Nachaithong Theeranuch, Chanlek Narong, Moontragoon Pairot, Thongbai Prasit
Materials Science and Nanotechnology Program, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand.
Giant Dielectric and Computational Design Research Group (GD-CDR), Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand.
Molecules. 2021 May 27;26(11):3230. doi: 10.3390/molecules26113230.
(Co, Nb) co-doped rutile TiO (CoNTO) nanoparticles with low dopant concentrations were prepared using a wet chemistry method. A pure rutile TiO phase with a dense microstructure and homogeneous dispersion of the dopants was obtained. By co-doping rutile TiO with 0.5 at.% (Co, Nb), a very high dielectric permittivity of ε' ≈ 36,105 and a low loss tangent of tanδ ≈ 0.04 were achieved. The sample-electrode contact and resistive outer-surface layer (surface barrier layer capacitor) have a significant impact on the dielectric response in the CoNTO ceramics. The density functional theory calculation shows that the 2Co atoms are located near the oxygen vacancy, creating a triangle-shaped 2CoVTi complex defect. On the other hand, the substitution of TiO with Nb atoms can form a diamond-shaped 2Nb2Ti complex defect. These two types of complex defects are far away from each other. Therefore, the electron-pinned defect dipoles cannot be considered the primary origins of the dielectric response in the CoNTO ceramics. Impedance spectroscopy shows that the CoNTO ceramics are electrically heterogeneous, comprised of insulating and semiconducting regions. Thus, the dielectric properties of the CoNTO ceramics are attributed to the interfacial polarization at the internal insulating layers with very high resistivity, giving rise to a low loss tangent.
采用湿化学方法制备了低掺杂浓度的（Co，Nb）共掺杂金红石TiO₂（CoNTO）纳米颗粒。获得了具有致密微观结构和均匀掺杂剂分散的纯金红石TiO₂相。通过用0.5原子百分比的（Co，Nb）对金红石TiO₂进行共掺杂，实现了非常高的介电常数ε'≈36105和非常低的损耗角正切tanδ≈0.04。样品-电极接触和电阻性外表面层（表面势垒层电容器）对CoNTO陶瓷的介电响应有显著影响。密度泛函理论计算表明，2个Co原子位于氧空位附近，形成三角形的2CoVTi复合缺陷。另一方面，用Nb原子取代TiO₂可以形成菱形的2Nb₂Ti复合缺陷。这两种类型的复合缺陷彼此相距很远。因此，电子钉扎缺陷偶极子不能被认为是CoNTO陶瓷介电响应的主要起源。阻抗谱表明，CoNTO陶瓷是电非均匀的，由绝缘和半导体区域组成。因此，CoNTO陶瓷的介电性能归因于具有非常高电阻率的内部绝缘层处的界面极化，从而产生低损耗角正切。
