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Title: Electron-doping through La{sup III}-for-Sr{sup II} substitution in (Sr{sub 1-} {sub x} La {sub x} ){sub 2}FeTaO{sub 6}: Effects on the valences and ordering of the B-site cations, Fe and Ta

Abstract

We have employed aliovalent A-site cation substitution, La{sup III}-for-Sr{sup II}, to dope the Sr(Fe{sub 0.5}Ta{sub 0.5})O{sub 3} perovskite oxide with electrons. Essentially single-phase samples of (Sr{sub 1-} {sub x} La {sub x} )(Fe{sub 0.5}Ta{sub 0.5})O{sub 3} were successfully synthesized up to x{approx}0.3 in a vacuum furnace at 1400 deg. C. The samples were found to crystallize (rather than with orthorhombic symmetry) in monoclinic space group P2{sub 1}/n that accounts for the partial ordering of the B-site cations, Fe and Ta. With increasing La-substitution level, x, the degree of Fe/Ta order was found to increase such that the La-richest compositions are best described by the B-site ordered double-perovskite formula (Sr,La){sub 2}FeTaO{sub 6}. From Fe L {sub 3} and Ta L {sub 3} XANES spectra it was revealed that upon electron doping the two B-site cations, Fe{sup III} and Ta{sup V}, are both prone to reduction. Magnetic susceptibility measurements showed spin-glass type behaviour for all the samples with a transition temperature slightly increasing with increasing x. -- Graphical abstract: Valence states of Fe and Ta are controlled in the partially ordered perovskite oxide (Sr,La){sub 2}FeTaO{sub 6}, through aliovalent La{sup III}-for-Sr{sup II} substitu0010ti.

Authors:
 [1];  [2];  [3];  [3];  [4];  [1];  [5]
  1. Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)
  2. (Finland)
  3. Department of Chemistry and Center for Nano Storage Research, National Taiwan University, Taipei, (China)
  4. National Synchrotron Radiation Research Center, Hsinchu, (China)
  5. Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan). E-mail: karppinen@msl.titech.ac.jp
Publication Date:
OSTI Identifier:
20784838
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 179; Journal Issue: 1; Other Information: DOI: 10.1016/j.jssc.2005.10.004; PII: S0022-4596(05)00464-0; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTROSCOPY; CATIONS; IRON COMPOUNDS; LANTHANUM COMPOUNDS; MAGNETIC SUSCEPTIBILITY; MONOCLINIC LATTICES; ORTHORHOMBIC LATTICES; OXIDES; PEROVSKITE; SPACE GROUPS; SPIN GLASS STATE; STRONTIUM COMPOUNDS; TANTALUM COMPOUNDS; TRANSITION TEMPERATURE; VALENCE; X-RAY SPECTROSCOPY

