THE IMPACT OF ACCEPTOR DOPANT MAGNESIUM AND OXYGEN VACANCY DEFECTS ON THE LATTICE OF BARIUM STRONTIUM TITANATE

ABSTRACT

The effects of defects on the local and long range lattice parameters of barium strontium titanate were examined with ab-initio, density function theory (DFT) models, and the theoretical results were experimentally verified. Magnesium was examined as a B-site acceptor dopant in conjunction with oxygen vacancy defects. DFT results indicated that the lattice length between nearest titanium atoms would contract when magnesium was introduced onto the titanium site; however, the long-range titanium-titanium length would expand, resulting in an average lattice expansion for low magnesium dopant concentrations. Oxygen vacancies caused an expansion of the local lattice constant, the degree of which was influenced by the local strontium to barium ratio. The experimental results verified the generally observed theoretical trends.

Keywords:

• DFT
• ab-initio
• BST
• magnesium oxide
• oxygen vacancy

ACKNOWLEDGMENTS

The authors would like to acknowledge the work done to support this research by Poran Joshi, Melanie Cole, Samuel G. Hirsch, Cliff Hubbard, Eric Ngo, and George R. Martin.

Notes

^a)Shell is defined relative to the Mg position in the (2×2×10) supercell