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Title: Neutron structural characterization, inversion degree and transport properties of NiMn{sub 2}O{sub 4} spinel prepared by the hydroxide route

Abstract

Graphical abstract: A pure specimen has been synthesized by the hydroxide route. This spinel, studied by NPD, shows an important inversion degree, λ = 0.80. A bond-valence study shows that the tetrahedral Mn ions are divalent whereas the octahedral Mn and Ni are slightly oxidized from the expected 3+ and 2+ values, respectively. The mixed valence Mn{sup 3+}/Mn{sup 4+} accounts for a hopping mechanism between adjacent octahedral sites, leading to a significant conductivity. Highlights: ► A low-temperature hydroxide route allowed preparing almost pure specimens of NiMn{sub 2}O{sub 4}. ► NPD essential to determine inversion degree; contrasting Ni and Mn for neutrons. ► Bond valence establishes valence state of octahedral and tetrahedral Ni and Mn ions. ► Thermal analysis, transport measurements complement characterization of this oxide. ► A structure–properties relationship is established. -- Abstract: The title compound has been synthesized by the hydroxide route. The crystal structure has been investigated at room temperature from high-resolution neutron powder diffraction (NPD) data. It crystallizes in a cubic spinel structure, space group Fd3{sup ¯}m, Z = 8, with a = 8.3940(2) Å at 295 K. The crystallographic formula is (Ni{sub 0.202(1)}Mn{sub 0.798(1)}){sub 8a}(Ni{sub 0.790(1)}Mn{sub 1.210(1)}){sub 16d}O{sub 4} where 8a and 16d stand for themore » tetrahedral and octahedral sites of the spinel structure, respectively. There is a significant inversion degree of the spinel structure, λ = 0.80. In fact, the variable parameter for the oxygen position, u = 0.2636(4), is far from that expected (u = 0.25) for normal spinels. From a bond-valence study, it seems that the valence distribution in NiMn{sub 2}O{sub 4} spinel is not as trivial as expected (Ni{sup 2+} and Mn{sup 3+}), but clearly the tetrahedral Mn ions are divalent whereas the octahedral Mn and Ni are slightly oxidized from the expected +3 and +2 values, respectively. The mixed valence observed at the octahedral sites provides the charge carriers that, by a hopping mechanism between Mn{sup 3+}/Mn{sup 4+} adjacent sites, leads to a significant conductivity, up to 0.85 S cm{sup −1} at 800 °C in air.« less

Authors:
;  [1];  [2];  [2];  [3];  [4]
  1. Departamento de Química, Laboratorio de Fisicoquímica Inorgánica, Universidad Nacional del Sur, INQUISUR, 8000 Bahía Blanca (Argentina)
  2. Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco, E-28049 Madrid (Spain)
  3. Institut Laue Langevin, BP 156X, Grenoble F-38042 (France)
  4. Departamento de Química Inorgánica, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid (Spain)
Publication Date:
OSTI Identifier:
22215099
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 47; Journal Issue: 6; Other Information: Copyright (c) 2012 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:
36 MATERIALS SCIENCE; CRYSTALLOGRAPHY; CUBIC LATTICES; ELECTRICAL PROPERTIES; HYDROXIDES; MANGANESE IONS; NEUTRON DIFFRACTION; NEUTRONS; SPACE GROUPS; SPINELS; THERMAL ANALYSIS

Citation Formats

Sagua, A., Lescano, Gabriela M., Alonso, J.A., E-mail: jaalonso@icmm.csic.es, Martínez-Coronado, R., Fernández-Díaz, M.T., and Morán, E. Neutron structural characterization, inversion degree and transport properties of NiMn{sub 2}O{sub 4} spinel prepared by the hydroxide route. United States: N. p., 2012. Web. doi:10.1016/J.MATERRESBULL.2012.03.012.
