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Title: Site identity and importance in cosubstituted bixbyite In 2O 3

Abstract

The bixbyite structure of In 2O 3 has two nonequivalent, 6-coordinate cation sites and, when Sn is doped into In 2O 3, the Sn prefers the “b-site” and produces a highly conductive material. When divalent/tetravalent cation pairs are cosubstituted into In 2O 3, however, the conductivity increases to a lesser extent and the site occupancy is less understood. We examine the site occupancy in the Mg xIn 2–2xSn xO 3 and Zn xIn 2–2xSn xO 3 systems with high resolution X-ray and neutron diffraction and density functional theory computations, respectively. In these sample cases and those that are previously reported in the M xIn 2–2xSn xO 3 (M = Cu, Ni, or Zn) systems, the solubility limit is greater than 25%, ensuring that the b-site cannot be the exclusively preferred site as it is in Sn:In 2O 3. Prior to this saturation point, we report that the M 2+ cation always has at least a partial occupancy on the d-site and the Sn 4+ cation has at least a partial occupancy on the b-site. The energies of formation for these configurations are highly favored, and prefer that the divalent and tetravalent substitutes are adjacent in the crystal lattice, which suggestsmore » short range ordering. Diffuse reflectance and 4-point probe measurements of Mg xIn 2–xSn xO 3 demonstrate that it can maintain an optical band gap >2.8 eV while surpassing 1000 S/cm in conductivity. Furthermore, understanding how multiple constituents occupy the two nonequivalent cation sites can provide information on how to optimize cosubstituted systems to increase Sn solubility while maintaining its dopant nature, achieving maximum conductivity.« less

Authors:
ORCiD logo [1];  [1];  [2];  [3];  [1];  [1]
  1. Northwestern Univ., Evanston, IL (United States)
  2. Osmaniye Korkut Ata Univ., Osmaniye (Turkey)
  3. Cukurova Univ., Adana (Turkey)
Publication Date:
Research Org.:
Northwestern Univ., Evanston, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1356105
Grant/Contract Number:
FG02-08ER46536
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Crystals
Additional Journal Information:
Journal Volume: 7; Journal Issue: 2; Journal ID: ISSN 2073-4352
Publisher:
MDPI
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; bixbyite; indium oxide; transparent conducting oxide

Citation Formats

Rickert, Karl, Harris, Jeremy, Sedefoglu, Nazmi, Kavak, Hamide, Ellis, Donald E., and Poeppelmeier, Kenneth R. Site identity and importance in cosubstituted bixbyite In2O3. United States: N. p., 2017. Web. doi:10.3390/cryst7020047.
Rickert, Karl, Harris, Jeremy, Sedefoglu, Nazmi, Kavak, Hamide, Ellis, Donald E., & Poeppelmeier, Kenneth R. Site identity and importance in cosubstituted bixbyite In2O3. United States. doi:10.3390/cryst7020047.
Rickert, Karl, Harris, Jeremy, Sedefoglu, Nazmi, Kavak, Hamide, Ellis, Donald E., and Poeppelmeier, Kenneth R. Thu . "Site identity and importance in cosubstituted bixbyite In2O3". United States. doi:10.3390/cryst7020047. https://www.osti.gov/servlets/purl/1356105.
@article{osti_1356105,
title = {Site identity and importance in cosubstituted bixbyite In2O3},
author = {Rickert, Karl and Harris, Jeremy and Sedefoglu, Nazmi and Kavak, Hamide and Ellis, Donald E. and Poeppelmeier, Kenneth R.},
abstractNote = {The bixbyite structure of In2O3 has two nonequivalent, 6-coordinate cation sites and, when Sn is doped into In2O3, the Sn prefers the “b-site” and produces a highly conductive material. When divalent/tetravalent cation pairs are cosubstituted into In2O3, however, the conductivity increases to a lesser extent and the site occupancy is less understood. We examine the site occupancy in the MgxIn2–2xSnxO3 and ZnxIn2–2xSnxO3 systems with high resolution X-ray and neutron diffraction and density functional theory computations, respectively. In these sample cases and those that are previously reported in the MxIn2–2xSnxO3 (M = Cu, Ni, or Zn) systems, the solubility limit is greater than 25%, ensuring that the b-site cannot be the exclusively preferred site as it is in Sn:In2O3. Prior to this saturation point, we report that the M2+ cation always has at least a partial occupancy on the d-site and the Sn4+ cation has at least a partial occupancy on the b-site. The energies of formation for these configurations are highly favored, and prefer that the divalent and tetravalent substitutes are adjacent in the crystal lattice, which suggests short range ordering. Diffuse reflectance and 4-point probe measurements of MgxIn2–xSnxO3 demonstrate that it can maintain an optical band gap >2.8 eV while surpassing 1000 S/cm in conductivity. Furthermore, understanding how multiple constituents occupy the two nonequivalent cation sites can provide information on how to optimize cosubstituted systems to increase Sn solubility while maintaining its dopant nature, achieving maximum conductivity.},
doi = {10.3390/cryst7020047},
journal = {Crystals},
number = 2,
volume = 7,
place = {United States},
year = {Thu Feb 09 00:00:00 EST 2017},
month = {Thu Feb 09 00:00:00 EST 2017}
}

