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Title: Characterization of ordering in A-site deficient perovskite Ca 1–xLa 2x/3TiO 3 using STEM/EELS

Abstract

The vacancy ordering behavior of an A-site deficient perovskite system, Ca 1–xLa 2x/3TiO 3, was studied using atomic resolution scanning transmission electron microscopy (STEM) in conjunction with electron energy-loss spectroscopy (EELS), with the aim of determining the role of A-site composition changes. At low La content (x = 0.2), adopting Pbnm symmetry, there was no indication of long-range ordering. Domains, with clear boundaries, were observed in bright-field (BF) imaging, but were not immediately visible in the corresponding high-angle annular dark-field (HAADF) image. These boundaries, with the aid of displacement maps from A-site cations in the HAADF signal, are shown to be tilt boundaries. At the La-rich end of the composition (x = 0.9), adopting Cmmm symmetry, long-range ordering of vacancies and La 3+ ions was observed, with alternating La-rich and La-poor layers on (001)p planes, creating a double perovskite lattice along the c axis. These highly ordered domains can be found isolated within a random distribution of vacancies/La 3+, or within a large population, encompassing a large volume. In regions with a high number density of double perovskite domains, these highly ordered domains were separated by twin boundaries, with 90° or 180° lattice rotations across boundaries. In conclusion, the occurrencemore » and characteristics of these ordered structures are discussed and compared with similar perovskite systems.« less

Authors:
 [1];  [2];  [2];  [3];  [4];  [5];  [1];  [1];  [1];  [6]
  1. Univ. of Oxford, Oxford (United Kingdom)
  2. SuperSTEM Lab., Warrington (United Kingdom)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  4. Univ. of Sheffield, Sheffield (United Kingdom); Univ. of Liverpool, Liverpool (United Kingdom)
  5. Univ. of Sheffield, Sheffield (United Kingdom)
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1328524
Grant/Contract Number:
AC05-00OR22725; AC02-05CH11231
Resource Type:
Journal Article: Published Article
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 55; Journal Issue: 19; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Danaie, Mohsen, Kepaptsoglou, Demie, Ramasse, Quentin M., Ophus, Colin, Whittle, Karl R., Lawson, Sebastian M., Pedrazzini, Stella, Young, Neil P., Bagot, Paul A. J., and Edmondson, Philip D. Characterization of ordering in A-site deficient perovskite Ca1–xLa 2x/3TiO3 using STEM/EELS. United States: N. p., 2016. Web. doi:10.1021/acs.inorgchem.6b02087.
Danaie, Mohsen, Kepaptsoglou, Demie, Ramasse, Quentin M., Ophus, Colin, Whittle, Karl R., Lawson, Sebastian M., Pedrazzini, Stella, Young, Neil P., Bagot, Paul A. J., & Edmondson, Philip D. Characterization of ordering in A-site deficient perovskite Ca1–xLa 2x/3TiO3 using STEM/EELS. United States. doi:10.1021/acs.inorgchem.6b02087.
Danaie, Mohsen, Kepaptsoglou, Demie, Ramasse, Quentin M., Ophus, Colin, Whittle, Karl R., Lawson, Sebastian M., Pedrazzini, Stella, Young, Neil P., Bagot, Paul A. J., and Edmondson, Philip D. 2016. "Characterization of ordering in A-site deficient perovskite Ca1–xLa 2x/3TiO3 using STEM/EELS". United States. doi:10.1021/acs.inorgchem.6b02087.
