Issue 4, 2023

Controlling dielectric properties of Nb + X (X = Al, Ga, In) co-doped and Nb-doped rutile-type TiO2 single crystals

Abstract

Co-doping of heterovalent ions to rutile-type TiO2 has recently attracted attention as a new concept for designing high-permittivity materials with local structure engineering. However, the role of co-dopants in permittivity enhancement remains an open question. In the present study, dielectric measurements are performed in Nb + X (X = Al, Ga, In) co-doped and Nb-doped rutile-type TiO2 single crystals before and after annealing in X2O3 powders. The apparently huge permittivity, on the order of 105, is observed in all as-grown samples. Systematic analyses of dielectric relaxation observed in the as-grown samples clarify that thermally excited carriers render the sample semiconducting, thus giving rise to the apparently huge permittivity. In the post-annealed samples, in contrast, the huge permittivity disappears, and the dielectric loss markedly decreases to indicate recovery of the insulating property. X-ray fluorescence analyses show that the insulation recovery stems from migration of X cations into the single crystal, which is caused by the post-annealing. The post-annealing time dependence of the dielectric properties indicates that minute control of the Nb-to-X ratio is crucial for simultaneously achieving both the large permittivity and the fine insulating property in the co-doped TiO2. The present results offer an important clue toward clarifying the mechanism of permittivity boosting in co-doped TiO2.

Graphical abstract: Controlling dielectric properties of Nb + X (X = Al, Ga, In) co-doped and Nb-doped rutile-type TiO2 single crystals

Supplementary files

Article information

Article type
Paper
Submitted
21 صفر 1444
Accepted
21 جمادى الأولى 1444
First published
22 جمادى الأولى 1444

J. Mater. Chem. C, 2023,11, 1304-1310

Controlling dielectric properties of Nb + X (X = Al, Ga, In) co-doped and Nb-doped rutile-type TiO2 single crystals

S. Kakimoto, Y. Hashimoto, T. Kuwano, K. Kimura, K. Hayashi, M. Hagiwara, K. Deguchi and H. Taniguchi, J. Mater. Chem. C, 2023, 11, 1304 DOI: 10.1039/D2TC03914A

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