Comprehensive examination of dopants and defects in BaTiO${}_{3}$ from first principles

Comprehensive examination of dopants and defects in BaTiO $_{3}$ from first principles

V. Sharma, G. Pilania, G. A. Rossetti, Jr., K. Slenes, and R. Ramprasad

Phys. Rev. B 87, 134109 – Published 30 April 2013

Abstract

An extensive assessment of the physicochemical factors that control the behavior of dopant-related defects in BaTiO $_{3}$ has been performed using high-throughput first-principles computations. Dopants spanning the Periodic Table—44 in total—including K-As, Rb-Sb, and Cs-Bi were considered, and have allowed us to reveal previously unknown correlations, chemical trends, and the interplay between stability, chemistry, and electrical activity. We quantitatively show that the most important factor that determines dopant stability in BaTiO $_{3}$ is the dopant ionic size (followed by its oxidation state). Moreover, we are also able to identify definitively dopants that are O vacancy formers and suppressors, and those that would lead to $p$ -type versus $n$ -type conduction. Our results are in agreement with available experimental data (with no violations thus far), and point to an attractive computational route to dopant selection in BaTiO $_{3}$ as well as in other materials.

Received 3 March 2013

DOI:https://doi.org/10.1103/PhysRevB.87.134109

Authors & Affiliations

V. Sharma¹, G. Pilania¹, G. A. Rossetti, Jr.¹, K. Slenes², and R. Ramprasad^1,*

¹Materials Science and Engineering, Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, USA
²TPL, Inc., 3921 Academy Parkway North, NE, Albuquerque, New Mexico 87109, USA

^*rampi@uconn.edu

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Vol. 87, Iss. 13 — 1 April 2013

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Images

Figure 1
Computed and experimental (Ref. 46) formation energies of the 45 stable simple oxides (of K-As, Rb-Sb, and Cs-Bi), relevant to the present study. The solid line fit corresponds to the $- 0.77$ eV energy correction required to account for the GGA overbinding of the O $_{2}$ molecule. The dashed line corresponds to the fit obtained when the formation energies were computed using the uncorrected oxygen chemical potential.Reuse & Permissions
Figure 2
(a) Variation of the rhombohedral angle as a function of dopant (at the Ti site). The horizontal line indicates the value corresponding to undoped BTO. (b) Variation of lattice parameter as a function of dopant (at the Ti site) along with available experimental results. (c) The effective Shannon's ionic radius of dopants. A comparison of (b) and (c) indicates a close correlation between the dopant ionic radius and the lattice constant of doped BTO.Reuse & Permissions
Figure 3
Calculated formation energies for introducing a dopant (at the Ba or Ti site), and a dopant in the presence of adjacent O $_{vac}$ in BTO, for dopants in the (a) $3 d$ , (b) $4 d$ , and (c) $5 d$ series along with their neighboring Group IA to VA elements of the Periodic Table. Circle and square correspond to dopant at Ba and Ti site, respectively, while open (filled) symbols represent the dopant in presence (absence) of O $_{vac}$ .Reuse & Permissions
Figure 4
Calculated dopant formation energies as a function of variation in (a) the oxidation state, and (b) the ionic radius of the dopants relative to the host atom. (c) Same as (b), but with the dopants distinguished by their oxidation states (relative to that of the host atom the replace) using different symbols.Reuse & Permissions
Figure 5
Calculated total density of states of BTO doped at the (a) Ba site, and at the (b) Ti site, with the 3 $d$ transition and neighboring Group IA to VA elements. The highlighted panel shows the DOS of pure BTO. The vertical line corresponds to the Fermi level, obtained by alignment of electrostatic potentials of the defect supercell and pure BTO.Reuse & Permissions
Figure 6
Calculated dopant formation energies in the presence (open) and the absence (solid) of an O $_{vac}$ . Blue and red colors correspond to the dopant at the Ba and Ti sites, respectively. An asterisk (*) indicates cases in which the Ba site is favored in the absence an O $_{vac}$ , but the Ti site is favored in the presence of an O $_{vac}$ . The nominal oxidation state and the electrical nature of a dopant are depicted on the top horizontal axis.Reuse & Permissions

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