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  • The anion-deficient, fluorite-related structures of the manganese-based minerals bixbyite (Mn{sub 2}O{sub 3}), braunite (Mn{sub 7}SiO{sub 12}), braunite II (CaMn{sub 14}SiO{sub 24}) and parwelite (Mn{sub 10}Sb{sub 2}As{sub 2}Si{sub 2}O{sub 24}) are reinterpreted in terms of the coordination defect (CD) theory to gain new insights into their structural interrelationships. CDs are extended, octahedral defects centred by an anion vacancy and including its immediate atomic environment: it is represented as {open_square}M{sub 4}O{sub 6}, where the symbol {open_square} is the anion vacancy. The bixbyite motif is a CD dimer (two edge-sharing octahedra), and this motif repeats, by further edge-sharing, around the 2-fold screw axesmore » of the cubic structure. These same dimers are present in each of the other structures, but the presence of Si{sup 4+} in braunite and braunite II, together with that of other foreign cations such as As{sup 5+} and Sb{sup 5+} in parwelite, leads to different juxtapositions of these motifs. Moreover, the structure of braunite, Mn{sup 2+}(Mn{sup 3+}){sub 6}SiO{sub 12}, reflects the clustering of 12 Mn{sup 3+}-centred octahedra (MnO{sub 6}) around a central SiO{sub 4} tetrahedron to generate a structure for the [(Mn{sup 3+}){sub 6}SiO{sub 12}]{sup 2-} anion which is almost identical to that of the well-known cuboctahedral structure of the PO{sub 4}-centred heteropolytungstate anion, [(W{sup 6+}){sub 12}PO{sub 40}]{sup 3-}. The structure of braunite II, [Ca(Mn{sup 3+}){sub 14}SiO{sub 24}], is simply an intergrowth of slabs of bixbyite- and braunite-type structures, linked by the CaO{sub 8} cubes of the latter. Our various analyses of the reported structure of parwelite in terms of the only possible vacancy assignment have led to some apparent anomalies. We report briefly on these, and have decided to seek confirmation of the reported structure as a consequence. Despite the increasing complexity of these structures, there are clear and defining relationships in the distribution of CDs. The assumption of a close relationship to the fluorite parent in all these structures is based on the observation that the cation sub-lattices are essentially face-centred cubic, with the anions in the tetrahedral sites, so there is little variation from this between one structure and another. The cation contents, however, are very different in the four structures discussed here - a single cation species in bixbyite, two in the braunites and four in parwelite. This factor, and the topology of the CD arrangements, are structure-determining and confirm the close relationships between these four minerals. - Graphical abstract: The anion-deficient, fluorite-related structures of the manganese-based minerals bixbyite (Mn{sub 2}O{sub 3}), braunite (Mn{sub 7}SiO{sub 12}), braunite II (CaMn{sub 14}SiO{sub 24}) and parwelite (Mn{sub 10}Sb{sub 2}As{sub 2}Si{sub 2}O{sub 24}), are reinterpreted in terms of the Coordination Defect (CD) theory to gain new insights into their structural interrelationships. CDs are extended, defects centred by an anion vacancy and including its immediate atomic environment of 4 tetrahedrally coordinated metals and 6 octahedrally coordinated O atoms: it is represented as {open_square}M{sub 4}O{sub 6}, where the symbol {open_square} is the anion vacancy. The arrangement of {open_square}M{sub 4} tetrahedra in bixbyite is shown in the [111] projection.« less