@article{osti_1328524,
title = {Characterization of ordering in A-site deficient perovskite Ca1–xLa 2x/3TiO3 using STEM/EELS},
author = {Danaie, Mohsen and Kepaptsoglou, Demie and Ramasse, Quentin M. and Ophus, Colin and Whittle, Karl R. and Lawson, Sebastian M. and Pedrazzini, Stella and Young, Neil P. and Bagot, Paul A. J. and Edmondson, Philip D.},
abstractNote = {The vacancy ordering behavior of an A-site deficient perovskite system, Ca1–xLa2x/3TiO3, was studied using atomic resolution scanning transmission electron microscopy (STEM) in conjunction with electron energy-loss spectroscopy (EELS), with the aim of determining the role of A-site composition changes. At low La content (x = 0.2), adopting Pbnm symmetry, there was no indication of long-range ordering. Domains, with clear boundaries, were observed in bright-field (BF) imaging, but were not immediately visible in the corresponding high-angle annular dark-field (HAADF) image. These boundaries, with the aid of displacement maps from A-site cations in the HAADF signal, are shown to be tilt boundaries. At the La-rich end of the composition (x = 0.9), adopting Cmmm symmetry, long-range ordering of vacancies and La3+ ions was observed, with alternating La-rich and La-poor layers on (001)p planes, creating a double perovskite lattice along the c axis. These highly ordered domains can be found isolated within a random distribution of vacancies/La3+, or within a large population, encompassing a large volume. In regions with a high number density of double perovskite domains, these highly ordered domains were separated by twin boundaries, with 90° or 180° lattice rotations across boundaries. In conclusion, the occurrence and characteristics of these ordered structures are discussed and compared with similar perovskite systems.},
doi = {10.1021/acs.inorgchem.6b02087},
journal = {Inorganic Chemistry},
number = 19,
volume = 55,
place = {United States},
year = 2016,
month = 9
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1021/acs.inorgchem.6b02087

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  • The vacancy ordering behavior of an A-site deficient perovskite system, Ca 1–xLa 2x/3TiO 3, was studied using atomic resolution scanning transmission electron microscopy (STEM) in conjunction with electron energy-loss spectroscopy (EELS), with the aim of determining the role of A-site composition changes. At low La content (x = 0.2), adopting Pbnm symmetry, there was no indication of long-range ordering. Domains, with clear boundaries, were observed in bright-field (BF) imaging, but were not immediately visible in the corresponding high-angle annular dark-field (HAADF) image. These boundaries, with the aid of displacement maps from A-site cations in the HAADF signal, are shown tomore » be tilt boundaries. At the La-rich end of the composition (x = 0.9), adopting Cmmm symmetry, long-range ordering of vacancies and La 3+ ions was observed, with alternating La-rich and La-poor layers on (001)p planes, creating a double perovskite lattice along the c axis. These highly ordered domains can be found isolated within a random distribution of vacancies/La 3+, or within a large population, encompassing a large volume. In regions with a high number density of double perovskite domains, these highly ordered domains were separated by twin boundaries, with 90° or 180° lattice rotations across boundaries. In conclusion, the occurrence and characteristics of these ordered structures are discussed and compared with similar perovskite systems.« less
  • The crystal structure of new A-site deficient La{sub 5/3}MgTaO{sub 6} perovskite was investigated by neutron, X-ray and electron diffraction. Neutron and X-ray powder diffraction spectra were refined in the monoclinic I2/m space group, with the parameters of the unit cell a=5.6304(2)A, b=5.6226(2)A, c=7.9434(2)A and {beta}=90.04(1){sup o}. This structural model presumes a random distribution of the vacancies and takes into account both a rock salt-type Mg{sup 2+}/Ta{sup 5+} cation ordering and a{sup -}a{sup -}c{sup 0} configuration of the octahedral tilting. Electron diffraction showed that the crystal structure is more complex at the local level due to a short-range vacancy ordering. Thismore » observation in combination with the symmetry analysis leads to the conclusion that the C2/m symmetry with 2{radical}2a{sub p}x2{radical}2a{sub p}x2a{sub p} supercell is more adequate for the description of the crystal structure in the local level. Dielectric measurements performed in a wide frequency range were correlated with the crystal structure and compared with other ordered double perovskites. Far-infrared spectroscopy was used to characterize the lattice contribution to the dielectric response at the microwave frequencies. The complex dielectric function was evaluated and extrapolated down to the gigahertz range. The effect of the vacancies on the intrinsic dielectric losses is discussed based on the spatial phonon correlation model.« less
