Influence of Oxygen Vacancies on the Impedance Spectrum of Al<sub>2</sub>O<sub>3</sub>–Na<sub>0.5</sub>K<sub>0.5</sub>NbO<sub>3</sub> Composites
oleh: Alexander Martin, Kyle G. Webber, Keni-chi Kakimoto
| Format: | Article |
|---|---|
| Diterbitkan: | MDPI AG 2023-03-01 |
Deskripsi
Composites based on ferroelectric Na<sub>0.5</sub>K<sub>0.5</sub>NbO<sub>3</sub> (NKN) and paraelectric Al<sub>2</sub>O<sub>3</sub> were observed using impedance spectroscopy at different temperatures. This allowed for the evaluation of the conduction processes of the bulk and grain boundary, revealing the occurrence of interdiffusion and changes in the conductive properties. The effective conductivity decreased with the increase in Al<sub>2</sub>O<sub>3</sub>, which is due to the highly resistive nature of Al<sub>2</sub>O<sub>3</sub>. Interestingly, the activation energy for the bulk response increased from 0.87 ± 0.06 eV to approximately 1.12 ± 0.03 eV, and the activation energy of the grain boundary decreased from 1.26 ± 0.09 eV to 0.99 ± 0.09 eV. These observations of the activation energy revealed the interdiffusion of Al<sup>3+</sup> ions, leading to the formation of oxygen vacancies in close vicinity to the grain boundary. As a result, the conduction path for charge carriers shifted to take place predominantly along the grain boundary.