Microstructural Evolution and High-Performance Giant Dielectric Properties of Lu<sup>3+</sup>/Nb<sup>5+</sup> Co-Doped TiO<sub>2</sub> Ceramics

Giant dielectric (GD) oxides exhibiting extremely large dielectric permittivities (ε’ > 10<sup>4</sup>) have been extensively studied because of their potential for use in passive electronic devices. However, the unacceptable loss tangents (tanδ) and temperature instability with respe...

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Autores principales: Noppakorn Thanamoon, Narong Chanlek, Pornjuk Srepusharawoot, Ekaphan Swatsitang, Prasit Thongbai
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Publicado: MDPI AG 2021
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spelling oai:doaj.org-article:b9a8a6e15a3349138573be1ca90f5d382021-11-25T18:29:22ZMicrostructural Evolution and High-Performance Giant Dielectric Properties of Lu<sup>3+</sup>/Nb<sup>5+</sup> Co-Doped TiO<sub>2</sub> Ceramics10.3390/molecules262270411420-3049https://doaj.org/article/b9a8a6e15a3349138573be1ca90f5d382021-11-01T00:00:00Zhttps://www.mdpi.com/1420-3049/26/22/7041https://doaj.org/toc/1420-3049Giant dielectric (GD) oxides exhibiting extremely large dielectric permittivities (ε’ > 10<sup>4</sup>) have been extensively studied because of their potential for use in passive electronic devices. However, the unacceptable loss tangents (tanδ) and temperature instability with respect to ε’ continue to be a significant hindrance to their development. In this study, a novel GD oxide, exhibiting an extremely large ε’ value of approximately 7.55 × 10<sup>4</sup> and an extremely low tanδ value of approximately 0.007 at 10<sup>3</sup> Hz, has been reported. These remarkable properties were attributed to the synthesis of a Lu<sup>3+</sup>/Nb<sup>5+</sup> co-doped TiO<sub>2</sub> (LuNTO) ceramic containing an appropriate co-dopant concentration. Furthermore, the variation in the ε’ values between the temperatures of −60 °C and 210 °C did not exceed ±15% of the reference value obtained at 25 °C. The effects of the grains, grain boundaries, and second phase particles on the dielectric properties were evaluated to determine the dielectric properties exhibited by LuNTO ceramics. A highly dense microstructure was obtained in the as-sintered ceramics. The existence of a LuNbTiO<sub>6</sub> microwave-dielectric phase was confirmed when the co-dopant concentration was increased to 1%, thereby affecting the dielectric behavior of the LuNTO ceramics. The excellent dielectric properties exhibited by the LuNTO ceramics were attributed to their inhomogeneous microstructure. The microstructure was composed of semiconducting grains, consisting of Ti<sup>3+</sup> ions formed by Nb<sup>5+</sup> dopant ions, alongside ultra-high-resistance grain boundaries. The effects of the semiconducting grains, insulating grain boundaries (GBs), and secondary microwave phase particles on the dielectric relaxations are explained based on their interfacial polarizations. The results suggest that a significant enhancement of the GB properties is the key toward improvement of the GD properties, while the presence of second phase particles may not always be effective.Noppakorn ThanamoonNarong ChanlekPornjuk SrepusharawootEkaphan SwatsitangPrasit ThongbaiMDPI AGarticlegiant/colossal permittivityTiO<sub>2</sub>impedance spectroscopytemperature coefficientIBLCOrganic chemistryQD241-441ENMolecules, Vol 26, Iss 7041, p 7041 (2021)
institution DOAJ
collection DOAJ
language EN
topic giant/colossal permittivity
TiO<sub>2</sub>
impedance spectroscopy
temperature coefficient
IBLC
Organic chemistry
QD241-441
spellingShingle giant/colossal permittivity
TiO<sub>2</sub>
impedance spectroscopy
