High-frequency electron paramagnetic resonance investigation of Mn3+ centers in SrTiO3

Azamat, D. V.; Badalyan, A. G.; Dejneka, A.; Трепаков, В. А.; Jastrabı́k, L.

doi:10.1016/j.jpcs.2012.02.009

Cited by 16 publications

(17 citation statements)

References 32 publications

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“…The data in Figure show the previously reported Mn 2+ (246 MHz) and Mn 4+ (210 MHz) resonance signals assigned to the Mn″ Ti and

{Mn}_{Ti}^{\times}

defect centers, respectively . In Figure , a new, unreported signal is shown for SrO‐rich samples with Sr/Ti > 1.001.…”

Section: Resultssupporting

confidence: 61%

“…For samples processed in air, the majority defects other than oxygen vacancies at room temperature should be Mn 3+ and Mn 4+ . However, in this study, as well as multiple EPR studies performed on manganese‐doped SrTiO 3 , the concentrations of Mn 2+ and Mn 4+ at room temperature are always of similar magnitude . According to Figure , if Mn 2+ and Mn 4+ both sit on the perovskite B ‐site, it should be nearly impossible to observe both defects simultaneously for any equilibrated state.…”

Section: Discussionsupporting

confidence: 46%

“…For rare‐earth ions, precise control of the site distribution in a perovskite lattice is difficult to achieve, and the literature consensus is that transition metal ions do not exhibit similar amphoteric behavior in perovskites . However, on the basis of the theoretical argument presented in Figure , we hypothesize that transition metal ions should be capable of occupying both sites.…”

Section: Introductionmentioning

confidence: 87%

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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 SrTiO₃

Maier

Johnston‐Peck

Donohue

2016

Adv Funct Materials

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8325wileyonlinelibrary.com materials contain trace impurities, and these impurities, even at parts-per-billion concentration, can control the electronic properties of the oxide. [1] Impurities and dopants take the form of fixed valence or redox-active ions. [3] Common fixed-valence ions have a full valence shell, like Al 3+ , Mg 2+ , Na + , K + , Sc 3+ , and Y 3+ , and the valence state of the ion is stable regardless of processing conditions. Most of these fixed valence ions are abundant in nature, making them common impurities in oxide materials. [1,2] Ions like Na + and K + commonly sit on the large 12-coordinated A-site, and ions like Mg 2+ and Al 3+ sit on the smaller B-site. Regardless of the site of substitution, these ions have less charge than the ions sitting on the intrinsic A and B-sites like Sr 2+ and Ti 4+ in SrTiO 3 , resulting in acceptor-type doping of the material. Acceptor doping most commonly results in ionic charge compensation mechanisms: oxygen vacancies (donor point defects) are introduced via surface exchange with the atmosphere followed by bulk ionic diffusion into the lattice during processing. [4] For materials containing these types of fixed-valence ions, oxygen vacancies are frozen-in at sub-processing temperatures at concentrations similar to the magnitude of the impurity or dopant. [1,2] This type of charge compensation mechanism is desired for applications that utilize the perovskite structure and its derivatives for solid oxide fuel cells, resistive switches, and thermoelectrics. [5][6][7][8][9][10][11] Conversely, large concentrations of oxygen vacancies are detrimental to the device reliability of perovskite dielectrics, ferroelectrics, multiferroics, and piezoelectrics. [12][13][14][15][16][17][18][19][20] Unlike fixed-valence impurities, redox-active ions like Fe 2+/3+/4+ or Mn 2+/3+/4+ have multiple accessible valence states. In contrast to fixed-valence acceptors, the oxygen vacancy concentration can be engineered in oxides with redox-active ions. Processing or post-processing annealing in the appropriate temperature/pO 2 environment can result in isovalent doping (i.e., Mn 4+ on a Ti 4+ site, oxygen vacancy concentration low) or aliovalent doping mechanisms (i.e., Mn 2+/3+ on a Ti 4+ site, oxygen vacancy concentration high). [2] As a result, incorporation of a redox-active ion into the lattice allows more control over the ionic conductivity of the sample. Equilibrating the system under different oxygen activities enables orders of magnitude changes in the oxygen vacancy concentration.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, ...

