Crystal structure and electronic properties of bulk and thin film brownmillerite oxides

Young, Joshua; Rondinelli, James M.

doi:10.1103/physrevb.92.174111

Cited by 79 publications

(71 citation statements)

References 58 publications

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“…Our calculations are based on VASP's implementation [21] of density functional theory with the projector augmented waves method [22] parameterization was used to describe the exchange-correlation, which is more suited to describe solids' properties [20,[24][25][26][27]. Plane waves with kinetic energy cutoff of 500 eV were used to expand the wavefunctions, with larger cutoff of 600 eV leading to changes of ~ 0.05 eV in the formation energies.…”

Section: Methodsmentioning

confidence: 99%

Sc and Nb dopants in SrCoO3 modulate electronic and vacancy structures for improved water splitting and SOFC cathodes

Tahini

Tan

Zhou

et al. 2017

Energy Storage Materials

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SrCoO 3 is a promising material in the field of electrocatalysis. Difficulties in synthesising the material in its cubic phase have been overcome by doping it with Sc and Nb ions [Mater. Horiz. 2015, 2, 495-501]. Using ab initio calculations and special quasi random structures we undertake a systematic study of these dopants in order to elucidate the effect of doping on electronic structure of the SrCoO 3 host and the formation of oxygen vacancies. We find that while the overall electronic structure of SrCoO 3 is preserved, increasing the Sc fraction leads to a decrease of electrical conductivity, in agreement with earlier experimental work. For low Sc and Nb doping fractions we find that the oxygen vacancy formation increases relative to undoped SrCoO 3 . However, as the dopants concentration is increased the vacancy formation energy drops significantly, indicating a strong tendency to accommodate high concentration of oxygen vacancies and hence non-stoichiometry. This is explained based on the electronic instabilities caused by the presence of Sc ions which weakens the B-O interactions as well as the increased degree of electron delocalization on the oxygen sublattice. Sc dopants also shift the p-band centre closer to the Fermi level, which can be associated with experimentally reported improvements in oxygen evolution reactions. These findings provide crucial baseline information for the design of better electrocatalysts for oxygen evolution reactions as well as fuel-cell cathode materials.

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Section: Methodsmentioning

confidence: 99%

Sc and Nb dopants in SrCoO3 modulate electronic and vacancy structures for improved water splitting and SOFC cathodes

Tahini

Tan

Zhou

et al. 2017

Energy Storage Materials

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“…The FeO 4 tetrahedral chains are directed along the a o axis. The epitaxial strain from the substrate and the thermodynamic parameters during the growth can be employed to determine the orientation of the brownmillerite crystal and FeO 4 tetrahedral chains . Using pulsed laser epitaxy, we fabricated single‐crystalline epitaxial SrFeO 2.5 thin films on cubic (Nb‐doped) SrTiO 3 substrates with the following orientation relationships: SrFeO 2.5 (

\overset{1}{true}

01) o //SrTiO 3 (001) c and SrFeO 2.5 [010] o //SrTiO 3 [100] c (subscript “c” denotes cubic) (Figure b,c).…”