Citation Formats

Rautama, E.-L., Laboratory of Inorganic and Analytical Chemistry, Helsinki University of Technology, FIN-02015 HUT, Chan, T.S., Liu, R.S., Chen, J.M., Yamauchi, H., and Karppinen, M.. Electron-doping through La{sup III}-for-Sr{sup II} substitution in (Sr{sub 1-} {sub x} La {sub x} ){sub 2}FeTaO{sub 6}: Effects on the valences and ordering of the B-site cations, Fe and Ta. United States: N. p., 2006. Web. doi:10.1016/j.jssc.2005.10.004.
Rautama, E.-L., Laboratory of Inorganic and Analytical Chemistry, Helsinki University of Technology, FIN-02015 HUT, Chan, T.S., Liu, R.S., Chen, J.M., Yamauchi, H., & Karppinen, M.. Electron-doping through La{sup III}-for-Sr{sup II} substitution in (Sr{sub 1-} {sub x} La {sub x} ){sub 2}FeTaO{sub 6}: Effects on the valences and ordering of the B-site cations, Fe and Ta. United States. doi:10.1016/j.jssc.2005.10.004.
Rautama, E.-L., Laboratory of Inorganic and Analytical Chemistry, Helsinki University of Technology, FIN-02015 HUT, Chan, T.S., Liu, R.S., Chen, J.M., Yamauchi, H., and Karppinen, M.. Sun . "Electron-doping through La{sup III}-for-Sr{sup II} substitution in (Sr{sub 1-} {sub x} La {sub x} ){sub 2}FeTaO{sub 6}: Effects on the valences and ordering of the B-site cations, Fe and Ta". United States. doi:10.1016/j.jssc.2005.10.004.
@article{osti_20784838,
title = {Electron-doping through La{sup III}-for-Sr{sup II} substitution in (Sr{sub 1-} {sub x} La {sub x} ){sub 2}FeTaO{sub 6}: Effects on the valences and ordering of the B-site cations, Fe and Ta},
author = {Rautama, E.-L. and Laboratory of Inorganic and Analytical Chemistry, Helsinki University of Technology, FIN-02015 HUT and Chan, T.S. and Liu, R.S. and Chen, J.M. and Yamauchi, H. and Karppinen, M.},
abstractNote = {We have employed aliovalent A-site cation substitution, La{sup III}-for-Sr{sup II}, to dope the Sr(Fe{sub 0.5}Ta{sub 0.5})O{sub 3} perovskite oxide with electrons. Essentially single-phase samples of (Sr{sub 1-} {sub x} La {sub x} )(Fe{sub 0.5}Ta{sub 0.5})O{sub 3} were successfully synthesized up to x{approx}0.3 in a vacuum furnace at 1400 deg. C. The samples were found to crystallize (rather than with orthorhombic symmetry) in monoclinic space group P2{sub 1}/n that accounts for the partial ordering of the B-site cations, Fe and Ta. With increasing La-substitution level, x, the degree of Fe/Ta order was found to increase such that the La-richest compositions are best described by the B-site ordered double-perovskite formula (Sr,La){sub 2}FeTaO{sub 6}. From Fe L {sub 3} and Ta L {sub 3} XANES spectra it was revealed that upon electron doping the two B-site cations, Fe{sup III} and Ta{sup V}, are both prone to reduction. Magnetic susceptibility measurements showed spin-glass type behaviour for all the samples with a transition temperature slightly increasing with increasing x. -- Graphical abstract: Valence states of Fe and Ta are controlled in the partially ordered perovskite oxide (Sr,La){sub 2}FeTaO{sub 6}, through aliovalent La{sup III}-for-Sr{sup II} substitu0010ti.},
doi = {10.1016/j.jssc.2005.10.004},
journal = {Journal of Solid State Chemistry},
number = 1,
volume = 179,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2006},
month = {Sun Jan 15 00:00:00 EST 2006}
}
  • Substitution of divalent Sr by trivalent La is found to affect the valence states of both of the two B-site cations, Fe and Ta, in the double perovskite oxide (Sr{sub 1-} {sub x} La {sub x} ){sub 2}FeTaO{sub 6}. Moreover, it improves the degree of order of these cations. From {sup 57}Fe Moessbauer spectra the average Fe valence was found to decrease with increasing La substitution level, x. However, the valence of Fe decreased less than expected if the valence of Ta was assumed to remain constant. Hence, we conclude that also the valence of Ta decreases. - Graphical abstract:more » Both the degree of order and the valence states of Fe and Ta are controlled in the (Sr{sub 1-} {sub x} La {sub x} ){sub 2}FeTaO{sub 6} double perovskite oxide through aliovalent La{sup III}-for-Sr{sup II} substitution.« less
  • Highlights: • Five new double perovskites of formula Sr{sub 2}LnMoO{sub 6} were synthesized. • All the samples crystallize in the monoclinic P2{sub 1}/n space group. • Strong reducing conditions were used in order to stabilized Mo(V) cations. • A complete ordering between the rare earth and molybdenum ions was observed. • Magnetism agrees with the crystal distortions observed from Rietveld analysis. - Abstract: We describe the preparation, crystal structure determination and magnetic properties of a new series of ordered double perovskite oxides Sr{sub 2}LnMoO{sub 6} (Ln = Eu, Gd, Dy, Ho, Er, Yb) with Mo{sup 5+} and Ln{sup 3+} electronicmore » configurations. These compounds have been obtained by solid state reaction under reducing conditions in order to stabilize Mo{sup 5+} cations. Structural characterization by XRPD and NPD was performed when Ln = Ho, Er, Yb and just XRPD for absorbing Ln = Eu, Gd, Dy. At room temperature, an excellent Rietveld fit was obtained for all the samples in a monoclinic symmetry, space group P2{sub 1}/n, with long-range ordering of Ln and Mo atoms. Magnetic susceptibility measurements show that some of these materials present magnetic ordering below 25 K and the determined effective magnetic moments are consistent with those expected for the pair Ln{sup 3+}–Mo{sup 5+}. All the phases have negative values​​ of the Weiss temperature indicating dominance of antiferromagnetic interactions.« less
