Substitutional Mechanisms and Structural Relaxations for Manganese in SrTiO3: Bridging the Concentration Gap for Point-Defect Metrology

• DOI: 10.1021/acs.chemmater.0c01082
• Publication Date: 2020-05-07T19:18:20Z
• Authors: Russell A. Maier; Eric Cockayne; Matthew Donohue; Giannantonio Cibin; Igor Levin
• Keywords: Ionic radius

The methodology for experimentally verifying the point-defect chemistry (site of substitution, valence, and charge-compensation mechanisms) in manganese-doped SrTiO3 ceramics is presented dilute nondilute dopant concentrations. Experimental theoretical techniques have strengths weaknesses depending upon defect types concentrations, so a combinatorial-characterization approach required. Using electron-paramagnetic resonance X-ray-absorption fine-structure measurements combined with density functional theory calculations, mechanisms local structural relaxations five unique manganese centers are identified. Mn4+, as an isovalent dopant, occupies octahedrally coordinated Ti sites without need charge compensation; its smaller ionic radius relative to accommodated by isotropic contraction [MnO6] octahedra. Mn3+ aliovalent that also favors octahedra exhibiting Jahn–Teller distortions. difference associated Mn3+Ti4+ substitution compensated formation oxygen vacancies. A more complex behavior observed Mn2+ species, which can occupy either Sr or on Sr/Ti ratio. effects Mn concentration high-temperature annealing site preference (i.e., vs Ti) negligible. species strongly off-centered relatively large cuboctahedral cages within framework. dynamic nature displacements these configurations confirmed using ab initio molecular dynamics simulations.