Sagua, A., Lescano, Gabriela M., Alonso, J.A., E-mail: jaalonso@icmm.csic.es, Martínez-Coronado, R., Fernández-Díaz, M.T., & Morán, E. Neutron structural characterization, inversion degree and transport properties of NiMn{sub 2}O{sub 4} spinel prepared by the hydroxide route. United States. doi:10.1016/J.MATERRESBULL.2012.03.012.
Sagua, A., Lescano, Gabriela M., Alonso, J.A., E-mail: jaalonso@icmm.csic.es, Martínez-Coronado, R., Fernández-Díaz, M.T., and Morán, E. Fri . "Neutron structural characterization, inversion degree and transport properties of NiMn{sub 2}O{sub 4} spinel prepared by the hydroxide route". United States. doi:10.1016/J.MATERRESBULL.2012.03.012.
@article{osti_22215099,
title = {Neutron structural characterization, inversion degree and transport properties of NiMn{sub 2}O{sub 4} spinel prepared by the hydroxide route},
author = {Sagua, A. and Lescano, Gabriela M. and Alonso, J.A., E-mail: jaalonso@icmm.csic.es and Martínez-Coronado, R. and Fernández-Díaz, M.T. and Morán, E.},
abstractNote = {Graphical abstract: A pure specimen has been synthesized by the hydroxide route. This spinel, studied by NPD, shows an important inversion degree, λ = 0.80. A bond-valence study shows that the tetrahedral Mn ions are divalent whereas the octahedral Mn and Ni are slightly oxidized from the expected 3+ and 2+ values, respectively. The mixed valence Mn{sup 3+}/Mn{sup 4+} accounts for a hopping mechanism between adjacent octahedral sites, leading to a significant conductivity. Highlights: ► A low-temperature hydroxide route allowed preparing almost pure specimens of NiMn{sub 2}O{sub 4}. ► NPD essential to determine inversion degree; contrasting Ni and Mn for neutrons. ► Bond valence establishes valence state of octahedral and tetrahedral Ni and Mn ions. ► Thermal analysis, transport measurements complement characterization of this oxide. ► A structure–properties relationship is established. -- Abstract: The title compound has been synthesized by the hydroxide route. The crystal structure has been investigated at room temperature from high-resolution neutron powder diffraction (NPD) data. It crystallizes in a cubic spinel structure, space group Fd3{sup ¯}m, Z = 8, with a = 8.3940(2) Å at 295 K. The crystallographic formula is (Ni{sub 0.202(1)}Mn{sub 0.798(1)}){sub 8a}(Ni{sub 0.790(1)}Mn{sub 1.210(1)}){sub 16d}O{sub 4} where 8a and 16d stand for the tetrahedral and octahedral sites of the spinel structure, respectively. There is a significant inversion degree of the spinel structure, λ = 0.80. In fact, the variable parameter for the oxygen position, u = 0.2636(4), is far from that expected (u = 0.25) for normal spinels. From a bond-valence study, it seems that the valence distribution in NiMn{sub 2}O{sub 4} spinel is not as trivial as expected (Ni{sup 2+} and Mn{sup 3+}), but clearly the tetrahedral Mn ions are divalent whereas the octahedral Mn and Ni are slightly oxidized from the expected +3 and +2 values, respectively. The mixed valence observed at the octahedral sites provides the charge carriers that, by a hopping mechanism between Mn{sup 3+}/Mn{sup 4+} adjacent sites, leads to a significant conductivity, up to 0.85 S cm{sup −1} at 800 °C in air.},
doi = {10.1016/J.MATERRESBULL.2012.03.012},
journal = {Materials Research Bulletin},
number = 6,
volume = 47,
place = {United States},
year = {Fri Jun 15 00:00:00 EDT 2012},
month = {Fri Jun 15 00:00:00 EDT 2012}
}