  • High precision measurements of the vapor pressure differences between some deuterated benzenes B-d/sub x/ (x=1, para-2, and 6) and protio benzene B-d/sub 0/; between para- and ortho-, and para- and meta-dideuterobenzene; and between perdeuterocyclohexane C-d/sub 12/ and protiocyclohexane C-d/sub 0/ were made from near the freezing point to the normal boiling point. The data are best represented as the logarithmic ratios ln R (d/sub 6/) =ln (P/sub d/0/P/sub d/6) =1226.5/T/sup 2/-12.178/T, ln R (para/ortho) =ln (P/sub parahyphend/2/P/sub orthohyphend/2) =2.6/T/sup 2/, and ln R (para/meta) =ln (P/sub parahyphend/2/P/sub metahyphend/2) =-2.0/T/sup 2/, together with the deviations from the law of the meanmore » ..delta.. (d1) =6-(ln R (d/sub 6/)/lnR (d/sub 1/))=0.177-3.6 x 10/sup -4/t and ..delta.. (d/sub 2hyphenpara/=3-(ln R (d/sub 6/)/ln R (d/sub 2hyphenpara/))=0.028 +1.0 x 10/sup -4/t. The isotope effects are inverse and display significant deviations from the law of the mean. The cyclohexane results are given by ln R (C-d/sub 12/) =-2188.4/T/sup 2/-18.587/T. New measurements of the vapor pressures of benzene--cyclohexane solutions are also reported between 5 and 80 /sup 0/C. The data are in good agreement with the best earlier work. Excess free energies of the equimolar solutions B-h/sub 6//B-d/sub 6/ and C-h/sub 12//C-d/sub 12/ have been measured between 20 and 80 /sup 0/C. Suitable fits to the data yield the following results (30 /sup 0/C); G/sup ex/(B-h/B-d), G/sup ex/(C-h/C-d); H/sup ex/(B-h/B-d),« less
  • We report the synthesis of Aurivillius-type phases incorporating magnetic M {sup 4+} cations (M=Mn, Ru, Ir), based on the substitution of M {sup 4+} for Ti{sup 4+} in Bi{sub 2}Sr{sub 2}(Nb,Ta){sub 2}TiO{sub 12}. Key to incorporating these magnetic transition metal cations appears to be the partial substitution of Sr{sup 2+} for Bi{sup 3+} in the {alpha}-PbO-type layer of the Aurivillius phase, leading to a concomitant decrease in the M {sup 4+} content; i.e., the composition of the prepared compounds was Bi{sub 2-} {sub x} Sr{sub 2+} {sub x} (Nb,Ta){sub 2+} {sub x}M {sub 1-} {sub x} O{sub 12}, x{approx}0.5. Thesemore » compounds only exist over a narrow range of x, between an apparent minimum (x{approx}0.4) Sr{sup 2+} content in the {alpha}-PbO-type [Bi{sub 2}O{sub 2}] layer required for Aurivillius phases to form with magnetic M {sup 4+} cations, and an apparent maximum (x{approx}0.6) Sr{sup 2+} substitution in this [Bi{sub 2}O{sub 2}] layer. Rietveld-refinement of synchrotron X-ray powder diffraction data making use of anomalous dispersion at the Nb and Ru K edges show that the overwhelming majority of the incorporated M cations occupy the central of the three MO{sub 6} octahedral layers in the perovskite-type block. Magnetic susceptibility measurements are presented and discussed in the context of the potential for multiferroic (magnetoelectric) properties in these materials. - Graphical abstract: Structure of Bi{sub 1.5}Sr{sub 2.5}Nb{sub 2.5}Ru{sub 0.5}O{sub 12}.« less
  • Crystals of Sr{sub 4−x}Ln{sub x}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} (x=0; x∼0.15 for Ln=La, Pr, Nd, Sm. Eu, Gd, Dy; x∼0.3 for Ln=Gd) were isolated upon using high-temperature, solid-state methods in molten-salt media. These compounds are isostructural with the previously reported Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} (Ln=La, Sm, Gd) series that contains the same [MnO{sub 4}]{sub ∞} spin chains. The synthesis of the Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} (x=0) phase was carried out by a double aliovalent substitution with respect to the Sr{sup 2+} and Ge{sup 4+} ions that replace Na{sup +}/Ln{sup 3+} and As{sup 5+} in Na{sub 3}LnMn{submore » 3}O{sub 3}(AsO{sub 4}){sub 3}, respectively. The title series contains mixed-valent Mn(III)/Mn(IV) and shows a limited range of solid solution, both of which were not observed in the previously reported Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} series. To form the Sr{sub 4−x}Ln{sub x}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} solid solution, one of the Sr{sup 2+} sites, i.e., the original Ln-site in Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}, is partially substituted by Ln{sup 3+} in a statistical disorder of Sr{sub 1−x}/Ln{sub x}. Initial magnetic investigations of selected derivatives reveal higher ferromagnetic ordering temperatures than those reported for the Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3} series, presumably attributed to a lesser degree of canting as a result of introducing non-Jahn–Teller Mn{sup 4+} ions. Also intriguing is the observation of multiple anomalies at low temperatures which appear to be of electronic origins. - Graphical abstract: Sr{sub 4−x}Ln{sub x}Mn(III){sub 2+x}Mn(IV){sub 1−x}O{sub 3}(GeO{sub 4}){sub 3}. Display Omitted - Highlights: • Double aliovalent substitution: Sr{sub 4}Mn{sub 3}O{sub 3}(GeO{sub 4}){sub 3} with respect to Na{sub 3}LnMn{sub 3}O{sub 3}(AsO{sub 4}){sub 3}. • Solid solution with respect to statistical disorder of Sr{sub 1−x}Ln{sub x} in one of the two Sr sites. • Mn{sup 3+}/Mn{sup 4+} magnetic ions are spatially arranged in a triangular kagomé fashion. • Enhanced ferromagnetic ordering attributed to doping non-Jahn–Teller Mn{sup 4+}.« less