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Studies on magnesium- and titanium-substituted LaCoO<inf>3</inf>
Date Issued
01-01-1979
Author(s)
Ramadass, N.
Gopalakrishnan, J.
Sastri, M. V.C.
Abstract
Crystallographic, electrical and magnetic studies have been carried out on the Mg2+- and Ti4+-substituted LaCoO3 systems, LaCo1-xMgxO3 and LaCo1-xTix03. In the magnesium system, substitution occurs up to x = 0.1, retaining the rhombohedral perovskite structure of LaCoO3. Magnesium substitution results in a lowering of the activation energy for electrical conduction, an enhancement of the positive Seebeck coefficient and a decrease of the magnetic moment per cobalt ion, owing to the creation of CoIV ions (holes). In the titanium system, isomorphous substitution of titanium occurs in LaCoO3 up to x = 0.2. For x ≤ 0.1, the rhombohedral perovskite structure is retained. For x = 0.2, the composition has the cubic perovskite structure. For x > 0.2, the compounds have a distorted perovskite structure exhibiting oxidative non-stoichiometry. The resistivity and its activation energy increase with x beyond x = 0.05. Ti4+ acts as an n-type dope up to x = 0.05, beyond which the samples revert to p-type semiconductivity. © 1979.
Volume
65