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Published online by Cambridge University Press: 16 February 2011
Orthorhombic perovskite-type (La0.1Ca0.9)(Mn1-xCox)O3 was synthesized in the range 0.00 ≤ x ≤ 0.08. The Rietveld analysis indicates that the (Mn, Co)-O(1 and 2) distances are independent of the composition (x). Measurements of the electrical resistivity (ρ) and the Seebeck coefficient (α) indicate that (La0.1Ca0.9)(Mn1-xCox)O3 is an n-type semiconductor at the low temperature. At the high temperature, (La0.1Ca0.9)(Mn1-xCox)O3 exhibits a metal-insulator transition in the range 0.0 ≤ x ≤ 0.04. The metal-insulator transition temperature (Tt) increases with increasing the Co3+ ion content, while dρ/dT in the metallic region decreases with increasing the Co3+ ion content. The variation of Ea and T+ is explained by the difference in the electronegativity between Mn and Co atoms. The variation of dρ/dT in the metallic region is explained by the increase in the collective o bond.