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(Magic Dopant) Amphoteric Behavior of a Redox‐Active Transition Metal Ion in a Perovskite Lattice: New Insights on the Lattice Site Occupation of Manganese in SrTiO 3
Author(s) -
Maier Russell A.,
JohnstonPeck Aaron C.,
Donohue Matthew P.
Publication year - 2016
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201602156
Subject(s) - materials science , manganese , dopant , electron paramagnetic resonance , inorganic chemistry , stoichiometry , redox , valence (chemistry) , transition metal , perovskite (structure) , doping , crystallography , chemistry , nuclear magnetic resonance , catalysis , organic chemistry , biochemistry , physics , optoelectronics , metallurgy
It is demonstrated that a transition metal redox‐active ion can exhibit amphoteric dopant substitution in the SrTiO 3 perovskite lattice. In stoichiometric SrTiO 3 , the manganese dopant is preferably accommodated through isovalent substitution as Mn 2+ on the strontium site and as Mn 4+ on the titanium site. Previous studies have suggested that either type of substitution is possible for compositions with tailored Sr/Ti stoichiometry. Using electron paramagnetic resonance (EPR) spectroscopy, the site occupancy of dilute concentrations of manganese is investigated in SrTiO 3 as a function of the Sr/Ti ratio. The tuned Sr/Ti ratio can be used to manipulate the nature of the manganese substitution, and it is shown that Sr‐rich compositions (Sr/Ti > 1.001) processed in air result in B ‐site isovalent doping. For B ‐site substituted manganese ions, a new EPR signal for aliovalent Mn 2+ is observed in compositions annealed under reducing atmosphere. The concentration of oxygen vacancies observed with EPR is also shown to depend on the Sr/Ti stoichiometry. With improved control over the site of substitution and valence state, doping with a transition metal redox‐active ion may facilitate the ability to engineer new electronic functionality into the perovskite lattice.