Section: Classification Of Transition‐metal Oxide Ferroelectrics Basementioning

confidence: 99%

A Room‐Temperature Ferroelectric Ferromagnet in a 1D Tetrahedral Chain Network

et al. 2019

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conventional displacive-type ferroelectricity in a 3D space, e.g., relative shifts of the transition-metal cation or lone-pair ions, geometric ferroelectricity does not require strong hybridization between the transition-metal and oxygen ions. [7][8][9][10] This removes the constraint of d 0 -ness of the transition-metal ion, thereby allowing magnetism to coexist with ferroelectricity. In addition, while the soft-phonon mode at the Brillouin zone-center manifests displacive ferroelectricity, [11,12] the collective distortion of the 2D network results in zone-boundary soft-phonon modes for geometric ferroelectrics. [3] What about in 1D networks? Spatial inversion symmetry breaking can be intuitively envisioned in 1D chain networks as well, especially with an MO 4 tetrahedral unit. An MO 4 tetrahedron has one of the lowest symmetries among the MO x polyhedra and can form corner-shared 1D chains within crystals (Table 1). More interestingly, a collective distortion of the 1D network can introduce an unconventional polar state resulting from both the displacement of ions and the rotation of the tetrahedra.Ferroelectricity occurs in crystals with broken spatial inversion symmetry. In conventional perovskite oxides, concerted ionic displacements within a 3D network of transition-metal-oxygen polyhedra (MO x ) manifest spontaneous polarization. Meanwhile, some 2D networks of MO x foster geometric ferroelectricity with magnetism, owing to the distortion of the polyhedra. Because of the fundamentally different mechanism of ferroelectricity in a 2D network, one can further challenge an uncharted mechanism of ferroelectricity in a 1D channel of MO x and estimate its feasibility. Here, ferroelectricity and coupled ferromagnetism in a 1D FeO 4 tetrahedral chain network of a brownmillerite SrFeO 2.5 epitaxial thin film are presented. The result provides a new paradigm for designing low-dimensional MO x networks, which is expected to benefit the realization of macroscopic ferro-ordering materials including ferroelectric ferromagnets. Multiferroic MaterialsComplex transition-metal oxides can be analytically viewed as a network of transition-metal-oxygen polyhedra (MO x ) ( Table 1). A collective distortion of such networks in a (quasi) 2D space can lead to inversion symmetry breaking and geometric ferroelectricity through trilinear coupling among distortions and electric polarization. [1][2][3][4][5][6] In comparison with the

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“…Brownmillerite oxides such as SrFeO 2.5 (BM-SFO) are of particular interest due to their wide range of physical properties including thermoelectricity, fast oxygen-ion transport, catalysis, and topotactic phase transformation at low temperatures 15,16 . These properties allow BM oxides to be exploited for extensive applications such as in solid-oxide fuel cells, sensors, membranes for oxygen separation, photon catalysis, and memristors [17][18][19] .…”

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confidence: 99%

Effects of the Heterointerface on the Growth Characteristics of a Brownmillerite SrFeO2.5 Thin Film Grown on SrRuO3 and SrTiO3 Perovskites

Jo¹,

Nallagatlla

Acharya

et al. 2020

Sci Rep

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Manipulation of the heterointerfacial structure and/or chemistry of transition metal oxides is of great interest for the development of novel properties. However, few studies have focused on heterointerfacial effects on the growth characteristics of oxide thin films, although such interfacial engineering is crucial to determine the growth dynamics and physical properties of oxide heterostructures. Herein, we show that heterointerfacial effects play key roles in determining the growth process of oxide thin films by overcoming the simple epitaxial strain energy. Brownmillerite (SrFeO 2.5 ; BM-SFO) thin films are epitaxially grown along the b-axis on both SrTiO 3 (001) and SrRuO 3 / SrTiO 3 (001) substrates, whereas growth along the a-axis is expected from conventional epitaxial strain effects originating from lattice mismatch with the substrates. Scanning transmission electron microscopy measurements and first principles calculations reveal that these peculiar growth characteristics of BM-SFO thin films originate from the heterointerfacial effects governed by their distinct interfacial structures. These include octahedral connectivity between dissimilar oxides containing different chemical species and a peculiar transition layer for BM-SFO/SrRuO 3 /SrTiO 3 (001) and BM-SFO/SrTiO 3 (001) heterostructures, respectively. These effects enable subtle control of the growth process of oxide thin films and could facilitate the fabrication of novel functional devices.

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Crystal structure and electronic properties of bulk and thin film brownmillerite oxides

Cited by 79 publications

References 58 publications

Sc and Nb dopants in SrCoO3 modulate electronic and vacancy structures for improved water splitting and SOFC cathodes

Sc and Nb dopants in SrCoO3 modulate electronic and vacancy structures for improved water splitting and SOFC cathodes

A Room‐Temperature Ferroelectric Ferromagnet in a 1D Tetrahedral Chain Network

Effects of the Heterointerface on the Growth Characteristics of a Brownmillerite SrFeO2.5 Thin Film Grown on SrRuO3 and SrTiO3 Perovskites

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