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Effects of octahedral tilting on the site of substitution of manganese in CaTiO3

DOI: 10.1016/j.actamat.2021.116688 DOI Help

Authors: Russell A. Maier (National Institute of Standards and Technology) , Kevin F. Garrity (National Institute of Standards and Technology) , Andrew Ozarowski (Florida State University) , Matthew P. Donohue (National Institute of Standards and Technology; University of Maryland) , Giannantonio Cibin (Diamond Light Source) , Igor Levin (National Institute of Standards and Technology)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acta Materialia , VOL 4

State: Published (Approved)
Published: January 2021
Diamond Proposal Number(s): 16478

Abstract: Electron paramagnetic resonance (EPR) and X-ray absorption fine structure measurements were combined with first principles calculations to investigate the substitutional behavior of Mn ions in perovskite CaTiO3 ceramics. While transition-metal dopants in perovskite-structured oxides often act as aliovalent defects, Mn in CaTiO3 is amphoteric and regardless of processing conditions concurrently occupies both Ca and Ti sites as Mn2+ and Mn4+, respectively. Contrary to the behavior of Mn in SrTiO3 and BaTiO3, which exhibit larger geometric perovskite tolerance factors, in CaTiO3, it is determined that Mn2+ prefers A-site substitution. Density functional theory (DFT) calculations provide insight to the unique defect chemistry of Mn-doped CaTiO3 compared to SrTiO3 and BaTiO3, highlighting the role of octahedral rotations which accommodate ionic size mismatch between the larger host and smaller dopant cations on the cuboctahedral sites without significant dopant-ion displacements. Superposition models of the EPR zero-field splitting parameters for multiple types of Mn defect centers were considered based on the structural parameters of DFT calculations, and these results, combined with the EPR, DFT, and X-ray absorption analysis, were used to determine the point defect substitution mechanisms of Mn-CaTiO3.

Journal Keywords: Point Defect; Perovskite; EPR; DFT; XAFS

Subject Areas: Materials

Instruments: B18-Core EXAFS

Added On: 27/01/2021 09:23

Discipline Tags:

Ceramics Chemistry Materials Science Inorganic Chemistry Perovskites Metallurgy

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS) Extended X-ray Absorption Fine Structure (EXAFS)