Phase stabilisation of hexagonal barium titanate doped with transition metals: A computational study

• Published in: Journal of solid state chemistry 2013-04, Vol.200, p.310-316
• Main Authors: Dawson, J.A., Freeman, C.L., Harding, J.H., Sinclair, D.C.
• Format: Article
• Language: English
• Subjects: BARIUM; Barium titanates; BaTiO3; BINDING ENERGY; Charge; CHARGE STATES; Compensation; Computer simulation; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Dielectric, piezoelectric, ferroelectric and antiferroelectric materials; Dielectrics, piezoelectrics, and ferroelectrics and their properties; DIMERS; DOPED MATERIALS; Doping; Exact sciences and technology; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; IRON IONS; Nickel; NICKEL IONS; OXIDATION; PEROVSKITES; Physics; SIMULATION; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; TITANATES; Titanium; TRANSITION ELEMENTS; Transition metal doping; Transition metals
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2013.01.043

Interatomic potentials recently developed for the modelling of BaTiO3 have been used to explore the stabilisation of the hexagonal polymorph of BaTiO3 by doping with transition metals (namely Mn, Co, Fe and Ni) at the Ti-site. Classical simulations have been completed on both the cubic and hexagonal polymorphs to investigate the energetic consequences of transition metal doping on each polymorph. Ti-site charge compensation mechanisms have been used for the multi-valent transition metal ions and cluster binding energies have been considered. Simulations show a significant energetic gain when doping occurs at Ti sites in the face sharing dimers (Ti2 sites) of the hexagonal polymorph compared with the doping of the cubic polymorph. This energetic difference between the two polymorphs is true for all transition metals tested and all charge states and in the case of tri- and tetra-valent dopants negative solution energies are found for the hexagonal polymorph suggesting actual polymorph stabilisation occurs with the incorporation of these ions as observed experimentally. Oxidation during incorporation of Ni2+ and Fe3+ ions has also been considered. The representation of the strongest binding energy clusters for tri-valent dopants—(a) Ti2/O1 cluster and (b) Ti2/O2 cluster. [Display omitted] ► Classical simulations show a significant energetic gain when doping occurs at Ti sites in the face sharing dimers (Ti2 sites) of the hexagonal polymorph compared with the doping of the cubic polymorph. ► This energetic difference between the two polymorphs is true for all transition metals tested and all charge states. ► In the case of tri- and tetra- valent dopants negative solution energies are found for the hexagonal polymorph suggesting actual polymorph stabilisation occurs with the incorporation of these ions.