First principles study of Ca in BaTiO₃ and Bi_0.5Na_0.5TiO₃

Abstract

BaTiO₃–Bi_0.5Na_0.5TiO₃ is one of the promising candidates as a high-temperature relaxor with a high Curie temperature and several preferred dielectric characteristics. It has been found experimentally for a long time that adding calcium to BaTiO₃–Bi_0.5Na_0.5TiO₃ improves its temperature characteristic of the capacitance [J. Electron. Mater. 39, 2471]. In this study, Calcium (Ca) defects in perovskite BaTiO₃ and Bi_0.5Na_0.5TiO₃ have been studied based on first-principles calculations. In both BaTiO₃ and Bi_0.5Na_0.5TiO₃, our calculations showed that Ca atom energetically prefers to substitute for the cations, that is Ba, Bi, Na and Ti, depending on the growth conditions. In most cases, Ca predominantly substitutes on the A-site without providing additional electrical carriers (serve as either neutral defects or self-compensating defects). The growth conditions where Ca can be forced to substitute for B-site (with limited amount) and the conditions where Ca can be forced to serve as an acceptor are identified. Details of the local structures, formation energies and electronic properties of these Ca defects are reported.

Keywords:

• BaTiO₃
• (Bi_0.5Na_0.5)TiO₃
• perovskite oxides
• first-principles calculations

Acknowledgements

Computations were carried out at the Synchrotron Light Research Institute (Public Organization), Thailand. We thank Prof. Walter R.L. Lambrecht for useful discussions and suggestions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials. One of the authors (IF) was partially supported by the Development and Promotion of Science and Technology Talents Project (DPST, Thailand).