  • An example for kinetic control of a solid-state phase transformation, in which the system evolves via the path with the lowest activation barrier rather than ending in the thermodynamically most favorable state, has been demonstrated. As a case study, the phase transitions of indium sesquioxide (In{sub 2}O{sub 3}) have been guided by theoretical calculations and followed in situ under high-pressure high-temperature conditions in multi-anvil assemblies. The corundum-type rh-In{sub 2}O{sub 3} has been synthesized from stable bixbyite-type c-In{sub 2}O{sub 3} in two steps: first generating orthorhombic Rh{sub 2}O{sub 3}-II-type o′-In{sub 2}O{sub 3} which is thermodynamically stable at 8.5 GPa/850 °C and,more » thereafter, exploiting the preferred kinetics in the subsequent transformation to the rh-In{sub 2}O{sub 3} during decompression. This synthesis strategy of rh-In{sub 2}O{sub 3} was confirmed ex situ in a toroid-type high-pressure apparatus at 8 GPa and 1100 °C. The pressure–temperature phase diagrams have been constructed and the stability fields of In{sub 2}O{sub 3} polymorphs and the crystallographic relationship between them have been discussed. - Graphical abstract: In situ energy-dispersive XRD patterns in multi-anvil assemblies show the sequence of phase transition c-In{sub 2}O{sub 3}→o′-In{sub 2}O{sub 3}→rh-In{sub 2}O{sub 3} under particular pressure and temperature conditions. The tick marks refer to the calculated Bragg positions of bixbyite-type (c-In{sub 2}O{sub 3}), Rh{sub 2}O{sub 3}-II-type (o–-In2O{sub 3}) and corundum-type (rh-In{sub 2}O{sub 3}). - Highlights: • The solid-state synthesis methods can be employed for obtaining metastable phases. • The phase transition of In{sub 2}O{sub 3} was guided by DFT calculations. • The phase transition of In{sub 2}O{sub 3} was followed in situ under HP–HT conditions. • Orthorhombic o′-In{sub 2}O{sub 3} polymorph was synthesized from c-In{sub 2}O{sub 3} at 8.5 GPa/850 °C. • Metastable rh-In{sub 2}O{sub 3} was obtained from o′-In{sub 2}O{sub 3} at 5.5 GPa during decompression.« less
  • A critical comparison of X-ray powder diffraction data, combined with experimental work, shows that {open_quotes}monoclinic B-type{close_quotes} La{sub 2}O{sub 3} and Pr{sub 2}O{sub 3} described in the literature are in fact rare earth silicates of the hexagonal apatite-type structure. A comparison of X-ray powder data reveals that both compounds are identical with La{sub 9.33}(SiO{sub 4}){sub 6}O{sub 2} and Pr{sub 9.33}(SiO{sub 4}){sub 6}O{sub 2}, respectively. This confirms the currently acknowledged stability diagram of the rare earth sesquioxides.
  • Ternary single crystalline bixbyite Pr{sub x}Y{sub 2-x}O{sub 3} films over the full stoichiometry range (x = 0-2) have been epitaxially grown on Si (111) with tailored electronic and crystallographic structure. In this work, we present a detailed study of their local atomic environment by extended X-ray absorption fine structure at both Y K and Pr L{sub III} edges, in combination with complementary high resolution x-ray diffraction measurements. The local structure exhibits systematic variations as a function of the film composition. The cation coordination in the second and third coordination shells changes with composition and is equal to the average concentration,more » implying that the Pr{sub x}Y{sub 2-x}O{sub 3} films are indeed fully mixed and have a local bixbyite structure with random atomic-scale ordering. A clear deviation from the virtual crystal approximation for the cation-oxygen bond lengths is detected. This demonstrates that the observed Vegard's law for the lattice variation as a function of composition is based microscopically on a more complex scheme related to local structural distortions which accommodate the different cation-oxygen bond lengths.« less