temperature coefficient
IBLC
Organic chemistry
QD241-441
Noppakorn Thanamoon
Narong Chanlek
Pornjuk Srepusharawoot
Ekaphan Swatsitang
Prasit Thongbai
Microstructural Evolution and High-Performance Giant Dielectric Properties of Lu<sup>3+</sup>/Nb<sup>5+</sup> Co-Doped TiO<sub>2</sub> Ceramics
description Giant dielectric (GD) oxides exhibiting extremely large dielectric permittivities (ε’ > 10<sup>4</sup>) have been extensively studied because of their potential for use in passive electronic devices. However, the unacceptable loss tangents (tanδ) and temperature instability with respect to ε’ continue to be a significant hindrance to their development. In this study, a novel GD oxide, exhibiting an extremely large ε’ value of approximately 7.55 × 10<sup>4</sup> and an extremely low tanδ value of approximately 0.007 at 10<sup>3</sup> Hz, has been reported. These remarkable properties were attributed to the synthesis of a Lu<sup>3+</sup>/Nb<sup>5+</sup> co-doped TiO<sub>2</sub> (LuNTO) ceramic containing an appropriate co-dopant concentration. Furthermore, the variation in the ε’ values between the temperatures of −60 °C and 210 °C did not exceed ±15% of the reference value obtained at 25 °C. The effects of the grains, grain boundaries, and second phase particles on the dielectric properties were evaluated to determine the dielectric properties exhibited by LuNTO ceramics. A highly dense microstructure was obtained in the as-sintered ceramics. The existence of a LuNbTiO<sub>6</sub> microwave-dielectric phase was confirmed when the co-dopant concentration was increased to 1%, thereby affecting the dielectric behavior of the LuNTO ceramics. The excellent dielectric properties exhibited by the LuNTO ceramics were attributed to their inhomogeneous microstructure. The microstructure was composed of semiconducting grains, consisting of Ti<sup>3+</sup> ions formed by Nb<sup>5+</sup> dopant ions, alongside ultra-high-resistance grain boundaries. The effects of the semiconducting grains, insulating grain boundaries (GBs), and secondary microwave phase particles on the dielectric relaxations are explained based on their interfacial polarizations. The results suggest that a significant enhancement of the GB properties is the key toward improvement of the GD properties, while the presence of second phase particles may not always be effective.
format article
author Noppakorn Thanamoon
Narong Chanlek
Pornjuk Srepusharawoot
Ekaphan Swatsitang
Prasit Thongbai
author_facet Noppakorn Thanamoon
Narong Chanlek
Pornjuk Srepusharawoot
Ekaphan Swatsitang
Prasit Thongbai
author_sort Noppakorn Thanamoon
title Microstructural Evolution and High-Performance Giant Dielectric Properties of Lu<sup>3+</sup>/Nb<sup>5+</sup> Co-Doped TiO<sub>2</sub> Ceramics
title_short Microstructural Evolution and High-Performance Giant Dielectric Properties of Lu<sup>3+</sup>/Nb<sup>5+</sup> Co-Doped TiO<sub>2</sub> Ceramics
title_full Microstructural Evolution and High-Performance Giant Dielectric Properties of Lu<sup>3+</sup>/Nb<sup>5+</sup> Co-Doped TiO<sub>2</sub> Ceramics
title_fullStr Microstructural Evolution and High-Performance Giant Dielectric Properties of Lu<sup>3+</sup>/Nb<sup>5+</sup> Co-Doped TiO<sub>2</sub> Ceramics
title_full_unstemmed Microstructural Evolution and High-Performance Giant Dielectric Properties of Lu<sup>3+</sup>/Nb<sup>5+</sup> Co-Doped TiO<sub>2</sub> Ceramics
title_sort microstructural evolution and high-performance giant dielectric properties of lu<sup>3+</sup>/nb<sup>5+</sup> co-doped tio<sub>2</sub> ceramics
publisher MDPI AG
publishDate 2021
url https://doaj.org/article/b9a8a6e15a3349138573be1ca90f5d38
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