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Title: Relaxation behavior of oxygen deficient strontium manganite

Abstract

Conduction behavior of nanocrystalline oxygen deficient ceramic-SrMnO{sub 3–δ}(δ∼0.14) has been studied. The structural analysis of nano-SrMnO{sub 2.86} follows hexagonal unit cell structure with P6{sub 3}/mmc (194) space group belonging to 6/mmm point group with 4H – layered type hexagonal-cubic layers. The system have lattice parameters; a = 5.437(92) Å, c = 9.072(92) Å, c/a∼1.66 (85) with α =90° γ= 120° and cell volume, V= 232.35(18). The relaxation times estimated from complex impedance and modulus relaxation spectrum, show the thermally activated system with corresponding activation energies as 0.66 eV and 0.51 eV The stretching factor ‘β’ from the scaled modulus spectrum shows the poly-dispersive non-Debye nature of the system. The hopping number ‘n’ shows the influence of ionic charge carriers which controls the conduction mechanism of nano-SrMnO{sub 2.86}.

Authors:
;  [1]
  1. Department of Physics, Indian Institute of Technology-Patna, Patna- 800013 (India)
Publication Date:
OSTI Identifier:
22269319
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1591; Journal Issue: 1; Conference: 58. DAE solid state physics symposium 2013, Patiala, Punjab (India), 17-21 Dec 2013; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 77 NANOSCIENCE AND NANOTECHNOLOGY; ACTIVATION ENERGY; CERAMICS; CHARGE CARRIERS; CONTROL; CRYSTALS; HCP LATTICES; LATTICE PARAMETERS; LAYERS; NANOSTRUCTURES; OXYGEN; RELAXATION; SPACE GROUPS; SPECTRA; STRONTIUM

