Dielectric Responses of (Zn0.33Nb0.67) x Ti1- xO2 Ceramics Prepared by Chemical Combustion Process: DFT and Experimental Approaches

Theeranuch Nachaithong; Pairot Moontragoon; Prasit Thongbai

doi:10.3390/molecules27186121

Dielectric Responses of (Zn_0.33Nb_0.67) _x Ti_{1- x}O₂ Ceramics Prepared by Chemical Combustion Process: DFT and Experimental Approaches

Molecules. 2022 Sep 19;27(18):6121. doi: 10.3390/molecules27186121.

Authors

Theeranuch Nachaithong¹, Pairot Moontragoon^{2

3

4}, Prasit Thongbai⁴

Affiliations

¹ Materials Science and Nanotechnology Program, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand.
² Institute of Nanomaterials Research and Innovation for Energy (IN-RIE), Khon Kaen University, Khon Kaen 40002, Thailand.
³ Thailand Center of Excellence in Physics, Commission on Higher Education, Bangkok 10400, Thailand.
⁴ Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand.

Abstract

The (Zn, Nb)-codoped TiO₂ (called ZNTO) nanopowder was successfully synthesized by a simple combustion process and then the ceramic from it was sintered with a highly dense microstructure. The doped atoms were consistently distributed, and the existence of oxygen vacancies was verified by a Raman spectrum. It was found that the ZNTO ceramic was a result of thermally activated giant dielectric relaxation, and the outer surface layer had a slight effect on the dielectric properties. The theoretical calculation by using the density functional theory (DFT) revealed that the Zn atoms are energy preferable to place close to the oxygen vacancy (Vo) position to create a triangle shape (called the ZnVoTi defect). This defect cluster was also opposite to the diamond shape (called the 2Nb2Ti defect). However, these two types of defects were not correlated together. Therefore, it theoretically confirms that the electron-pinned defect-dipoles (EPDD) cannot be created in the ZNTO structure. Instead, the giant dielectric property of the (Zn_0.33Nb_0.67)_xTi₁_-xO₂ ceramics could be caused by the interfacial polarization combined with electron hopping between the Zn²⁺/Zn³⁺ and Ti³⁺/Ti⁴⁺ ions, rather than due to the EPDD effect. Additionally, it was also proved that the surface barrier-layer capacitor (SBLC) had a slight influence on the giant dielectric properties of the ZNTO ceramics. The annealing process can cause improved dielectric properties, which are properties with a huge advantage to practical applications and devices.

Keywords: DFT; TiO2; dielectric constant; electron hopping; loss tangent.

Abstract

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