High temperature transport properties of co-substituted Ca1−xLnxMn1−xNbxO3 (Ln = Yb, Lu; 0.02 ≤ x ≤ 0.08)

Nag, Abanti and Bose , Rapaka SC (2016) High temperature transport properties of co-substituted Ca1−xLnxMn1−xNbxO3 (Ln = Yb, Lu; 0.02 ≤ x ≤ 0.08). Materials Research Bulletin, 74 . pp. 41-49. ISSN 0025-5408

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    Abstract

    The co-substituted Ca1�xLnxMn1�xNbxO3 (Ln = Yb, Lu; 0.02 � x � 0.08) are synthesized by solid-state reaction and the electronic transport properties are investigated. Rietveld refinement confirms the formation of single phase orthorhombic structure with gradual increase of cell parameters with doping level. The electronic transport properties such as Seebeck coefficient and electrical resistivity decrease with increasing the dopant concentration for both the co-substituted compositions. All the compositions of Ca1�xLnxMn1�xNbxO3 show nonmetal-like temperature dependence of resistivity; whereas metal-like temperature dependence of thermopower. This inconsistency is explained by the formation of oxygen vacancy associated defect centres that originates from partial reduction of Mn4+ to Mn3+ due to cosubstitution. The defect centres act as extrinsic carriers and cause additional contribution to the entropy of the system, leading to increase of Seebeck coefficient as a function of temperature. The transport mechanism of charge carriers is explained in the framework of Mott’s small polaron hopping mechanism.

    Item Type: Journal Article
    Additional Information: Copyright to this article belongs to M/s. Elsevier
    Uncontrolled Keywords: A.Oxides;A.Electronic materials;D.Defects;D.Crystal structure;D.Thermoelectrics
    Subjects: CHEMISTRY AND MATERIALS > Chemistry and Materials (General)
    Division/Department: Materials Science Division, Other
    Depositing User: Ms. Alphones Mary
    Date Deposited: 25 Apr 2016 09:27
    Last Modified: 25 Apr 2016 09:27
    URI: http://nal-ir.nal.res.in/id/eprint/12459

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