  • Graphical abstract: This figure shows the specific magnetization curves of the as-prepared MFe{sub 2}O{sub 4} (M = Ni, Co, Mn, Mg, Zn) powders obtained from room temperature VSM measurement. These curves are typical for a soft magnetic material and indicate hysteresis ferromagnetism in the field ranges of ±500 Oe, ±1000 Oe, and ±2000 Oe for the CoFe{sub 2}O{sub 4}, MgFe{sub 2}O{sub 4} and MnFe{sub 2}O{sub 4} respectively, whereas the samples of NiFe{sub 2}O{sub 4} and ZnFe{sub 2}O{sub 4} show a superparamagnetic behavior. Highlights: ► Nanocrystalline MFe{sub 2}O{sub 4} powders were synthesized by a novel hydrothermal method. ► Metal acetylacetonates andmore » aloe vera plant-extracted solution are used. ► This biosynthetic route is very simple and provides high-yield oxide nanomaterials. ► XRD and TEM results indicate that the prepared samples have only spinel structure. ► The maximum M{sub s} of 68.9 emu/g at 10 kOe were observed for the samples of MnFe{sub 2}O{sub 4}. - Abstract: Nanocrystalline spinel ferrite MFe{sub 2}O{sub 4} (M = Ni, Co, Mn, Mg, Zn) powders were synthesized by a novel hydrothermal method using Fe(acac){sub 3}, M(acac){sub 3} (M = Ni, Co, Mn, Mg, Zn) and aloe vera plant extracted solution. The X-ray diffraction and selected-area electron diffraction results indicate that the synthesized nanocrystalline have only spinel structure without the presence of other phase impurities. The crystal structure and morphology of the spinel ferrite powders, as revealed by TEM, show that the NiFe{sub 2}O{sub 4} and CoFe{sub 2}O{sub 4} samples contain nanoparticles, whereas the MnFe{sub 2}O{sub 4} and MgFe{sub 2}O{sub 4} samples consist of many nanoplatelets and nanoparticles. Interestingly, the ZnFe{sub 2}O{sub 4} sample contains plate-like structure of networked nanocrystalline particles. Room temperature magnetization results show a ferromagnetic behavior of the CoFe{sub 2}O{sub 4}, MnFe{sub 2}O{sub 4} and MgFe{sub 2}O{sub 4} samples, whereas the samples of NiFe{sub 2}O{sub 4} and ZnFe{sub 2}O{sub 4} exhibit a superparamagnetic behavior.« less
  • We studied the transport, magnetic, and structural properties of spinel MnTi{sub 2}O{sub 4} and V-doped samples, MnTi{sub 2-x}V{sub x}O{sub 4}, to clarify the relation between charge, spin, and orbital degrees of freedom of 3d electrons in this series of compounds. A structural phase transition occurs in MnTi{sub 2}O{sub 4} at 180 K, which is presumably dominated by the ordering of t{sub 2g} orbitals, but it can be easily suppressed by the V doping to the Ti site. Associated with this suppression of the structural anomaly, a ferrimagnetic and electrically conducting state appears in MnTi{sub 2-x}V{sub x}O{sub 4} with finite valuesmore » of x. Fairly large magnetoresistance was observed in this state, whose sign changes from positive to negative with an increase in the V concentration x. With approaching the other end of this series, MnV{sub 2}O{sub 4}, the electrical resistivity increases again and another type of structural phase transition occurs at 53 K. Large magnetostriction was observed in MnV{sub 2}O{sub 4}, the only compound in this series to have both a ferrimagnetic state and tetragonal lattice distortion.« less
  • The present study describes the preparation, characterization, and thermal decomposition of the compound Ni(MnO{sub 4}){sub 2}.xH{sub 2}O, which was synthesized by a coprecipitation method at a low temperature. The role of this compound as a precursor in the synthesis of a Ni-Mn spinel was determined via X-ray, TG-DTA, electron diffraction, and EDAX measurements.
