A neutron diffraction study of LaCoO3 in the temperature range 4.2 &lt; T &lt; 1248 K

Thornton, G.; Tofield, B.C.; Hewat, A.W.

doi:10.1016/0022-4596(86)90035-6

Cited by 283 publications

(221 citation statements)

References 13 publications

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“…XRD Table 2. The lattice parameters and cell volumes of the perovskite phase were almost similar for both samples and in agreement with the literature [29]. The crystallite size was estimated using the Scherrer formula (D = 0.9λ/β cosθ, where d, λ, θ, and β are the crystallite size, Xray wavelength (1.5418 Å), Bragg diffraction angle, and full width of the half maximum (FWHM) of the diffraction peak, respectively).…”

Section: Resultssupporting

confidence: 84%

Micro Emulsion Synthesis of LaCoO₃Nanoparticles and their Electrochemical Catalytic Activity

Islam

Jeong

Ghani

et al. 2015

Journal of Electrochemical Science and Technology

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The micro emulsion method has been successfully used for preparing perovskite LaCoO 3 with uniform, fine-shaped nanoparticles showing high activity as electro catalysts in oxygen reduction reactions (ORRs). They are, therefore, promising candidates for the air-cathode in metal-air rechargeable batteries. Since the activity of a catalyst is highly dependent on its specific surface area, nanoparticles of the perovskite catalyst are desirable for catalyzing both oxygen reduction and evolution reactions. Herein, LaCoO 3 powder was also prepared by sol-gel method for comparison, with a broad particle distribution and high agglomeration. The electro catalytic properties of LaCoO 3 and LaCoO 3 -carbon Super P mixture layers toward the ORR were studied comparatively using the rotating disk electrode technique in 0.1 M KOH electrolyte to elucidate the effect of carbon Super P. Koutecky-Levich theory was applied to acquire the overall electron transfer number (n) during the ORR, calculated to be ~3.74 for the LaCoO 3 -Super P mixture, quite close to the theoretical value (4.0), and 2.7 for carbon-free LaCoO 3 . A synergistic effect toward the ORR is observed when carbon is present in the LaCoO 3 layer. Carbon is assumed to be more than an additive, enhancing the electronic conductivity of the oxide catalyst. It is suggested that ORRs, catalyzed by the LaCoO 3 -Super P mixture, are dominated by a 2+2-electron transfer pathway to form the final, hydroxyl ion product.

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Section: Resultssupporting

confidence: 84%

Micro Emulsion Synthesis of LaCoO₃Nanoparticles and their Electrochemical Catalytic Activity

Islam

Jeong

Ghani

et al. 2015

Journal of Electrochemical Science and Technology

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“…However, detailed neutron diffraction studies 10,11 have failed to detect the expected symmetry change from c R3 to 3 R , associated with the ordered phase. Therefore, the theory was modified 9 to exclude long-range-ordering, in favor of a phase in which dynamic 3 LS Co + / 3 HS Co + ordering would occur with a short correlation radius.…”

Section: Hsmentioning

confidence: 99%

Structural phenomena associated with the spin-state transition inLaCoO3

2002

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The structural properties of LaCoO 3 were studied by means of high-resolution neutron powder diffraction in the temperature range 5£T£1000 K. Changes of the Co +3 spin states in this temperature interval are shown to affect not only the unit cell volume, as previously known, but also internal parameters such as the metal-oxygen bond lengths.These data, as well as the temperature-dependent magnetic susceptibility, can be qualitatively modeled based on a 3-state (low-spin, intermediate-spin and high-spin) activated behavior, but correction terms are required for quantitative agreement. Our fits consistently indicate that the ionic radius of the intermediate-spin state (~0.56 Å) is smaller than the low-spin/high-spin average (~0.58 Å). We also present evidence of a third lattice, anomaly, occurring around 800 K, which we attribute to the formation of oxygen vacancies.

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“…The crystal structures of the end members, LaMnO 3 and LaCoO 3 were found to be orthorhombic (space group Pnma, Z = 4) [16] and rhombohedral (space group R c 3 , Z = 2) [17], respectively. The compounds with 0.15 < x < 0.50 have been found to be orthorhombic [18,19].…”

mentioning

confidence: 98%

“…The structural properties of LaMn 1-x Co x O 3 were characterized in several publications [15][16][17][18][19]. The crystal structures of the end members, LaMnO 3 and LaCoO 3 were found to be orthorhombic (space group Pnma, Z = 4) [16] and rhombohedral (space group R c 3 , Z = 2) [17], respectively.…”

mentioning

confidence: 99%

Phonon Raman scattering in LaMn1−xCoxO3 (x=0, 0.2, 0.3, 0.4, and 1.0)

Gnezdilov

Yeremenko

Pashkevich³

et al. 2003

Low Temperature Physics

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The Raman-active phonons in perovskite-like LaMn 1-x Co x O 3 (x = 0, 0.2, 0.3, 0.4, and 1.0) were studied by measuring Raman spectra at temperatures of 295 and 5 K. The changes in the spectra with Co doping are correlated with the decrease of orthorhombic distortions. Surprisingly more phonon lines than allowed for the rhombohedral LaCoO 3 structure were observed. The manganese perovskites of the type R 1-x A x MnO 3 (R = rare earth, A = Ca, Sr, Ba, or Pb) have been subject of scientific investigations for many decades. Recently, this interest has been renewed due to the observation of a colossal magnetoresistance [1,2], charge, spin, and orbital ordering effects as a function of Mn 3+ /Mn 4+ ratio [3][4][5]. Another system, Mn-site-doped, with the composition LaMn 1-x D x O 3 (D = Cr, Fe, Co, or Ni) was intensively studied in the 60's, but colossal magnetoresistance was not mentioned in them until the 90's [6]. While Raman spectra of La-site-doped compounds have been reported in numerous of publications [7][8][9][10][11][12][13], surprisingly nothing was done on Mn-site-doped compounds. In this work we report the results of an optical phonon study in the perovskite oxides LaMn 1-x Co x O 3 (x = 0, 0.2, 0.3, 0.4, and 1.0). The end member of this system, namely LaCoO 3 has been the subject of continuing interest since the 50's due to unusual magnetic properties and two spin-state transitions [14,15].

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A neutron diffraction study of LaCoO3 in the temperature range 4.2 < T < 1248 K

Cited by 283 publications

References 13 publications

Micro Emulsion Synthesis of LaCoO₃Nanoparticles and their Electrochemical Catalytic Activity

Micro Emulsion Synthesis of LaCoO₃Nanoparticles and their Electrochemical Catalytic Activity

Structural phenomena associated with the spin-state transition inLaCoO3

Phonon Raman scattering in LaMn1−xCoxO3 (x=0, 0.2, 0.3, 0.4, and 1.0)

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A neutron diffraction study of LaCoO3 in the temperature range 4.2 < T < 1248 K

Cited by 283 publications

References 13 publications

Micro Emulsion Synthesis of LaCoO3Nanoparticles and their Electrochemical Catalytic Activity

Micro Emulsion Synthesis of LaCoO3Nanoparticles and their Electrochemical Catalytic Activity

Structural phenomena associated with the spin-state transition inLaCoO3

Phonon Raman scattering in LaMn1−xCoxO3 (x=0, 0.2, 0.3, 0.4, and 1.0)

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Micro Emulsion Synthesis of LaCoO₃Nanoparticles and their Electrochemical Catalytic Activity

Micro Emulsion Synthesis of LaCoO₃Nanoparticles and their Electrochemical Catalytic Activity