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“…The data in Figure show the previously reported Mn 2+ (246 MHz) and Mn 4+ (210 MHz) resonance signals assigned to the Mn″ Ti and

{Mn}_{Ti}^{\times}

defect centers, respectively . In Figure , a new, unreported signal is shown for SrO‐rich samples with Sr/Ti > 1.001.…”

Section: Resultssupporting

confidence: 61%

Section: Discussionsupporting

confidence: 46%

Section: Introductionmentioning

confidence: 87%

See 1 more Smart Citation

(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 SrTiO₃

Maier

Johnston‐Peck

Donohue

2016

Adv Funct Materials

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“…EPR-active species involving Mn ions in the +2, +3, and +4 oxidation states in SrTiO 3 have previously been reported (Müller, 1959; Serway et al, 1977; Azamat et al, 2012). However, Mn 3+ exhibits large zero-field splitting due to the S = 2 electronic spin state and thus, it is EPR-silent at conventional X-band frequencies (Azamat et al, 2012). The room temperature quantitative X-band EPR spectra of the Mn-doped SrTiO 3 samples are shown in Figure 3 as a function of reduction temperatures ranging from T red = 300–425°C.…”

Section: Resultsmentioning

confidence: 84%

Reversible Control of the Mn Oxidation State in SrTiO3 Bulk Powders

et al. 2019

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We demonstrate a low-temperature reduction method for exhibiting fine control over the oxidation state of substitutional Mn ions in strontium titanate (SrTiO 3 ) bulk powder. We employ NaBH 4 as the chemical reductant that causes significant changes in the oxidation state and oxygen vacancy complexation with Mn 2+ dopants at temperatures <350°C where lattice reduction is negligible. At higher reduction temperatures, we also observe the formation of Ti 3+ in the lattice by diffuse-reflectance and low-temperature electron paramagnetic resonance (EPR) spectroscopy. In addition to Mn 2+ , Mn 4+ , and the Mn 2+ complex with an oxygen vacancy, we also observe a sharp resonance in the EPR spectrum of heavily reduced Mn-doped SrTiO 3 . This sharp signal is tentatively assigned to surface superoxide ion that is formed by the surface electron transfer reaction between Ti 3+ and O 2 . The ability to control the relative amounts of various paramagnetic defects in SrTiO 3 provides many possibilities to study in a model system the impact of tunable dopant-defect interactions for spin-based electronic applications or visible-light photocatalysis.

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“…For instance, donor trivalent dopants Er, Sm, La, Y, Gd, Nd, Sm, Eu, Dy, Tm, Yb, Lu, and Pr have been studied at A ‐site (replacing Sr 2+ ) in STO for various applications such as ferroelectrics, magnetism, oxygen sensors, and SOFC anode materials. On the other hand, samples with addition of acceptor trivalent dopants Y, Fe, Mn, Al, Cr, Sm, and Pr at B ‐site in STO were investigated for ionic conductivity applications as the charge compensating mechanism is the formation of oxygen vacancies. The aforementioned studies underscore the significance of understanding the role of trivalent dopants in STO.…”

Section: Introductionmentioning

confidence: 99%

Influence of Chemistry and Misfit Dislocation Structure on Dopant Segregation at Complex Oxide Heterointerfaces

Dholabhai

Martínez

Uberuaga

2018

Advcd Theory and Sims

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Complex oxide heterostructures and thin films have emerged as promising candidates for diverse applications. Lattice mismatch between the two oxides lead to the formation of misfit dislocations, which influence vital material features. Trivalent dopant segregation to misfit dislocations at semi-coherent oxide heterointerfaces, while not well understood, is anticipated to impact interface-governed properties. Here, atomistic simulations elucidating the influence of misfit dislocations on dopant segregation at SrTiO 3 /MgO heterointerfaces are reported. SrO-and TiO 2 -terminated interfaces that have differing misfit dislocation structure were considered for trivalent dopants segregation. At SrO-terminated interface, dopants tend to segregate toward but not precisely to the heterointerface, whereas at TiO 2 -terminated interface, dopants exhibit a thermodynamic preference to accumulate at the heterointerface. Most favorable segregation sites at SrO-terminated interface are located within the coherent terrace, whereas those at TiO 2 -terminated interface are at misfit dislocation intersections. Atomic layer chemistry and the resulting misfit dislocation structure at the heterointerface, along with concomitant strain at the heterointerface due to mismatched dopants, play a critical role in influencing the observed trends for dopant segregation. Overall, the present results offer a fundamental atomic scale perspective of dopant behavior at semi-coherent complex oxide heterointerfaces and the interplay between dopant chemistry, interface chemistry, and misfit dislocation structure.

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High-frequency electron paramagnetic resonance investigation of Mn3+ centers in SrTiO3

Cited by 16 publications

References 32 publications

(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 SrTiO₃

(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 SrTiO₃

Reversible Control of the Mn Oxidation State in SrTiO3 Bulk Powders

Influence of Chemistry and Misfit Dislocation Structure on Dopant Segregation at Complex Oxide Heterointerfaces

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High-frequency electron paramagnetic resonance investigation of Mn3+ centers in SrTiO3

Cited by 16 publications

References 32 publications

(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 SrTiO3

(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 SrTiO3

Reversible Control of the Mn Oxidation State in SrTiO3 Bulk Powders

Influence of Chemistry and Misfit Dislocation Structure on Dopant Segregation at Complex Oxide Heterointerfaces

Contact Info

Product

Resources

About

(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 SrTiO₃

(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 SrTiO₃