“…The resistance of all the materials increased linearly with decreasing temperature, showing similar activation energy for the conduction process as was observed for the La 0.6 Ca 0.4 Mn 1−y Ni y O 3 system [24]. These results agree with a hopping of small polarons as dominating mechanism for the electrical conduction.…”
“…The resistance of all the materials increased linearly with decreasing temperature, showing similar activation energy for the conduction process as was observed for the La 0.6 Ca 0.4 Mn 1−y Ni y O 3 system [24]. These results agree with a hopping of small polarons as dominating mechanism for the electrical conduction.…”
“…The stronger polarization of B-O may trap the transport of carriers and consequently decrease the electrical conductivity. Similar findings were reported by Vashook et al in Ni doped (LaCa)MnO 3−ı system [24].…”
“…It is known [17] that La 1−x Sr x MnO 3+ı compounds are characterized by oxygen excess (ı) that can reach 0.2 depending of Sr content, temperature and oxygen concentration in environment. Oxygen contents for the analogous La 0.6 Ca 0.4 Mn 1−x Ni x O 3−ı compounds we estimated before as 3.08 (x = 0.2) and 2.95 (x = 0.6) [18].…”
Section: Oxidation States Of the Transition Metal Cations Inmentioning
confidence: 71%
“…The double exchange theory describes the mechanism as a simultaneous exchange of two electrons with a parallel spin in the chain · · · -Mn 3+ -O 2− -Mn 4+ -· · · from Mn 3+ to Mn 4+ via the Mn 3d and O 2p orbitals which were found to be partially hybridized [25][26][27]. A possible explanation of the conductivity behavior via double exchange theory is explained elsewhere [18] for La 1−x Ca x Mn 1−y Fe y O 3 systems. Because of the similarities between Co and Fe ions in size, electronegativity and oxidation state the transfer of that theory to the La 0.6 Ca 0.4 Mn 1−x Co x O 3 system might be possible.…”
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