  • In this paper, a series of pure Ni{sub 1-x}Zn {sub x}Fe{sub 2}O{sub 4} (0 {<=} x {<=} 1) spinel ferrites have been synthesized successfully using a novel route through calcination of tailored hydrotalcite-like layered double hydroxide molecular precursors of the type [(Ni + Zn){sub 1-x-y}Fe {sub y} {sup 2+}Fe {sub x} {sup 3+}(OH){sub 2}] {sup x+}(SO{sub 4} {sup 2-}) {sub x/2}.mH{sub 2}O at 900 deg. C for 2 h, in which the molar ratio of (Ni{sup 2+} + Zn{sup 2+})/(Fe{sup 2+} + Fe{sup 3+}) was adjusted to the same value as that in single spinel ferrite itself. The physico-chemical characteristicsmore » of the LDHs and their resulting calcined products were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Moessbauer spectroscopy. The results indicate that calcination of the as-synthesized LDH precursor affords a pure single Ni{sub 1-x}Zn {sub x}Fe{sub 2}O{sub 4} (0 {<=} x {<=} 1) spinel ferrite phase. Moreover, formation of pure ferrites starting from LDHs precursors requires a much lower temperature and shorter time, leading to a lower chance of side-reactions occurring, because all metal cations on the brucite-like layers of LDHs can be uniformly distributed at an atomic level.« less
  • Trace amounts of H/sub 2/O and limited exposure to air of reaction mixtures of UCl/sub 4/ and 12-crown-4, 15-crown-5, benzo-15-crown-5, 18-crown-6, or dibenzo-18-crown-6 in 1:3 mixtures of CH/sub 3/OH and CH/sub 3/CN resulted in the hydrolysis and oxidation of UCl/sub 4/ to (UO/sub 2/Cl/sub 4/)/sup 2/minus//. In the presence of these crown ethers, it has been possible to isolate intermediate products via crystallization of crown complexes of the (UO/sub 2/Cl/sub 4/)/sup 2/minus// ion, the (UCl/sub 6/)/sup 2/minus// ion, and (UO/sub 2/Cl/sub 2/(OH/sub 2/)/sub 3/). The neutral moiety crystallizes as a hydrogen-bonded crown ether complex; however, crown ether complexation of amore » counterion, either an ammonium ion formed during the oxidation of U(IV) or a Na/sup +/ ion leached from glass reaction vessels, resulted in novel crystalline complexes of the ionic species. ((NH/sub 4/)(15-crown-5)/sub 2/)/sub 2/(UO/sub 2/Cl/sub 4/) /times/ 2CH/sub 3/CN, ((NH/sub 4/)(benzo-15-crown-5)/sub 2/)/sub 2/(UCl/sub 6/) /times/ 4CH/sub 3/CN, and ((NH/sub 4/)(dibenzo-18-crown-6))/sub 2/(UO/sub 2/Cl/sub 4/) /times/ 2CH/sub 3/CN have been structurally characterized by single-crystal X-ray diffraction techniques. The results of all the crystal studies are presented in detail. The ammonium ions interact with the crown ethers via hydrogen-bonding and electrostatic interactions. 15-Crown-5 and benzo-15-crown-5 form 2:1 sandwich cations, allowing no H/sub 4/N/sup +//hor ellipsis/(UO/sub 2/Cl/sub 4/)/sup 2/minus// interaction. The dibenzo-18-crown-6 complexed ammonium ions are 1:1 and form bifurcated hydrogen bonds with the chlorine atoms in the (UO/sub 2/Cl/sub 4/)/sup /minus// anion. The formation of (Na(12-crown-4)/sub 2//sub 2/(UO/sub 2/Cl/sub 4/) /times/ 2OHMe and (UO/sub 2/Cl/sub 2/(OH)/sub 2/)/sub 3/) /times/ 18-crown-6 /times/ H/sub 2/O /times/ OHMe has been confirmed by preliminary single-crystal X-ray diffraction studies.« less