2007
DOI: 10.1590/s0100-40422007000700004
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Propriedades estruturais e microestruturais de manganitas dopadas com cobre

Abstract: Recebido em 20/2/06; aceito em 15/2/07; publicado na web em 6/8/07 STRUCTURAL AND MICROSTRUCTURAL PROPERTIES OF Cu-DOPED MANGANITES. We report a structural study on polycrystalline La 0.86 Sr 0.14 Mn 1-y Cu y O 3+δ samples (y = 0, 0.05, 0.10, 0.15, 0.20) using refinement of powder X-ray diffraction data and analysis of scanning electron microscopy images. It is found that the structure remains rhombohedral through the whole series, with a decrease in the average Mn-Mn bond distances, slight variations in Mn-O-… Show more

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(4 citation statements)
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“…A more detailed analysis of the value of the peak frequency reveals a small and smooth displacement of the central peak as a function of x (figure 4(b)). This feature can be associated with slight structural changes caused by the Cu for Mn substitution [18], as shown in figures 4(c) and (d). As mentioned above, the 139 La NMR frequency in zero-field measurements is dictated by the magnitude of the transferred hyperfine field, from neighbouring Mn ions, which depends on the overlap of the Mn t 2g orbitals with the on-site La s orbitals, mediated by p oxygen orbitals [6].…”
Section: La Nmr Spectramentioning
confidence: 83%
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“…A more detailed analysis of the value of the peak frequency reveals a small and smooth displacement of the central peak as a function of x (figure 4(b)). This feature can be associated with slight structural changes caused by the Cu for Mn substitution [18], as shown in figures 4(c) and (d). As mentioned above, the 139 La NMR frequency in zero-field measurements is dictated by the magnitude of the transferred hyperfine field, from neighbouring Mn ions, which depends on the overlap of the Mn t 2g orbitals with the on-site La s orbitals, mediated by p oxygen orbitals [6].…”
Section: La Nmr Spectramentioning
confidence: 83%
“…The final sintering was performed in an oxygen atmosphere at 1400 • C for 30 min and this was followed by a period of 24 h at 1300 • C. Powder x-ray diffraction (XRD) showed the formation of a rhombohedral R 3M structure for all samples, with decreasing unit cell volume and a small increase of lattice distortion for samples with larger values of x. From the XRD patterns, the values of the oxygen non-stoichiometry parameter δ were estimated to be in the range 0.023-0.030 [18]. The positive values of δ indicate the presence of cation vacancies in the structure of the analysed compounds, associated with the oxygen-rich atmosphere used in the syntheses [16].…”
Section: Experimental Methodsmentioning
confidence: 99%
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