  • Highlights: • Eu{sup 3+}-doped CaZrO{sub 3}-based compounds were synthesized by the solid state reaction. • PL emission intensity at 614 nm was changed by the second dopant cations. • The site substituted by Eu{sup 3+} cations was investigated by using XRD and ALCHEMI technique. • The dominant Eu{sup 3+} substitution site was found as the B site (Zr{sup 4+}) in the CaZrO{sub {sup 3}}. • The dominant Eu{sup 3+} substitution site could be strongly influenced by the co-dopants. - Abstract: Eu{sup 3+}-doped CaZrO{sub 3}, SrZrO{sub 3}, and Mg{sup 2+}- or Sr{sup 2+}-co-doped CaZrO{sub 3} were synthesized by conventional solid statemore » reaction and their photoluminescence (PL) properties were characterized. The Eu{sup 3+}-doped CaZrO{sub 3}-based compounds exhibited characteristic emissions of Eu{sup 3+} (f–f transition). The intensity of the main PL emission peak at 614 nm increased with Mg{sup 2+} co-doping, while it decreased with the amount of co-doped Sr{sup 2+}. The site substituted by Eu{sup 3+} cations in the CaZrO{sub 3}-based compounds was investigated by X-ray diffraction analysis and energy-dispersive X-ray analysis based on the electron channeling effects in transmission electron microscopy. The Eu{sup 3+} cations were determined to occupy mainly the B site (Zr{sup 4+}) in CaZrO{sub 3}. The dominant Eu{sup 3+} substitution site was also strongly influenced by the co-dopant, and the ionic radius of the co-dopant was identified as an important factor that determines the dominant Eu{sup 3+} substitution site.« less
  • The new vacancy ordered perovskite-type compound Ba{sub 3}Fe{sub 3}O{sub 7}F (BaFeO{sub 2.33}F{sub 0.33}) was prepared by topochemical low-temperature fluorination of Ba{sub 2}Fe{sub 2}O{sub 5} (BaFeO{sub 2.5}) using stoichiometric amounts of polyvinylidene difluoride (PVDF). The vacancy order was found to be unique so far for perovskite compounds, and the connectivity pattern can be explained by the formula Ba{sub 3}(FeX{sub 6/2}) (FeX{sub 5/2}) (FeX{sub 3/2}X{sub 1/1}), with X=O/F. Mössbauer measurements were used to confirm the structural analysis and agree with the presence of Fe{sup 3+} in the above mentioned coordination environments. Group–subgroup relationships were used to build a starting model for themore » structure solution and to understand the relationship to the cubic perovskite structure. Furthermore, a comparison of a variety of vacancy-ordered iron-containing perovskite-type structures is given, highlighting the factors which favour one structure type over the other depending on the composition. - Graphical abstract: The crystal structure of Ba{sub 3}Fe{sub 3}O{sub 7}F in comparison to other perovskite type ferrites. - Highlights: • The crystal structure of Ba{sub 3}Fe{sub 3}O{sub 7}F in comparison to other perovskite type ferrites. • Ba{sub 3}Fe{sub 3}O{sub 7}F was synthesized by low temperature fluorination of Ba{sub 2}Fe{sub 2}O{sub 5}. • Ba{sub 3}Fe{sub 3}O{sub 7}F shows a unique vacancy order not found for other perovskite type compounds. • The structure of Ba{sub 3}Fe{sub 3}O{sub 7}F was solved using group–subgroup relationships. • A systematic comparison to other ferrite type compounds reveals structural similarities and differences. • The A-site coordination of the cation is shown to play an important role for the type of vacancy order found.« less
  • A solid solution system of the double perovskite La{sub 2/3}TiO{sub 3} and the GdFeO{sub 3}-type perovskite CaTiO{sub 3}, (1{minus})xCaTiO{sub 3}-xLa{sub 2/3}TiO{sub 3} has been prepared to investigate the crystal structure and the dielectric properties. In this system, the structure changed from pseudo-cubic perovskite to tetragonal double perovskite at x{approx}0.7, and to orthorhombic double perovskite at x{approx}0.9. Microwave dielectric measurement showed a decrease in dielectric constant and temperature coefficient of the resonant frequency and an increase in Q value with increasing x. The sample with x{approx}0.96 showed excellent microwave characteristics, especially high Q(2700) along with high {var_epsilon}{sub r} at 10 GHz.more » In the low frequency dielectric measurement, dielectric relaxation could be observed in the composition range x{le}0.3. The dielectric relaxation showed strikingly different behaviors depending on the annealing process in oxygen after sintering.« less