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Title: Reduction of Ln 2 Ti 2 O 7 Layered Perovskites: A Survey of the Anionic Lattice, Electronic Features, and Potentials

Authors:
; ; ; ORCiD logo; ; ; ; ORCiD logo; ; ORCiD logo
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
FOREIGN
OSTI Identifier:
1352264
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 29; Journal Issue: 3
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Pussacq, Tanguy, Kabbour, Houria, Colis, Silviu, Vezin, Hervé, Saitzek, Sébastien, Gardoll, Olivier, Tassel, Cédric, Kageyama, Hiroshi, Laberty Robert, Christel, and Mentré, Olivier. Reduction of Ln 2 Ti 2 O 7 Layered Perovskites: A Survey of the Anionic Lattice, Electronic Features, and Potentials. United States: N. p., 2017. Web. doi:10.1021/acs.chemmater.6b03808.
Pussacq, Tanguy, Kabbour, Houria, Colis, Silviu, Vezin, Hervé, Saitzek, Sébastien, Gardoll, Olivier, Tassel, Cédric, Kageyama, Hiroshi, Laberty Robert, Christel, & Mentré, Olivier. Reduction of Ln 2 Ti 2 O 7 Layered Perovskites: A Survey of the Anionic Lattice, Electronic Features, and Potentials. United States. doi:10.1021/acs.chemmater.6b03808.
Pussacq, Tanguy, Kabbour, Houria, Colis, Silviu, Vezin, Hervé, Saitzek, Sébastien, Gardoll, Olivier, Tassel, Cédric, Kageyama, Hiroshi, Laberty Robert, Christel, and Mentré, Olivier. Tue . "Reduction of Ln 2 Ti 2 O 7 Layered Perovskites: A Survey of the Anionic Lattice, Electronic Features, and Potentials". United States. doi:10.1021/acs.chemmater.6b03808.
@article{osti_1352264,
title = {Reduction of Ln 2 Ti 2 O 7 Layered Perovskites: A Survey of the Anionic Lattice, Electronic Features, and Potentials},
author = {Pussacq, Tanguy and Kabbour, Houria and Colis, Silviu and Vezin, Hervé and Saitzek, Sébastien and Gardoll, Olivier and Tassel, Cédric and Kageyama, Hiroshi and Laberty Robert, Christel and Mentré, Olivier},
abstractNote = {},
doi = {10.1021/acs.chemmater.6b03808},
journal = {Chemistry of Materials},
number = 3,
volume = 29,
place = {United States},
year = {Tue Jan 24 00:00:00 EST 2017},
month = {Tue Jan 24 00:00:00 EST 2017}
}
  • Neutron powder diffraction data of the oxides Ln{sub 2}Ba{sub 2}Cu{sub 2}Ti{sub 2}O{sub 11} (Ln = La, Nd) are presented and analyzed by means of Rietveld profile refinements. These data confirm the existence, in both cases, of a tetragonal superstructure based on a quadrupole perovskite (a{sub p} x a{sub p} x 4a{sub p}). Whereas the Nd derivative presents complete long range order of Cu/Ti, Ln/Ba, and oxygen vacancies, in the lanthanum derivative this order is only partial. 9 refs., 2 figs., 4 tabs.