Citation Formats

Pandey, Namita, E-mail: namita205@gmail.com, and Thakur, Awalendra Kumar, E-mail: namita205@gmail.com. Relaxation behavior of oxygen deficient strontium manganite. United States: N. p., 2014. Web. doi:10.1063/1.4872972.
Pandey, Namita, E-mail: namita205@gmail.com, & Thakur, Awalendra Kumar, E-mail: namita205@gmail.com. Relaxation behavior of oxygen deficient strontium manganite. United States. doi:10.1063/1.4872972.
Pandey, Namita, E-mail: namita205@gmail.com, and Thakur, Awalendra Kumar, E-mail: namita205@gmail.com. Thu . "Relaxation behavior of oxygen deficient strontium manganite". United States. doi:10.1063/1.4872972.
@article{osti_22269319,
title = {Relaxation behavior of oxygen deficient strontium manganite},
author = {Pandey, Namita, E-mail: namita205@gmail.com and Thakur, Awalendra Kumar, E-mail: namita205@gmail.com},
abstractNote = {Conduction behavior of nanocrystalline oxygen deficient ceramic-SrMnO{sub 3–δ}(δ∼0.14) has been studied. The structural analysis of nano-SrMnO{sub 2.86} follows hexagonal unit cell structure with P6{sub 3}/mmc (194) space group belonging to 6/mmm point group with 4H – layered type hexagonal-cubic layers. The system have lattice parameters; a = 5.437(92) Å, c = 9.072(92) Å, c/a∼1.66 (85) with α =90° γ= 120° and cell volume, V= 232.35(18). The relaxation times estimated from complex impedance and modulus relaxation spectrum, show the thermally activated system with corresponding activation energies as 0.66 eV and 0.51 eV The stretching factor ‘β’ from the scaled modulus spectrum shows the poly-dispersive non-Debye nature of the system. The hopping number ‘n’ shows the influence of ionic charge carriers which controls the conduction mechanism of nano-SrMnO{sub 2.86}.},
doi = {10.1063/1.4872972},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1591,
place = {United States},
year = {Thu Apr 24 00:00:00 EDT 2014},
month = {Thu Apr 24 00:00:00 EDT 2014}
}
  • A new ordered oxygen-deficient perovskite, LaBaMn{sub 2}O{sub 5.5}, has been synthesized, using the topotactic deoxygenation of the ordered LaBaMn{sub 2}O{sub 6} perovskite. The crystal structure of this manganite was solved in the space group Ammm (a = 3.86 {angstrom}, b = 8.19 {angstrom}, c = 15.47 {angstrom}) from neutron powder diffraction data. The [Mn{sub 2}O{sub 5.5}]{sub {infinity}} framework is built up of row of MnO{sub 6} octahedra and MnO{sub 5} pyramids running along {rvec a}. This structure is intermediate between that of the ordered LaBaMn{sub 2}O{sub 6} perovskite and that of LaBaMn{sub 2}O{sub 5}: it consists of ordered barium andmore » lanthanum layers stacked alternatively along {rvec c}, oxygen vacancies being located at the level of the La layers. The magnetic structure is original: manganese spins form ferromagnetic spin-ladders along the {rvec b} axis that are antiferromagnetically coupled along the {rvec a} and {rvec c} axis. The HREM investigation shows the existence of 90{degree} oriented domains and twinning phenomena.« less
  • Photovoltaic effects have been observed in oxygen-deficient La{sub 0.6}Ca{sub 0.4}MnO{sub 3-{delta}} thin film obliquely deposited on Si substrate. The oxygen vacant sites can raise the photovoltaic sensitivity of the manganite thin film, and the photovoltaic sensitivities of 33.4 V/W and 2.84x10{sup 5} mV/mJ are observed when the film is irradiated by a 635 nm continuous wave laser and by a 532 nm pulsed laser of 7 ns duration, respectively. The open-circuit photovoltage of the film, when irradiated by the pulsed laser, has an abnormal change with a fast positive response of about 17 ns and the change of voltage polaritymore » after the laser pulse. It is found that the thickness of the film has important effects on the photoelectric characteristics and the abnormal photovoltage comes from the thickness difference.« less
  • The La{sub 0.8}Na{sub 0.1}MnO{sub 3} oxide was prepared by the solid-state reaction and annealed in air. The X-ray diffraction data reveal that the sample is crystallized in a rhombohedral structure with R3{sup ¯}c space group. Magnetic study shows a second-order magnetic phase transition from ferromagnetic to paramagnetic state at the Curie temperature T{sub C} = 295 K. In addition, the magnetizations as a function of temperature and the magnetic field is used to evaluate the magnetic entropy change ΔS{sub M}. Then, we have deduced that the La{sub 0.8}Na{sub 0.1}MnO{sub 3} oxide has a large magnetocaloric effect at room temperature. Such effect is givenmore » by the maximum of the magnetic entropy change ΔS{sub Mmax} = 5.56, and by the Relative cooling power (RCP) factor which is equal to 235 under a magnetic field of 5 T. Moreover, the magnetic field dependence of the magnetic entropy change is used to determine the critical exponents β, γ, and δ which are found to be β = 0.495, γ = 1.083, and δ = 3.18. These values are consistent with the prediction of the mean field theory (β = 0.5, γ = 1, and δ = 3). Above all, the temperature dependence of electrical resistivity shows a metal–insulator transition at T{sub ρ}. The electrical resistivity decrease when we apply a magnetic field giving a magnetoresistance effect in the order of 60% at room temperature.« less
  • Exposure of La0.9Sr0.1MnO3+δ to repeated oxygen partial pressure cycles (air/10 ppm O2) resulted in enhanced densification rates, similar to behavior shown previously due to thermal cycling. Shrinkage rates in the temperature range 700 to 1000oC were orders of magnitude higher than Makipirtti-Meng model estimations based on stepwise isothermal dilatometry results at high temperature. A maximum in enhanced shrinkage due to oxygen partial pressure cycling occurred at 900oC. Shrinkage was greatest when LSM-10 bars that were first equilibrated in air were exposed to gas flows of lower oxygen fugacity than in the reverse direction. The former creates transient cation and oxygenmore » vacancies well above the equilibrium concentration, resulting in enhanced mobility. These vacancies annihilate as Schottky equilibria is re-established, whereas the latter condition does not lead to excess vacancy concentrations.« less