics were examined with X-ray diffraction and scanning electron microscopy. Complex impedance spectroscopy measurements have been carried out to investigate electrical properties in wide frequency range (0.1 Hz – 1 MHz) at different temperatures. Contributions from grain boundaries and from the grain interiors can be distinguished in the complex impedance plots. Moreover, (K_0.470Na_0.545)(Nb_0.55Ta_0.45)O₃ ceramics were found to exhibit negative temperature coefficient of resistance.

Keywords:

• Lead-free electroactive perovskite
• KNNT ceramics
• complex impedance
• electric conductivity