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The giant dielectric behavior of CaCu3Ti4O12 (CCTO) has been widely investigated owing to its potential applications in electronics; however, the loss tangent (tanδ) of this material is too large for many applications. A partial substitution of CCTO ceramics with either Al3+ or Ta5+ ions generally results in poorer nonlinear properties and an associated increase in tanδ (to ~0.29-1.15). However, first-principles calculations showed that self-charge compensation occurs between these two dopant ions when co-doped into Ti4+ sites, which can improve the electrical properties of the grain boundary (GB). Surprisingly, in this study, a greatly enhanced breakdown electric field (~200-6588 V/cm) and nonlinear coefficient (~4.8-15.2) with a significantly reduced tanδ (~0.010-0.036) were obtained by simultaneous partial substitution of CCTO with acceptor-donor (Al3+, Ta5+) dopants to produce (Al3+, Ta5+)-CCTO ceramics. The reduced tanδ and improved nonlinear properties were attributed to the synergistic effects of the co-dopants in the doped CCTO structure. The significant reduction in the mean grain size of the (Al3+, Ta5+)-CCTO ceramics compared to pure CCTO was mainly because of the Ta5+ ions. Accordingly, the increased GB density due to the reduced grain size and the larger Schottky barrier height (Φb) at the GBs of the co-doped CCTO ceramics were the main reasons for the greatly increased GB resistance, improved nonlinear properties, and reduced tanδ values compared to pure and single-doped CCTO. In addition, high dielectric constant values (ε′ ≈ (0.52-2.7) × 104) were obtained. A fine-grained microstructure with highly insulating GBs was obtained by Ta5+ doping, while co-doping with Ta5+ and Al3+ resulted in a high Φb. The obtained results are expected to provide useful guidelines for developing new giant dielectric ceramics with excellent dielectric properties.


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Enhanced giant dielectric properties and improved nonlinear electrical response in acceptor-donor (Al3+, Ta5+)-substituted CaCu3Ti4O12 ceramics

Show Author's information Jakkree BOONLAKHORNaNarong CHANLEKbJedsada MANYAMcPornjuk SREPUSHARAWOOTa,dSriprajak KRONGSUKa,dPrasit THONGBAIa,d( )
Giant Dielectric and Computational Design Research Group (GD-CDR), Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand
Synchrotron Light Research Institute (Public Organization), 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand
National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Pathum Thani 12120, Thailand
Institute of Nanomaterials Research and Innovation for Energy (IN-RIE), NANOTEC-KKU RNN on Nanomaterials Research and Innovation for Energy, Khon Kaen University, Khon Kaen 40002, Thailand

Abstract

The giant dielectric behavior of CaCu3Ti4O12 (CCTO) has been widely investigated owing to its potential applications in electronics; however, the loss tangent (tanδ) of this material is too large for many applications. A partial substitution of CCTO ceramics with either Al3+ or Ta5+ ions generally results in poorer nonlinear properties and an associated increase in tanδ (to ~0.29-1.15). However, first-principles calculations showed that self-charge compensation occurs between these two dopant ions when co-doped into Ti4+ sites, which can improve the electrical properties of the grain boundary (GB). Surprisingly, in this study, a greatly enhanced breakdown electric field (~200-6588 V/cm) and nonlinear coefficient (~4.8-15.2) with a significantly reduced tanδ (~0.010-0.036) were obtained by simultaneous partial substitution of CCTO with acceptor-donor (Al3+, Ta5+) dopants to produce (Al3+, Ta5+)-CCTO ceramics. The reduced tanδ and improved nonlinear properties were attributed to the synergistic effects of the co-dopants in the doped CCTO structure. The significant reduction in the mean grain size of the (Al3+, Ta5+)-CCTO ceramics compared to pure CCTO was mainly because of the Ta5+ ions. Accordingly, the increased GB density due to the reduced grain size and the larger Schottky barrier height (Φb) at the GBs of the co-doped CCTO ceramics were the main reasons for the greatly increased GB resistance, improved nonlinear properties, and reduced tanδ values compared to pure and single-doped CCTO. In addition, high dielectric constant values (ε′ ≈ (0.52-2.7) × 104) were obtained. A fine-grained microstructure with highly insulating GBs was obtained by Ta5+ doping, while co-doping with Ta5+ and Al3+ resulted in a high Φb. The obtained results are expected to provide useful guidelines for developing new giant dielectric ceramics with excellent dielectric properties.

Keywords:

CaCu3Ti4O12 (CCTO), impedance spectroscopy, nonlinear electrical properties, dielectric constant, loss tangent, first-principles calculations
Received: 27 February 2021 Revised: 20 April 2021 Accepted: 09 May 2021 Published: 26 July 2021 Issue date: December 2021
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Publication history
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Publication history

Received: 27 February 2021
Revised: 20 April 2021
Accepted: 09 May 2021
Published: 26 July 2021
Issue date: December 2021

Copyright

© The Author(s) 2021

Acknowledgements

This work was supported by the Basic Research Fund of Khon Kaen University. It was partially supported by the Research Network NANOTEC (RNN) program of the National Nanotechnology Center (NANOTEC), NSTDA, Ministry of Higher Education, Science, Research, and Innovation (MHESI, Thailand) (Grant No. P1851882), and Khon Kaen University, Thailand. J. Boonlakhorn would like to thank the Graduate School of Khon Kaen University (Grant No. 581T211) for his Ph.D. scholarship.

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