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Experimental study and DFT calculations of improved giant dielectric properties of Ni2+/Ta5+ co-doped TiO2 by engineering defects and internal interfaces |
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| Affiliation: | 1. Giant Dielectric and Computational Design Research Group (GD–CDR), Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand;2. Synchrotron Light Research Institute (Public Organization), 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand;3. Department of Physics, Hokkaido University, Sapporo 060-0810, Japan;4. Materials Science, School of Mechanical, Industrial & Manufacturing Engineering, Oregon State University, Corvallis, OR 97331, USA;1. State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, Jilin, China;2. Key Laboratory of Material Physics of Ministry of Education, School of Physical Engineering, Zhengzhou University, Zhengzhou 450052, Henan, China;1. School of Materials Science and Engineering, Xi''an University of Technology, Xi’an, Shaanxi 710048, China;2. Advanced Material Analysis and Test Center, Xi’an University of Technology, Xi’an, Shaanxi 710048, China |
| Abstract: | High-performance ceramics with chemical formula (Ni1/3Ta2/3)xTi1?xO2 with excellent dielectric properties are demonstrated. The dopants of Ni2+ and Ta5+ in TiO2 caused the formation of oxygen vacancies and free electrons. The (Ni1/3Ta2/3)xTi1?xO2 exhibited low loss tangent of 0.046 and a high dielectric permittivity of 3.5–4.5 × 104 with a very weak dependence on temperature (?60 to 200 °C). Broadband dielectric spectroscopy shows at least four dominant sources in the dielectric relaxation response in the temperature range of ? 253–210 °C. DFT calculations indicate the formation of defect clusters, which are the largest contributors to the dielectric response, and these are found to be dominant even at temperatures down to ? 253 °C. Both grain boundary and surface layer mechanisms in the ceramics contribute to the dielectric response at the relatively high temperatures. The sample–electrode contact effect associated with oxygen vacancy diffusion is dominant at high temperatures above 150 °C. |
| Keywords: | Broadband dielectric spectroscopy Colossal dielectric permittivity X-ray photoelectron spectroscopy DFT |
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