  • The Ln{prime}Ln{double_prime}Ba{sub 2}Cu{sub 2}Ti{sub 2}O{sub 11} materials, with their unique A-site ordering and reduced bond lengths, are very attractive candidates for superconductivity. This paper reports specific variations in the inner architecture to achieve appropriate carrier concentration and in-situ thermopower and conductivity studies. Both nominally undoped materials, with the stoichiometries Ln{prime}Ln{double_prime}Ba{sub 2} Cu{sub 2}Ti{sub 2}O{sub 11} (Ln{prime}Ln{double_prime} = LaY and NdDy), and chemically substituted derivatives, NdDyBa{sub 2-x}Sr{sub x}Cu{sub 2+y} Ti{sub 2-y}O{sub 11} and La{sub 1+x}YBa{sub 2-x}Cu{sub 2+y} Ti{sub 2-y}O{sub 11}, were investigated using equilibrium high-temperature electrical property measurements. The solid solution limits and the effect of high oxygen pressure treatments weremore » investigated. The normal state conductivity and thermopower are reported as a function of oxygen partial pressure, temperature, and composition, and Jonker analyses are used to make comparisons to known superconductors. The electrical property measurements are used to elucidate the internal chemistry of these complex solid state materials. 34 refs., 8 figs.« less
  • Polycrystalline samples of Ln{sub 2}Sr{sub 2}PtO{sub 7+{delta}} (Ln=La, Pr, Nd) were prepared by conventional solid state synthesis. The three compounds are new examples for n=2 members of the [A{sub 2}{sup '}O{sub 1+{delta}}][A{sub n}B{sub n-1}O{sub 3n}] family of hexagonal perovskites containing platinum as the B-type cation. XRD Rietveld refinements show the platinates to crystallize in space group R3-bar and, in the case of Pr and Nd, revealed a complete ordering of Ln/Sr on the two distinct A-type positions, while for La a partial disorder was observed. By XANES investigations at the Pt-L{sub III} threshold the oxidation state +4 for platinum wasmore » found. Thermogravimetry revealed a small oxygen excess for Ln=La and Pr ({delta}=0.13 and 0.07), pointing to the presence of peroxide ions as already observed for isostructural Ru- and Ir-based compounds. UV-Vis measurements were done for the yellow lanthanum and the green neodymium compound. They revealed two optical band gaps of 2.52 and 3.05 eV, respectively. Magnetic measurements showed La{sub 2}Sr{sub 2}PtO{sub 7+{delta}} to be diamagnetic as expected for Pt{sup 4+} with low-spin (t{sub 2g}{sup 6}) configuration. For Ln=Pr and Nd the observed strong paramagnetism can be explained solely by the magnetic moments of the rare earths. - Graphical abstract: Hexagonal perovskites of the [A{sub 2}{sup '}O{sub 1+{delta}}][A{sub n}B{sub n-1}O{sub 3n}] family have so far only been known for the transition metals Mn, Nb, Ru, and Ir. In this paper, three new n=2 examples containing platinum as B-type cation are presented. The structure and physical properties of the three title compounds were investigated by XRD Rietveld refinements, thermogravimetry, X-ray absorption spectroscopy, magnetic measurements and optical spectroscopy.« less
  • Thin films of RE{sub 2}Ti{sub 2}O{sub 7} (RE=La, Nd, Sm, Gd) were deposited on single crystal SrTiO{sub 3} (110) substrates at 900 deg. C using pulsed laser deposition. X-ray diffraction (XRD) results showed sharp (00k) peaks (in theta-2theta scans) with narrow rocking curves (omega-scan peak widths of 0.4-0.9{sup o}), indicating that all compositions adopted the (110)-layered perovskite structure. While this is the stable structure for RE=La and Nd, it is metastable for RE=Sm and Gd. The metastable compounds are formed directly through epitaxial stabilization at these high temperatures and are shown to be isostructural to monoclinic La{sub 2}Ti{sub 2}O{sub 7}.more » The a, b, and c lattice parameters decreased monotonically with decreasing size of the RE cation, while the monoclinic angle remained fairly constant. The epitaxial relationship between the (110)-layered RE{sub 2}Ti{sub 2}O{sub 7} films and the SrTiO{sub 3}(110) substrate was found by XRD and transmission electron microscopy to be {l_brace}001{r_brace}<010>{sub film}||{l_brace}110{r_brace}<11-bar0>{sub SrTiO{sub 3}}. The single-phase, metastable, epitaxial, 100 nm thick films maintained the layered perovskite structure even after annealing at 900 deg. C for two hours in 200 Torr of oxygen. - Graphical abstract: Epitaxial thin films of RE{sub 2}Ti{sub 2}O{sub 7} (RE=Gd, Sm, Nd, and La) were deposited on single crystal SrTiO{sub 3} (110) substrates using pulsed laser deposition (PLD). All compositions adopted the monoclinic (110)-layered perovskite structure, which is the stable phase for La{sub 2}Ti{sub 2}O{sub 7} and Nd{sub 2}Ti{sub 2}O{sub 7} but is metastable with respect to the pyrochlore phase for Sm{sub 2}Ti{sub 2}O{sub 7} and Gd{sub 2}Ti{sub 2}O{sub 7}.« less
  • Powder neutron diffraction was used to elucidate the structures of Gd{sub 2}Ba{sub 2}Cu{sub 2}Ti{sub 2}O{sub 11}, Sm{sub 2}Ba{sub 2}Cu{sub 2}Ti{sub 1.5}Sn{sub 0.5}O{sub 11}, and Sm{sub 2}Ba{sub 2}Cu{sub 2}Ti{sub 1.55}Sn{sub 0.2}Sc{sub 0.25}O{sub 11}. The structure is confirmed to be B cation oxygen deficient perovskite. Structural implications of crystal doping of the A site by Ca is reported. 14 refs., 5 figs., 4 tabs.