Electrical properties and charge compensation mechanisms of Cr-doped rutile, TiO<sub>2</sub>

Dang, Yun ORCID: 0000-0002-0140-0140, Phuah, Xin Li, Wang, Han, Yang, Bo, Wang, Haiyan and West, Anthony R
(2021) Electrical properties and charge compensation mechanisms of Cr-doped rutile, TiO<sub>2</sub>. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 23 (38). pp. 22133-22146.

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Cr-doped rutile, Ti<sub>1-<i>x</i></sub>Cr<sub><i>x</i></sub>O<sub>2-<i>x</i>/2-<i>δ</i></sub>, powders and ceramics with 0 ≤ <i>x</i> ≤ 0.05 were prepared by solid state reaction and sintered at 1350 °C. Cr distribution is homogeneous with no evidence of either segregation or crystallographic shear plane formation. For high <i>x</i> compositions, >∼0.01, Cr substitution is charge-compensated ionically by oxygen vacancies with two Cr<sup>3+</sup> ions for each vacancy and the materials are electronically insulating. For low <i>x</i> compositions, the materials are semiconducting. This is attributed to a new charge compensation mechanism involving Ti<sup>3+</sup> ions created in response to the local electroneutrality requirement for two trivalent cations to be in close proximity to each oxygen vacancy. At very low dopant concentrations, ≪0.01, the dopants are well-separated and instead, some Ti<sup>3+</sup> ions act as a second dopant to preserve local electroneutrality. For intermediate <i>x</i> compositions, a core-shell structure is proposed consisting of semiconducting grain interiors containing Ti<sup>3+</sup> ions surrounded by a more insulating shell with Cr<sup>3+</sup> ions as the only acceptor dopant. Lattice parameters show unusual, non-linear Vegard's law behaviour characterised by a maximum in cell volume at intermediate <i>x</i> ∼ 0.005, that is attributed to the composition-dependent presence of Ti<sup>3+</sup> ions.

Item Type: Article
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 06 Dec 2021 11:43
Last Modified: 17 Oct 2023 20:24
DOI: 10.1039/d1cp01735g
Open Access URL: https://pubs.rsc.org/en/content/articlelanding/202...
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3144759